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The Mother Earth News magazine had several articles about making methane from manure and other organic wastes. I don't remember just when those articles ran, but I think it was probably back in the 70's, when TMEN was really a "back to the land" and self sufficiency magazine. I think that the old issues of TMEN are available, probably on ebay, and I think they also may be available on CD or DVD from the people who now publish TMEN. They also may have an index on CD that would be a lot easier to use to locate the articles than digging through a whole bunch of magazines. If I tried that, I would undoubtedly get sidetracked reading something else I found that interested me! It is too bad that TMEN now is just another "country" and econut magazine..... As I remember it, the important part of collecting the gas was to do it in such a way that no air or oxygen got mixed with it, as that would make the methane potentially explosive. One way of doing this was to have a chamber floating on the slurry that would catch the rising bubbles of methane, and as the chamber filled up, it would float higher and higher, slightly pressurizing the methane inside. It would take quite a large digestor to produce enough methane to consider using it in a vehicle. In the early 80's an agency I worked for experimented with using natural gas (which is almost all methane) to power a full sized Chevrolet car. To do this, a special natural gas "carb" was added to the 350 V8 engine and special high pressure tanks that looked like welding tanks virtually filled the trunk. The gasoline equipment was retained and there were various valves, regulators and piping involved in the system. The system worked, but the car had much less power using natural gas and the tanks only had enough natural gas capacity to go a little over 50 miles. And since the only place to go to get the very high pressure natural gas was the gas company, the people who used that car thought that it wasted a whole lot of time for them and usually ended up running on the easily available gasoline. There also was some concern as to what might happen in a bad collision, considering the very high pressures inside the tanks. The experiment was judged to be a failure overall, and no other vehicles were converted to natural gas. I was not directly involved with that experiment, and do not know just what kind of equipment was used to make the Chevy run. I did drive it a few times and the Chevy felt like it had about half as much power using natural gas as it did using gasoline. I doubt that the engine was modified internally at all. Maybe with higher compression or a more sophisticated fuel system, the natural gas would have done better. I have driven machines that ran on propane that seemed to run great. The problem of pressurizing the natural gas (or methane) is a tough one. I was told that the gas company spent many thousands of dollars to get set up to pressurize natural gas for vehicle use. I don't know if they are still using the system. I would think it would have to have a BUNCH of safeguards to prevent escape and potential explosion or ignition of the natural gas. Maybe a dairy, feed lot or hog farm would generate enough manure to justify collecting methane on a large scale, and building the waste handling system with that in mind. I think that some municipal sewage systems collect the methane from their digestors and use it to produce heat in other stages of the process. In Spokane, they sometimes burn off sewage gas above the sewage treatment plant--I have seen it. With all the media attention about global warming and how much methane makes that worse, maybe you could get some kind of a government grant to study the possibilities of collecting an using methane that otherwise would escape to the air. I am not kidding--I have heard of large grants being given for things that are a whole lot less practical. Good luck. An interesting subject!
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