Methane is the smallest hydrocarbon. It's easily generated from fermenting
manure, which the Chinese have been doing for years for cooking gas. It's
clean burning as fuels go.
People of India have used it extensively, in small, household methane
generators made of 55-gallon drums.
When I first found my part of the Ozarks, I became friends with people at
New Life Farm, a group of above-average hippies trying to develop and use
sensible technology. It is where I saw my first ram pump. The NLFers got a
grant and had built a methane digester with two huge tanks, gas regulators,
etc. The process was basically feeding the monster with pig manure which
created the gas, which was then pressure-regulated and piped to the kitchen
and heating devices. For reasons I don't think I ever heard, they gave up
on it. One possibility is that it was oversized and required too much manure.
Considering all the stink about sewage lagoons at hog factories, it seems a
problem with an obvious solution.