Methane and Propane as Auto Fuels

by Jerry Friedberg

(Alternative Sources of Energy Magazine, Dec. '76)

Lots of exciting material has appeared recently on methane, an alternative fuel you can make yourself from organic materials - - manure, garbage, and vegetable matter. We've learned a lot about general theory specific experiments, and detailed plans for construction of small and large methane-producing plants. None of the literature, however, deals in depth with the potentials, problems, and nuts-and-bolts of making and using your own auto fuel. This article deals specifically with "home-made" methane as an auto fuel, the pros and cons, together with another leading alternative, propane.

When manure, vegetable matter, and water are put into airtight containers called digesters, in the presence of initial starter bacteria, decay takes place releasing gas that can be collected and used for fuel. This gas, bio-gas, can be used for lighting, cooking, powering engines, and other common fuel uses - - and the sludge that remains in the digester after the bio-gas is released is extremely valuable as a fertilizer.

Now the good news: the research octane rating of bio-gas is over 110, compared to 82-100 for gasoline, so that bio-gas can be used as auto fuel with even the highest compression auto engines. Pound for pound, bio-gas gives roughly the same mileage as gasoline, and is rather easy on engines and the environment. But where natural gas and gasoline are fossil fuels, taken fromoil wells and coal mines, ultimately limited in supply, and involving dependence on vast corporate undertakings, bio-gas can be made by anyone, on scales large and small, from a wide variety of organic "waste" materials.

The idea of producing your own auto fuel from "waste" materials right at hand is very exciting. In practice, however, it's a far larger, more difficult, and more costly project than first appears. Anyone wanting to do it would best know the negative side of the picture as well as the positive. Here are some of the problems, followed by a fresh look at the whole subject.