Alternative GREEN Furnace - Non-Fossil-Fueled - Construction

High-Performance HeatGreen Home Heating System Version 3a Construction

Benefits of this HG 3a system include:
  • Never pay heating bills again!
  • Great for the Environment!
  • No burning, no fire, no flame at all!
  • No chimney to waste heat out to the atmosphere; in fact, extremely high overall energy efficiency results!
  • Never use fossil fuels again!
  • Build this device yourself for around $200!

  • Step-by-step Instructions included here.
  • A medium-sized house in a northern climate may lose 45,000 Btu/hr on a really cold January night. Since 2007, this HeatGreen 3a device has shown that it can supply 90,000 Btu/hr! Providing 45,000 Btu/hr for a warm and cozy house on that cold night is fairly easy!

This presentation was first placed on the Internet in February 2007. At least 63,000 visitors have read about the HG concept since then (to early 2010). Since we don't charge for this information, we have no way of knowing when people actually build HG units, but we believe that at least several hundred have been built so far, in at least ten different countries.

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Rotating Five-foot diameter HG 3a showing two digital thermometers, two air ducts and two water pipes, axle shaft, feed door opening, and pink heat insulation (built in May 2007 of $200 new materials). This is a Normal-sized Rotating Five-foot diameter HG 3a showing two digital thermometers (internal air and water), two air ducts and two water pipes, axle shaft, feed door opening, and pink heat insulation. Maximum heat production about 90,000 Btu/hr for about two days at a load. In milder weather, it can provide a constant 30,000 Btu/hr for about a week per loading. (built in May 2007 of $200 new materials).

Rather small Rotating Three-foot diameter HG 3a (built in 2009). This small unit can only contain about 20% as much organic material as the standard-sized HG 3a shown above, so it can only heat one or two rooms for a while. Rather small Rotating Three-foot diameter HG 3a (someone built in 2009). This small unit can only contain about 15% as much organic material as the standard-sized HG 3a shown above, and it's maximum heat production is only about 1/4 of that of the standard-sized HG 3a, or about 25,000 Btu/hr, for a little more than a full day per load, so it can only realistically heat one or two rooms.

BETTER than Biogas!

This "active" version of the HeatGreen system has great flexibility and sufficient capability for nearly any residential heating application. It is absolutely "green" and eliminates the need for the buying or using of any fossil fuels.

The relatively small device described here (a little larger than the size of an upright piano and weighing empty around 140 pounds) (and with all construction instructions included below) is around 5 feet in diameter and 2 feet thick. It can easily create the continuous 45,000 Btus per hour of constant heating that a medium-sized home in a cold climate like Chicago needs in January or February, and has shown that it can easily produce twice that amount of heat, or over 90,000 Btus of hour. It uses SCRAP cut lawn grass and autumn leaves, which decompose and release amazing amounts of heat in the process. We capture that heat and use it! (It needs to be refilled with any of a wide range of organic materials, every few days or every week or two, depending on the outdoor temperatures.)

This presentation is primarily centered on describing how to build this HG 3a unit with around $200 of locally available materials. Since there are a wide range of climates in the world, and sizes and types of homes, and an immense number of different ways this device can be used, we will include an assortment of simple calculations and explanations, such that each locality or each person could modify the standard HG 3a unit for specific needs. If you want to learn more about how and why the HG heating systems work so well, the presentation at General Description may be useful. That presentation also has a link to a more comprehensive presentation which includes the Biochemistry and Thermodynamics aspects, which we think most people do not want to have to confront!

As noted above, the standard HG 3a unit is relatively modest in size, for several reasons. It is designed to be light enough when empty (140 pounds or so) to easily be carried (or rolled!). It is designed to be of dimensions where standard-sized pieces of plywood are very efficiently used with very little waste, and also so that it can fit through standard doorways. It also is designed so that when completely filled, it does not weigh much more than a filled food freezer, and therefore will not stress building floor structures. The dimensions provide an inside capacity of around 40 cubic feet, so depending on the density of the organic material used, around 400 pounds (at 10 pounds per cubic foot dry density) to 800 pounds (at 20 lb/cu ft) of material usually can be put into it at a time. (Certain materials like sawdust or feed corn are of higher density and greater amounts can be loaded at a time.)

If we consider the most conservative value of 400 pounds of material being placed in it, here are two common possibilities that can happen.

Both of these scenarios are describing the performance of the STANDARD version of the device, the HG 3a, described below. They tend to require a good deal of time and effort regarding loading material. Long ago, people used to load coal in a furnace to heat their homes, and it turns out that roughly the same total amount of weight of organic material needs to be loaded here as was done then. Actually, somewhat less because coal furnaces were around 60% efficient, meaning that 40% of the heat energy in the coal either went up the chimney as waste heat or was left as clinkers. This system has no chimney, and when operated best, can decompose nearly everything you put into it that is organic in chemical composition. I have experimentally measured around 94% overall efficiency at several times.

There are millions of people who are willing to chop trees up into firewood and carry ten or more tons (five cords) of that wood to piles where they need to then split it (which I personally really hate doing!); then let the wood dry for eight months or more; and then they carry those tons of wood again, now into the house to load it into a woodsstove every few hours. The HG 3a device has many advantages over burning wood, although there are still some tons of organic material that needs to be carried at some point. No chopping or carrying of firewood, NO SPLITTING OF WOOD (yay!), no stacking it to dry for many months, only loading once every few days instead of every few hours, MUCH higher overall efficiency, a cost to you of around $200 to make an HG 3a rather than more than $3000 to buy a modern airtight woodstove plus a few thousand more for the chimney that it needs, and NO FLAME for far safer operation (and therefore, no actual chimney)!

We note that there were companies and individuals who were available (for payment) to deliver and even load the coal in those furnaces so the homeowner did not have any inconvenience, and that seems possible again with this HG 3a device. We think that tens of thousands of lawn-care businesses might be ideal for this function! In the Summer, they mow and collect and then have to dispose of many tons of cut grass and of leaves in the Autumn. If instead of disposing of them, they were spread out and dried like farmers do for hay, they might have a simple and easy way to make bales, in other words, a supply of very large amounts of the needed materials. Some types of materials could be baled up as hay or straw is. Then, in the Winter, when they currently have nothing to do (except play cards), the lawn-care people could contract to visit homes with HG 3a devices every few days to load and maintain them. Seems to me that MILLIONS of people might have a possible source of income, a paying job! Consider the possibility that such a local lawn-care company would contract to do this maintenance for a winter for say $500. The homeowner would love that, only paying $500 rather than maybe $2,000 to heat his/her house. The lawn-care company would now have something for employees to do in winter, and it would also be nicely profitable! One employee should be able to service four houses per hour or around 32 per day. On average (due to the climate and weather) servicing the HG 3a about every five days seems to work fine. That means ONE employee should be able to service around 150 houses, each for $500 or $75,000 income that the lawn-care company otherwise never would have! The company could be fairly generous in paying the worker(s) and still keep a lot of that $75,000 of cash inflow from each 150 customers! This is using materials that are available to the company FOR FREE, and it even eliminates them having to find somewhere to dispose of it! And the employees would have continuous jobs and not just seasonal! Everyone can win!

It is certainly possible to make larger scale versions of this (which will then no longer fit through a standard doorway). One that is twice the dimensions could hold eight times as much material, or around 3200 pounds. Still at a decomposition rate of 5 pounds per hour (during January or February in a northern climate), that is full home heating for about 640 hours or about 27 days of whole house heating before a new load of organic material needs to be loaded in it. Keep in mind that the building floor structure would then have to be able to support roughly the weight of a car, and the ceiling would need to be over 12 feet high for that particular size and shape! But the same diameter as a standard HG 3a could be made but twice as thick, etc, to increase the capacity. There are some structural considerations when such changes are made, such as stiffeners, which may be needed. However, for really large scale heat loads, it is probable that simply making two or more HG 3as or of building the rather different HG 2a may be a better choice.

During early 2011, an interesting modification was developed for the HG 3a device. Where the entire HG 3a device slowly rotates in order to ensure that every piece of organic material gets air and water for ideal decomposition and also to minimize the clumping that seems to quickly occur if the device is not rotated for some hours, this variation is built the same as the HG 3a except for a couple minor differences. Where the HG 3a axle is mounted rigidly to the sidewalls of the chamber, and the entire chamber therefore rotates, the HG 3b axle passes THROUGH the entire unit. That (iron pipe) axle therefore rotates in a NON-ROTATING CHAMBER. The axle shaft has two PIPE CROSSES inside the chamber, which each have two stub pipes, four in total, which are each 2 feet long. The four pipes act like the flailing arms inside of a farmer's flail-type manure spreader. They rotate much faster than the very slow rotation of the HG 3a chamber. The motor and mechanism needed for the rotation is simpler and cheaper than that needed for the HG 3a device.

In my own experiments in developing this system, I had results that certainly impressed me! For a fairly large four-bedroom home near Chicago, which is VERY old (originally built as a one-room schoolhouse in 1856!) and only partially insulated now, the first winter of using an HG 3a unit (2007-2008) resulted in only using around $198 worth of natural gas for the entire year. Much of that was used by the gas water heater during the summer months when I was not experimenting! But some also was used during times when I had taken the HG 3a apart to change something or test something! The next winter of use of the HG 3a unit (2008-2009) resulted in around $192 worth of natural gas (bills) being consumed during the entire year. Again, most of that was used by the gas water heater during the summer months when I was not using the HG 3a unit, and it was also partly due to increases in the cost of natural gas. All in all, not bad! A house that used to require $1500 to $2000 consumption of natural gas each year has only used around 1/8 that much while I have been using the HG 3a (during the winter). It seems very likely that the consumption might drop to near zero if I would start to use the HG 3a all year!

I later learned that even when I used ZERO natural gas in a month, the gas company still charges me around $16 for an assortment of charges, which therefore totals around $190 per year. The question has become whether I want to keep the gas turned on as a POSSIBLE BACKUP to the HG 3a, or whether I want to tell the gas company to shut it off completely, to save that $190 charges per year! For now, I am leaving the gas turned on, as I may feel lazy or ill and possibly not interested or capable of bringing in a bale of stuff. I know this from entirely heating a very large farm house with the JUCA woodstove I invented in 1973. I actually dismantled the conventional furnace then for parts for some experiments I wanted to do. But I found that I could not vacation in Florida as I had done for many previous years, as the house could not load its own woodstove for heat!

This HG 3a design also has the built-in capability of providing large amounts of domestic hot water. The arrangement described below can contain either 8 gallons or 14 gallons (of around 150°F water), which can fully heat up from a standard municipal cold water supply in roughly 15 minutes, which can therefore provide a virtually endless supply of hot water for bathtubs or clothes washing. (A full bathtub of wonderfully hot water at fifteen minute intervals for all the kids you have!) (Or all the hot water needed for full loads of a clothes washing machine every fifteen minutes.) The water heating performance of the configuration described below is around 24,000 Btu/hr to 27,000 Btu/hr, reasonably comparable with conventional hot water heaters (which are often rated somewhat higher at the INPUT amount of natural gas consumed). It can easily be increased or decreased depending on the size of your family.

Cooking inside it seems to be an interesting ability, although there seems to be a slight complication due to the very slow tumbling of the device! The cooking action resembles a Crockpot or Slow-Cooker regarding the wonderful taste of the results, but also the time required. This capability requires a modification of the device's door structure, but it nicely cooks hamburgers and many other foods, although the 150°F available temperature requires longer cooking times than on a stovetop. For example, hard-boiled eggs needs about nine hours to be fully done, but they seem to me to be even tastier than normal HB eggs, more delicate, possibly due to not needing the boiling water. In my opinion, cooked sweet corn (45 to 60 minutes) is more tender and delicious than when cooked in other ways. When the corn is cooked while still in the husk, it probably maintains all the natural vitamins as well, which get lost in standard cooking methods. The same seems to be true of other vegetables, possibly because I do not use water for any of those functions (except for things like the hard-boiled eggs and spaghetti). It also does seem to virtually not matter how long the eggs, corn, vegetables or hamburgers are left in the cooker, as even after 12 hours my experiments have all been delicious! This method of cooking is absolutely safe, possibly even more so than conventional cooking, as ALL dangerous pathogens are easily killed at these temperatures, as long as the food rises to above 125°F. With conventional cooking, sometimes the center of a thick piece of meat does not get up above that necessary 125°F, where people can then still have E. coli and other pathogens still present in the meat. That is not possible here. However, "Rare" may not be a possibility, as the low heat for a long time penetrates completely through even thick items of food.

I have discovered that it also can brew amazingly tasty coffee and tea, similar to how "sun tea" is made that is so tasty! But where sun tea is generally rather weak, this system brews tea or coffee that is of conventional strength of taste. There is no harshness in the taste, really amazing.

(Sorry about these tangential comments from the heating system, but new and different uses seem to keep appearing for it!)

(As a side note, many house furnaces are rated at 125,000 Btu/hr or so. That is actually INPUT energy rating, the amount of natural gas burned, for example, where some of the created heat goes up the chimney, leaving a maximum of around 100,000 Btu/hr of actual heat which could be available for the house. Conventional furnaces are designed so that their burner should be on 2/3 of the time when the outdoor temperature is the Design Temperature for that climate [ which is -10°F or -23°C for the Chicago area ]. This means that that 125,000 Btu/hour (input) conventional furnace really is intended to provide a MAXIMUM of around 67,000 Btu/hr of CONSTANT heat supply on the coldest night of the year. Generally, calculations for a well-insulated house near Chicago shows that the design heat loss is around 40,000 to 50,000 Btu/hr AVERAGE on that coldest day. This is why we are discussing heat productions of 45,000 Btu/hr as being sufficient and 90,000 Btu/hr as being too much heat!)

I also learned a lot about this with my 1973-1983 years with my JUCA woodstove. I had designed the stove (actually a central wood furnace with three glass walls to watch the fire), to have a CONTINUOUS heat output of 226,000 Btus per hour. Being in an 1896, uninsulated, three-story, eleven room farmhouse, encouraged me to design big! But since it created CONSTANT heat, it easily acted like a conventional furnace of double that rating, and it always heated the entire house very easily.

This 3a Version appears to have some major advantages over earlier HG units. Several are due to the fact that the entire drum "tumbles" every hour or so. It move so slowly that it is hard to even notice that it is moving at all! The decomposing material inside does not "clump up" too badly, as some types of materials can tend to do over the time of the decomposition. This tumbling also allows more free access of the oxygen to all the material, which is why it is capable of such fast performance. Even the supply (puddle) of several gallons of excess water that we keep in the bottom tends to get stirred together with all the material, ensuring that all material has sufficient moisture available for good decomposition, again enhancing performance. Plenty of oxygen and plenty of water available and nice warm environment, for each sub-microscopic thermophilic bacterium! They love it! As a result, they decompose virtually anything that is organic rather quickly. The quickness of the decomposition is related to how THICK the individual pieces are, and cut lawn grass therefore decomposes especially fast and effectively. (Some types of material take longer, such as used car tires or used motor oil or most types of plastic or thick pieces of wood.) Another advantage is that the drum rotation could be slowed to once per day instead of once per hour, which degrades the performance somewhat for INTENTIONALLY lower heat production, by nicely slowing down the rate of consumption of the material, when less heat is needed for the house. (Slower decomposing material, such as straw, can also be used to cause less heat production.) (I personally do not like a once-a-day rotation rate because some types of material then seem to have time enough to clump all together like coat hangers in a closet do. Once-an-hour rotation seems to eliminate this complication for nearly all materials.)

This (small) Version of the HeatGreen home heating system is capable of producing all the heat you could want, but it also can consume the organic materials you put into it very rapidly, but only because its capacity is fairly small! That means that this small system CAN provide all the heat necessary to entirely heat a moderate-sized house in the worst of the winter, BUT for only two or three days before it would need to again be filled with another 400 pounds of material! This is somewhat labor-intensive, and so we also mention a larger-scale Version of this rotating HeatGreen system.

It is generally convenient to load in a partial bale of material each day, which lets the previous bacteria to keep merrily chewing up the organic materials, while also allowing some hours for the new material to warm up enough to take over. When done well, that both provides a nice consistent amount of heat for the house and also avoids you having to start it all up from scratch very often.

You will build a device that resembles a large exercise wheel for a hamster. Or a Galapagos Tortoise, as it is bigger and very slow moving. We will describe one that is about five feet in diameter and two feet thick, such that it can be carried through standard doorways. As noted above, that size has an internal volume of around 40 cubic feet. At a density of the organic material put into it of 10 pounds per cubic foot, that means around 400 pounds of organic material can be loaded to decompose, which will give off a total of around 3,500,000 Btus of heat energy during that decomposition process. (A pound of many organic materials contains around 9,000 Btus of chemical energy which was first obtained from sunlight by chlorophyll during photosynthesis. 400 lb * 9,000 Btu/lb is that three and a half million available Btus, once the bacteria convert the chemical energy into heat energy during decomposition.) (Some organic materials are more compact than that, such as feed corn, where more weight of material can be put in it at a time.) These are DRY weights and not when sopping wet, where the density and weight are much higher. HARDWOOD is around 35 pounds per cubic foot and SOFTWOOD is around 28 pounds per cubic foot. Grass and hay and straw and wood chips have a lot of air spaces in them, which reduces the average density as indicated above.)

(These are simple and inexpensive enough to build, requiring only around $200 of materials from a local store, that it could make sense to build two of them for your house. IF you have difficulty in keeping them going, you could schedule loading material in them at different times, so that the initial heat-up time while the process is beginning would not be a problem, as the other one would be fully heating the house then. Of course, once you learn how to operate an HG 3a where you do not regularly kill the bacteria off, just adding partial bales or loads can keep a single device operating for an entire winter! But there is a severe learning curve in first learning to keep the [thermophilic] bacteria alive. You WILL tend to kill them off a few times before you learn! Also, if your water supply or air supply to one of them was interrupted, or any other problem occurred that caused the bacteria to stop doing their thing, the other one could still be comfortably heating your house.)

A wonderful idea toward enhancing the HG 3a device

Some people had built an unusual variant of my HG 2 system, and their ideas caused me to be inspired regarding a REALLY good idea for any or all of the HG devices! This might be worth considering! Especially if you should discover that you tend to kill off all your bacteria as you are trying to learn how to use the unit! Whether it is a giant HG 2 device or a much smaller HG 3a or HG 3b device, this modification is pretty close to earth-shaking! Since most everyone seems to decide to build either HG 3a or HG 3b units, I will discuss those here regarding what needs to be done.

For the past five years, I have often joked about how incredibly sensitive the Thermophilic bacteria are, where I sometimes have claimed that if you cross your eyes, all your bacteria might immediately die! Everyone else who has experimented with these devices has certainly felt great frustration at having to start the process over after you have done what seemed to be very minor harassments of your bacteria.

This is simple! During a TRAINING PERIOD while the owners are getting to learn how to properly supply the Thermophilic bacteria with the oxygen, the carbon dioxide and the heat they need to thrive, this idea is just so simple and obvious that I am very disappointed in myself for having taken five years to get here! You get an OLD (but safe) gas-fired clothes dryer. You connect the 4" vent duct to it and feed it into the chamber of the HG device. It is wonderful if you can buy a high temperature thermostat to put inside the HG 3a. Specifically, there is a very cheap type (around $5) which is called a disk thermostat. The rating that I like best is the one at 135°F. Any local heating-plumbing store should have that for $5.

So here is what happens. You toss ANY collection of organic materials into the HG 3a chamber. Just the tossing of cold material into the unit have been able to cause the bacteria to all die! They are AMAZINGLY sensitive!

Where it had always been critically necessary that you be extremely attentive to temperature, oxygen and water, or else you would off your bacteria, now it is entirely different! When you first close the door, the material is still cold, about the 70°F material that you had just tossed in. But since the thermostat recognizes that it is NOT warm enough in there, the gas burner of the clothes dryer turns on and also the motor which blows the hot air through the vent pipe also turns on. In other words, in just a few seconds, you have started to ARTIFICIALLY heat the entire interior of the HG unit up to around 140°F. It turns out that You have actually also provided OXYGEN for them at the same time!

Your Thermophilic bacteria are as happy as they could be! You won't be able to see their tiny little smiling faces, but trust me on this one! Of course, the actual point of this whole thing is that the bacteria start decomposing organic materials and creating a lot of heat. As soon as they have begun generating enough heat to keep everybody happy (which is surprisingly fast), the thermostat sees that there is no longer any need for the clothes dryer to run any more. Actually. just three to five minutes seems to be all it could ever need!

AND the reasoning is that YOU will LEARN how it is all to work, and you will likely never again need to use the clothes dryer for the artificial heating. Or maybe, only very rarely! Basically, the only time that it would then ever need to turn on again would be if you have forgotten to load the unit or something similar!

I think that as the owner learns how to make fewer mistakes, it might be less necessary to be providing this additional artificial heating, as the Thermophilic bacteria are perfectly capable of producing amazing amounts of heat on their own! You might note that I might be sounding somewhat insulting regarding ARTIFICIAL heat! It's true! I am sort of a purist on this, and the fact that Nature has created the amazing Thermophilic bacteria, it seems to me that we have some sort of responsibility to learn how to provide for them. Think of it as not having just one pet dog, but many billions of pet thermophilic bacteria. Take care of them and they will take care of you!

Personally, I like the safety aspects of the fact that the natural HG devices do not involve any flame or fire, and that the sopping wet contents ensure that no dangerous fire could possibly ever happen. But as a Training Aid to Rookie owners of an HG device, I guess I can tolerate a tiny amount of fossil fuel consumption, BUT ONLY UNTIL YOU LEARN YOUR CHOPS!

Either gas-fired or electric clothes dryer should be able to keep your bacteria cozy and happy. In any case, the 4" dryer vent is fed into the HG chamber. (No, I think it would be a terrible idea to also try to dry clothes in it, as you would then be ignoring the well-being of your bacteria!) But then a temperature sensor (or 135°F thermostat switch) inside the chamber could automatically turn on the clothes dryer to send some really hot air into the chamber, which also would provide extra oxygen for the bacteria's enjoyment! Once the owner learns how to operate the HG properly, the thermophilic bacteria inside will generate plenty of heat so that the thermostat switch would never again need to turn on the clothes dryer!

Given my personal experiences with killing off a lot of bacteria over the past five years, this modification seems excellent. Of course, the usual safety precautions need to be attended to. IF you have very dry bales of grass or hay, stacked somewhere near your HG device, you CANNOT ever leave any such material very near a fire-containing clothes dryer which might turn itself on! Got it?

Parts Materials

(Prices shown are retail prices from 2007 from a local home supply store)

FunctionQuantityItemRetail Cost
Main Structure Sidewalls2 sheets of 3/4" thick GOOD QUALITY CDX plywood, of 5- or 7-plies. $21.44 * 2 = $42.88
Main Structure Perimeter1 sheet of 1/4" thick plywood.$13.88
Side Insulation4 2" thick or 8 1" thick sheets of 4x8' foam building insulation, 2" or 1" thick, either interior (white) or exterior (underground). either $6.49 each for interior 1" or $12.29 for exterior 1" each. I spent $47.92
Perimeter Insulation4sheets of 4x8' foam building insulation, 1" thick, interior (white) $6.49 each or $25.96
Attach foamseveral tubes foam adhesive (like PL300).$3.99 each or $11.97
Screwsseveral boxes#10 by 1.5" woodscrews. $2.24 each per 25 or $6.72
Waterproof barrier1a reinforced plastic tarp, around 16 by 20 feet or larger$14.98
Interior structure and water holder1 100-foot roll of 1.25" or 1.5" (black) polyethylene water line (BLUE label is for potable water) 1.25" is $32.48
Fittings for that pipemiscadaptors, clamps, tees.
Axle mounts21" pipe flanges$3.18 each
Air pathmisc4" PVC elbows and pipe.
Axles21" iron pipe sections at least 6" to 10" long..
Water pipe connections2 .
Air path2standard flexible dryer vent hoses..
Water connections2standard washing machine supply hoses..
miscmiscmiscellaneous pipe adaptors and hardware..

This should total around $200 of materials.

Note: These instructions are for a unit that is made of very commonly available materials, which are of rather low cost. We have also designed this to be buildable by anyone who has moderate skills as a handyman. There are ways to build many variants of this unit. One example is to line the entire inside with fiberglass instead of the cheap and simple tarp we suggest here. Since most modern tarpaulins are actually made of petroleum-based materials, it might be that over a period of years, the bacteria might slowly decompose the tarp. Since a layer of fiberglass is actually primarily made of silicon / glass materials, that should last for many, many years, but the cost and effort would be much higher initially.

There have also been people who have welded up HG 3a units out of aluminum plates, which seems like a good idea but it requires specialized welding abilities and may be more expensive to build. People have tried to make really little ones out of a 55-gallon drum, but in my opinion, they can only contain so little material that re-loading every hour seems likely, which I personally do not like the idea of! People have also made variants which I have thought were goofy, like cubical ones, triangular ones, and ones that included rather flimsy wall materials or axle shaft materials. I ENCOURAGE having creative thoughts, because these things are rather cheap and quick to build, and someone occasionally comes up with a variant which is very beneficial! In my opinion, the sort of large farm water tanks made of fiberglass or PVC are too expensive, but otherwise fine. It DOES seem attractive to build them out of PVC, for strength, durability, simplicity, and quickness of construction, but again the cost becomes an issue.

If weight is not considered an issue, it would even be possible to weld this up out of Corten steel, which is resistant to nearly all types of degradation.

I give permission for any person or company to build as many as 20 of these units without further permission. Beyond that number, I do NOT give authorization without a written (paper) authorization. Specifically, I do NOT give permission to any company to mass produce my invention, made out of any material, such as out of a material such as PVC, without my approval.


On a sheet of the thick plywood, make a mark 30.25" from one end and 17.75" from a long side (or 30.25" from the opposite long side). This will become the location of the axle centerline, so you can now drill a small hole there. Using that location and a 30.25" long stick or string, draw a circle around that point. The circle should just touch the opposite edge of the plywood as well as the end of the sheet. Using a sabre saw, carefully cut out that piece. image-b
It represents most of one side of the structure, and should be 60.5" in total diameter with a D-shaped piece missing.

Place this piece on top of the remaining piece of the plywood sheet, and trace out the edge, where the curve passes through a point that is 12.5" from the (opposite) end of the sheet. When this D-shaped piece is cut out, it is the remaining part of the full circle. These dimensions were chosen such that the full circle of the full side can be made from a single sheet of plywood.

Do the same for the other sheet to get the opposite side of the structure.

Provisions for the axle now need to be installed. I have been installing "1-inch pipe flanges" at the center of both side circles, and using bolts and nuts to secure them rather than the usual woodscrews. Put the CARRIAGE BOLT heads INSIDE the chamber so that there are no sharp projections to rub against the plastic tarp. Countersunk FLAT-HEAD machine bolts could also be used here. The later pipe nipples of 1" pipe are strong enough to be the axle shaft and do not bend with the weight of all the material in the chamber.

(After a year of use, this last statement seems to be uncertain. When the chamber is regularly filled with 400 pounds or more of material, plus water, I have found that the [stretching] loading on the small bolts can actually make them longer! Also, the heads of the Carriage bolts tend to be able to crush the plywood a little. These effects tend to make the axle shafts we will later screw into the flanges be able to tilt a little, where the two axle half-shafts may no longer be co-axial. A simple solution to this exists. Buy two pieces of 1/4" thick steel plate, around one foot square. Attach those plates to the plywood sidewalls and then use high-strength bolts to attach the flange to the steel plate. There should then never be any axle-shaft angle changes.)

Next, the sheets of side foam insulation can be marked out and cut very much like the plywood sheets were, except that now the desired radius is 34.25" instead of 30.25". Foam adhesive works great in mounting them. The foam is added as two separate 2" layers, or four separate 1" layers, to have an insulation rating of R-20. These side insulation slabs extend 4" beyond the circular body, so that sheets of the 1" layers of (white) foam for the circumference can be cut down the middle to get strips of 24" by 96". THAT foam MUST be the 1" thick size, and the interior type, so it can be bent enough to follow the curvature of the perimeter. If you work in a warm area, the white circumference foam should be able to bend to follow the curvature. (Exterior foam is higher density and therefore more rigid and brittle, and would break). Again, four layers of the foam around the edges provides the desired R-20 insulation.

At this point, only the foam for the one side can be mounted, with the rest of the insulation being attached later. But even it can be left for later to avoid it being damaged during construction. All the foam can be added once the device is supported on its pedestal stand, where it can be rotated to ease addition of the foam pieces.

None of this foam is ever likely to be exposed to moisture, so white is fine, where the outdoor or underground type is required for wet locations. You could always get another poly tarp and surround the whole device, for example if it could ever be rained on.

Cut the thin plywood sheet (crossways, so that it can be bent easiest) into four pieces which are now each 24" by 48". They will be the "rim" which surrounds the two side circles to form the main body of the device.

The thin plywood can be bent enough to follow that gentle curvature of the circle edges. The strips of the thin plywood are therefore screwed to the outer edge of the plywood circle, with two of the four pieces straddling the joint with the D-shaped piece for greatest strength and durability. For reasons that will be clear shortly, it is actually easiest if you ONLY screw the thin plywood pieces to ONE of the two circles at this time. This results in the thin plywood trying to flare out. A simple way to deal with this is with a 20-foot long piece of rope, which is temporarily tied around the loose edges of those thin plywood pieces to resemble the circle that they will eventually be. A tow-rope or a load-binder could also be used.

You might notice the (white) indication of the construction adhesive used to join the sidewalls to the circular pieces. Also note that the joints between those four pieces are carefully arranged to not be at the same location where the joints between the two parts of the circle are, for greater structural strength.

You now have a 60.5" diameter disk with a two-foot-high circular barrier around it.

Place the tarp inside that pit, relatively centered. It actually is slightly off center, such that all the edges of it can reach the opening you will later make in the second circular unit to feed material into the device. That makes sure that the tarp has no edges or seams or overlaps inside the chamber which might someday become less than water-tight. image-j
(IF you are going to add the water heating capability) Get the coil of poly pipe. We show the pipe as it is bought, along with some of the hose clamps which will be used with it.

We note here an unusual aspect of this usage of black polyethylene pipe. That material is generally heated to at least 270°F in heat-forming it into various shapes. Because of this, the maximum recommended temperature for black poly objects is therefore usually set at 180°F. However, a Safety Factor of around five is applied in the official guidelines when black poly pipe carries pressurized water, and that maximum recommended temperature is often set at 120°F. The Safety Factor is applied so that there is no chance that an exposed heated pipe might burst and spurt scalding hot water out that might hurt people. In this particular application, the entire 100-foot length of the poly pipe is enclosed inside the decomposition chamber, so that danger could not occur. In addition, such black poly pipe is commonly used as agricultural irrigation piping, where on a hot summer afternoon in a hot climate, the ambient temperature can near 150°F (just like football fields and auto racetracks are sometimes at such temperatures.) We have found no problems whatever in using the black poly pipe inside our chambers, although the clamps can need to be screwed a little tighter after the poly conforms more to the shape of the barb-fitting elbows.

What you are going to do is follow the natural curved shape of that poly pipe (because it is bought in a coil). You are going to use two standard hose clamps, but not in the traditional way. You will use a short piece of metal barstock, between the first two turns of coil of the pipe, to clamp each of the two clamps to which makes a poly pipe circle of a very specific and very sturdy diameter. You will slightly increase the diameter of this first loop, up to where the OUTSIDE diameter is slightly over 60.5". The two clamps are on the two turns of the coil, with the end one about a foot or two from the very end of the poly pipe, but the two clamps are linked together to establish this sturdy diameter. When they are tightened, they will fix that outside diameter of that ring of poly pipe to slightly greater than the diameter dimension you choose. That diameter is chosen so that the coil will be a very tight fit, virtually a press-fit, inside the chamber. When it is pressed down into the corner of the chamber, it will securely hold the tarp in the corner there. Roughly one foot of the pipe extends beyond where the clamp is, so that an (elbow) water connection can be made, which will then extend so both ends of that 100-foot long pipe will extend to outside the chamber.

It is very important to make sure that no sharp corners of any metal could ever rub against and tear the tarp. Wrapping a layer of non-biodegradable duct-like tape is a reasonable way of protecting the tarp surface from all the clamps, especially the extended ends.

That coil of filled poly water pipe can be for a number of different functions. In the Applications Sections below, there are systems that use a SEPARATE (enclosed) supply of low pressure water to CIRCULATE heat to rooms of the house using standard Hydronic pumps and radiators. Similar SEPARATE water systems could heat a swimming pool or hot tub. If the coil is to be used to provide Domestic hot water for the house faucets, it will be filled with water at the prevailing water pressure of the Municipal or well water supply. Since it is not possible for the water to ever get warmer than 150°F, it can never have any threat of boiling.

There are also around eight to a dozen extra clamps needed on that first turn of pipe. (the photo shows only the first loop in place, with the rest of the poly pipe still waiting to be spread out to press against the circular walls.) The extra hose clamps will be roughly equally spaced around the circumference of the ring, to be able to clamp upward metal spacer bars securely to the pipe and later also to the identical poly coil which will be made for the opposite corner of the chamber. The spacer bars can be either 1/8 by 3/8 flatbar strips or 5/16 or 3/8 diameter round rod. For the standard size of chamber described here, 24 inch long pieces of that rod or bar are fine. Around 2.5 inches from each end, a right angle bend is made, with the result being a sturdy spacer bar which will keep the two outermost coils of poly pipe at 19.25 inches apart. (The curved plywood perimeter is 24 inches, minus two pieces of side plywood and the two diameters of poly pipe, leaving very close to 19.25 inch separation needed).

Notice that the detail of the narrow photo here shows that I put a twist in the flatbar stock, which allows the barstock to fit more closely along the sidewalls, which allows the poly pipe to fit better.

(These strips of metal are NOT bolted anywhere, as that would require punctures of the plastic tarp, and leaks! They will only be held in place by being SQUEEZED between the two sidewalls! Which also helps hold the tarp where it needs to be, also without any actual adhesive or clamps.

The radius of the first and last loop keeps the pipe pressed against the outer (circular) wall and the spacer bars keep the pipe circles pressed firmly against the sidewalls. The rest of the pipe, around five turns, is reasonably snugly pressed against the outer wall. A few additional standard stainless steel hose clamps are used to clamp the intermediate loops to a FEW of the spacer bars, to keep them spaced apart across the width of the chamber, roughly with 3" spacing between each loop.

I am also experimenting with other methods of affixing the poly pipe to the spacer bars. The cheapest and simplest is to use electrical Cable Ties, (shown as the attachment type in the next photo here, to attach to the middle spacer bar shown, but nearly invisible because they are black) but I have doubts whether they will be able to stay tight over the years due to the heat and the motion. I suspect that when I check them in a few years, they may be loose! I am also experimenting with using 16 inch long pieces of scrap SOLID house wiring, wrapped DOUBLE around the pipe and spacer bar (shown in the rightmost portion of the next photo, again with black insulation on the wires so they are hard to see). They figure to be durable, but again the motion over several years may loosen them. But they are much less expensive than the hose clamps which are clearly the best. So I am just using the standard stainless hose clamps on just the two opposite spacer bars, one being shown near the left side in that next photo) which should ensure that the poly pipe will never be able to go very far anywhere. The Cable Ties and pieces of wire are therefore not critical in the operation, and I consider them somewhat optional. If it turns out that Cable Ties will still be fairly tight after several years, that may be the future way to go.

This photo has all the turns of poly pipe securely attached. Notice that the actual spacing of the poly pipe is not critical, and I have some variation in the demo setup.

One of the main functions of this poly pipe is therefore to press the tarp against the circular corner, without needing any kind of adhesive. A second function CAN BE to contain water which will get heated. If 1.25" poly is used, the full hundred feet of it will hold and heat up around 8 gallons of water at a time. If 1.5" poly is used, 14 gallons. If 2" poly is used, around 24 gallons. If 3" poly can be found at a tolerable price, it would hold around 50 gallons of water at a time. Four-inch poly exists, but it is sold in straight sections rather than in a coil, which makes its use a little more difficult, although that would contain even more water at a time. For really big water capacities, rigid PVC 4 inch pipe is probably best and easiest. We find the 8 or 14 gallon to be sufficient, since new water coming in gets heated quite quickly due to all the tube surface area exposed to the 150°F environment inside the chamber. Even 8 gallons of 150°F water mixes with about 14 gallons of 55°F tap water to easily fill a bathtub with 22 gallons of wonderful 90°F bath water! Showers use less hot water and are even more reliable. Washing many consecutive loads of clothes in the hottest of water might be a reason to consider the larger diameter poly, or multiple coils of it inside the structure.

Below, we will calculate that if all the hot water is removed, it generally only takes about 15 minutes for new cold water to become heated fully to the 150°F, so those hot baths could be repeated all day long, as long as they were at about 15 minute intervals!

The two outer rings of pipe therefore press the tarp into the corners of the chamber, without any adhesive and without any fasteners which might have to penetrate the tarp.

At the very ends of the coil of pipe, standard barbed elbows are attached. (the gray barbed fitting is seen near the very middle of this inner photo, elbowed up which will be extended against the sidewall). One end will be connected to an input water supply (of cold water) and the other will be connected to an output pipe of hot water. This arrangement ensures that ONLY hot water could possibly be provided, that any new cold water has to pass through the entire 100-foot length of the coil of pipe, and be fully heated up, before it could ever get to the output connector.

There are alternate ways of installing and spacing this poly pipe. Keep in mind that its primary function is to press the tarp tightly into the corners of the chamber. Having water inside it is simply a bonus regarding making hot water! By using an entire 100-foot long roll of the poly pipe, there are minimal pipe fittings that could ever later leak. It turns out that the tumbling action of hundreds of pounds of the organic material tends to knock loose any poorly attached spacers or clamps!

The second plywood circle can now be installed, again using construction adhesive and screws. Obviously, all the tarp edges are first pushed into the chamber, as shown in the first photo here. Realize that the tarp has covered up the TOPMOST circle of poly pipe, which will therefore press the tarp nicely into the circular corner there. The tarp edges will later be pulled snug along the inside surface (not visible) so that all the edges of the tarp will extend through the material feeder opening, which is indicated by the lines marked out in the second photo here. This particular unit was made to have a 16" square feed door.

I generally climbed on top of this second plywood piece, to squeeze the poly pipes and spacers inside so that everything was snug inside the chamber, and so that the top edge of this plywood piece matches up with the upper edges of the curved perimeter plywood pieces. This makes sure that nothing can move around inside the chamber. Good quality construction adhesive and screws are again used to construct this.

You can also see in the second photo here where the remaining D-shaped piece of plywood will go. Please ignore the two PVC closet (toilet) floor flanges in the photo because a better way has been found to install the air tubes.

You obviously realize that the tarp edges will be pulled through the opening and secured on the OUTSIDE of the side plywood. This will ensure that there are NO openings anywhere in the tarp surface inside the chamber, where water or water vapor could ever escape and cause unplanned decomposition of the structure itself! As long as you did not puncture the tarp anywhere, it should now essentially be able to hold water, except where the feed door assembly will be attached.

This photo shows the device with the remaining D-shaped piece of plywood added and then a trapezoidal-shaped hole was cut. This hole accomplishes many functions. We made this hole 16" in height, approximately centered between the axle shaft and the perimeter (about 7" from each). We made the top 16" wide to allow the 16" square access opening, and we made the bottom 26" wide to permit space for the large PVC pipes. First, the hole allows all the edges of the poly tarp inside to stick through, so there are NO holes or punctures anywhere in the inner tarp surface, which should make it absolutely water-tight and vapor-tight. There will be a piece of discarded industrial conveyor belting cut to be mounted over this opening, which will have five different holes cut in it. (1) a large 16-inch square hole will have a removable door over it, to allow loading in the organic materials and possibly reach inside to remove anything that has not decomposed. The hole is trapezoid-shaped to allow space for (2,3) two 4" PVC schedule-40 pipes (one through each of the wider corners). Above the PVC pipes are (4,5) two smaller holes for the poly water pipes which are inside. This hole and the covering piece of conveyor belting is large enough that if it should ever become necessary to do any work inside the chamber, it should be possible to have suitable access in there.

The second photo simply shows all the edges of the poly tarp being brought out through that hole, to show how they will all be extended a little way along the outside and then tacked or stapled to the outside, several inches back from the edges of the hole. All those edges will actually simply get pinched between the plywood sidewall and the thick piece of conveyor belting, which will securely hold it in place.

These next two photos show the device standing up in its correct upright position, with 10" long (galvanized) pipes threaded in the pipe flanges, and those pipe sections supported on sturdy triangular support pillars. The support stand has stiffeners to make sure that it could not move or collapse when a lot of weight of organic material and water is inside. We also added 6" x 24" stiffeners of the 3/4" plywood scraps over each of the seams of the perimeter 1/4" plywood, which otherwise tends to bulge out a little there.

Even with no actual bearings at all, and just the pipe sections resting on the top of the support pillars, the device rotates extremely easily. Just the couple pounds difference due to the missing wood from the hole tends to make it want to rotate so that the hole is generally upward, which indicates that only a very small motor is needed to rotate it. That is NOT actually true once the material inside has clumped up! When the heavy piece of conveyor belting is added and the fill door, the weight changes enough that it then wants to turn the other way. A counterweight can be added opposite the fill opening, to either balance it or to get it to want to keep the fill hole naturally upward.

These two pictures obviously do not yet show the white foam insulation layers, or the conveyor belting material piece or the pipe connections or the entry door. You can note that the two pictures show the device in positions about 60 degrees apart, which commonly takes about 15 minutes to move that far. Once the foam is added, not much else is then visible except for the hole and piece of conveyor material, pipe ends and feed door.

The stiffeners we added to the chamber mean that the first layer of the 1" white foam insulation needs to be cut shorter to fit between those stiffeners, but that then allows the other three layers to fit excellently. (seen below)

We intentionally included a conventional room door in the photos to confirm that the size of this device is between 5 and 6 feet in diameter, and a little over two feet in total thickness.

The first photo here shows the first layer of the one-inch white foam skipping the area where we added the stiffeners.

The second photo here shows the four layers of that foam in place.

The first photo here shows the entire device with the perimeter foam in place (although a small section of the outer layer is not yet in place in this photo).

The front will soon be covered by the side foam, and the piece of scrap conveyor belting will cover over the trapezoid hole, where only the final 16-inch square hole will remain and the two pairs of pipes adjacent to it.

The second photo here shows the perimeter of the unit. This shows the foam left exposed. We do not see any major reason that cannot be left, with a few related thoughts. The white foam is very susceptible to being damaged, so if the device is where it might be bothered by kids or pets, it might make sense to go to the extra trouble of covering it with thin (masonite) paneling or wall paneling or even an external tarp. The one which was assembled for the photos here will have a covering of (artificial) naugahyde, to resemble a piece of furniture. The white foam also disintegrates pretty quickly if it gets wet, so if that is a possibility, then the same should be done. It can also be painted, decorated, to become an active artistic object. If it is in a location in the house, kids' school projects or awards could be attached to it, where they would forever be moving around. It could also become the world's slowest moving Mobile sculpture!

The blue or pink foam is far more resistant to moisture and abrasion, BUT it tends to shatter rather than bend around the curvature, so if you try to use that material, be very careful about that.

The next two photos show the piece of surplus conveyor belting I like to use for around the door and pipes. Companies that use such industrial conveyors need to occasionally replace the belting. They do NOT like to have to pay to have it hauled away, so many such companies tend to have some piles of discarded conveyor belting lying somewhere out in a field. They seem to enjoy the chance to get rid of some of it (for free!). But I have never asked for just two feet of it! I generally have taken whatever piece of scrap belting they had easiest access to. They seem to commonly chop it apart into 50 to 100 foot long pieces, just so they could more easily haul it out to the field! The belting that I have used has all been of a thickness of 0.400 inch, but the thickness for our purposes is irrelevant. The one shown here was from a 36 inch wide conveyor (width is also irrelevant) and the piece used here was squared out to 26 inches long (high in our case). The upper corners were trimmed to better fit against the plywood backing. You may be able to see around a dozen small holes we drilled for the mounting bolts to pass through it.

The first picture shows the surplus conveyor piece with the 16 inch square hole that will be for the access door, and the two smaller round holes for the poly water pipes and the two larger round holes for the two 4 inch PVC sewer lines.

The second photo here is because these details are not easily seen when the items are mounted on the unit. It shows that a 90 degree street elbow immediately goes through each of the larger holes, one pointed up and the other down. The reason for this may turn out not to actually be that important, but we think it might be. You will be feeding in air, consisting primarily of oxygen and nitrogen into one of these large pipes (on the far side), and "used air" containing a substantial amount of carbon dioxide will therefore be pushed out the other (nearer pipe). It turns out that carbon dioxide is more than 1.5 times as dense as normal air. We believe that there is very little air motion inside the chamber, so maybe a good deal of the carbon dioxide might settle toward the bottom (rather than the normal action of simply mixing with the air). So we provide the longer (26") PVC pipe going downward to be able to remove the gases down near the bottom, which we expect to contain an excess of carbon dioxide. This, while the air/oxygen that we are sending in might tend to initially stay nearer the top, so we provide the upward (11") pipe to cause the air sent in to stay farther from the used gases that we want to exhaust.

It will require thorough chemical analysis to determine this, but for now we are assuming it to happen. In the event that the carbon dioxide and air mix more than we are expecting, the only real difference is that a larger blower (relatively speaking, still rather tiny in reality) is needed to expel more of the air inside the chamber to replace it with fresh air for the bacteria to use.

IF the "exhaust" gases are to be used to (later) provide increased carbon dioxide for a high-performance greenhouse, we think this simple feature might allow a greater percentage of carbon dioxide in that exhausted air, while also then requiring less power in the air blower to cause that circulation.

Once this assembly is in place, none of it is easily visible, so it is shown here separate from the device.

Finally, not yet shown here are the standard "closet (toilet) flanges" to mount those pipes really securely without having to make any holes in the tarp lining inside the chamber. These will be considered in the next section.

These two photos look nearly identical!

The (black) conveyor belting piece just discussed is actually mounted here, but then it is entirely covered by the four pieces of wood. The wood pieces function as many things, including squeezing the overlapped poly tarp edges under the conveyor piece for good airtightness and watertightness. They also provide a strong frame for the door which will later be mounted, as well as a solid structure for the hinge supports and latch for that door.

They also provide a strong structure to support the four pipes which must pass through the sidewall of the unit.

These photos might be confusing as the tarp surface which is seen through the door opening is actually the OPPOSIDE sidewall of the chamber!

The street elbows have some radius, so we found it necessary to mount the closet flanges slightly raised up, on the 2x10 lumber scraps, to get the PVC pipes inside the chamber nearer to the side wall, to less interfere with the movement of all the material that you will put inside it to tumble around. The first photo here shows the closet flanges which are permanently attached to the short interior PVC pipes and mounted to the wood frame structure.

The second photo here shows a SECOND pair of closet flanges which are BOLTED, flange to flange, to the permanent ones. The result is that there is a short stub pipe which will stick out through the thickness of the foam insulation. It allows easy connection to the necessary SMALL blower for the one and to a possible outlet duct to a nearby greenhouse or elsewhere for the other. As will be seen in the next photo, ALL this is covered over by the outer two inches thick of the foam, where the only things visible there are the two pipe stubs sticking slightly through the foam.

As just noted, only the very outermost ends of the 4" PVC pipe connections are now visible, regarding the airpath.

The barb elbows of the water connections are also visible just outward of (above in the photo) the larger connections.

The overall final appearance is therefore quite clean looking, with only the access door (not yet shown here) and the four pipe connections visible at all.

Two digital thermometers are also seen here, which are somewhat optional. They cost around $13 each, from any of many sources. Some such thermometers have a design limit of 140°F, which would be a problem. Most can operate to 160°F, which is excellent. These shown happen to operate up to 110°C or 230°F, which is not really necessary. One of these monitors the temperature inside the chamber and the other monitors the temperature of the water in the poly tubing. The two readings are nearly always virtually the same, except when massive hot water usage has occurred, and the recovery rate of the water heating can be then monitored. I find the greatest value of monitoring the chamber temperature to be when any variation occurs. It helps me know what I might want to do, regarding adding more water or turning on the air blower or speeding up or slowing down the tumbling. As long as the device can rotate regularly, and there is plenty of free water in a puddle inside it, and there is plenty of air/oxygen being blown into the chamber, the decomposition process seems to be very reliable. If TOO MUCH airflow is provided, it can operate at a lower temperature. As long as that temp is at least 125°F, that is no problem regarding thermophilic bacteria activity and it can even ensure excellent decomposition efficiency. If thicker pieces of material are used, or there is too much airflow provided, then the chamber operates cooler and therefore due to the different (mesophilic) bacteria, and the chamber temp stays below 125°F, with slower decomposition, which seems desirable during milder weather. However, if the chamber has already been operating at the higher temperatures, and then it drops to the lower temperatures, then the thermophilic bacteria can die, and a re-start might be needed in order to again get it up to the higher temperature operation, with some new mesophilic bacteria from a couple handfuls of black dirt. If the temp ever gets ABOVE 150°F, I generally turn the blower on, to make sure the thermophilic bacteria do not die from excessive heat. It is currently still unknown just how high a temperature they can survive, so this might eventually be increased to 155°F or 160°F or higher.

This particular HG 3a unit has an additional thermometer inside it as an experiment. There are REMOTE SENSING thermometers which cost around $25 or so at many big box stores. They are generally sold as thermometers to monitor OUTDOOR temperature. They do not require wires between the temp sensor and the readout, so the wires seen in the photos may not be required. However, the manufacturers do not give any information regarding how well the remote sensor unit can withstand long periods at fairly high temperatures and very high humidity.

INSIDE the door opening, the crinkly appearance is that of the plastic tarp along the opposite wall. You can also see the top of the pile of partial hay bales and straw bales inside, which then filled a little over half of it up.

On the opposite side of the unit, NONE of these are visible, and it is a simple smooth flat circle of surface!

The blower (see comments below) gets attached (to our right larger connection) and the other connection could either be left unconnected (which then exhausts high humidity and carbon dioxide and some occasional musty smells into the room area) or a flexible dryer vent hose could send those exhaust materials outdoors or to some other area. The fact that there is a lot of available warmth, a lot of humidity and a lot of carbon dioxide, makes it an ideal source for feeding into a nearby greenhouse, which can greatly increase the growth of fruits and vegetables.

Hinge mounts for the feed door can be securely mounted to the (now invisible) 2x10 pieces of lumber which framed the sides of the door opening. A (here horizontal) rod then becomes the hinge axle for the door being then able to open upward. I find it efficient to use one hand to raise the feed door and the other hand to toss in whatever new material is to go into the chamber. This then does not cause the door to the 150°F chamber to be open for more than a few seconds at a time. If the door is left open for a few minutes, the chamber cools down to below the 125°F that the thermophilic bacteria best thrive in, so it is best to not leave the feed door open for any longer than necessary.

The poly pipe barb fittings can be connected to adaptors to standard hose or iron pipe, conveniently using standard washing machine supply hoses. One attaches to a water supply source (with a check-valve to ensure that hot water is not fed backwards into a cold water supply line) and the other connected to hot water taps or other usage of hot water.

The entire (ugly pink) foam insulation surface can be covered by an assortment of decorations or materials. Fake naugahyde is of moderate expense and easy to work with, and capable of making many attractive appearances. If this device is to be installed outdoors or in a rough environment, it may be appropriate to cover it all in weatherproof and/or damage resistant material.

After three and a half years of learning about these HG devices, I have found that nearly everyone kills off the thermophilic bacteria MANY TIMES, before they eventually figure out what they are doing wrong. In general, they all (including me!) did the same thing wrong. Once the device has warmed to over 125°F, the original Mesophilic bacteria seem to all die and they get replaced by Thermophilic bacteria. That is a GOOD thing, as Thermophilic bacteria attack many more types of organic materials, and decompose them DOZENS OF TIMES FASTER! The Mesophilic bacteria seem to be rather sturdy and even hard to kill, where the Thermophilic bacteria seem to die if you cross your eyes at them! As long as you then forever keep the interior above 125°F, everything proceeds excellently! But when you turn on a BIG blower to send in a burst of COLD air, the Thermophilic bacteria are badly affected and they tend to all suddenly die! SO DON'T DO THAT!

Up above, I mentioned the idea someone came up with of attaching a warm air furnace and hot water pipes as a Training Aid for you as you are learning how not to kill off your thermophilic bacteria. In the event that you have great difficulties in this regard, it may be worth doing. By installing a thermocouple switch inside the chamber, that switch could detect any time the temperature dropped below, say, 135°F, then that switch could turn on a small furnace and its small blower that would then send some extra 145°F air into the chamber! This can actually ensure TWO of the bacteria's main needs, the supply of warmth and of air/oxygen. A separate digital hygrometer inside the chamber (humidity measurer) could alert for any need for extra (hot) water to be squirted into the chamber! In this way, it may be fairly difficult to foul anything up enough to kill off your bacteria!

I need to provide you some numbers here toward your learning curve! I will provide THREE important examples to learn from:

A Successful first load of All Fresh Cut Lawn Grass

In your FIRST RUN, the bacteria will likely not be truly happy yet, and so they may have difficulty in keeping the temp above 125°F. So you may only have the much slower Mesophilic bacteria working. At THAT RATE OF DECOMPOSITION, maybe half a pound of material being decomposed per hour, by standard thermodynamic biochemistry, we know that they need to use up about 0.6 pound of oxygen per hour. Since air is only about 1/5 oxygen, that means that the bacteria will need to use up around 3 pounds of air per hour. A pound of air takes up around 13 cubic feet, so this is saying that DURING AN HOUR, around 40 cubic feet of air needs to get replaced, AT THAT RATE OF OPERATION.

For the record, decomposing 0.5 pound of material per hour creates around 4,500 Btu/hr (since one pound of many organic materials contains around 9,000 Btu/lb.) This is comparable to a 1500 Watt or 5,000 Btu electric space heater.

We had mentioned above that the chamber we designed and described here has an internal volume of around 40 cubic feet. Some of that is taken up with organic materials, but 30 cubic feet of air inside the chamber is realistic. So at the rate of operation described here, as a SUCCESSFUL first load, the air inside the chamber will be completely used up in maybe 45 minutes. But it will NOT start out at that rate! While the interior temperature is an earlier 80°F or 90°F, VERY little oxygen gets consumed (see the next example). So you probably do NOT have to send in fresh air 45 minutes after starting. Watch the inside temperature. AFTER IT HAS CROSSED 110°F, you can start counting your 45 minutes! So replacement air will then be necessary, to not kill the bacteria from suffocation and lack of oxygen.


Say you get an electric blower which YOU consider to be SMALL, maybe 300 cfm. You have TWO issues here! IF you intend to replace ALL the 30 cubic feet of air inside the chamber, let's calculate how long your blower should be run! Thirty cubic feet PER FORTY FIVE MINUTES is the same as about 2/3 cubic foot of air per minute needed. But you have a blower that moves 300 cfm, right? You would need to turn that blower on for, WHAT?, 1/450 of a minute or ONE SEVENTH OF A SECOND in order to replace that 2/3 CUBIC foot, and then immediately shut it off until doing it again a minute later! (It would be a nightmare to be turning a switch on and then off again 1/7 second later, every minute!) So you might wait 15 minutes, to replace 1/3 of all the air inside the chamber, 10 cubic feet. This then would need that blower to be on for around 1/30 minute, or two seconds. Notice this is still a VERY short period for the blower to be on!

But you actually cause ANOTHER problem even with that 2 second air blast. You got rid of 1/3 the 130°F air inside the chamber and it suddenly replaced it all with COLD air (65°F room air or 40°F garage air)! So the AVERAGE air temperature inside your chamber now drops to around 110°F (2/3 of the air is still at the 130°F and one third is at 65°F). So without realizing it, you again may have just killed off all your thermophilic bacteria due to being too cold for their survival!

OK. Now you see the two issues that you WILL cause as you start learning to use an HG 3a!

EVERYONE seems to turn their electric blowers on for several minutes, making sure that they are not SUFFOCATING their bacteria, sure that they have gotten good oxygen into the thermophilic bacteria. But they are already mass murderers, in having killed off all the bacteria by making them too cold to survive, within the first couple seconds!

I suppose you could knit billions of really tiny jackets for your bacteria???

See the value of having a REALLY, REALLY SMALL FAN OR BLOWER?

You read these words but you will not actually believe this stuff until you have killed off a lot of bacteria! I know because that was true of me!

So you need a LOT LESS fresh air than you realize. But even the little blower fan from a computer moves a lot of air. But you will soon see why a BIG blower is needed, AFTER you figure out what you are doing! Stay tuned!

So I have a recommendation for EVERYONE! Still build the HG 3a as described above, with the 4" PVC air path connections in and out. But while you are LEARNING to operate it, buy two "PVC Reducer Bushings" to block off MOST of that open area (for now). Like all the way down to 1" or even 3/4" open area (on BOTH). THEN, if you use a blower that is too large and strong, the skinny airpath restricts the amount of actual (cold) air that you could be sending in. Say you get it restricted enough so that the airflow is just TEN cubic feet per minute. Remember that you have about THIRTY cubic feet of (very hot) air inside the chamber, which gets used up in around 45 minutes. So say you turn on your SUPER RESTRICTED electric blower now FOR EXACTLY ONE MINUTE. You would then replace TEN cubic feet of the thirty cubic feet inside there, which LEAVES 20 cubic feet of hot air inside next to the hot decomposing organic material. In other words, under these conditions, if you have a timer turn this RESTRICTED blower on for a minute, once every 15 minutes, you may not even kill many bacteria! Hooray! There are even better ways you can even out the temperature inside the chamber with an even SMALLER blower, fan and airflow. Imagine if you could provide 0.7 cfm. THEN your micro-blower could stay on permanently! So there are ways you could cycle a small blower or fan on and off regularly, or get a micro blower to stay on continuously. Size? Maybe about the size of a fan needed to give a parakeet a gust of air. REALLY small!

You will have supplied them with the oxygen they desperately need, without freezing them to death (literally)! And the chamber interior can then remain above the necessary 125°F, they will have plenty of oxygen and water and water vapor inside where you might hear microscopic chomping sounds from the thermophilic bacteria decomposing the organic materials you had dumped into the HG 3a chamber.

Got the picture?

It is REALLY important to be constantly monitoring the temperature inside the chamber for the first few times you are practicing. Later, that will not be necessary, for entirely different reasons!

The bacteria DO desperately need fresh air to both survive and to do what we want, but they cannot handle TOO MUCH cold air!

SO, one result during the past three and a half years is that nearly everyone has used electric blowers or fans that have been FAR too big! Someone recently told me of trying an electric hair dryer. Interesting idea, of providing HOT air, but that seems rather expensive and wasteful to me. And those things move hundreds of cfm of air, so again, just a second or two, until you get farther along in your learning.

A less successful first load of straw, leaves, etc

In this FIRST RUN, the bacteria will likely NOT be happy. In fact, only the Mesophilic bacteria will likely be doing anything because you never got the interior up to the necessary 125°F for the Thermophilic bacteria to take over. IF they are struggling to keep the internal temp at 90°F, the rate of decomposition is very slow. At THAT RATE OF DECOMPOSITION, maybe half a pound of material being decomposed per DAY, by standard thermodynamic biochemistry, they need to use up about 0.6 pound of oxygen PER DAY. Since air is only about 1/5 oxygen, that means that the bacteria will need to use up around 3 pounds of air per DAY or 1/8 pound per hour. A pound of air takes up around 13 cubic feet, so this is saying that DURING AN HOUR, around 1.5 cubic feet of air needs to get replaced, AT THAT RATE OF OPERATION.

For the record, decomposing 0.5 pound of material per DAY creates around 200 Btu/hr (since one pound of many organic materials contains around 9,000 Btu/lb.) Not much!

Above, we thought we had problems in too big a blower when the need was 24 times as great, so imagine now! In fact, THIS example suggests a DIFFERENT approach on your part! Notice that in TWENTY HOURS of operation, around 30 cubic feet of air would be needed, in other words, ONE CHAMBER FULL OF AIR. So the suggestion, if your first load is anything other than freshly cut lawn grass, is to just CLOSE BOTH AIR PATHS COMPLETELY! That will allow the operation to proceed for essentially an entire day, before the bacteria start coughing for lack of air. YOU would get a chance to see how the whole thing works, although there is a good chance that you may be sacrificing some innocent bacteria in the process! If you followed the restrictors reasoning above, and your internal temperature is staying down in the 90°F or 100°F range, maybe a ONE SECOND burst after six or eight hours. They are VERY little! There are a LOT of them (billions) in there, but they still have very small nostrils.

Between these two examples described, you can then LEARN to let surprisingly small amounts of air in, keeping good notes while you do. You WILL learn and soon have really happy bacteria munching away and producing heat for you.

Full Bore Operation

This is at the maximum performance which I have yet seen, around 10 pounds of material being decomposed each hour. This is around TWENTY TIMES the rate of decomposition that the SUCCESSFUL FIRST RUN was. Meaning that twenty times the rate of air supply is needed.

For the record, decomposing 10 pound of material per hour creates around 90,000 Btu/hr (since one pound of many organic materials contains around 9,000 Btu/lb.) That is plenty heat for nearly any house on the coldest day of the winter, anywhere on Earth.

THIS is actually why I designed this thing with 4" diameter air paths! The bacteria then NEED TO USE UP around 800 cubic feet of air per hour, or around 14 cfm, an actual significant rate of airflow which NEEDS a larger diameter pair of airpaths!

The fact that I DESIGNED it with 4" diameter airpaths was sort of because I had done the calculations to KNOW what would be necessary when it was really operating excellently. I had not then realized that nearly everyone would have lots of early problems in providing TOO MUCH COLD air and killing off their bacteria. The solution of still building it normally and sliding in (TEMPORARY) PVC Reducer Bushings seems to solve the beginners' problems while still being able to operate impressively after learning has progressed!

You are not actually done yet!

Once you have really figured it out!

There is another calculation that arises but only AFTER you really have figured out what you are doing!

Take this last example, of the maximum performance which I have seen in an HG 3a, around 90,000 Btu/hr. It turns out that with the MINIMUM NEEDED AIRFLOWS we calculated above, the air inside the chamber would get FAR TOO HOT, and you would kill the bacteria in yet another way. Nothing to really worry about, because few people seem to get to that point yet! And installing a thermostat inside the chamber to turn on the blower switch at 150°F, will keep you from frying your bacteria!

It turns out that Thermodynamics enables us to calculate just how hot the gases would get! There is a number known as the Heat Capacity (or Specific Heat) of any material, which indicates how much heat is needed to raise one pound of the material by one degree Fahrenheit. For water, (at a certain temperature and pressure), it is DEFINED as being 1.000 Btu/lb/°F. For air (at reasonable temperature and pressure) it is 0.241 Btu/lb/°F. We just calculated that we will be creating hot gas at around 800 cfh, which is roughly SIXTY POUNDS of air per hour. If we obtain fresh air at 70°F and exhaust it at 150 °F, then we will be raising that air by about 80°F. So we can do a simple calculation here. This will determine how much heat will be carried away by that 150°F air leaving the chamber. Our 60 lb of air per hour times 80°F increase in its temperature times our factor of 0.241 tells us that the exiting air at 150°F would carry away around 1200 Btu/hr. See the problem?

We will ACTUALLY be having 90,000 Btus of heat that we are creating and we need to get rid of somehow. What we just calculated indicates we could not just rely on the NEEDED airflow to be able to carry away enough heat. If we did, we would have to be sending out exiting air at well over 1,000°F to carry away that much heat! Do you see the solution?

Once the unit was starting to really roll, the temperature of the air and material inside the chamber will rise to 150°F, and would continue to rise, which would kill off your bacteria! So HERE is where you need to turn on your blower for a different purpose, actually the purpose the whole thing was designed for! Since you NEED to get rid of 90,000 Btus, you can do the calculation we just did backwards! You know the amount of heat, and the temp differential, and now we need to know HOW MUCH AIR HAS TO BE EXPELLED at 150°F, to keep it going evenly. Still here? Well, that number TO CARRY AWAY THE HEAT, is about 75 times as much air flow as is NEEDED regarding the oxygen supply. So where while learning, we were totally concerned about having proper airflow and avoiding it getting to COLD, NOW we have the opposite situations! Instead of having 14 cfm leaving the device, in order to carry away all the heat the little critters produce, we will need to be sending around 1,000 cfm of 150°F air being sent out of the unit!

This is SIGNIFICANT airflow and heat flow! Your conventional furnace has a blower which moves at least 1,000 cfm, but it probably cannot achieve 150°F, it probably can only produce around 125°F. Still, you have always found that plenty to keep your house cozy! Here, these tiny bacteria are willing to supply you with that much and actually nearly double what you have ever been used to having! (Actually, I rarely operate mine above 45,000 Btu/hr, as that matches the performance of the conventional [gas] furnace that I used to use.)

Now you see even better WHY I picked the (giant) 4" PVC airpaths for in and out. All the struggles that rookies have in getting an HG 3a to operate correctly SEEMS to be because of TOO LARGE an airpath. But actually, a single 4" airpath is actually NOT LARGE ENOUGH for that 90,000 Btu/hr level of operation. I only maxxed my HG 3a unit out to 90,000 Btu/hr once, just to confirm to myself that it could do it, and when I could not get rid of all that heat, I killed my bacteria that day (by frying them)! I generally keep the operation of MY HG 3a down to below 45,000 Btu/hr, and a truly powerful (second) blower forces enough air through the HG 3a unit so that I do not cook my bacteria.

The RANGE of operation of this heating system is extremely broad. At the one end, where rookies play, the necessary amount of airflow (for oxygen reasons) is VERY low. At the other end, when it is really pumping out heat, airflow has to resemble a tornado! Other heating systems only operate at one amount of heat output, so only one blower speed is ever necessary. It is a complication that you need to deal with!

We can re-visit the Less Successful mode, and see the reason the unit has so much thermal insulation around it! We calculated above that the unit then creates only 200 Btu/hr from action of the (mesophilic) bacteria. There are around 75 square feet of the R-20 insulation. If we say that the bacteria were able to get it up to around 100°F inside the chamber, and the garage that it is in is at 50°F, we can calculate the total heat loss through the insulation. It is 75 square feet times 50°F temperature differential divided by the 20 or around 180 Btu/hr total heat loss. Since we are only creating 200 Btu/hr, there is very little heat remaining that needs to exist from the exiting pipe.

This is because of the excellent R-20 insulation. At only R-15 insulation the total heat loss would be greater than the amount of heat the bacteria are creating, and the interior could not maintain that 100°F temperature. With all operation where greater amounts of heat are created, the heat loss effect of the external walls becomes less important, and it is nearly irrelevant at high outputs. At our full bore situation, where the chamber interior is at 150°F, the heat loss is then (150 - 50) * 75 / 20 or 375 Btu/hr, out of the 90,000 Btu/hr that the unit was then producing. Nearly ALL the heat created can then be sent to other rooms through ducts, over 89,500 Btu/hr.

So the importance of the insulation is greatest at lowest performance!

This all confirms that ONCE you get your unit operating even moderately well, it gets easier and easier to do it! Like riding a bike, I guess, really hard at first but then really easy to do! And sort of for a similar reason. At 1 mph, it is hard to keep a bike balanced, but once you can accomplish 5 mph or 10 mph, it is really easy!

ANOTHER enhancement regarding these matters regarding consistent performance of the HG 3a has recently arisen (late in 2010)! TOO MUCH oxygen is NOT the problem! Too much COLD AIR is! So a logical enhancement seems to be in providing a "incoming air pre-heater"! Having any COLD incoming air have to pass THROUGH a 15-foot or 20-foot long tube INSIDE the chamber will warm that incoming air up! And so, within reason, if you happen to send in too much fresh air, you will not be killing your bacteria from cold. In fact, you may not even be chilling them at all, and that seems like an ideal situation, where all your bacteria will then have lots of oxygen, lots of water and water vapor, and still be cozy warm, their ideal environment. No need for heavy bacteria overcoats! This enhancement might definitely make the HG 3a far less susceptible to suddenly having the bacteria all die and having the unit go cold and therefore having to start it all over again. THIS may enable the HG 3a to be REALLY "user-friendly"!

Notice that I just described how you WILL kill your bacteria from making them too cold, and also by making them too hot. We have also discussed suffocating them with too little oxygen, and drowning them under water. TRY to behave better and to treat your bacteria properly, OK?

If you and your bacteria can come to get along, they WILL keep your entire house as cozy as you could ever dream of! But they DO have quirky needs, which it will take you a while to learn!

Here are two factoids for your interest:

From Biochemistry, when ONE POUND of (glucose) decomposes, it chemically requires around 1.1 POUND of oxygen for the reaction to occur. Since air is only 1/5 oxygen, that means that 5.5 pounds of air is consumed. This reaction then creates 1.5 pound of carbon dioxide and 0.6 pound of water. (More precise numbers are 180 grams of glucose uses 192 grams of oxygen, or 900 grams of air, to create 264 grams of carbon dioxide and 108 grams of water.) The air is around 72 cubic feet.

Any other amount of organic material has proportionate numbers. For example, when ONE-TENTH POUND of (glucose) decomposes, it chemically requires around 0.11 POUND of oxygen for the reaction to occur. Since air is only 1/5 oxygen, that means that 0.55 pounds of air is consumed. This reaction then creates 0.15 pound of carbon dioxide and 0.06 pound of water. The air is about 7 cubic feet.

Since photosynthesis initially creates glucose, all other organic materials are later made from glucose, and we are making a reasonable assumption that other organic materials are very close to glucose in their Biochemistry reactions.

The plumbing (and potentially air) connections would be an additional problem if the device was allowed to always rotate in one direction. There ARE special rotary fittings available but they tend to be expensive. Instead, we have designed it where the entire assembly rocks back and forth, ONLY ROTATING ABOUT 3/4 turn and then reversing. All of the material inside still gets to be gravity-tumbled inside, but the plumbing and air path connections become far simpler. The air hoses for air/oxygen in and carbon dioxide out can then be simple standard clothes dryer vent flexible hoses. The water connections can be standard hoses used to connect a washing machine to house piping. They should all last a number of years. Keep in mind that this rotates so slowly that it is hard to even notice, the FASTEST being around once per hour. (An electric motor can then be used with a LOT of gear reduction, to rotate the drum. This motor might then be DIRECT CURRENT, where simply using a relay to reverse the wires makes the motor turn the other way, so it could oscillate back and forth its 270° of rotation. This limited rotation aspect also permits adding a "cooking chamber" which would never have to cross under the mass of material inside the chamber.

You have scraps of pieces of the thicker plywood. An optional feature you might consider is to cut out a number of arc shaped pieces, which have an inner radius of maybe 28" and an outer radius of slightly over 34.5". They would be mounted to either of the side wood circles (by screws and construction adhesive) such that a larger radius of the plywood (of just over 34.5") is present there. The only purpose for this is so the wood could extend beyond the 4" thick of foam insulation which surrounds the entire structure. An electric motor with a small pulley on it could then rub against that (circular) edge to very slowly rotate the whole thing. The rotation (actually rocking) rate only needs to be once per hour, so the motor would use that 30:1 torque multiplication to turn the entire unit. (It CAN be rotated faster if you wish but there is no known advantage in doing so.)

A "trap door" then must be made in one of the sides. It should not be closer than 6" from the circular rim, but can otherwise be of somewhat optional shape and size. It will provide a way for you to reach inside to mount the few last small items, and it will also be the opening through which you will later add organic materials. It obviously should be large enough so both of these tasks are as easy as possible.

The door needs to fit decently tightly, and it needs to have a SEPARABLE provision for its two or four layers of foam insulation attached to it. The outdoor foam can be an advantage for the outermost layer, just to be more abrasion resistant.

The "remaining items" are the water pipe connections and the airflow connections.

We know that we desire a standard decomposition rate of around 5 pounds of material per hour, with a maximum of 10 pounds per hour. From our previous discussions in related web-pages regarding the biochemistry of what is going on, we know that this will create around 45,000 Btu/hr (90,000 Btu/hr) of heat. We also can calculate the amount of air needed and exhaust removed for those decomposition rates. You can confirm this with the equations given in those other pages. We learned that about 12.6 gram-moles of chemical reaction occurs per hour. Our five pounds of glucose combines with about 5.3 pounds of oxygen in the intake air, to form about 7.3 pounds of carbon dioxide and about 3 pounds of water (or water vapor). Air is only around 1/5 oxygen, so we will need to supply around 26 pounds of air per hour, each of which takes up around 13 cubic feet. This means that we need an INFLOW of around 338 cubic feet per hour, or 6 cubic feet per minute (6 CFM). This is a VERY small air flow rate! Because of the Law of Partial Pressures, the outgoing exhaust air cannot be more than around 4.4% carbon dioxide. We know that we need to exhaust about 7.3 pounds of carbon dioxide every hour, so this means that we need to exhaust around 140 pounds of exhaust AIR each hour, which each take up around 14 cubic feet (due to the higher temperature of that exhaust gas). This tells us that we should expect to need to exhaust around 1960 cubic feet per hour of air or 33 CFM. Note that we could supply 6 cfm of air to provide the needed oxygen, but that airflow might not exhaust enough carbon dioxide!

We should use this larger number regarding the exhaust in designing the airflow through the system. It is still a rather small air flow rate. When we might reduce the actual airflow, the main effect is that there is still a lot of carbon dioxide near the bacteria, so they can less easily get to oxygen, which can slow down the process. In other words, we can have a moderate level of control as to how efficiently the bacteria are decomposing the material in the chamber by how regularly we have the small blower pushing new air/oxygen into the chamber. We may also want to double that capability, in case we should ever want it to decompose the maximum 10 pounds per hour, which means we should provide airpath sizes where 66 CFM of air can pass. We choose to use a 4" dryer duct size of connection for the airflows, along with a very small blower (in the INLET side) which can easily move around that level of airflow. This is actually a convenient size, as it means that commonly available flexible dryer vent hose can be used.

The (two) 4" diameter holes are made with their centerlines 4" in from the outer edge (in other words, 27" from the axle. We chose to use (toilet) closet floor flanges, to be able to ensure that we can mount them with no moisture or air leaks through the sidewall (due to the fact that we have to penetrate the tarp there). Caulking is used UNDER the flange (and against the tarp) for this reason. Flat-headed bolts are used to mount these closet flanges rather than the usual wood screws, for better strength and durability.

A variant of this is shown in these photos, where the cutout for the door opening (in the plywood sidewall) is made a trapezoidal shape which allows the entire area for the door AND tubes and pipes to NOT have to penetrate the tarp itself (but rather the piece of black conveyor belting shown).

One is mounted near one side of the circle, and the other is mounted on the opposite side of the (same side) circle. One will generally stay near the top (due to the oscillatory motion) and it will provide air/oxygen IN for the device, but ONLY when it is near the top as it rotates. The other will then be near the bottom, where the more dense (heavier) carbon dioxide tends to accumulate. Due to the air/oxygen being pushed into the chamber by the blower, the carbon dioxide will be forced out through that lower hole. Standard 4" PVC elbows and pipe sections (just beyond the 4" thickness of the insulation) gets this connection to be near the axle shaft where the flexible dryer vent hose attaches to it there, to finally connect to 4" PVC pipes which are mounted to the fixed support stand of the system.

If the capability of providing domestic hot water is to be also used, those connections can be handled in similar ways, where the connection uses standard (flexible) clothes washing machine supply hoses for the water connections, also near the axle of the system so that there is minimal actual motion of the flexible hoses. Such hoses usually come with a built-in filter which should be removed for greater water flow rates.

Standard (micro) switches could be installed to stop the device from rotating beyond the desired 270° of rotation and to cause the motor to reverse, so it would then constantly oscillate back and forth. This actually results in one portion of the inside of the chamber never having to pass through the puddle of water that is always kept in the bottom. This is essentially why it can have an openable door in the location shown in the photos, as that door area can never be at the very bottom where there MIGHT be several inches of water in a puddle!

An attractive possibility which I am currently (12/07) experimenting with is where a (sturdy) 6" or 8" diameter thick aluminum pipe is installed across the entire 24" width of the chamber, but which has an end cap and is well grouted to be watertight. I see this as an attractive "cooking chamber" where even hard boiled eggs (without any water!) and hamburgers can be cooked. The cooking is at a slower rate than on a stovetop burner, but the 150°F temperature of the chamber is quickly conducted through the aluminum walls to provide close to a 150°F oven-like cooking temperature. That is plenty to kill any dangerous germs (only around 125°F is needed for that), and food seems to cook very evenly, without ever burning the surfaces, in around two to three times as long as on a stovetop! I am looking forward to seeing if spaghetti can be cooked in it!

This (standard-sized) unit has a total diameter of around 5'9" so it can easily be carried (or rolled) through normal doorways. However, the width dimension of what we have described here is essentially 32", so if it has to pass through a standard 32" wide interior doorway, you may need either hold off installing one layer of the side foam or remove the casing trim of the doorway!

This unit has a total surface area of about 72.5 square feet. The insulation that we have described is all R-20. The temperature difference if this unit is placed in the heated portion of a house is around (145°F - 70°F) 75°F. This indicates that the heat loss outward through the insulation is 72.5 * 75 / 20 or 272 Btu/hr. This very minimal loss allows the contents of the chamber to rapidly get up to its operating temperature. (This very low value might indicate that future units might not need quite as much insulation, to still perform well.)

When the chamber contains 400 pounds of organic material and also 200 pounds of water, the thermal capacity is around 350 Btu/degree. That means that it first requires 350 times 75°F or 26,000 Btus of heat to be internally developed to first get up to 150°F. It also means that the interior material can release 350 * 25°F or around 9,000 Btus of energy in dropping the interior temperature the 25°F from 150°F down to 125°F, the general range of operation of the thermophilic bacteria of this device. If the entire amount of 150°F hot water is removed (as for clothes washing or a really hot bath), when the pipe all fills with cold (55°F) water, it briefly uses much of the capability of the system to heat up all that new water up to the 150°F, a process that generally should only take around 15 minutes of the heat to accomplish. The warm air heating capability therefore drops somewhat when large amounts of hot water are withdrawn, but recovery is generally within 15 minutes max.

A variant Regarding the Support and Mounting

This is essentially exactly the same device but with two differences. (1) there are NO axles and mounting pillars at all; and (2) additional plywood is attached to the sidewalls, to create a rigid and very strong plywood ring on both sides of the unit. (This variant is VERY easy to roll around to get it into the desired room in a house, as the plywood rings extend slightly beyond the insulation and are therefore like giant wooden wheels! Which is actually the point. They have an ACCURATE consistent outer diameter, where they can each ride on top of two rollers which are mounted to a base assembly. There is NOTHING actually holding the HG unit in place (except gravity) and it could be lifted off of the rollers if needed. This results in a smoother, cleaner appearance, and there are no obstructions to get tangled with the hoses or vents. With this variant, there is no obvious way to keep the unit from rotating beyond the 270 degrees that is possible with the HG 3a unit assembled above. Care would be needed to not allow the hoses and vent connections to get all twisted up. This variant may eventually be called the HG 3ab unit.

A groove can be made in the edges of a full-diameter 3/4" plywood circle, to essentially act as a giant PULLEY of 69" in diameter! An electric motor (like from an old washer or drier) could have a very small pulley on the shaft (maybe 1.75" pitch diameter). This would provide a torque multiplier of around 40:1, and would also slow down the rate of rotation to 1/40 of that of the motor itself. Additional pulleys or gearing might be appropriate to cause the whole thing to rotate fairly slowly.

Getting Heat Out For the House

There are multiple ways to get the usable heat out of this device for a house. They each have different overall efficiencies, complexities, costs, and potential advantages and disadvantages. These different methods use the exact same device described in the construction above. These are presented in no particular order:

Using it, Selection of Organic Materials to Use

The DIMENSIONS of the organic materials are extremely important regarding how QUICKLY the process occurs. THICKNESS is the most important of the dimensions.

If good quality lawn grass is cut, the blades of grass tend to be in the 0.05" inch thick range, and they begin to decompose amazingly quickly, in just a few hours.

If FIELD grasses are collected, the blades may be twice as thick and so the process is slower, often around half as fast.

If farm hay is used, performance is generally comparable to field grasses.

Most autumn tree leaves seem to be about as thick as cut lawn grass, so they are able to decompose rather quickly.

If sturdier weeds, and especially larger and thicker weeds are used, the process is slower, generally in proportion to the THICKNESS of the pieces.

If farm straw is used, performance is generally comparable to common weeds.

If even small twigs are included, their greater thickness tends to cause far slower decomposition, again roughly in proportion to the thickness of the twigs. Quarter-inch thick twigs can be expected to take most of a week to decompose.

Thicker branches take even longer. One-inch thich branches seem to take as much as a month to decompose, although it seems to depend in species of wood, with softwoods being faster and hardwoods being slower.

Putting any pieces of wood thicker than one inch seems inadvisable (with the one exception of really rotten wood as noted below), because of how slow they decompose.

You can estimate the rate for any other types of organic materials by the above guide. For example, sawdust generally has rather thin and small dimensions, and it (rightfully) can be estimated to decompose very fast. Newspaper CAN if the sheets can become separated, but if the newspaper is rolled up or otherwise compact, its decomposition can take quite a while.

There are certain exceptions. Egg shells tend to take a lot longer to decompose than most other things of their thickness. It appears to be due to their high density and probably the calcium in them. Plastic bags tend to take quite a while to decompose, although the reason is still unclear.

I have discovered that in relatively MILD weather (like September or November or March or April in Chicago) it is possible and even attractive to load it primarily with wood chips or similar THICKNESS pieces. Such materials decompose far to slowly for the greater heating needs of January and Februry, but they seem ideal for the milder parts of the winter. They produce and give off much less heat AND they last for a number of weeks! ALL of September seems to require only one loading of such materials! (the black dirt is still necessary to provide the needed bacteria.) October seems likely to require two loadings, of mostly such materials but mixed with some weeds and field grasses and some leaves.

So I now tend to SAVE the cut lawn grass to be used mostly during January and February, when greatest heat output is needed.

I have also discovered another handy thing about that cut lawn grass. I now use a BAGGING MOWER but mow the lawn with the bag REMOVED. The cut grass then lays on the lawn for about three days. It turns yellow as it dries. Then I put the bag on the mower and run it around the yard again! It now sucks up all that dried grass, so I can immediately put it into leaf bags or storage bins until I will want to use it several months later. Otherwise, cut, wet lawn grass seems to quickly go into its own mode of natural decomposition, where it then heats up in the storage container and starts consuming itself!

Finally, it appears that each square inch of surface area of ANYTHING I put in the HG 3a is able to produce roughly ONE-FOURTH Btu/hour. When I have used wood chips that are around 50 pieces per pound, when I have put 400 pounds of them in the HG 3a device, that would be around 20,000 separate pieces. If each has a total surface area of one square inch, that would total about 20,000 square inches. At 1/4 Btu/hr/square inch, that comes out to about 5,000 Btu/hr total heat production for the unit, which seems about in line with the performance I have seen in this low-output mode of operation. (the 3.6 million Btus of chemical energy in those 400 pounds of such wood chips would then last for around 720 hours or 30 days at that rate!)

That is an excellent situation during MILD weather when little heating is needed for the house!

A pound of cut grass seems to usually contain maybe 3,000 blades of grass. If each are 2 inches long and 1/8 inch wide, the total area of each grass blade (both sides) would be about 1/2 square inch. At 3,000 blades per pound, 400 pounds of such grass would contain about 1,200,000 blades or around 600,000 square inches total area. At 1/4 Btu/hr/square inch, this arrangement could produce around 150,000 Btu/hr total output. (the 3.6 million Btus of chemical energy in those 400 pounds of cut grass would then last for around 24 hours at that rate!)

That is a little more than I have yet obtained, but I have never put in a full load of just cut lawn grass! But when MOSTLY using cut lawn grass, I have obtained the 90,000 Btu/hr mentioned in these pages.

You might see that thick pieces of firewood have such small total surface area that little heat gets produced. Consider a standard piece of 6 inch diameter firewood which is two feet long. The total surface area is about 500 square inches. Using the numbers above, this would imply that only around 125 Btu/hr of heat would be generated. Such a piece weighs about 14 pounds, so it would contain around 121,000 Btus of chemical energy in it. That piece of firewood WOULD gradually decompose in the HG 3a unit, but it would likely take about 121,000/125 or 1,000 hours! That is close to two months! So it WOULD work, but the heat output is so extremely low (130 Btu/hr) that it does not seem very desirable.

Yes, a really LARGE HG unit that could contain a THOUSAND such pieces of such firewood (14,000 pounds of wood) might produce the heat needed to heat a house. Another possible future application! Or an explanation for why it is much more acceptable to mix in pieces of firewood inside the larger Version 2 or Version 4 systems.

Suggestions regarding people's experiences of putting specific materials into HG 3a units.

This is ONLY for people who enjoy pain! Here is the THEORETICAL explanation regarding the heat radiation that is created by each blade of grass or leaf inside the unit!

There is a relationship that has long been known in science and Engineering called the Stefan-Boltzmann Law. It calculates the amount of radiative energy produced by any hot object inside a cooler environment. It is fairly simple in its crudest form:

Q = σ * (T14 - T24) * A

The temperatures are the temperature of the object doing the radiating (1) and the temperature of the surrounding surfaces (2). A is the surface area of the object doing the radiating. And the sigma σ symbol is a constant, called the Stefan-Boltzmann constant, which is 0.1713 * 10-8 Btu/square foot/hour/((absolute degrees R)4)

When wood is burned in a woodstove, the flame temperature is around 2300°F or 2760°R. These calculations show that a square foot of burning wood (actually in flame) creates around 100,000 Btu/hr of radiant (mostly infrared) heat. A woodstove generally only has 1/8 to 1/3 square foot actually on fire at any instant, so it creates the output that woodstoves are known to generate!

OUR situation is at a far lower temperature! We only create heat of around 1/3000 as much (per square foot). If we assume that the actual temperature at the bacterium is 160°F and the actual temperature of all the walls are 140°F, we can use the Stefan-Boltzmann Law to calculate that each square FOOT of material should be creating radiation of about 32 Btu/hour. Therefore, each square INCH would be creating 32/144 or 0.22 Btu/hour. This is in pretty good agreement with my experimental findings of 0.25 Btu/hour from the material in my HG 3a units.

We also need to note that when we use ALL chunks of larger material, we are INTENTIONALLY not creating as much heat output, but this also results on the temperatures being lower. If we use mostly straw and field grasses and weeds, we might assume that the actual temperature at the bacterium under such conditions is 140°F and the actual temperature of all the walls are 120°F, we can use the Stefan-Boltzmann Law to calculate that each square FOOT of material should be creating radiation of about 29 Btu/hour. Therefore, each square INCH would be creating 29/144 or 0.20 Btu/hour.

If we use mostly wood chips, we assume that the actual temperature at the bacterium under such conditions is 120°F and the actual temperature of all the walls are 100°F, we can use the Stefan-Boltzmann Law to calculate that each square FOOT of material should be creating radiation of about 25 Btu/hour. Therefore, each square INCH would be creating 25/144 or 0.18 Btu/hour.

In case you were interested, you now know WHY the various organic materials you can put into an HG 3a unit generate different amounts of heat output. The greatest factor is the total surface area which can interact with oxygen and therefore create and radiate heat away, but even the overall temperature of the activity has additional effects!

This also explained why a woodstove only needs to have a FRACTION of a square foot of wood actually on fire at any instant, and we need to have a LOT of square feet of surface area decomposing, to produce similar amounts of heat output.

There is a way to estimate the amount of water you should put in when you start this unit up. If we are considering around 400 pounds of organic matter inside the chamber, we will consider the two extreme situations:

IF the grass, weeds, or leaves are fresh, essentially still alive, then they already contain within them a large amount of water. In this case, very little additional water needs to be added at the start. I add around five gallons so that there is a decent sized puddle in the bottom of the chamber. Then, as the device rotates, all of the organic material has a chance to get wet from passing through this puddle.

If the grass, leaves, straw, or hay is fully dried (for better storage), then a large amount of water needs to be added FOR FULL SPEED OPERATION. We know that the glucose weighs about 180 pounds per pound-mole, and the water weighs around 18, but there are six waters necessary for the reaction so they total 108 pounds. Using this proportion, if we start with 400 pounds of FULLY DRIED material, we would need to add around 240 pounds of water! That is around 30 gallons!

So you need to judge how damp or dry the material is when you first start the unit, to estimate the amount of water you need to add. However, that amount of water is for MAXIMUM performance! By providing LESS water than that to dried materials, the decomposition can be substantially slowed down, which is wonderful for milder weather!

Once it is in operation, you should only need to add extra water due to two conditions: (1) the air exhausted from the unit carries a substantial amount of moisture/humidity in it. This amount of moisture loss depends on the actual temperature of the air exiting the unit, as that air is essentially always at 100% humidity. But it can be fairly substantial, and you are likely to need to add extra water on a regular basis. (2) if you add in materials such as dried leaves or dried hay, you will need to also add the appropriate amount of water.

Except for the moisture that leaves in the vent pipe, we note (from above) that the decomposition of 400 pounds of organic material will PRODUCE about 240 pounds of water, and so it tends to provide its own supply of water to a great extent.

Storing the Organic Materials

If you are able to mow the lawn all year, you may not need to store amounts of the material to decompose for a winter. But most of us live in climates where we need to plan ahead.

It is impossible to store most organic very long if they are not dried out, as the decomposition process will occur naturally in the presence of moisture, resulting in rotting and decay (and foul smells due to anaerobic processes occurring). Therefore, if you need to store materials for more than a week or two, you need to dry it out. Farmers have long had appropriate processes, in drying hay and straw before baling it up to be able to last many months. Also in drying feed corn for storage in grain silos. Even in leaving corncobs and crop debris out in the fields so that the sun can dry it all out naturally. Essentially the same processes can be used to dry cut grass and leaves in order to bale them up for later use.

Such bales then obviously need to be stored in a dry location. When they get damp, they start to rot and decay. THAT can sometimes cause an unexpected hazard in large stacks of hay bales! If one of the bales got wet, the decomposition process can begin, which creates the heat we have been discussing. There have been cases where large stacks of hay bales have spontaneously caught fire due to such internally generated heat. Therefore, really large stacks of hay bales should be avoided.

Similarly, great care needs to be taken regarding WHERE these bales are stored! If a single person wanders by and tosses a cigarette butt onto the stack of bales, a very serious problem can quickly develop. So you need to find a location where such a danger either cannot occur or if it does, it would not affect too much else. Farmers generally store hay bales in a building separate from where they keep valuable animals or equipment for this reason.

The storage of so much material that has been very well dried, and which is therefore extremely combustible, is a matter that requires great attention to ensure safety.

There seem to be endless new uses for this critter! Here are several more that I have started to experiment on!

I find the need to add two personal comments here!

(1) People seem to INSIST on "improving" anything and everything with their own ideas! It does not seem to matter whether they actually have any education, knowledge or experience in the specific subjects or talents or abilities! An example has come to my attention, which will probably be repeated countless thousands of times in the future. A woman, with NO construction experience whatever, and no education or background in either Engineering or Design, decided to "make changes" in the above instructions, and intended to also improvise in the actual construction due to her lack of tools and experience. She decided to change the dimensions of the device, change the construction of it in dozens of ways, such as using two layers of thin used plywood for the sidewalls, and in using very small diameter pex tubing instead of the far larger poly tubing that is specified here. In addition, she did not like the limitations of how it is described to be used, and improvized her own ideas on how and where she would install it, such as building an insulated room inside her garage, and then doing incomprehensible things to pipes and ducts to provide heat for rooms and functions throughout her house. As near as I can tell, she is NOT using even a single one of the above directions as it is described, modifying or entirely dismissing every single one of them! What was the point of even providing construction instructions if they will be absolutely ignored? Will I expected to be responsible when such an extremely modified attempt will only partially do what is described here?

I realize that people throw away the instructions for the Christmas bicycle they need to try to assemble for their child; it seems to be part of human nature. That's fine, as long as I do not get blamed for the results of such "improvements"!

Here's another example, of hundreds of such things that we know about. In the late 1970s, someone near Detroit bought one of the JUCA woodstove/furnaces that I manufactured. As was usual, he easily heated his house entirely, and like other JUCA owners, bragged to relatives, friends and neighbors that he was no longer paying any heating bills (where they were!) A neighbor soon bought his own JUCA to eliminate HIS heating bills. We knew nothing about all this for around four years, at which time he called us to register a complaint. Since that was the FIRST complaint that we had ever received regarding a JUCA's operation, we were extremely interested in knowing why it was not doing as he was expecting. He said that the neighbor's whole house was very comfortable, while his had many cold rooms, and also that he was using around 20 cords of wood (while the neighbor was using about 4 cords to completely heat his house for the entire Detroit winter. It was very puzzling! After probably twenty long phone calls, where the owner always insisted that the unit was EXACTLY LIKE the neighbor's [but faulty] we still had no clue as to why he was not getting the normal massive JUCA heat. But finally, I happened to ask him regarding confirming that he could press his hand against the JUCA for at least a minute while it was operating. He laughed, and said that he did not dare even touching it for a fraction of a second!

Since we had learned by then that a lot of housecats discovered that sleeping on top of the JUCA was a cozy place, this was clearly very strange. We asked the logical next question, regarding WHICH JUCA blower he had been using. He was puzzled by that question! He said that the blower was STILL IN THE BOX! He said that when they received their JUCA, it was bigger than they had expected it to be. When it was also necessary to mount the blower on the back of the JUCA unit, which causes the JUCA to be around 10" (or more) farther out into the room, they DECIDED not to use the JUCA blower! For four years, they had been trying to operate a JUCA without even having a blower on it! (JUCAs are all forced-air furnaces, which REQUIRE the blower to be operating nearly all the time. In fact, they decided to push the (big) JUCA completely against the rear wall, which even blocked off the opening where the blower should have been mounted. So the unit could not even thermosiphon to circulate the warm(hot) air naturally!

They had done absolutely everything possible to defeat the proper operation of the JUCA unit! For four years before complaining to us! It is actually astounding that they did not burn their house down, since they therefore had a large unit that was so hot that they feared touching it, pressed right against a rear wall!

It turned out that since he knew that the neighbor was entirely heating his house with his JUCA, he decided to just constantly be loading wood into his, to try to match the performance!

Too bad he never read the Installation Instructions or the Operator's Manual, which both make crystal clear that the blower MUST be running nearly all the time.

We later discovered that the neighbor had also bought an optional (larger) JUCA blower which is necessary to feed the WARM air through the house ducts to all the rooms. This customer didn't see any value in a blower in the first place, so he certainly would never have seen cause to get an even BIGGER blower (which would have pushed the JUCA even farther out into the room!)

It would be one thing if there had only been one such customer who entirely ignored all instructions! But over the years, we learned that that joke about the Christmas bicycle is actually very commonly true! So, a Disclaimer! IF you choose to follow the construction instructions (above) fairly well, the HG 3a will work like a charm. However, if you greatly alter even ONE characteristic of it (without actually knowing enough Engineering to be able to actually calculate the proposed improvement), you are on your own!

(2) An immense number of people seem to not comprehend the concept of a GIFT! The exact same thing occurs in the Free Air Conditioning web-pages, which I have provided, FOR FREE, since late 2000, where all the necessary construction and planning information is included, as well as all the information regarding the Engineering concepts behind why it works so well. However, so far, over SIX THOUSAND PEOPLE have DEMANDED that I provide them PROOF that it works! Several thousand others have demanded that I give them names and addresses and phone numbers of some of the 9,000+ people who have installed and are using the (Free A/C) system. The same is already starting regarding this HeatGreen heating system.

This information is provided by a fairly intelligent Nuclear Physicist FOR FREE! I thought that was a nice and generous gesture! WHY do people think they deserve to get "free custom personal Engineering" or to receive whatever they might consider to be proof or to be allowed to annoy some happy family with hours of endless questions? This DID used to sometimes happen with the JUCA Super-Fireplace whole-house-heating woodstove that I DID actually sell for many years. The owners nearly always found it very annoying, except for people who THEY INVITED to their homes! But when a CUSTOMER was considering BUYING A PRODUCT, it seemed vaguely credible that they might want to annoy owners of my woodstoves like that. A woman from Alaska ended that! She DEMANDED that I give her a dozen names and phones of owners (who had each generously offered to talk to potential customers). I expected her to pick out one of the twelve, and then to make a politely brief phone call. But NOOOO! She spend a dozen evenings, calling each of those families for phone calls which I was told were all between two to three hours! The entire quiet evening for a family was gone for every single one of those wonderful families! (All that to consider buying a $1400 woodstove which we had GUARANTEED [since 1989] to be able to ENTIRELY HEAT ANY HOUSE.) But she alone managed to infuriate all dozen of those people, each of whom then immediately asked to have their names removed.

A single inconsiderate woman really destroyed a fine way that JUCA owners had been previously able to help people who are not familiar with the performance of JUCA units. Unbelievable. Now, do YOU think that I am going to put ANYONE at risk of having that happen to them, WHEN THERE IS NOT EVEN ANY PRODUCT BEING SOLD?

(I may have a very old Bridge in Manhattan to sell you if you do!) But separate from that, apparently no one has ever heard of the Gift Horse story! For the Free Air Conditioning, and for this HeatGreen system with its several configurations, and with the free system to monitor Children's Bodyfat in a fun and easy way, and in the method to try to drag Beached Whales back to the ocean, and on and on; IF you demand PROOF, then I would PREFER that you simply go away and stop bothering me. Go stare in the mouth of some horse somebody has offered to give to you! In fact, I make VERY sure that I provide massive Engineering and scientific proofs for each of the statements made regarding any of these systems which I offer.

You actually DO have access to a way to PROVE that the HG3a or the Free A/C works as described. You could HIRE a top quality Thermodynamics Engineer (at around $400/hour), and he/she can then duplicate the Engineering which I provide in the web-pages. A talented Engineer should be able to research that my information is sound and then calculate the needed things in maybe 25 to 40 hours of work. Of course, this means that you will have to pay that Engineer between $10,000 and $16,000 to confirm the information WHICH I HAVE GIVEN YOU FOR FREE!

In order that you not waste $200 on building materials from a local store!

I can only say, DUH!

Please do NOT be annoying me with demands for proof (before you dare spend $200 for materials), OR where you will insist that YOUR application IS UNIQUE and you therefore REQUIRE me to personally Engineer (the exact same unit) for your needs. IF you are willing to pay me at the standard $400/hour rate for such advanced Engineering, and will provide a Retainer for a number of hours to start with, I MIGHT be willing to listen. But probably still NO! If you are so convinced that you have a totally unique situation, then get that local Engineer to do the Engineering and Design for you!

The main presentation was first placed on the Internet in February 2007. This high-performance version presentation was first placed on the Internet in November 2007.

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C Johnson, Theoretical Physicist, Physics Degree from Univ of Chicago