Methane in landfill gas is 20x more potent as a greenhouse gas than much maligned CO2 (plant food). Landfills all over the world are emitting this gas (as do cattle). Although there are some attempts at capturing it as a fuel, many locations flare it, or ignore it altogether. The Bloom Energy fuel cell is one way to convert this gas into electricity, and engines can be modified to burn the gas as well (much less expensively than a fuel cell).
Biogas is produced by anaerobic digestion or fermentation of biodegradable materials such as biomass, manure, sewage, municipal waste, green waste, plant material and energy crops.
We have materials available to teach you how to produce (and use) this fuel in your own backyard at http://www.green-trust.org/products/.