How Energy Is Produced - The Renaissance of Renewable Energy - page 129

Figure 4.40. A 10-kilowatt modern pellet stove. Thanks to the convenience and high
calorific value of pellets, combined with government incentives, this technology has taken
off in many Western countries. Source: La Nordica Extraflame.
Copying Cows: Biogas
Two billion years ago, before algae and plants boosted the oxygen content of the
atmosphere through photosynthesis, anaerobic bacteria were the most common form of life
on Earth (Biello 2009 ) . They are still around in force, digesting organic matter in airless
conditions, thriving in swamps, oil fields, rice paddies, landfill sites, and in the guts of
ruminant mammals.