YOU probably PAY someone to haul away and dispose of the cut lawn
grass and the autumn leaves that you bag up.
I don't do that! I SAVE all that 'lawn debris' and replace more than
$3 of my house winter heating bills with each such bag!
(I am even 'willing' to haul away the bags of grass that neighbors
put on the curb!)|
I have a simple experiment for you! Once you cut your lawn, SAVE enough grass to fill ONE standard garbage bag with the cut lawn grass, and tie it closed. Then wait about three hours, open the bag and stick your hand deep inside it, preparing to jerk it out when you burn your hand with the heat! Until you actually DO this, you will not believe this system works, but once you burn your hand from self-heated lawn grass, you will understand!
Some basic facts of nature and science have virtually always been nearly completely neglected! Plants grow everywhere! We know that virtually all of them grow by a process called Photosynthesis. This requires and absorbs sunlight. Science knows that about 9,000 Btus or 2,600 Watt-hours of sunlight gets absorbed to form each pound of virtually any type of plant material. There is a universal law of science called the Conservation of Energy. This means that EVERY weed and leaf and blade of grass contains a lot of (chemical) energy which all necessarily has to be released when that piece of organic material later dies and decomposes back into water vapor and carbon dioxide.
This concept and system is simply based on you WAITING THERE for organic material to decompose, in order to collect the energy (heat) which is given off! This might seem like it must be an irrelevant amount of energy, but it turns out to be an incredible amount!
Another interesting fact is that ALL of the energy gets released during that natural decomposition, where it is a process with 100% efficiency!
When I mow my grass, I sometimes get around 200 pounds of grass clippings (in 7 bags). Some of that is water but at 9,000 Btu/pound, that is around 1,200,000 Btus of heat energy which will be given off when it decomposes. This is a LOT! On the coldest February days in Chicago, my large house loses LESS than that amount per two really cold days! It also could and can provide ALL the house's heat for half the entire month of March or October! Put another way, you can think of every large garbage bag of cut grass in terms of the three dollars of fossil fuel heating fuel you will otherwise buy! I can tell you that it makes a chore like mowing a lot more fun when you see some bags which will eliminate $20 of winter heating bills! In the Fall, my yard produces about 26 bags of leaves, roughly 780 pounds which can produce around 5 million Btus of heat for my house.
If the yard around your house is fairly large, an acre, then a really amazing fact exists which no one seems to have ever noticed before! In a given calendar year, the (9 tons of) fallen autumn leaves, cut grass particles and other dead organic materials which had grown on that acre due to Photosynthesis, will decay. You knew that! What you didn't know is that the process of that NATURAL decay or decomposition gives off heat in the process, an amazing amount, around 170,000,000 Btus or 50 MegaWatt-hours of energy! (If your yard is smaller, 1/4 acre, then around 40,000,000 Btus or 12 MWh of heat energy is released during the year.) This becomes REALLY interesting when you note that you likely pay around $500 to buy natural gas or electricity to heat your domestic hot water during the year, because the water heater loses around 10,000,000 Btus or 3 MWh of heat during the entire year, in heating and maintaining your hot water supply.
There is NO FIRE created so this is far safer than conventional furnaces, which burn fossil-fuels to create 3,800°F (2,100°C) fire just to provide the 150°F (65°C) warm water you enjoy in your house! This system uses NATURAL DECOMPOSITION of decaying lawn materials to easily produce that desired 150°F (65°C) warm water directly! Actually, that heat IS always created during natural decay, but no one has ever collected it for useful purposes. Right now, that heat is being given off, outside your window, over many months and over the large area of your yard, where the average heat given off is only around 1/2 of a Watt per square foot, so no one seems to have even NOTICED the available heat before! Doesn't it makes FAR more sense to simply COLLECT this naturally occurring and immediately available heat, which does not COST you anything and which is already sitting there outside your window? AND it does not consume precious earth resources or produce the environmental consequences of burning fossil fuels. It uses absolutely GREEN materials, which are going to decay naturally anyway, to entirely heat your home and hot water!
By enclosing the decomposing organic materials inside a well-insulated chamber, and by providing appropriate water and air so the bacteria which do the decomposition are happiest, this heat energy can be captured, to then either heat your home's air or your hot water, or both. I realize that no one believes that 'stupid grass cuttings' can ever represent such a heating source, but I can assure you that in the seven years I have used my device to decompose weeds and grass to heat my house, there have been several times when I have stuck my hand inside the chamber, without any glove, and my hand got Second Degree Burns from the 140°F decomposing material inside. Sometimes, even I am not too smart, as I know better and I also remember previous times I have accidentally done that! Duh!
First placed on the Internet in March 2007 Prototype unit first built March 2007, which then fully heated an entire large house in Chicago winters from 2007-2014
People commonly confuse this system with the long known process of
Composting, which is known to create some warmth. It is actually
rather different, being a far more sophisticated version of that
basic idea. Where Composting (and natural decay) generally relies on
mesophilic bacteria to biochemically decompose some organic materials,
this system generally encourages a far more effective thermophilic
bacteria to do it many times faster, many times more efficiently,
and which produces far more warmth. We designed and Engineered
a system which then maximizes overall performance. Where Composting
which is done well can have an overall energy efficiency of around
50%, and conventional fossil-fuel-fired furnaces commonly can
have around 80% overall energy efficiency, this system can commonly
convert around 94% of the lawn debris into wonderful heat for your
house! (That 94% actually disappears, into becoming the heat energy
you want, along with water vapor and carbon dioxide that had been
initially used to create the plants by photosynthesis!) So, in
addition to being GREEN, it also happens to have
higher overall efficiency than virtually any other heating system!
Self-Sufficiency - Many Suggestions|
Public Services Home Page
It is extremely likely that WITHIN 60 PACES OF YOU RIGHT NOW, there
is a MASSIVE energy source which is absolutely FREE! It is on the scale
of 67,000 horsepower-hours of (heat) energy! Or 50,000 kilowatt-hours
(again, of heat energy). Or 170,000,000 Btus. That's an astounding
amount of heat energy! It is totally free AND it replenishes itself
NATURALLY every year! note 1|
You probably collect and bag grass cuttings when you mow your lawn, as millions of others do. You call it Yard Waste! And you rake and bag leaves in the Fall. What if we told you that as all those leaves and cut grass blades decompose, they NATURALLY give off heat. A LOT of heat! In a single acre of lawn, forest or even weeds, the total amount of heat which IS NOW being released (over about a six-month period of decomposition) is around that 170,000,000 Btus. That's an astonishing amount of heat energy, given that your medium-sized house in a cold climate probably has a total winter heat loss of around 50 million Btus and you use another 25 million Btus of fuel to heat your hot water! YOUR innocent-looking yard has available an immense amount of absolutely free, NATURAL and GREEN heat energy, which is NOW being constantly released by simple natural decomposition of organic materials. All this while YOU are paying billionaires in Saudi Arabia for heating oil??? Take a look out your window at your yard!
What if we now told you that every one of those bags of leaves or grass is therefore worth $3 or $4 or more? You probably now pay giant corporations around $2,000 every winter for fossil fuels to heat your home and water. Consider this: A 20-pound bag of ANY organic matter contains around 180,000 Btus of chemical energy, which was captured from sunlight by the photosynthesis of carbon dioxide and water vapor, and which will ALL necessarily be released as heat as the material naturally decomposes! We have Engineered a method of CAPTURING a large portion of that released heat, to either heat your home or to heat your domestic hot water or both! You probably now pay at least $4 for heating oil or $3 for natural gas to create as much heat as one bag of that Yard Waste could easily provide. Do you still want to pay someone to haul those bags away? And ... the biggest bonus of all, by eliminating your need for fossil fuels, you will be contributing toward solving the global warming catastrophe.
The ONLY "down-side" is that quite a few such bags are needed! Yes, a single acre of land can provide it all, but that still is quite a few bags of grass and leaves and weeds!
If you intend to ENTIRELY heat all the year's hot water for a medium-sized home, and it is in a cold northern US climate, more than 100 such (small) bags might be needed! But most or all of that can be collected from YOUR OWN yard, so nothing should have to be bought!
Other people might decide to BUY around a hundred bales of straw or hay, and there are MANY other sources of such materials. Your neighbors probably now complain about having to pay to have bags of grass and leaves hauled away, and you could generously offer to help solve their problem!
They have a vested interest in wanting to keep control of the source of the fuel that you need to heat your house and water! Their approach is to PARTIALLY decompose organic materials (Biofuels) (in an anaerobic process). WE want to TOTALLY decompose them! (in an aerobic process, which is far more efficient.) In our case, we are then able to capture VIRTUALLY 100% of the heat that can get released by the decomposition. THEY actually allow around half of the decomposition process to occur with no attempt at capture of energy (and sometimes even require ADDITIONAL energy to be supplied to drive their processes.) In general, most Biogas processes MUST be done in anaerobic conditions (where there is NOT enough Oxygen present to completely decompose the organic materials. WHY do they do that? Because many of the anaerobic processes result in Methane gas being produced. Methane gas is essentially identical to what people call Natural Gas. It has the advantages of being able to be compressed, stored, transported and saved for later, all good things. Our PRIMARY process is simply to produce ALL the heat that can be squeezed out of any organic materials, but we therefore concede NOT being easily able to STORE that heat.
But their approach causes, at best, only about 50% of the available energy to be converted into Methane. Our approach causes nearly 100% of the available energy to be converted into usable heat.
So our process and our devices are DIFFERENT from what the giant corporations talk about as THE FUTURE. We think that it is better to be capturing around twice the amount of energy, as long as we have fairly quick usage of that energy. The energy is produced AT THE LOCATION OF NEED, rather than having to be trucked or piped from somewhere else. This does not interest the giant companies, as they want to have energy supplies being in products that THEY can sell! We agree that they have an advantage of talking about a fuel which CAN be used for many industrial processes and for vehicles.
The system and the devices we describe CAN be used to produce Methane gas, primarily by simply NOT allowing sufficient oxygen in to the bacteriafootnote so that they can do a complete job of decomposing the materials. MAYBE that might become a useful variant regarding providing fuel for vehicles if a lot of CNG (compressed Natural Gas) vehicles start using the roads. For now, we feel it is better to focus on TOTALLY decomposing the organic materials to get every possible Btu of heat out of them!
IF the purpose is to heat a house or hot water, there seems no competition with our approach! Instead of using processing which only have around 50% efficiency, our approach gets essentially double that. Instead of creating a fuel which be BURNED to produce hot gases at around 3800°F, in order to heat air or water up to 120°F or 140°F, wasting a lot of heat in that process, we simply heat the air or water directly. Instead of requiring distant mining companies to extract fossil fuels from deep in the Earth, we use NATURAL materials on your own lawn which will naturally decompose anyway. Without constantly having fire present inside furnaces or hot water heaters, there is no fire which ever exists in our approach, which is far safer. Instead of spending $1500 or $2000 every year to heat your house and hot water, you can collect FREE lawn debris from your own lawn!
We admit that there is convenience factor of paying some giant corporation to supply you with a pipeline full of heating oil or natural gas or of a lot of electricity for electric heating. In contrast, you must collect and store several tons of cut lawn grass and autumn leaves, and then carry it to put it into the device, an amount that is nearly comparable to the amount of firewood you might need to cut and store and carry if you intend to heat your house by burning wood.
The comfort level inside a house is essentially identical to that from a conventional central furnace, even using a wall thermostat to keep room temperatures exactly what you want them to be. Finally, by making use of a process which was gradually going to occur naturally anyway, the decomposition of grass, leaves, weeds and other organic debris, you are a LOT more civicly responsible in not adding gases from burning fossil fuels to the Earth's biosphere.
We concede that if you have needs to smelt aluminum ore or to create steel, this process cannot produce the very high temperatures necessary for such industrial processes. We are merely pointing out that the needs of an average family can be excellently fulfilled by using the natural decomposition that we recommend.
First, the preliminary solid scientific information that you may want to know and learn regarding Global Warming:
The REALLY interesting part is that it is the EXACT SAME CHEMICAL PROCESS of oxidation that is occurring as we do in burning our fossil fuels! It creates the same carbon dioxide and water vapor and energy. It's just that it occurs much, much slower. So slow that virtually no one ever even notices it. But it NATURALLY creates around FORTY TIMES all the energy that all humans now use up!
Do the math! You mow your lawn each week, for maybe 25 weeks. Even if you only get ONE bag each time, there's your 500 pounds! You certainly have far more than that available, if you actually collected it all.
That heat is not noticed because it is created slowly, over months, and over a large area, and winds and rain carry away and distribute that heat so that no one can tell it is there. But it IS there!
Gardeners and farmers will say that the composting process takes between six months and two years to complete, and that only around half of the weight of the material disappears. The remaining material is the humus or compost that they actually want, the material they then spread in their gardens or fields as a sort of fertilizer. However, most gardeners and farmers are not aware that there are "fast" ways to do composting. Some operations use an assortment of ways of tumbling the material in rotating drums, (such as what is referred to as In-Vessel processing) or with other devices (such as Tunnel Composting), and get the entire Composting process to complete IN JUST 48 or 72 HOURS! They have also found that with certain conditions, it is possible to have the decomposition process proceed to nearly completely consume ALL the material rather than just half.
Actually, our process does NOT actually resemble what is called Composting, except for the fact that the basic chemical decomposition reaction is the same. Other than that, there are hardly even many similarities! We do NOT have significant material (humus) remaining and we do not need six months or two years to accomplish the process!
We do not see great value in having our home heating system perform quite that well, although it definitely can and has been experimentally proven to do so. A rather small system could be made that could only hold around 300 pounds of organic material (not much larger than a recliner chair), with that highest performance built in. The 2.7 million Btus of heat energy created is sufficient to entirely heat a fairly large home for the three days that it would be producing that heat (the 72 hours), but then that would mean that another 300 pounds of material would have to be loaded in every three days during the coldest part of the winter. That seems undesirably labor intensive.
Therefore, we describe systems below that are (generally) larger than that, with capacity for around 1500 pounds (for several weeks or a month of whole house heating before maintenance is needed) or capacity of around 9,000 pounds to provide all the heat needed for the entire six months of winter. A high-performance system IS included in the choices of what you can make.
You can see that the grass continued to rapidly rise in temperature, all because of lots of very active bacteriafootnote, and just 24 hours after I had dumped that newly-mown grass in the bin, the average temperature of the bin crossed 120°F! I still find that mind-blowing!
That particular experiment was intended to be a preliminary one, and no source of additional oxygen was provided, which is what caused the curve to start flattening out. Other than the naturally moist cut grass, only a handful of black dirt was tossed in, as a reliable source for bacteriafootnote, nothing else! In the modest bacteriafootnotel activity that I had expected, I thought they would have plenty of oxygen for at least a few weeks. They used up most of the oxygen in the bin in a day and a half! Later experiments where a tube was added that supplies air (oxygen) show that the graph stays straight longer, and only then levels off in the 140°F to 150°F range. THAT leveling off is actually because that excess heat starts to kill off some of the bacteriafootnote doing the work, so I make a point of keeping the bin temperature under around 150°F. You might also notice an interesting detail that the ambient temperature of my basement rose a couple degrees after the warm daytime and dropped during the cooler nights, as we might expect.
In case it is not clear, THIS is a "carbon-neutral" situation. Plants live and grow, and REMOVE 300 billion tons of carbon dioxide from the atmosphere every year, naturally, by photosynthesis, in forming the glucose and other organic molecules of life. When that material dies and decomposes, it completes the cycle, what is called the Carbon Cycle. Fossil Fuels cause a problem because they had removed their carbon dioxide from the atmosphere many millions of years ago. The fact is that we are now mining and pumping all the fossil fuels we can find, and then burning them at very high rates, that now releases huge amounts of carbon (dioxide) that had been trapped in those fuels for those millions of years. The carbon dioxide itself is not a problem! The fact that we are RAPIDLY ADDING a lot of "new" carbon dioxide to the atmosphere IS! The organic-decomposition-based concept here is entirely different, simply keeping the EXISTING carbon in the biosphere and atmosphere in circulation. Totally NATURAL and Carbon-neutral.
Those materials were going to decompose NATURALLY anyway! We are just causing that natural process to occur where we can capture the heat it creates.
Conventional water heaters have substantial energy wastage through their insulation, so the actual net heating effect is substantially less than what you are now paying for. If you add up the actual hot water used each day, it is possible to get a rough idea of how much actual heat is in a month's worth of hot water used, and for a normal family, that can be around 200 KBtu/month. But that conventional water heater uses up around 250 Therms/year or 20 Therms/month. A Therm is 100 KBtu, so this means that you pay for 2,000 KBtu of gas for heating the water, but only wind up getting around 1/8 of that in actual used hot water! The rest gets lost as radiation by the hot tank to a cool basement. (not the ideal present technology!)
On a different subject, you may be familiar with a Compost Pile. This is where a farmer or a gardener simply piles up grass, leaves, twigs, corncobs, and other plant residues, with actually very little else even being required (although additions can make it work faster), and those materials gradually decompose, over a period of from six months to two years. From the gardener or farmer's point of view, they like the fact that undesirable scrap is removed without any hauling expense but also because what is left after the Composting is a material that is very rich in the phosphorus, nitrogen and other nutrients (called compost or humus) that all soil benefits from.
Farmers are aware that the Compost pile generates some heat, and scientists know that different types of bacteriafootnote are most effective at breaking down the material at different temperatures. Initially, certain types of bacteria (mesophilic, which are common in the soil) do most of the work, up to around 85°F to 100°F or so. Mesophilic bacteria tend to only be able to break down certain simple hydrocarbon and carbohydrate molecules. Above that temperature, those bacteria tend to die off and a higher temperature bacteria (thermophilic, heat-loving) take over, and they are far more efficient at causing the breakdown of nearly anything containing carbon and/or hydrogen. Standard Composting practice is to try to get the middle of the Compost pile to about 55°C or 130°F, because at those temperatures, most human and animal microbial pathogens tend to be killed, which tends to make the whole process a sterilizing process (from an infectious viewpoint!) So farmers and gardeners know that it is good to have some heat inside the Compost pile, to make it work better!
On a more technical level, the bacteria which do this process are actually doing it for their own purposes. Depending on how much oxygen is available to them, there are two very different processes which can occur. We will briefly discuss Anaerobic decomposition later. In aerobic decomposition, what we feel is more desirable, it is common that bacteria can initially convert around 40% of the energy of the glucose into Adenosine Triphosphate (ATP), which is the primary energy source found in all living things. The remaining 60% of the energy in the glucose is released as heat. The bacteria use the ATP as the source of energy for their existence. When ATP loses one phosphate group, it degrades into ADP and 7 KCalories of usable energy. Nearly all biological processes in all living things use the ATP-to-ADP process to power transmission of nerve signals, the synthesis of proteins, the movements of muscles and cell division, among many other processes. (I realize that 99.99% of people do not really care about such details!) When bacteria eventually die, this ATP and all the other components of the bacteria decompose like everything else. This has the effect of increasing the final amount of heat produced from that 60% to very nearly 100% of the amount of energy that photosynthesis first installed into the glucose. It makes the decomposition process amazingly efficient from an energy perspective. In comparison, we note that modern automobiles have around 21% overall thermal efficiency regarding the energy in the gasoline they use up (which is up from the 15% of the 1970s).
Notice that WITHOUT the insulation, the bin temperature rises, but rather slowly. This is actually the situation of a conventional Compost pile, where it takes months to get the CENTER of the pile up to the most productive hotter temperatures. In six days, it only rose by about 3 degrees! WITH the insulation, we can see that the leaves rose by over 20 degrees, around seven times as fast.
The high level of insulation is a critical component to why this system works so amazingly well.
We had found that the molecular weight of the glucose was 180, which means that 180 grams of glucose is one mole of that material.
That means that when photosynthesis CREATES 180 grams of glucose, 686 Kcal of energy (from sunlight) is required, and when that glucose later decomposes back into carbon dioxide and water vapor, 686 Kcal of energy is released. In most biological functions, much of that energy is used for building cell components or transporting materials, but in the very end, it necessarily always winds up as heat energy.
In case this technical metric stuff is losing you, 180 grams is around 0.4 pound, and the 686 Kilocalories of energy is around 2700 Btu. This means that a pound of glucose contains around 7,000 Btu of energy in it, relatively similar to the known energy content of firewood and all other organic materials (6,500 to 10,000 Btu/lb). Sorry about the technical nature of some of this stuff, but we wanted to make sure to prove why this works as it does!
Say we arrange a big pile of dead plant (leaves, grasses, weeds, crop residues, straw, hay, corncobs, feed corn, etc) (and even animal) materials which is around four feet square by five feet high, or 80 cubic feet. (THIS is the size of the chamber that we are going to discuss below!) That material is not packed very well, so it is common that it only weighs around 20 pounds per cubic foot, or a total of 1,600 pounds of matter involved.
We could make a quick estimate of the chemical energy in that pile of organic material as being 7,000 Btu/pound times 1,600 pounds or around 11,000,000 Btus of chemical energy (which will eventually ALL be released as heat).
We can calculate more accurately how much energy of decomposition is in that pile. We first change the weight into metric, 725 kilograms or 725,000 grams. As we had done before, we then divide this by the 180 grams in a mole to find that we have 4,000 moles of glucose (which was initially created by photosynthesis in plants). Multiplying this by the 686 Kcal/mole tells us we have 2.8 million Kcal of chemical energy in the glucose in that pile. We can convert this back to the English system to see that we confirm that we are looking at 11 million Btus of chemical energy present. (This is a significant amount of energy!)
This amount of energy is comparable to the amount of energy that a gas- or electric-water heater produces in around a six-month period. So we know that we have a large enough pile of material to decompose to provide all the hot water we will need! (unless we have 14 kids!)
There is one other consideration we need to consider, how quickly the system can recover once we have drawn lots of bathtubs of hot water! We can calculate this fairly easily. We know that we have 11 million Btus produced over about a six-month period (4,320 hours). We can divide and see that our pile will be actually creating about 2,500 Btu/hr of heat. If we entirely empty out our 40-gallon chamber of 150°F water (which is enough for about six decently full bathtubs of 90°F bathwater), then we will have removed about 300 pounds of water (40 gallons) each of which had around 95 Btus of heat in it (150°F - 55°F), which means that we removed around 28,000 Btus of heat in that water. At creating 2,500 Btu per hour, we can see that it would take around 11 hours before it was ready to again supply six bathtubs of hot water! However, the pile of material has some heat storage of its own, and rather than simply removing the heat of the water, what would actually happen is that the outer parts of the pile would cool down a little, which provides some extra short-term recovery heat for the new water. The thermal conductivity of the tank would allow rather rapid transfer of heat into the water, so the tank would actually heat up top give those six new bathtub-fulls in just two or three hours, much like the performance of a conventional water heater.
The point here is that this calculation shows that if you have a small family, you will never run out of hot water! However, if you have twelve kids and they take daily baths, and you run clothes washers a lot, too, you may need to consider a larger arrangement.
We are therefore going to enable that entire pile to decompose, essentially naturally, over maybe six months (or faster), where the glucose (C6H12O6) oxidizes aerobically [chemically combines with oxygen from the air] ( the 6 O2 molecules) and therefore breaks down to create ONLY molecules of water (H2O) and carbon dioxide (CO2) and a MASSIVE release of energy!
We are greatly simplifying things here! Organic materials are not simply glucose! Plants and animals use glucose as an energy source to create all the more complex molecules that are needed for the living process. However, all those complex carbohydrates are still able to decompose into the same water and carbon dioxide, sometimes releasing even more energy that we have described here. In fact, much of the glucose is connected together in long chains of molecules into cellulose, which is the primary component of all plants. The cellulose you toss into your pile therefore actually has even more energy in it than we have been calculating. The advantage is actually an increase of around 20% extra available chemical energy.
Firewood is a good example to prove this. It is primarily cellulose. If a pound of (dry) firewood were simply glucose, our molal calculations would show that we had 454 grams or 2.52 moles of glucose in the pound of (dry) firewood. At 686 Kcal/mole, we have 1730 Kcal/pound of wood. This is around 6,900 Btu/pound of glucose. But we know that the high heat value (dry) for firewood is around 8,660 Btu/pound. That difference is primarily due to the energy added to the glucose to bind it together into the cellulose that plants and trees use for their structure. This proves that the actual performance would be 25% better than we have calculated!
There is also another possibility that can occur in a conventional Compost pile (which we will intentionally choose to avoid) where there is no available oxygen to participate in that decomposition. In that case, in an anaerobic process, the glucose (C6H12O6) can simply break down into carbon dioxide ( CO2) and methane gas ( CH4). This is currently considered a doubtful desire, because it forces an incomplete decomposition and therefore a smaller release of the chemical (heat) energy, but if the generated methane could be collected and compressed, it is essentially what we call Natural Gas. This might provide some limited ability to store some of the energy provided by this process, and specifically as a fuel that can burn at a much higher temperature (around 3,800°F) for possible needs of such high temperatures.
For now, we intend to simply use the natural aerobic process to generate all the heat possible from this process. For this, we will therefore need to ensure that there is always a sufficient supply of air/oxygen inside the pile of material.
There is one other detail to mention. The chemical reaction we have been discussing regarding photosynthesis and the opposite glucose decay have been technically incorrect. On BOTH sides of that equation are another six water molecules that are actually involved in the chemical reactions. We have left that out to simplify the equation as long as we have been discussing energy content issues, as the same molecules on both sides obviously cancel out. The main reason this is mentioned here is that a supply of water is also important inside the pile, which we will also ensure.
Our research is actually starting to suggest that this version has some real advantages over the others presented here, as well as being fairly small, about the size of an upright piano.
We will describe here a more sophisticated arrangement that will generally resemble a conventional small storage shed. We call this the HG 2. But it will be highly insulated and it will include several other features different from any garden shed. There are MANY possible variations from this specific plan possible!
We will make it of common, locally available materials. It will be sturdier than normal garden sheds, partly because it has to be able to contain and support around 1,600 pounds of material in its bin! The floor structure will therefore be made of 2x8 lumber, while the side walls will be made of 2x6 lumber. The top will again be 2x8, mostly so that more insulation can be used.
NOTE: There will actually be two structures here. You HAVE to make the inner one (the bin) absolutely airtight! Inside the bin, the conditions will be extremely hot and extremely humid, where virtually anything will quickly disintegrate and decompose (which is actually the whole idea!) By making that bin absolutely airtight, you will be able to keep the moisture/humidity inside the bin, so that the space OUTSIDE the bin will be hot but actually have extremely LOW relative humidity! This being the case, the wood construction and the conventional insulation will be fine and will last a long time. However, if you should leave even a small path for humid air to get out of the bin into that space, the entire structure could quickly disintegrate as well. You do NOT want that to happen!
These guidelines related to thickness of insulation are related to the local climate. These dimensions are generally universally useful; however, in very southern climates, less insulation might be used, while in Alaska, thicker insulation might be appropriate.
The floor structure is a simple framing pattern using 2x8 lumber
and a standard 3/4" plywood subfloor. It is made to be 6 feet
With the subfloor nailed on top, the floor would look like this.
It is important that it be flat and smooth, as there will later be
rollers, resembling refrigerator rollers, which will need to be
able to easily roll back and forth across this floor:
We can then build the 2x6 walls, again using standard practices.
We will build the walls to be 6 feet tall. Notice that there are
only three walls built, with (this) front wall entirely missing!
An important detail is that the boards surround that front opening
be all flat and plane, as there will later be another (movable)
structure with some gasketing on it that will slide in to be against
that opening to seal it up.
ALL of the inner surfaces of the chamber have conventional fiberglass house insulation installed, and then they are all covered with EITHER cheap paneling or even drywall. The important fact is to make everything air tight, where no heat can leak out.
We can examine the heat loss that will occur given our choices of insulation and the local climate. We will have 180 square feet (floor and walls) of R-19 insulation, and 36 square feet (ceiling) of R-30 insulation. If we assume that the interior of the decomposing material is generally at 140°F and that the average outdoor winter temperature is 40°F (a Chicago winter is around 30°F in the worst part of the winter but is milder for the other months, so 40°F is a reasonable average estimate for an entire winter), then we have an average temperature differential of 100°F. Standard insulation analysis gives us a total heat loss of around 1100 Btu/hour. In our expected main six months of processing, there are 4320 hours. At the beginning and the end of the process, the maximum heat will not be generated, but this suggests that for this level of insulation, we can expect the total six-month heat losses to be roughly 4 million Btus. We knew that we had 11 million to start with, so we will wind up with 7 million Btus for us to actually use. If you think about it, that 7 million Btus really cannot go anywhere else, and so we will be able to put it to use in heating up water!
We chose the insulation levels to provide limited losses while considering reasonable expense. You can use this same approach to see whether you might find any value in increasing the insulation to R-30 or higher.
You have probably noticed that we have not discussed the ceiling/roof area. We are actually going to leave that up to you, with the one requirement that it be insulated to at least R-19. The REASON why we are being vague here is that there are two different approaches you could choose regarding collecting the heat in hot water.
Note that this small structure must NOT be inside the house (mostly because of the possibilities of odd smells from the decomposition depending on what you pitch into it) but it should be as near the house as possible to shorten the plumbing connections. Those connecting pipes need to be extremely well insulated, at least R-50 and higher if possible.
This arrangement involves very little headroom, where the heat collecting tanks/pipes/radiators are all within a few inches of the ceiling. That permits the flat roof.
Interestingly, the installed T-P valve (temperature-pressure valve) is not needed, since this water heater could never get the water up to boiling! Again, the in and out pipe connections would go to the nearby house through highly insulated pipes.
There are two obvious approaches to this structure, with several other variations possible. We will discuss here making a bin out of wood and out of metal. The metal version would be more durable, but the wood version might be a better first stage to try, even though you know it may only last a year or two. It seems to allow many more options and easier changes to experiment with different arrangements of the components. So we will first discuss a wooden bin.
Basically, we will make a bin that can fairly easily fit through the five-foot wide and five-and-a-half-foot tall opening. We will want to have it on some sort of rollers so that the rather heavy filled bin can be slid into place after filling it outdoors. This could be as simple as a bunch of loose lengths of iron water pipe laid cross-ways on the floor, or more sophisticated to actually involve casters or rollers attached to the bin bottom.
We suggest making the bin 54" wide so that it has about three inches clearance on each side as you are moving it. The height of the bin would be about five feet. If made out of standard lumber, this would give the bin inside dimensions as close to the 4 x 4 x 5 used above in the performance calculations. (Obviously, a metal bin would be larger inside, so that around 20% additional organic material could be dumped in and therefore 20% greater total heat output generated.)
The FRONT wall of the bin needs to have flanges extending outward on both sides and across the top. This flange will have standard door weather-stripping attached to its rear side. In this way, when the bin is slid completely in place, that area overlaps the building door frame for a good tight fit. This vaguely resembles the way a dresser drawer overlaps the dresser body hole, but without any gasketing!)
None of the walls of the bin are insulated EXCEPT THE FRONT. The front needs to have at least R-19 insulation. One possibility for this is to make the front out of 2x6 lumber instead of 2x4 or 2x3 as the rest of the bin would be built of, so that it could have fiberglas R-19 insulation installed in it. Another possibility is to use BLUE foam house insulation, in several layers so that it is 4" thick for R-20 insulation.
The bin must have some special features.
To start with, none of them are in the bin, and filling is begun. Once the organic material got up to around the height of the lower pipes, they would be slipped in through the front hole and jammed into the closet flange. (The bought 10-foot-long pipe having been cut so that it extends about 6" past the front outer wall.) The holes in the pipes should be lined up top and bottom. More material is tossed in the bin, and the upper pipes slipped in at the appropriate time. This allows filling the whole bin without any void spaces under the pipes. When the whole process is done, these pipes may be easily removed so that the resulting humus can be removed from the bin so the next filling can be made.
Water flow rate might be experimented with. A very slow flow tends to cause most of the water to drain out through the first hole in the pipe, while a surge of water tends to go all the way to the end and pool there before draining out at the last holes. A mid-flow-rate can get water to drain out fairly equally along the dimension of the pile.
These thermometers are so cheap that three different thermometers could be installed in the same pipe, such that the sensors were 1/4, 1/2 and 3/4 of the way back across the bin. It would then be possible to monitor how evenly the decomposition was occurring, as even temperatures would indicate consistency while great differences might suggest that something was not ideal.
The second of these two electronic components is a humidity sensor. Only one of them is probably needed, for the very center of the pile.
There are many ways this can be provided. One obvious way would be to buy several "Earth augers" which would be installed parallel to those piles, with their end sticking out the front wall. At any point where it was felt that it would be beneficial to turn the pile, a wrench could be used to rotate each auger shaft, which would turn the auger inside the bin.
Given that this should be a minimal need, it seems that a far more economical approach might make sense. Get several more of the PVC pipe, but drill 1/2" holes through opposite walls, such that a foot-long piece of 1/2" metal rod could be stuck through and secured. The result would be the pipe having 4" long Barbs sticking out from opposite sides of the pipe. If maybe a dozen such rods were securely attached through such a pipe, and the pipe was installed similar to the air pipes discussed above, a pipe wrench on the stub of this pipe sticking out would be able to rotate it, which would force those barbs to stir up the material in the bin.
Higher-tech and more expensive variations of this are obviously possible. It is tempting to wonder if the air pipes could also handle this duty.
If that temperature does not rise or drops, check the humidity, to make sure it is in the 40% to 70% range. If it is low, add water. If it is high, you have added too much water.
If there is the smell of ammonia, that is an indication that you are not providing sufficient oxygen for the aerobic decomposition to fully occur. It is an indication that you probably need to add more air. Depending on what materials you use, they might stay tangled together (as hay seems to tend to do) where the air/oxygen cannot get to some parts of the organic material. This could indicate that the material needs to be stirred up or turned over to break up such clumps of material. The supply of air/oxygen and its ability to get to all the material is probably the most important factor to maintain.
If the humidity seems fine and the temperature starts to drop, the only additional thing you could do would be to turn the pile, to stir up the organic material, in case some of it had not had good access to the oxygen or the water.
If the temperature drops anyway, after an extended time, it might mean that the thermophilic part of the process is done.
If the temperature starts to rise too high (above 150°F) then you need to NOT encourage the thermophilic bacteria! But you could try to send more (cold) air through all the pipes to try to chill down the reaction.
To some extent, you need to find out how your own system responds to such things, so you can learn how best to help or slow the process in the future.
There is one other possibility. If you put in things that will only decompose slowly, such as tree branches, OR if you neglected to toss in organic material that contained sufficient nitrogen, the bacteria may not be able to fully thrive, and the temperature will never rise very high.
You can probably see that there are an immense number of variations possible in using this system!
We prefer the idea of starting out with the standard natural decomposition, with the idea that it would then have to be emptied and refilled just twice a year, maybe in the Spring and Fall. A faster decomposition process might require refilling it in the dead of winter, possibly unpleasant but possibly with little source of organic material to toss in!
However, there is a wide range of organic materials which is ideal for this process, all of which is normally considered annoying trash which needs to be disposed of! Consider the following energy contents, remembering that our glucose that this is all calculated on has an energy content of around 6,900 Btu/pound:
|coffee grounds||10,000 Btu/pound|
|wheat straw||8,500 Btu/pound|
|rice straw||6,000 Btu/pound|
|cattle manure||7,400 Btu/pound|
(Bagasse is the material remaining when the juice is squeezed out of sugar cane, relatively similar to all the plant parts left in a farming field after a harvester has removed the crop.) Note that all of these materials have attractive energy contents, and these each decompose fairly rapidly by the action of bacteria.
There are also entirely different processes that occur if the decomposition is done without sufficient air/oxygen. In that anaerobic decomposition, the process is always slow, and there are often foul-smelling gases produced. If you are properly doing aerobic decomposition, with moderately close C-N ratios, there should be virtually no smell created.
This device should produce an average of around 4.7 cubic feet of carbon dioxide every hour. It cannot be pure carbon dioxide but is limited by Dalton's Partial Pressures to around 4.4% of the air. This indicates that there could be around 110 cubic feet of air saturated with carbon dioxide which accumulates near the bottom of the bin every hour, air which has a carbon dioxide content of around 110 times that which exists in the natural atmosphere (44,000 ppm rather than 380 ppm). The reality of this system is that the airflow is generally around 2.5 times this, which makes the local concentration of carbon dioxide around 40 times the natural concentration.
So say that a very small fan is provided which could extract this gas. The removal of that gas would draw in new fresh air through the higher-up tubes, to supply the thermophilic bacteria the oxygen they will need. But we now could have a supply of carbon dioxide rich air.
There have been thousands of research experiments which have shown that virtually all plants grow better, faster and larger in an atmosphere of excess carbon dioxide. For example, Chen, K., G.Q. Hu, and F. Lenz, in 1997, (published in a German Journal) found that strawberry plants (fragraria x ananassa Duch. cv. 'Elsanta') grown in 1995 and 1996 had remarkable improvements in an atmosphere of excess carbon dioxide! For the two-month growth season, those strawberry plants were constantly in atmospheres of 300, 450, 600, 750, and 900 ppm CO2. (The highest of these was around three times natural concentration, with the first being relatively near natural). They found that flowering and fruit ripening started earlier and lasted longer where the higher carbon dioxide was present. Second blooms generally also developed. Fruit productivity was enhanced by increased pedicel number per plants, fruit setting per pedicel, fruit size, and dry matter content of the fruits. They found that the average fruit yield was (considering the 300 ppm as 100% yield): 450 ppm gave 170%. 600 ppm gave 370%. 750 ppm gave 460%. 900 ppm gave 510% yield!
They found that fruit quality was improved as well, and the total sugar accumulation in the fruits, especially sucrose was increased and that titratable acid content was reduced. Essentially all wonderfully desirable results!
This seems to suggest that if this discarded carbon-dioxide-rich air is sent into a nearby greenhouse, where the carbon dioxide concentration might be increased to three times natural, maybe five times as much fruit and vegetables might be grown from the same plants!
Note that the carbon-dioxide-rich air provided to the greenhouse is also around 150°F so that it can even provide natural heating for the greenhouse, reducing the need for artificial heating!
Thousands of other research experiments have been performed regarding a wide range of plants, which have all had similar results. Even crops like wheat and soybeans, and trees like cherry and spruce and white oak, have similar growth benefits.
(Some of those researches have found that carbon dioxide concentrations higher than around 1200 ppm are NOT as beneficial.)
Yet another possible Green benefit from this system!
You might note that this combined system actually collects the carbon dioxide that is naturally generated anyway, and then it allows those greenhouse plants to REMOVE IT FROM THE ATMOSPHERE! This is a tiny effect, but it actually tends to remove some of the excess carbon dioxide that we have put into the atmosphere due to our massive burning of fossil fuels!
This second enables production of FAR more heat than was described above, for much greater usable heat output, but it also then consumes the organic matter far more quickly! One of the basic desires of the system as described above was to not need any maintenance at all for the six month period of a winter (October through March). If the system is operated in a high-performance mode, it might produce ten times as much heat output per hour, but the organic materials would then be consumed ten times as fast, in three weeks instead of six months. Is that desirable? Each owner would have to decide that! To be able to generate enough heat to heat an entire house from a garden-shed-sized system is certainly an attractive idea, but to then have to empty and re-fill it every three weeks during the winter does not seem very enjoyable!
We have described the density of collected organic materials as being around 20 pounds per cubic foot. However, it might be less than that, depending on your methods. If grass clippings are not "squeezed" into a container, 10 lb/cf can be more normal. Also, what we are interested in is the actual weight of organic material, and if you collect sopping wet leaves, much of the weight might be just water leaving less of actual organic material.
We have described the bacterial activities as being entirely decomposition of the cellulose and glucose into water vapor and carbon dioxide. That is not entirely true, as the bacteria are actually doing this for their own purposes, including growth, so there is a percentage of the gross heat produced from the decomposition that gets used for the growth of the bacteria themselves. However, those bacteria will eventually die and decompose, and so that effect tends to become minimal.
We actually have materially altered the normal process of decomposition. In normal Composting, once the thermophilic bacteria have completed their high temperature work, they tend to die off, which allowed the mesophilic bacteria (remaining in cooler portions of the Compost pile) to quickly re-multiply and do the remaining lower temperature decomposition. But since we have enabled the entire pile to get up to the high temperatures, there really are virtually no mesophilic bacteria that can still be alive anywhere in the whole pile! Instead of the temperature dropping from the 150°F to 85°F for the final phases of the decomposition, it might instead drop to ambient, until and unless some mesophilic bacteria are again able to enter the scene.
However, this absolutely natural process is SO effective at creating heat energy, that no matter what you do, you are certain to get great benefits!
There are also some existing technologies, such as those based on the Seebeck Effect (discovered in 1821) which are thermoelectric generation. Semiconductor materials seem capable of decent potential efficiency levels, even at these very low temperatures, but new research would probably be required. If that is pursued, the system might DIRECTLY produce electricity as a by-product of its normal operation.
This could be created above ground or in the ground. In a remote Third World location, bales of straw might be used as the insulation, or many other locally available materials. The chambers should be resistant to rats and larger animals chewing through, either to get to food scraps or to a heated location during a winter. A thermometer is very useful because there is a common tendency to cause too great an airflow through the bin, which then does not allow the material to get up to the most effective operating temperature. Also, given the extreme amounts of heat energy which gets generated, overheating and killing the thermophilic bacteria can occur without knowledge of the temperature actually within the decomposing material.
This concept has only very recently been invented (February 2007). It figures to take two to three years before rigorous University Research Studies can be done to fully document it. If you have read the contents of the four associated web-page presentations, it must be clear that I am not sure the planet or civilization actually HAS an extra two or three years to delay in doing this. This presentation has tried to refer to the many hundreds of years where standard Composting has been done, where farmers have realized that heat develops in the middle of a decomposing organic pile. We have tried to also present the appropriate Biochemistry and Physics so that a reader might understand the science behind WHY it works. We have tried to present the math, in a relatively painless way, such that any reader might confirm or deny for him/herself the validity of this reasoning and the numbers presented.
So, each reader is free to wait those several years until University Research Studies prove it. However, we hope that we have presented things sufficiently so that many people will not see the need to wait those years and might decide to build this fairly simple system sooner. If so, and you decide to do this, you will certainly have your own ideas about how to do certain things. You might decide to install more or fewer tubes, of larger or smaller diameter. You may decide that the whole thing should be tall and skinny or short and wide. You may decide that there is some reason to tilt the whole thing! It will certainly work in any case! Maybe better or maybe not. We hope that people who try variations of what we have described will later e-mail us regarding any potential variations or improvements, and the actual results you achieved. If we could have a thousand people each doing this during this coming winter (07-08) and the next (08-09), we think we may be able to greatly refine the system, even before any official Research Studies get even initial data.
A few newscasts are starting to finally indicate how urgent and how drastic our problems are regarding Global Warming. If we wait for the governments to act, as slowly as they always seem to work, even their optimists are only expecting to make modest reductions by the year 2050. That will certainly be FAR too late. The premise of this page and this concept is that if instead a "grass roots" effort of countless millions of homes being heated in this way, we might actually be able to achieve in two or three years what Politicians seem to only dream about for more than 40 years from now! When TV ads say for you to "do your part to save the planet", this is the sort of thing they are probably intending to refer to!
So we are figuring that those first thousand people who make these will each have slightly different configurations, or they will have tossed in different organic materials. Some will discover brilliant insights in the process. It may actually turn out to be a wonderful thing if some bacon grease is included, or food scraps, or a small amount of used motor oil! No one will really know until someone tries such things! If this sounds potentially exciting, I think it is, because if YOU happen onto some awesome variation, this site can enable millions of others to also benefit from it!
The 170,000,000 Btus of chemical energy is simply sitting there! It no longer has any function regarding the biological operation or development of the living plants of which it used to be part. It is simply sitting there, as the organic materials are waiting to (slowly) NATURALLY decompose, which releases all that chemical binding energy as heat energy. It can be equally accurately described as 67,000 horsepower-hours of (heat) energy or 50,000 kilowatt-hours (again, of heat energy). They all mean the same thing. They are NOT mechanical energy or electrical energy, or even heat energy, but rather a potential energy of the chemical binding energies of the atoms in the complex carbohydrate molecules in organic materials. However, the first Law of Thermodynamics told us that Energy must be Conserved, that is that such energy cannot simply disappear. It MUST continue to exist, but it can be changed in form from one type of energy to another, as long as the total energy does not change. All REAL processes do not have perfect efficiency when changing from one form to another, where all the energy that might appear to be lost had simply been converted to heat energy, possibly as frictional losses or radiation or convention losses.
In this case, that 67,000 horsepower-hours of energy gets released very gradually and slowly, spread out over that entire one acre area. But still, during that six-month period (4,400 hours), there is an average of over 15 horsepower continuously released, although it occurs very irregularly in reality. That can also be described as being an average of around 11 kilowatts for that entire six month period! This seems impossible since no one has ever noticed it! After all, we don't have to run across the yard in winter because it is so hot!
We can see why this is the case if we consider it as the 170 million Btus of energy. Again, this is released over 4,400 hours, so we would have an average of around 39,000 Btu/hour. Keep in mind that this is normally spread out over the area of an acre, or 43,560 square feet. This is therefore around 0.9 Btu per square foot per hour, a rather small amount when we stick space heaters under our desks which produce 5,000 Btu/hr! Is there any wonder that no one has ever noticed a heat source which is less than 1/5000 of that of a lowly electric space heater?
The actual natural heat production is very irregular, as the mesophilic bacteria which operate at the lower temperatures are very affected by the temperature of the material they are trying to break down for energy. On intensely cold days, there is extremely little activity, while on milder Spring days, substantial decomposition occurs.
Note that the technology which we have developed generally relies on entirely different types of bacteria, the so-called thermophilic ones. They are far more efficient at the process BUT they also require an environment which is around 125°F to 150°F. This means that they rarely get a chance to do much, except on really hot sunny summer days when inside a pile of animal dung or similar Compost materials. This actually explains why the thick and effective insulation is so centrally important in the operation of this concept. If there should ever be found some bacteria which thrive on even warmer temperatures, like 170°F to 180°F, it figures that they might be even more rapid in accomplishing these functions. If there were ever to be any future in using this approach for vehicle fuels, that might a likely way to accomplish the rapidity needed in the energy release.
For the record, the first Footnote in the first Global Warming presentation of this series discusses that around 893 watts of incoming sunlight arrives at each square meter of area (due to the Solar Constant and the Earth's Albedo). Our one acre is around 4010 square meters, so the acre can receive a total of around 3.6 * 106 watts of sunlight. Due to day and night and other geometric effects, the actual daily average is 1/4 of this or 9.0 * 105 watts. Multiplying by 86400 seconds in a 24-hour day, this is 7.7 * 1010 watt-seconds, or 2.15 * 107 watt-hours each day. If we consider a growing season in the middle US to be half a year or 182 days, that means that roughly 3.9 * 106 kilowatt-hours (kWh) of sunlight energy had arrived on that acre during a single growing season.
We have just determined that the actual plant growth absorbs around 50,000 kWh of energy into the chemical binding energy of the organic molecules. We have just mathematically confirmed that the photosynthesis process has around 1% overall thermal efficiency (50,000 / 3.9 * 106). The second Footnote in our second Global Warming presentation provides the complete analysis of where all the thermal efficiency losses are in the natural photosynthesis process.
There are an assortment of different things that can be meant by this popular phrase. Unless you know the rules used in generating a specific number, the number might not have much meaning!
Published records showed that the US emitted a total of 5.498 billion tons of actual carbon dioxide in 1998. (of a world total of 18.96 billion tons.) There were then around 300 million of us in the United States, so we might fairly say that we each, man, woman and child, caused the emission of around 18.33 tons of carbon dioxide, (5498/300) so one might say that each American (including little babies!) had a Carbon Footprint of over 18 tons (of carbon dioxide) in 1998. However, the US changed policy some years back and decided to ONLY count the carbon atoms in that carbon dioxide, which makes for a somewhat smaller number! Atomic Carbon is actually about 27% of carbon dioxide by weight. By only counting the carbon atoms, they can therefore also correctly say that each American was responsible for about 5 tons of actual carbon atoms that were sent into the atmosphere (but ALL of them were as carbon dioxide atoms, and not one was ever a loose carbon atom! So the reason for the change of description appears to have been entirely political, just to make it APPEAR that the US was not sending such extraordinary amounts of carbon dioxide into the atmosphere! In any case, there are some people who use this peculiar method of description to say that we Americans are each responsible for a Carbon Footprint of around 5 tons each year. There are also people who see that 82% of that carbon dioxide production is directly due to the combined usage of motor vehicles and the creation of electricity, and those people ignore our heating our homes and only say that we each are responsible for about 15 tons of carbon dioxide or 4 tons of carbon equivalent. You can see that there is quite a range of numbers which can correctly be applied here. Also, I am not so sure that tiny babies should be blamed for this, and it might be more correct to describe a HOUSEHOLD FOOTPRINT for the 80 million families (of usually two parents and about two children) in the US. In that case, the appropriate number for a HOUSEHOLD CARBON FOOTPRINT might be described as being either around 70 tons of carbon dioxide or 20 tons of carbon equivalent.
Given that WE are the ultimate beneficiaries of all the electricity generated in the US and of all the vehicle traffic, but that we also primarily heat our homes and buildings with the rest, a case can be made that charitability of reducing the numbers might be inappropriate!
For this presentation, we use a very conservative 45 tons of carbon dioxide or 12 tons of carbon equivalent per family.
The 12 ton number essentially ignores the actual carbon dioxide and instead talk about the (somewhat hypothetical) MMTCe number. That number does not even refer to any real chemical, but instead tries to use the quantity of Elemental carbon that is present. We feel that saying that each American family is responsible for a 45 ton Footprint of carbon dioxide is most correct and descriptive.
We mention that, in 1998, official reports describe that the US sent 1,494.0 MMTCe of carbon dioxide into the atmosphere. This would be 1,494 million metric tons which we might try to allocate among the 300 million of us that then were Americans. Dividing, we then confirm that each American had a Carbon (equivalent) Footprint of 1,494/300 or about 5 tons of carbon. However, the reality is no different! A family with two children would still be blamed for 4 * 5 or 20 tons of elemental carbon, or the equivalent of 20 * (44/12) 73 actual tons of carbon dioxide, each year. We have used very conservative figures in the 45 actual tons that we discuss here.
These comments are meant to confirm that the figures for numbers of tons added to the atmosphere in the table above are accurate, as they agree with other ways used to describe our CO2 emissions.
We can look at this from an individual perspective. A single family in a medium-sized home in a temperate climate might burn 700 gallons of heating oil per winter (easily confirmed by looking at previous bills.) Each gallon of either heating oil or gasoline weighs around 6 pounds, so this is around 4200 pounds of heating oil burned each winter. We see note 14 note 9 that each pound of it burned creates 3.12 pounds of carbon dioxide which is released into the atmosphere. Multiplying (4200 * 3.12) we see that this representative family therefore produces 13,100 pounds of carbon dioxide due to heating their home each winter, which we generally refer to as seven tons.
If that same family had burned natural gas instead, they may have burned 1000 Therms of gas during that winter. This is around 100,000 cubic feet of natural gas burned, which weighs around 5100 pounds (one pound of natural gas is around 19.75 cubic feet). We see note 15 that each pound of natural gas burned creates 2.75 pounds of carbon dioxide which gets released into the atmosphere. Multiplying (5100 * 2.75), we see that the representative family produces 13,900 pounds of carbon dioxide due to heating their home each winter, which we generally refer to as seven tons.
There are many different types of coal that exist, and they each have different chemical compositions. However, the coals that are most usable as fuels tend to have at least 80% carbon in them Our coal is therefore about 80% Carbon.
A pound of Coal therefore contains very close to 0.8 pound of carbon in it. If it is burned extremely completely, we can assume that ALL that carbon will combine with oxygen from the air to form carbon dioxide. Using atomic weights again, we see that carbon dioxide is 12 + 16 + 16 or 44, since oxygen is 16. When the 12 weights of carbon is burned (oxidized), it therefore forms 44 weights of carbon dioxide. We had 4/5 pound of carbon to start with so we multiply 4/5 * 44/12 to get 44/15 or 2.93 pound of carbon dioxide formed for each pound of Coal burned.
We can examine the official Reports for any year, regarding the CONSUMPTION of Coal in that year. Such Reports tell us that 2.148 * 109 metric tons of oil equivalent of coal was burned in the year 2000 (worldwide). Such Reports give oil-equivalent numbers, because different kinds of coal have rather different energy contents. If we take oil to contain around 19,500 Btus per pound and an average coal to contain around 13,000 Btus per pound, we then have to multiply by 1.5 (or 19,500/13,000) to get the actual amount of tons of coal burned. Therefore we have 3.22 * 109 metric tons of coal burned in 2000.
We just determined that each pound of that coal creates 2.93 pounds of carbon dioxide when it burns. Therefore, in the year 2000, the amount of coal that was burned produced 3.22 * 2.93 * 109 metric tons or 9.44 * 109 metric tons of carbon dioxide.
THIS year, the massive increases in coal burning in China to produce electricity and to power their many factories indicates that at least 4.5 * 109 metric tons of coal is being burned, which is creating about 13.2 * 109 metric tons of carbon dioxide.
Production of Electricity from Coal
The United States currently produces around 51% of the electricity it uses by burning coal. The coal heats water into steam, which is sent into steam turbines, which spin giant alternators that create the alternating current electricity that we use.
Consider starting with two pounds of coal, which we just discussed contains 2 * 14,000 Btus of chemical energy in it, 28,000 Btus total. In electrical energy terms, that is about 8.2 kWh of available chemical energy.
As the two pounds of coal is burned, we learned above that 2.93 * 2 pounds or 5.86 pounds of carbon dioxide is formed.
It is not possible to burn coal with perfect efficiency, and it is also not possible to transfer all the heat created into forming steam from water. The mechanisms of the steam turbine and the electrical and magnetic fields of the alternator are also not of perfect efficiency. The net effect of all of this is that roughly 30% of the original energy in the coal is converted into actual electricity. (Nuclear powered plants are slightly more efficient, at around 32%, and fuel oil powered and natural gas powered plants are slightly less efficient, generally around 28% or 29%.) Much of the remaining 70% is INTENTIONALLY THROWN AWAY by cooling towers or equivalent equipment.
In any event, we now have 30% of the 28,000 Btus from our two pounds of coal as actual electricity, or 8,400 Btus, which is 2,46 kWh of actual electricity produced. This electricity then has to go through transformers to raise its voltage up high enough to be reasonably efficient in high-voltage transmission lines. It then is sent through such high-tension wires. The standard design rules are to design such lines so that 90% of the electricity put in one end of a 60-mile long stretch will come out the other end. Ten percent of the electricity is therefore lost as resistance heating by the wires, in every sixty miles of such lines. Once in a city, more transformers are used to lower the voltage to around 12,000 volts, for the lines that are up and down every street on utility poles. Then there is another transformer near your house that lowers that voltage even more to the 240 volts and 120 volts that you actually use in your house.
It turns out that all those transformers and especially all those wires have quite a bit of losses in them. There is yet another big problem! Electric power plants must constantly produce MORE electricity than is actually called for at any moment! Just in case millions of people all decide to make toast at the same instant! Or for the more common situation where millions of people get home from work and all turn on their central air conditioners. This results in really large losses of available electricity (which CANNOT be stored in any way as the alternating current that arrives at our houses.)
For an AVERAGE home at an AVERAGE distance from an electric powerplant, roughly 60% of the electricity put in the wires at the powerplant gets wasted as resistance heating and magnetic losses (much of which is lost as that electricity which must be created but will never be used), so only around 40% of that electricity produced and put into the wires actually gets to our houses!
The OVERALL efficiency of the entire coal-fired electricity generation and distribution system is therefore 30% * 40% or around 12%! Thirteen percent is a more commonly used value, really a disappointingly low percentage!
Since we are tracking the electricity from our two pounds of coal, we now find that only around 8,400 * 40% or 3,360 Btus of electricity actually gets to our house! And since 3,412 Btus is equal to one kiloWatt-hour, we have now found that each one kWh of electricity available at our homes required that two pounds of coal was burned up in that distant coal-fired powerplant. Saying this another way, for every kiloWatt-hour of electricity that you use up, there is about 5.86 pounds of carbon dioxide that gets added to the atmosphere at that distant coal-fired electric power plant.
If your own monthly electric bill shows a modest usage of 500 kWh, that means that you are RESPONSIBLE FOR 500 * 5.86 or 2930 pounds of carbon dioxide that months, about a ton and a half. In the year, that is around 18 tons of carbon dioxide. (This usage is not usually counted in the Carbon Footprint estimates!)
This burning of coal to produce electricity is the primary reason that coal is consumed in the US, so it accounts for most of the annual totals discussed above regarding coal burning.
We can use the information we just learned to find how much carbon dioxide that an electric powerplant releases in order to DUPLICATE the power in one gallon of gasoline. There are actually two different ways we can do this. (1) We know that a gallon of gasoline contains around 126,000 Btus (or around 37 kWh) of chemical energy in it. We just determined that two pounds of coal burned in an electric plant can be expected to provide around 0.98 kWh of electric power at our home. That electricity that arrives at our home then needs to go through a battery charger and then into a chemical lead-acid battery, with both processes having less than ideal efficiencies. The result is that around 0.64 kWh of electric energy is actually put into the batteries (from those two pounds of coal that were burned). When an electric vehicle or hybrid then uses that electricity stored in the batteries, the efficiency of the batteries are again in effect, as well as wiring, the electric motors, gears, shafts, and other mechanisms to actually make the tires of a vehicle rotate. The result is that around 0.42 kWh of ACTUAL electric energy gets used to move the vehicle.
It turns out that modern gasoline-powered vehicles are generally around 21% efficient. Therefore, of the 37 kWh of chemical energy in a gallon of gasoline, only around 7.7 kWh actually gets used to move the vehicle. We can therefore easily see that (7.7 kWh / 0.42 kWh) or about 18.5 groups of two-pounds of or 37 pounds of coal would need to be burned (at the distant electric power plant) to duplicate the actual useful benefit in a gallon of gasoline! We can also see that 18.5 groups of 5.86 pounds of carbon dioxide would be released from that coal burned, or 108 pounds of carbon dioxide! This all applies to Electric Vehicles (battery-power), Hybrid Vehicles that plug into house electricity, or (future) Hydrogen-powered Fuel Cell vehicles. A TERRIBLE situation!
We note (and calculate in a different Footnote) that an existing gasoline-powered vehicle only releases around 18.3 pounds of carbon dioxide into the atmosphere for each gallon of gasoline burned. We find it rather bizarre that politicians and the public considers it to be GREEN to consider electric battery-powered vehicles and hybrids, where they DIRECTLY CAUSE 108 pounds of carbon dioxide to be released into the atmosphere, SIX TIMES AS MUCH as the gasoline-powered vehicle causes in the first place! Is that GREEN???
If, instead, a battery-powered or hydrogen-powered or hybrid vehicle was used, we see that 108 pounds of carbon dioxide has to be released from the distant electric powerplant in order to provide the necessary electricity! Much of this is due to the fact that there are so many separate processes involved, and EACH of those processes each are less than 100% efficient. It all adds up!
So even though all the publicity and the excitement is around battery-powered vehicles being so GREEN, and that future hydrogen-powered vehicles will be the same, the fact that they have to receive their re-charging electricity from distant coal-fired electric powerplants actually makes them horribly UN-GREEN! Around six times as much carbon dioxide must be released into the atmosphere due to any electric powered vehicle than if the vehicle had had a standard gasoline engine! This is not to praise gasoline engines, as they are terribly inefficient! But the public is quite mislead by the people who are aggressively promoting electric vehicles and future hydrogen vehicles! The central claim on which people would be willing to buy such vehicles turns out to NOT be true (because the SOURCE of the electricity is from burning coal). IF the electricity could be gotten from solar or wind or hydroelectric, fine, they would be excellent! But it turns out that the practical matters in both solar PV operation and in wind turbine operation, make them VERY unlikely to actually ever provide all the miraculous claims made for them, at least for probably the next 50 years. We must remember that 51% of all the huge amount of electricity used in the United States is produced by burning coal.
The fact that the electric powerplant is many miles away seems to be the reason that people feel they can ignore whatever happens there! But it turns out that really bad things regarding carbon dioxide occur any time we want ANY electricity, whether for powering a vehicle or for making toast!
Burning Petroleum, Gasoline, Heating Oil, Jet Fuel, Diesel, Etc
There are many different types of petroleum which is pumped out of the ground. They all are primarily Carbon in composition, with the best varieties tending to be chemically around 85% Carbon. A pound of crude petroleum or its distilled products, gasoline, diesel fuel, home heating oil, jet fuel, kerosene, etc, therefore contains very close to 0.85 pound of carbon in it. If it is burned extremely completely, we can assume that ALL that carbon will combine with oxygen from the air to form carbon dioxide. Using atomic weights again, we see that carbon dioxide is 12 + 16 + 16 or 44, since oxygen is 16. When the 12 weights of carbon is burned (oxidized), it therefore forms 44 weights of carbon dioxide. We had 0.85 pound of carbon to start with so we multiply 0.85 * 44/12 to get 3.12 pound of carbon dioxide formed for each pound of Petroleum burned.
We can examine the official Reports for any year, regarding the CONSUMPTION of Petroleum in that year. Such Reports tell us that 3.54 * 109 metric tons of petroleum in the year 2000 (worldwide). If the Reports give the consumption in barrels instead, 7.33 barrels equals one metric ton. We just determined that each pound of that petroleum creates 3.12 pounds of carbon dioxide when it burns. Therefore, in the year 2000, the amount of petroleum that was burned produced 3.54 * 3.12 * 109 metric tons or 11.04 * 109 metric tons of carbon dioxide.
THIS year, we are burning up around 30 billion barrels of petroleum, which is about 4.1 * 109 metric tons of petroleum, which is creating about 12.8 * 109 metric tons of carbon dioxide.
Combustion of Gasoline
We can also consider gasoline by the gallon instead of the pound. One gallon of gasoline weighs around 6 pounds. Around 5.0 pounds of that is due to the carbon atoms in the complex carbohydrate molecules. When the Carbon atoms oxidize/burn they combine with oxygen from the air to form carbon dioxide. The ratios of the amounts are 12 grams of carbon combines with 2 * 16 grams of oxygen to form 44 grams of carbon dioxide. This means that we end up with 44/12 times as much carbon dioxide as we had carbon to start with (if the combustion is complete). In our case, starting with 5.0 pounds of carbon, the gallon of gasoline therefore forms about 5.0 * 44/12 or about 18.3 pounds of carbon dioxide.
Burning Natural Gas
Natural Gas is nearly all methane gas. That is chemically CH4. From Chemistry, we know that the Carbon atom has an atomic weight of 12 and each Hydrogen has one. The Methane molecule therefore has a total atomic weight of 16 (12 + 4). It is therefore 12 / 16 or 3 / 4 or 75% Carbon.
A pound of Natural Gas therefore contains very close to 3/4 pound of carbon in it. If it is burned extremely completely, we can assume that ALL that carbon will combine with oxygen from the air to form carbon dioxide. Using atomic weights again, we see that carbon dioxide is 12 + 16 + 16 or 44, since oxygen is 16. When the 12 weights of carbon is burned (oxidized), it therefore forms 44 weights of carbon dioxide. We had 3/4 pound of carbon to start with so we multiply 3/4 * 44/12 to get 11/4 or 2.75 pound of carbon dioxide formed for each pound of Natural Gas burned.
We can examine the official Reports for any year, regarding the CONSUMPTION of Natural Gas in that year. Such Reports tell us that 2.438 * 1012 cubic meters of natural gas was burned in the year 2000 (worldwide). We use the density of Natural Gas (Methane) (0.7168 gram/liter) to calculate that this amount is 1.74 * 109 metric tons of Natural Gas. We just determined that each pound of that natural gas creates 2.75 pounds of carbon dioxide when it burns. Therefore, in the year 2000, the amount of natural gas that was burned produced 1.74 * 2.75 * 109 metric tons or 4.81 * 109 metric tons of carbon dioxide.
THIS year, we are burning up about 3 trillion cubic meters of Natural Gas, which is about 2.1 * 109 metric tons of Natural Gas, which is creating about 5.9 * 109 metric tons of carbon dioxide.
Nature constantly recirculates Carbon throughout the biosphere. Using the energy from sunlight, plants perform the process of Photosynthesis to create new plant materials. Whether this is done in trees, bushes, grasses weeds or other land plants, or in algae or seaweed or other water plants, the process is generally always the same. Carbon dioxide from the air is chemically combined with water from the soil (or sometimes directly from the air) to create complex carbohydrate molecules. The Photosynthesis process usually proceeds by this chemical reaction:
(6) CO2 + (6) H2O + energy from sunlight ↔ C6H12O6 + (6) O2
The complex carbohydrate is a chemical called glucose. A wonderful side effect is that oxygen is also given off, which we are then able to breathe!
Plants then use that glucose and chemically convert it into all the thousands of other organic carbohydrate molecules on which all life depends.
In Biochemistry, we know that to form "one mole" of glucose, the plant needs to absorb 686 Kilo-calories of sunlight energy. A mole is the total atomic weight (in grams) of any chemical molecule, so we can add up the 6 Cs (each weight 12) and 12 Hs (each weight 1) and 6 Os (each weight 16), to find that a mole of glucose is 180 grams. We therefore know exactly how much sunlight energy was required to create any amount of new plant material created from the carbon dioxide and water.
Here is a simplified presentation of the basic biochemistry involved. It shows the arrangement of the chemical bonds in the glucose molecule, as well as the actual bond strengths of each of the bonds, which shows the theoretical basis for the 686 kCal of energy that is absorbed from sunlight during photosynthesis and released again during decomposition or respiration.
If you add up the total weights of the six carbon dioxide molecules that were used up, you can see that they weigh a total of 264 grams.
The Carbon Cycle is a CYCLE because, when the plants later die, they then naturally decompose (or which also occurs during a common process called Respiration) (with the help of many types of bacteria) back into carbon dioxide and water (or water vapor, the same thing). After an entire Cycle has occurred, the amount of Carbon has not significantly changed.
On the entire Earth, there is roughly 100 billion tons of Carbon involved with the Carbon Cycle each year. We notice that it accounts for 72 (6 * 12) of the weight of the glucose's 180 weight. Since the Carbon Cycle intimately involves the production of glucose, we can therefore know that 180/72 * 100 billion or about 250 billion tons of glucose is produced each year by all the world's plants. In the process, they REMOVE about 264/72 * 100 billion or around 350 billion tons of carbon dioxide from the Earth's atmosphere (and CREATE 192/72 * 100 billion or 260 billion tons of oxygen which we might then breathe!).
So, BRIEFLY, the Carbon Cycle, the total plant life on the Earth, REMOVES a large amount of carbon dioxide from the atmosphere.
However, those plants all eventually die, and when they do, that 250 billion tons of glucose decomposes. The decomposition process then USES UP the 260 billion tons of oxygen again and the glucose decomposes back into the original 350 billion tons of carbon dioxide and the original 150 billion tons of water.
No net advantage or disadvantage occurs regarding amounts of carbon or carbon dioxide or anything else occurs due to the Carbon Cycle. In fact, the exact same weight (mass) of each of the Elements always exists, around 100 billion tons of carbon, 17 billion tons of hydrogen and 400 billion tons of oxygen. The chemical processes of photosynthesis and decomposition just change the appearance as different atoms combine in different molecular combinations.
The entire Carbon Cycle and the entire field of Biochemistry is more complicated than this simplified discussion might indicate. But the basics are all exactly as described here.
The Carbon Cycle therefore RECIRCULATES all the carbon and carbon dioxide that is available, without ever INCREASING the amounts, except briefly by chemically converting the carbon dioxide (gas) into and out of parts of plants. When we burn fossil fuels, it is ENTIRELY different! We are digging up chemicals which are mostly carbon which have been BURIED for many millions of years. That carbon had therefore been OUT of the atmosphere and the Carbon Cycle for those millions of years. The fact that we dig/pump it all up and then BURN it, means that we are doing what is called oxidation:
C + O2 which gives CO2.
This is NEW carbon dioxide which could not have been created except for the fact that we chose to burn the fossil fuels. Once we have created this NEW carbon dioxide, it is essentially around forever (at least millions of years) AND it is now free in the Earth's atmosphere.
Where the Carbon Cycle never increased the total carbon dioxide in the atmosphere (except temporarily), our burning of fossil fuels IS increasing the total carbon dioxide in the atmosphere, on an accumulating quantity and essentially with forever consequences.
Of the hundreds of chemical methods we know of which can remove carbon dioxide from air, one seems to be far more promising than any others. It was invented around a hundred fifty years ago.
The Solvay Process is still used around the world, related to production of salt, glass, soap, detergent and centrally sodium carbonate. It uses salt water (brine) and ammonia and carbon dioxide to produce sodium bicarbonate and ammonium chloride. As carbon dioxide is bubbled up through the ammoniated brine solution, sodium bicarbonate is formed, which is insoluble and which then sinks to the bottom of the tank. When the ammonium chloride is later treated with lime, the ammonia is recovered and can then be put back in the first step of the process. The only requirements are therefore saltwater, carbon dioxide and lime. THAT is the reason the Solvay process might be a credible possibility, that really only seawater and limestone are needed, both of which are available in very large quantities. The carbon dioxide becomes chemically combined in the sodium bicarbonate, which is insoluble and it therefore precipitates (settles) to the bottom. The carbon dioxide is therefore removed from the air.
There are around 70 Solvay Process plants still in operation around the world. Unfortunately, the total amount of carbon dioxide removed from the Earth's atmosphere each year is very tiny when compared to the scale of our problems. All those industrial plants combined only process about 30 million tons of sodium carbonate each year, indicating that only around 15 million tons of carbon dioxide gets removed from the atmosphere each year. For even the Solvay Process to be of a large enough scale, around 2000 times as many Solvay Process plants would be required to process even just the 30 billion tons of carbon dioxide that we are adding to the atmosphere each year. That would require around 140,000 industrial factories each fully operating the Solvay Process.
All of the hundreds of other chemical processes that we know about which can remove carbon dioxide from air, have far less chance of accomplishing the SCALE that would be needed.
This Year's WORLD Carbon Dioxide Estimate
The set of three footnotes regarding coal, petroleum and natural gas have calculated that THIS year (2008), we are creating and releasing 13.2 billion tons; 12.8 billion tons; and 5.9 billion tons; respectively, of carbon dioxide, for a total of around 31.9 billion tons.
The United States generates around 1/4 of this world total each year.
We can describe this quantity in several different ways. By applying the density of carbon dioxide (1.977 gram/liter) we can see that a ton of carbon dioxide gas takes up about 1010 cubic meters of volume. Multiplying, we see that we have about 32.3 * 1012 cubic meters of carbon dioxide. That 32 trillion cubic meters is the same as about 1,140 trillion cubic feet!
(These presentations sometimes use a "more conservative" value of 400,000,000,000,000 cubic feet, as a value that is an average over the past twenty years or so.)
There are some people who get on TV and claim that they will simply collect the carbon dioxide and "sequester" it inside the Earth, such as in caves. They have clearly never done the math! If a volume of 1,140 trillion cubic feet were as a sphere (ball), it would be about 40 kilometers in diameter or 25 miles in diameter. It would have a volume of about 7,800 cubic miles! All the known caves in the world only have a total volume of a few cubic miles!
This analysis ONLY even refers to what we do in a SINGLE year, and we will add just as much again next year, and again the year after!
Your Heating Bills
If we consider an average-insulated, medium-sized (1600 sf) house in a climate like Chicago, it is likely that around 100 million Btus of fossil fuels are consumed each winter. Roughly 80 MBtu for heating the house and the other 20 MBtu to heat the domestic hot water.
Your furnace and hot water heater likely has a label on the side which describes the expected annual consumption of the fuel. For example, gas-fired water heaters probably have a label that indicates that the range of available water heaters use between 238 and 273 Therms of gas each year. Since each Therm is 100,000 Btus, this means that the water heater will use between 23.8 million and 27.3 million Btus of gas each year.
Heating systems are generally not especially efficient, and these amounts are generally consumed even though that house probably actually has a winter heat loss of around 50 MBtu. Most is lost up a chimney and during non-use due to a pilot flame.
If we assume that 100 MBtu total usage of fuels, we can examine the characteristics of the different fuels.
The other calculations in these connected pages were generally from the approach of Biochemists. The following is more strictly pure Physics. (Except for the fact that we will try to stay in the more familiar American units of measurement.)
We learned earlier that a mole of glucose is 180 grams and that it produces 686 Kcal or 2,722 Btu of energy. This is 15.1 Btu / gram of the glucose.
We also know that the chemical reaction is C6H12O6 + (6) O2 produces (6) H2O + (6) CO2. The six moles of oxygen are provided by air, which is only 21% oxygen and 79% nitrogen, which means that we also have 22.6 moles of nitrogen, which do not participate in the reaction but will have to be heated up along with the other produced gases.
For calculations, we will assume that the air enters at 60°F. The thermal capacity of each gas is available in charts or equations for any temperature. For example, the heat capacity of Oxygen gas (between room temperature and 5,000 degrees) is given by 11.515 - (172 / (T0.5)) + (1530 / T) [where T is the absolute temperature R and the result is in Btus per pound-mol of the gas]. Specifically (in Btu of energy in the gas per gram):
|520°R or 60°F||0||0||0|
|580°R or 120°F||0.663||0.650||0.934|
|600°R or 140°F||0.885||0.870||1.256|
|700°R or 240°F||2.445||1.974||2.907|
Therefore, our 6 moles of water vapor is 6 * 18 [molecular weight] or 108 grams. Given the values in the table above, we know that that amount of water vapor must contain 108 * 0.663 or 71.6 at 120°F or 108 * 0.885 or 95.6 Btu of energy at 140°F. We can do the same for the other gases and other temperatures, finding that we have 6 * 44 or 264 grams of carbon dioxide and 633 grams of nitrogen.
We therefore can total up the heat which must be transferred to the gases, to raise them to a specific temperature, which necessarily participated in the chemical reaction as follows:
|Water vapor||71.6 Btu||95.6 Btu||264.0 Btu||297.4 Btu|
|Nitrogen||408.4 Btu||550.6 Btu||1271.0 Btu||1415.1 Btu|
|Carbon dioxide||246.6 Btu||331.5 Btu||767.6 Btu||854.8 Btu|
|TOTAL||726.6 Btu||977.7 Btu||2302.6 Btu||2567.3 Btu|
We know that the mole of glucose will produce 2722 Btu of heat. However, the water vapor created must be evaporated with some of that heat, which is easily calculated as being 249.8 Btu. (That water vapor will later condense in other parts of the decomposing pile which recovers that energy.) So we have 2472 Btu of heat which must get taken away by the gases created. We can interpolate to learn that the maximum possible temperature of this process would be 253°F, given this situation of no excess air being provided. Of course, the bacteria would all have died far before that and this is merely the theoretical maximum possible.
It is more desirable to provide excess air, to increase the chance that each reaction site will have sufficient oxygen present and to reduce the chance of anaerobic decomposition. If we provide 50% excess air, these calculations are altered where another 14 moles of air which would have to be heated. This causes the maximum theoretical temperature to be lowered to 204°F.
Similar calculations show that if we provide greater than around 200% excess air, there would be so much cool air passing through the decomposing material that it would not be able to maintain the desired 150°F for the thermophilic bacteria to thrive. This gives a maximum limit to the airflow. It also provides a guide for how much airflow is necessary in the event that the temperature starts to exceed the 150°F where the thermophilic bacteria might be endangered, to rapidly cool down the pile. In other words, the size of a suitable blower that might be automatically started by an excessive temperature inside the pile.
We have shown here that it is not theoretically possible to have this concept create heat above around 250°F. This establishes that the performance of the decomposition is limited by the survival of the thermophilic bacteria.
We also know that six moles of oxygen is needed for the aerobic decomposition of each mole of glucose, which is 192 grams of oxygen. At the incoming temperature, this oxygen takes up around 5.5 cubic feet of volume. The incoming air therefore takes up around 26.2 cubic feet for each mole of glucose fully decomposed. If we have a situation where we have 25,000 Btu/hour being created, we know that we are decomposing around 9.2 moles of glucose (about 3.6 pounds) each hour, which therefore requires 240.5 cubic feet per hour, or around 4 CFM of incoming airflow. With 50% excess air, that would be around 6 CFM of incoming airflow. The outgoing airflow is slightly greater (about 20%), due to the higher temperature and the greater number of moles of gas leaving.
These are very minimal airflows and do not really need any significant blower (nearly all of which move over 100 CFM of air), although a computer cooling fan might be useful. As noted above, it is undesirable to inject greater than 200% excess air (12 CFM in this case) due to excessive cooling of the pile which would adversely affect the rate of decomposition and energy production.
Actual processes are never perfect, so all that theoretical energy cannot be actually obtained. We saw above that only around 2722 Btu of available chemical energy is actually involved in the glucose molecules. Any real organic material has components that are not C, H, or O. Some is material that is not organic related at all, considered ash after combustion. Other involve elements that get used in many complex organic molecules for specific purposes, such as the iron that is critically important in our blood, or the many other trace elements like that. Also, nitrogen from the air gets used in many organic molecules, as do phosphorus and other elements that are critically necessary (and even supplied to soil as needed nutrients!) Finally, especially in combustion, it is not possible for every molecule of oxygen from the air to be precisely where it is needed to enable the oxidation of every atom of carbon or hydrogen, so there is always necessarily some incomplete combustion, where some carbon and hydrogen is always left after such an oxidation. The Physics approach only looks at the theoretical maximum possible, meaning all real values have to be slightly less!
This is useful here in order to evaluate cellulose a little better. Cellulose is a long string of C6H10O5 assemblies (slightly modified glucose molecules linked together). With this analysis approach, we can see that we still have the same amount of Carbon fuel, but now ten Hydrogens instead of twelve. We therefore have a total of 3580 Btu of theoretical energy. Since this molecule has lower atomic weight (162 instead of 180), it contains slightly HIGHER energy per unit weight, 22.1 Btu / gram or 10,000 Btu / pound. This is the theoretical reasoning behind why cellulose has a higher energy content than glucose. It also shows that all actual fuel materials (as presented above) have slightly lower actual HHV measurable quantities than the theoretical energy contents of the fuel components themselves!
We can also add here the specific information for cellulose rather than the glucose we had generally been discussing. The following is generally available information, for example from the Incineration section of Mark's Standard Handbook for Mechanical Engineers.
The molar description of the cellulose decomposition:
C6H10O5 + 6 O2 gives 6 CO2 + 5 H2O
is 72 + 10 + 80 + 192 = 264 + 90 (by separate elements weight)
or 162 + 192 = 264 + 90 (by molecule weights).
By ratios to carbon, this is 1 + 0.14 + 1.11 + 2.667 = 3.667 + 1.25
By ratios to cellulose, it is 1 + 1.185 = 1.63 + 0.555
For calculating the needed air, first determine the needed oxygen for
each of the carbon and hydrogen:
carbon: 12 + 32 = 44
ratio: 1 + 2.667 = 3.667
hydrogen (full molecules): 4 + 32 = 36
ratio: 1 + 8 = 9
For a (gram-)mole of cellulose, 162 grams, we therefore need an amount of oxygen equal to 72 * 2.667 + 10 * 8 or 272 grams. If the air is 23.15% oxygen, this means we would theoretically need 1175 grams of air. The air generally does not perfectly go to where it is needed, and so EXCESS AIR is always provided, in this case, 40% excess air is suggested. This is now 1645 grams of air that should be provided for each 162 grams of cellulose that is to be completely decomposed.
This is 10.15 pounds of air that should be provided for each pound of cellulose, or around 132 cubic feet of air. These figures are similar to the calculations presented for glucose decomposition. For the 25,000 Btu/hr production we calculated above for the glucose, we get slightly greater needed airflow, but still around 6 cubic feet per minute.
We note that the "high performance" version of this system (Version 3a, the tumbling one) produces an easy 45,000 Btu/hr to heat a home and has experimentally shown to produce about double that, around 90,000 Btu/hr. We also note that 2,544 Btu/hr is the same as one horsepower of power. See where this is going? That fairly simple unit can CONSTANTLY produce around 45,000 / 2,544 or over 17 horsepower! And it has been shown to produce over 35 horsepower. Granted that it is as simple heat and not as mechanical power. But given that we have millions of active minds in our country, maybe someone can figure out a way to EFFICIENTLY convert that "low grade heat" into mechanical power???
So, just before bedtime, you take your car to a store to get a "bin" filled with bales of a high-performance variation of this decomposing material. Noting that we have already done some experiments with standard mowed lawn grass, where just 24 hours after being cut, it was already impressively producing heat from bacterial decomposition, say that someone discovers even faster ways to get this process rolling. So you get your (5?) compressed bales of this organic material of maybe 200 pounds total weight. We learned above that each pound of the organic material contains at least 8,000 Btu of chemical energy in it, so we are talking 1.6 million Btus of chemical energy total (in a fairly small bin). For comparison, a gallon of gasoline contains around 126,000 Btu of chemical energy, so we are talking here of the equivalent of around 13 gallons of gasoline. Starting to see why thing seems interesting?
It really does NOT seem to be much of a stretch to think that the 200 pounds of material that you put in your bin might be able to completely decompose in say, 12 hours. After all, in-vessel Composting already nearly accomplishes that, certainly in 24 to 48 hours! So we would have 200 pounds of material decomposing in 12 hours which is about 17 pounds per hour. That is around 155,000 Btu/hr or the equivalent to 61 horsepower. That may not represent sports car type of power, and it would tremendously depend on whether an efficient way to convert that heat energy into mechanical energy could be found, but we are here discussing driving for 12 hours, at highway speed, (where a medium sized vehicle generally requires around 40 horsepower (mechanical) to push its way through the air and against tire friction), all potentially from a bin full of cut lawn grass???
Yes, a bin that can hold 200 pounds of this stuff would be much larger than a car's gas tank, but still! This is an approach that involves NO FOSSIL FUELS and therefore no global warming effects! AND there would certainly be that delay of some hours while the rather slow decomposition process was working, to build up enough stored energy for you to actually drive somewhere the next morning!
Now, it may not be possible to actually DO this! During that night while you slept, it would be necessary for the bacteria to totally go berserk in generating heat, and then somehow that heat would have to be captured and saved for when you wanted to drive somewhere. Could anyone find some very unusual bacteria that could work that fast? Or, could some really ideal mixture of decomposing materials be found where the effect is fast enough? Like in a compressed, Swiss-cheese structure where oxygen could get everywhere fast enough? Could someone find some way to efficiently collect and save and store that much heat? Hard to say! But it certainly seems like an interesting idea to think about! IF someone actually comes up with something like that, EVERY vehicle on the planet would soon be built to use that method. Somebody probably has an opportunity to get fairly famous!
As to capturing and storing the heat, we mentioned above the Seebeck Effect and the possibility of a low pressure steam engine as being possible ways to produce some amount of electricity from this general effect. Neither of those is probably able to convert more than a few percent of the heat generated into electricity, though, so the idea of using electrical batteries might be a non-starter. But there are an immense number of very creative people out there (maybe including YOU) and someone might find a way to accomplish this process!
There ARE products on the market today which can operate fairly efficiently, but which need to use around twice the temperature differential that these devices can create. So the technology is certainly available. Unfortunately, those products are extremely expensive, and unless their cost drops dramatically, using a HeatGreen system to produce electricity may not be very realistic.
By the way, such an approach would almost certainly completely end the problem of smog in cities, and NOx pollution would also no longer occur.
However, it IS true that no present technology is remotely efficient at capturing low-grade heat to convert it into electricity. But it sure seems to me to be worth giving a lot of thought to!
The house-heating and hot water heating work great, and they have extremely high overall efficiency. That might NOT be possible with the idea of trying to convert that low-grade heat energy into either electricity or motive power. The reason is that there is something called the Carnot Cycle Efficiency, which is believed to always apply to all "thermal processes". Unfortunately, low-grade heat sources have extremely low Carnot Efficiencies (around 11% for this situation). This situation may therefore NOT allow the "efficient conversion" of those 40 or 60 horsepower of thermal energy discussed above into other forms of energy. But, the incentive seems to be there, so maybe someone can find some method of conversion that does not have the Carnot Cycle limitations. Note that the Carnot Cycle is actually a statement of the Second Law of Thermodynamics, which should indicate that it is very reliably true! A vehicle propulsion system where only 4 to 6 horsepower would be available might not be very attractive! But an electricity generation system which converted 11% of 13 kilowatts would provide a family with a constant supply of around 1.4 kilowatts of electric power, 24 hours each day, which DOES seem very attractive, even complying with Carnot Cycle Efficiency. Better yet, the remaining 89% of that low-grade heat energy could probably then still go to heating the home and domestic hot water. An interesting possibility!
The word bacteria has many wrong understandings. Yes, there are SOME types of bacteria which cause bad effects to other living things such as humans. However, most people seem to not know that YOUR large intestine primarily controls water balance and to obtain certain vitamins by the action of a type of bacteria called Escherichia coli, generally referred to as E. coli.
People also do not realize how SMALL bacteria are! If you collected about 30,000,000,000,000 (thirty trillion) average bacteria, they would collectively only weigh a single ounce!
Only a small fraction of the types of bacteria cause any diseases. Most bacteria only attack organic material only after it is dead. Were it not for bacteria that decompose animal waste matter and the bodies of dead animals and plants, these materials would accumulate almost indefinitely.
THESE are the thousands of types of bacteria that we refer to regarding the HG devices. These bacteria use many available organic materials (such as carbohydrates) as food, and using available oxygen, the bacteria OXIDIZE the organic molecules, which means that they break the complex molecules down into simpler molecules, while ultimately combining the carbon atoms from the molecules with oxygen atoms (oxidizing) to create carbon dioxide. The bacteria are persistent and creative in finding every carbon atom available, so this process can be incredibly efficient, converting virtually all the organic material into eventual carbon dioxide (gas) and water vapor.
This description is regarding their activities when sufficient oxygen is available, so-called AEROBIC decomposition. There are OTHER types of bacteria which operate where no oxygen is available. They operate rather differently, in processes called ANAEROBIC, where they tend to stop decomposition somewhat earlier, commonly when the carbon and hydrogen atoms have been discarded into the smallest molecules of those two elements, commonly METHANE gas, CH4. The overall efficiency of anaerobic bacteria is therefore much lower than aerobic, and so we designed the HG devices to operate on aerobic processes, for greatest overall effectiveness of decomposition, and therefore also the greatest amount of heat being released. There CAN be some useful reasons for intentionally wanting to cause anaerobic decomposition, specifically to create methane gas which might then be collected, compressed and stored for future use. HG devices CAN be modified for this process, but we still see greatest value in maximizing overall efficiency, and so aerobic decomposition.
Finally, there are different varieties of bacteria which live and thrive best under specific circumstances. We center our attention on two main varieties, often called mesophilic and thermophilic. If available organic material is near or below freezing, virtually no decomposition occurs. As temperature rises, the rate of decomposition also increases, as mesophilic bacteria becomes more active with warmer temperatures. This continues up to around 125°F. Around that temperature, the thermophilic bacteria, which had been essentially dormant at lower temperatures, become extremely active, and they also attack a much wider range of organic materials. Nearly as soon as thermophilic bacteria really get going, they can heat the material to greater than 135°F and the mesophilic bacteria die from excessive heat. After that, only the thermophilic bacteria remain alive, but they are extremely active in decomposing organic material many times faster than mesophilic bacteria could do. However, now that only one type of bacteria is still alive, the temperature in the material MUST be maintained at above 125°F, or else those thermophilic bacteria will die and the entire decomposition process immediately stops! If and when this occurs, a handful of black dirt can be thrown into the material inside the HG device, to provide new mesophilic bacteria so that the process can begin again, and then eventually convert to the action of the thermophilic bacteria once the material has again become warm enough.
C Johnson, Theoretical Physicist, Physics Degree from Univ of Chicago