The hydrocarbon methane (CH₄) is the major component of natural gas (around 90 percent) that is found in oil and gas wells throughout the world. Since the beginning of time, methane has also been produced by a number of biological sources—both natural and human—by the decomposition of organic material. From 1800 to 2000, atmospheric concentrations of methane, which are approximately 0.00017 percent, have grown around 150 percent. However, the patterns of methane emission is highly irregular and, for reasons yet unclear, the rate of increase slowed considerably from 1980 to 2000. The major natural releases of methane are from wetlands (marsh gas) and termites; the major human releases are from energy use, rice paddies, gaseous emissions from animals, human/animal wastes, landfills and biomass burning. Methane research is proceeding in two major directions: the energy course, looking for ways to make bioconversion of wastes to methane more economically attractive as an alternative fuel...