Methane Emission

FIGURE 10.33 Vertical distribution of reduction of range of electron acceptors in wetland soil profile. 

FIGURE 10.34 Fe(III) reduction, carbon dioxide production, methane production, and accumulation of Fe(II) in wetland soils. (Redrawn from Roden and Wetzel, 1996.) 

In soils, methane production rates are inhibited at soil depths with intense cycling of iron (Ratering and Schnell, 2000). However, the utilization of Fe(III) oxides depends on the appropriate form that is readily available or on microbial communities. In soils with a limited availability of Fe(III) oxides and other electron acceptors, methanogenesis is the dominant pathway to regulating organic matter decomposition and ultimately a major methane source to the atmosphere. 

The oxidation and precipitation of reduced Fe(II) and Mn(II) in the root zone (a result of oxygen transport by wetland plants) results in iron and manganese plaque formation on the root surfaces. Iron plaque on root surfaces can protect plants from reduced phytotoxins such as sulfide, but it can also potentially create a barrier limiting nutrient diffusion into the root. 

Iron and manganese, which serve as important electron acceptors, especially in mineral soils, can regulate methane production (an important greenhouse gas). Until electron acceptors with higher reduction potential (e.g., Fe(III), Mn(IV)) are exhausted, no methane will be produced. In wetland soils, methane production is inhibited in zones where intense cycling of iron occurs. 

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At some landfills, operators have installed flares to combust the gas without recovering any energy. Typically, these cases arise because electricity seU-back rates are too low to justify generation equipment, and laws require a reduction in methane emissions. 

Other energy sector concerns are methane emissions from unburned fuel, and from natural gas leaks at various stages of natural gas production, transmission and distribution. The curtailment of venting and flaring stranded gas (remotely located natural gas sources that are not economical to produce liquefied natural gas or methanol), and more efficient use of natural gas have significantly reduced atmospheric release. But growth in natural gas production and consumption may reverse this trend. Methane has... 

Longer ice-core records show that methane concentrations have varied on a variety of time scales over the past 220 000 years (Fig. 18-15) Qouzel et al, 1993 Brook et al, 1996). Wetlands in tropical (30° S to 30° N) and boreal (50° N to 70° N) regions are the dominant natural methane source. As a result, ice-core records for preanthropogenic times have been interpreted as records of changes in methane emissions from wetlands. Studies of modem wetlands indicate that methane emissions are positively correlated with temperature, precipitation, and net ecosystem productivity (Schlesinger, 1996). 

Boadi, D., Benchaar, C., Chiquette, J., and Masse, D. (2004). Mitigation strategies to reduce enteric methane emissions from dairy cows Update review. Can. J. Anim. Sci. 84,319-335. 

Chianese, D. S., Rotz, C. A., and Richard, T. L. (2009c). Simulation of methane emissions from dairy farms to assess greenhouse gas reduction strategies. Trans. ASABE 52,1313-1323. 

McGinn, S. M., Beauchemin, K. A., Coates, T., and Colombatto, D. (2004). Methane emissions from beef cattle Effects of monensin, sunflower oil, enzymes, yeast, and fumaric acid. /. Anim. Sci. 82, 3346-3356. 

Methane is emitted during the production and transport of coal, natural gas, and oil. Methane emissions also result from the decomposition of organic wastes in municipal solid waste landfills, and the raising of livestock. More information on methane. 

What has changed in the last few hundred years is the additional release of carbon dioxide by human activities. Fossil fuels burned to run cars and trucks, heat homes and businesses, and power factories are responsible for about 98% of carbon dioxide emissions, 24% of methane emissions, and 18% of nitrous oxide emissions. Increased agriculture, deforestation, landfills, industrial production, and mining also contribute a significant share of emissions (5). For example, in 1997, the United States emitted about one-fifth of total global greenhouse gases. 

In summary, from a clean-up point of view, the main hard point for NOvTrap concerns a process of richness >1, which minimizes methane emissions. 

Methane Emissions from Rice Production in the United States — A Review of Controlling Factors and Summary of Research... 

Keywords Methane, emissions, rice production, agriculture, soil texture... 

Methane emissions from any ecosystem, particularly a rice agroecosystem (Figure 1), are governed by the magnitude and balance of microbial CH4 production (methanogenesis) and oxidation (methanotrophy), which occur by separate microbial communities. The two groups... 

Figure 1. Chamber-based measurements of methane emissions from small plots at the Rice Research and Extension Center near Stuttgart, AR (top), and at the Northeast Research and Extension Center at Keiser, AR (bottom). Photographs taken by K. Brye.

Factors affecting methane emissions from rice... 

Kongchum M. Effect of plant residue and water management practices on soil redox chemistry, methane emission, and rice productivity. PhD Diss. Louisiana State Univ., Baton Rouge 2005. 

Rogers CW, Brye KR, Norman RJ, Gbur EE, Mattice JD, Parkin TB, Roberts TL. Methane emissions from drill-seeded, delayed-flood rice production on a silt-loam soil in Arkansas. J. Environ. Qual. 2013 42 1059-1069. 

Sass RL, Fisher FM, Harcombe PA, Turner FT. Mitigation of methane emissions from rice fields Possible adverse effects of incorporated rice straw. Global Biogeochem. Cyc. 1991 5 275-287. 

Sass RL, Andrews JA, Ding A, Fisher FM. Spatial and temporal variability in methane emissions from rice paddies Implications for assessing regional methane budgets. Nutr. Cycl. Agroecosys. 2002 64 3-7. 

Lindau CW, Bollich PK. Methane emissions from Louisiana first and ratoon crop rice. Soil Sci. 1993 156 42-48. 

Lindau CW, Bollich PK, DeLaune RD. Effect of rice variety on methane emission from Louisiana rice. Agric. Ecosys. Environ. 1995 54 109-114. 

Fitzgerald GJ, Scow KM, Hill JE. Fallow season straw and water management effects on methane emissions in California rice. Global Biogeochem. Cycl. 2000 14 767-776. 

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