Even if its precise definition isn’t at the tip of your tongue, most everyone gets the drift of what’s meant by the term ‘biogas.’ There is biology involved, and the result is gas. One example might be the funk in the air on the bus carrying the sauerkraut-eating team home after a weekend competition. Another type of biogas is cow belches, and the rotten-egg stink-bubbles that swarm to the surface when your boot disappears into swamp mud.
Those are all kinds of biogas, which is composed primarily of methane, CH4, at concentrations ranging from 50% to 60%. Methane is highly combustible, and can be used in place of natural gas for heat, or to run internal-combustion engines for the generation of electricity and other applications.