Bioenergy

Renewable bioenergy is derived from diverse sources and in multiple forms: gas, electricity, and liquid fuel. The energy is released by combustion of organic matter that contains carbon compounds. Significant questions surround the production of bioenergy, including the level of greenhouse gas (GHG) emissions released by bioenergy facilities and the displacement of other economic products by the expansion of bioenergy sources. Although any carbon fuel, including coal, petroleum, and natural gas, is organic; bioenergy refers to the alternative, renewable sources that are not as harmful to the atmosphere and are not depleted through use. Most discussions of bioenergy also anticipate production that does not require mining or drilling.

Bioenergy sources include (1) anaerobic digestion of many materials, such as animal and human waste; (2) biomass processing, as in the pyrolysis of wood chips; (3) algae production of oils or chemicals, including fuels; (4) chemical conversion of carbohydrates, such as sugar from corn or sugarcane into ethanol; and (5) direct combustion of such fuels as cosmetics oils or food waste. The most common product of the decomposition of organic substances is the gas methane (CH4). 

Methane is the most important component of natural gas from wells and provides the majority of the heating and much of the electric power generation in industrial countries. Methane in natural form is trapped in many locations, including peat bogs, ocean sediment, and coal. For the most part, renewable or alternative-energy policies refer to the diverse ways to produce methane under controlled conditions from natural materials, rather than from drilling wells.

A very important concern in regard to global warming is the potential for uncontrolled release of methane from these natural reservoirs, such as the Siberian peat bogs, directly into the atmosphere. A large increase in methane in the atmosphere would stimulate further global warming, perhaps inducing a cycle of warming–release–warming. The most significant alternative or bioenergy objective is to control the combustion of methane into less harmful carbon dioxide (CO2) and water.