Methane from termites

What about the production of methane from termites ... 

All I can say in response to this comment is that most other people s estimates of the possible errors in estimation of the release of methane from termites are outside that 10 to 20% range. There are several papers floating around in preprint form giving much lower estimates, and I am not yet in a position to judge all of the arguments. It seems to me that much of the problem has to do with how one extrapolates to the whole world. There is no question that termites put out methane. The question is whether they put out an amount of methane which is comparable to that which one is getting from some of these other biological sources. 

Seiler, W., R. Conrad, and D. Scharfle (1984b). Field studies of methane emissions from termite nests into the atmosphere and measurements of methane uptake by tropical soils. J. Atmos. Chem. 1, 171-186. 

Seidl, W. and G. Hanel (1983) Surface-active substances on rainwater and atmospheric particles. Pure and Applied Geophysics 121, 1077-1093 Seiler, W., and P. X Crutzen (1980) Estimates of gross and net fluxes of carbon between the biosphere and the atmosphere from biomass burning. Climatic Change 2, 207-247 Seiler, W., R. Conrad and D. Scharffe (1984) Eield studies of methane emission from termite nests into the atmosphere and measurements of methane uptake by tropical soils. Journal of Atmospheric Chemistry 1, 171-186... 

The simplest alkane (that is, with n = 1) is methane (CH4), which, in addition to several natural sources, is a natural product of the anaerobic bacterial decomposition of vegetable matter under water. Because it was first collected in marshes, methane became known as marsh gas. A rather improbable but proven source of methane is termites. When these voracious insects consume wood, the microorganisms that inhabit their digestive system break down cellulose (the major component of wood) into methane, carbon dioxide, and other compounds. It is estimated that termites produce 170 million tons of methane annually Methane is also produced in some sewage treattnent processes. Commercially, methane is obtained from natural gas. 

Methane is produced by bacteria under anaerobic conditions in wet environments such as wetlands, swamps and rice fields. It is also produced in the stomachs of cattle and by termites. Typical anthropogenic sources are from fossil fuels such as coal mining and as a byproduct in the burning of biomass. The latter sources are considerably heavier in C than the former. Recently, Keppler et al. (2006) demonstrated that methane is formed in terrestrial plants under oxic conditions by an unknown mechanism. The size of this methane source is stiU unknown but it might play an important role for the methane cycle. 

Natural sources of CO include CO from biomass burning and the oxidation of organics such as methane and isoprene, CO from biological processes in soils, CO from vegetation and termites, and CO from the ocean. 

It is estimated that about 500 million tons of methane are being added to the air each year (Craig and Chou, 1982), largely by anaerobic production in rice paddies and wetlands as well as from the metabolism of ruminant domestic animals and, possibly, African termites (Rasmussen and Khalil, 1981 Zimmerman et d., 1982). This gas is slowly oxidized by reactions with Hydroxyl free radical. Its atmospheric content is around 5 gigatons, indicating that the residence time in the atmosphere is about 10 years. As Figure 12 shows, since 1965 the atmospheric concentration of methane has increased by about 3096. If this rate continues, the methane concentration will have doubled early in the 21st century. 

A further mechanism that has yet to be considered is the role of macrofauna in the decomposition of organic matter. In the seasonally dry tropics, for example, it has been estimated that 20% of organic matter decomposition results from the action of termites (Holt and Coventry, 1990). Since methane is an abundant product of the decomposition of organic matter in termite nests, it is possible that the remaining SOC residue is sub.stantially enriched in " C. 

Methane production by termites was first reported by Cook (1932), who observed the evolution of a gas from a species of termite. Besides CH4 termites may... 

Hydrocarbons enter the atmosphere from both natural sources and human activities. Certain natural hydrocarbons are produced in large quantities by both coniferous and deciduous trees. Methane gas (CH ) is produced by such diverse sources as rice growing, ruminant animals such as cows, termites, ants, and decay-causing bacteria acting on dead plants and animals. Human activities such as the use of industrial solvents, petroleum refining and distribution, and the release of unburned gasoline and diesel fuel components account for a lai e amount of hydrocarbons in the atmosphere. 

Methane itself is a greenhouse gas released in large quantities from cattle, termite mounds, rice paddy fields and swamps. The methane produced is the product of bacteria living under anaerobic conditions. In recent years focus has been directed towards a potential source of methane that represents both an opportunity and a threat. Methane has been found stored in the sediments of the continental shelf beneath the deep ocean, underneath the permafrost of the Arctic and in deep Antarctic ice cores (Figure 10.60). In these circumstances the methane is stored in the form of methane clathrates. Clathrates are structures formed by the inclusion of atoms or molecules of one kind, in this case methane, in cavities of the crystal lattice of another, in this case ice. The open, hydrogen-bonded structure of ice (see Chapter 4) lends itself to the formation of such caged structures. 

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