One of the digesters (on the right) is in a greenhouse, as I mentioned, the other (on the left) gets some of its heat from the hand-made solar hot water panel in the center (decorated with the yellow National Geographic rectangle colors).
The solar hot water heater is just an old radiator painted black in an insulated wooden box with a plate of glass on it. It has a 12V water pump behind it that runs off of the 50 watt solar electric panel lying on the solar hot water heater. There is a thermostat in the box that turns on the pump whenever the heat gets to 40 C or higher and turns off when it drops below that. This pump circulates hot water to the 'water jacket' tank on the left. But both the greenhouse digester and the water jacket digester get their primary heat from hot water feeding -- i.e., whenever we use our Insinkerator to grind up the kitchen waste that is our primary feedstock we use hot water while we are grinding, which is pumped with the ground up food scraps into the tanks. They are also heated by our bath and shower and dishwasher hot water (yes, you can put soapy hot water into your biodigesters because the soaps, as long as they aren't specifically anti-bacterial, become additional food for the microbes in your digester, being made of glycerol and fatty acids and phosphates, all good food for microbes once they have done their cleaning work in the sink or bath).
All of our nice warm greywater goes into the biodigester tanks which are filled with plastic bioblocks to ensure that the bacteria can form good biofilms throughout the tanks, at all the depths and temperatures and feedstock concentrations, and so that they and the food particles don't get washed out every time we load the digesters with a hundred liters or so of hot bath water.
We have a vacuum tube heat-pipe solar hot water system on our roof for our baths and dishwasher and clothes washer (it gets up past boiling on sunny days because vacuum tubes are so efficient, and even works on cloudy days) but though our bath water heat is "free" we feel it is a waste to stand under the shower and let that great hot water pass over our head and body for mere seconds before washing down the drain. So much heat and energy investment lost -- until you hook it up to your biodigester and realize that the longer the shower you take the warmer you are making your biogas system bacteria. And that makes them HAPPY (while taking long hot showers or baths makes us happy, so it is a win win)!
So we really have two solar hot water systems -- one for us domestically and the other our little hand made one to keep the water jacket warm on sunny days and help the bacteria along.
Behind the yellow hand made solar hot water heater is the gas holder, made from a 300 liter garbage can upside down in a 500 liter rain water barrel with some pvc tubes around it to keep the gas holder from falling when it is full. Because the 300 liter barrel is taller than the 500 liter barrel it sits in (which is filled with water) we can't get all the gas out. We lose 100 liters of dead space when the tank is "empty" so we are really only working with 200 liters of usable biogas a day. That isn't so bad -- it still gives us more than a half hour of cooking gas every day from the previous days garbage, but if we were to start all over we'd try to find tanks of matching size (that isn't easy in Germany!) and we'd make them larger to store more gas (it is theoretically possible for a family of four to six people to generate a cubic meter of biogas from their food and toilet wastes every day, which would give the use values indicated in the following picture:
|Chinese Biogas manual from Knowledge Publications.com showing what can be done with 1 cubic meter (1000 liters) of biogas.|
1 cubic meter of biogas is equal to:
Illumination equaling that of a 60-100 watt bulb for 6 hours.
5.2 kg of CCl4 (Carbon tetrachloride)
0.7 kg petrol
can run a 1 horse-power motor for 2 hours
can generate 1.25 k electricity
can drive a 3-tonne lorry 2.8 km
can cook 3 meals for a family of 5-6
On the coldest days this December, when the outside temp got below freezing, the hot water feeding from our grey water kept things going. Here you see the temp in the water jacket in the left tank. The outside air was about 2 C and the bottom of the water jacket was 11.1 C while the water at the top was 16.4 C. That's not all that bad considering things had dropped below freezing over night and the biogas bacteria keep working (albeit more slowly) at 15 C.
The greenhouse biodigester did a bit better. The water in there stayed over 20 C (and the air temp surrounding the greenhouse, though there was no sun, was near 3 C).
Between the two digestors we keep getting our daily flame, day after day, year after year (our digestors have been running reliably for almost 4 years now!):
So we can cook no matter what energy crises the rest of the world is experiencing. And if we need to we can use the methane we make to in turn make electricity by piping it into the carburetor of our 4 stroke generator.
Biogas is a very safe fuel, which is why my wife feels confident holding the gas pipe and igniting it in the kitchen as we set up a picture intended to echo the famous one in National Geographic showing the tragedy of gas leaking into people's kitchens through fracking. In our case we are delighted to have free fuel which we make ourselves along with rich fertilizer from our garbage (the biodigester eliminates the need to compost).
The gas comes into our kitchen at a pressure we determine by placing bricks on the gas holder (for cooking we don't need any bricks at all because the weight of the plastic barrel is enough to push the gas to the stove once you have removed the usual restrictor pin from the stove). "Brickage" is useful for running an electric generator on the gas, or a gas space heater, but isn't necessary for either the stove or the Dometic gas refrigerator we have, which uses a very small flame.
The fire produced by biogas is clean, odorless, blue and hot, even though it contains about 30 percent CO2 and 70% methane. The CO2 reduces the flashpoint and makes it safer to work with. There are trace amounts of Hydrogen Sulfide which we don't bother to filter out when we aren't using the generator (when we do, we simply put steel wool in the tube for the sulfur to interact with so it doesn't eat at the engine). But we like having some H2S in the gas to give it that distinctive gas odor that would let us know if we left the gas on unlit. Once ignited it has no odor at all. Here my wife is cooking bacon covered dates today for our Christmas meal. There's nothing like cooking on gas -- clean, hot, delicious!
I would hook my faucet up to my own biogas digestor. Methane is lighter than air and outgasses from water. I would collect the water and pass it through a filter and drink it or cook with it -- once the methane has outgassed it is fine -- it is the same as using swamp or pond water, which has lots of methane bubbles dissolving in it, and filtering it.
The only problem with fracking, in my opinion, is that the greedy profiteers are unregulated and irresponsible and use toxic chemicals to get the methane out. These heavier hydrocarbons poison the water. They don't need to do this though -- they do it because it is cheaper. But those insidious chemicals don't show up in pictures like this -- they are invisible. And we don't discuss them enough as the real problem with fracking.
We make it an "either or" issue, turning environmentally minded people against a rapid conversion to natural gas which paves the way for a biogas or hydrogen future. This is dangerous to me, more dangerous than a few contaminated wells. There may not be any easy way to get to clean coal, but there are easy ways to get to clean gas.
What I'm not too keen about reading the nat geo piece this month is that it talks about methane, whether coming from the thermokarst lakes explored by our friend Katey Walter Anthony in Alaska and Siberia, or from fracking, as a controversial "problem" but doesn't talk about biogas as long term and quick to reach solution and the transitional nature of fossil natural gas to get there.
It doesn't talk about our own work with Katey on those flaming lakes harnessing the psychrophilic bacteria to replace fossil fuels. So yes, it is a dramatic photograph, but when I see it I see the wonderful flame of methane and think only of how quickly we can bring down the net carbon load in the atmosphere and the poisons and wars and terrorist threats from petroleum, coal and uranium. Please feel free to take me on about this, and share the debate with everyone you know. I think we need to push for safe fracking, compensate families that have had their water suppllies contaminated, pay the full costs of cleanup, and continue extracting natural gas in safe ways while turning all wastes into the real natural gas -- biogas. So... that's what's wrong with this picture as far as I'm concerned."
We talked about this with oil company execs who were our friends and band-mates in Egypt. They agreed with our logic: With home and community scale biogas and solar technologies in place we can stop subsidizing gas and electricity for the poor and middle class (and certainly the upper class). Private companies and governments can sell their fossil holdings to the highest bidder on the international market. The amounts they have available for sale at the higher price increase dramatically, easing tensions about shortages or unrest that drive investors away. Our proposal to them was that we use public funding and private grants to help groups like Solar CITIES do the simple training and building that lets every family have the security of the amount of gas their garbage can produce (about 2 hours per day). For-profit entities can rest easy knowing that all consumers will then be willing to pay top price ( in the case of the poor if and when they have money, but in any event enlarging the consumer base) for extra gas that they want for luxury uses (cooking for big parties, taking long hot showers, running air conditioners and refrigerators and plasma TV screens etc.) The lions share of the gas can go to industry and business who have the money to pay full market prices but need never fear costly and destabilizing shortages again.
So I think the problem -- the reason we aren't seeing more pictures like the ones from my home -- isn't interference from the big companies or governments. I think it is the ignorance and mythology that has infected the rest of us. We, ourselves, are actually the ones keeping these solutions from wider acceptance through belief in our own conspiracy theories and the inadvertant fear mongering and laziness they create.