The concentrations of greenhouse gases in the atmosphere are rising at a rapid rate which the human race has not experienced up to now. Methane which is the most important greenhouse gases after carbon dioxide is currently being paid the most attention. From recent assessments around the world, it is clear that the methane concentration in the atmosphere increased at 0.8-1.0% annually rate within the range of 1.7-1.8ppmv. The amount of emissions each year is presumed to be 410-660Tg, with an annual growth is 35-40Tg. Rapid development of animal agriculture industry has resulted in a remarkable imbalance between the increased amount of animal effluents and cultivated land area to apply them. An absolute shortage of land area to produce animal feed and animal production highly dependent on imported ingredients of concentrates have amplified the imbalance. Excess amounts of the untreated effluent results in high nitrate contamination in underground water and pathogens such as criptosporidium in surface water. The complaints of pollution problems from animal agriculture industry have increased as have the drastic expansion of animal populations in limited areas. In general, the environmentally toxic gases emitted from animal agriculture into the atmosphere does not become a problem as long as neither the odor nor the water pollution problem comes to light. Recognition of influence of methane emitted from animal agriculture on global warming as an environmental concern is still low because the gas is colorless, scentless, and does not pollute water. At last, grappling with the influence of methane emitted from enteric fermentation of farm animals on global warming has begun. The research and technical developments have sought natural manipulators and probiotics to control enteric methanogenesis instead of an anti-organism focus. Meanwhile, the annually accumulated animal effluent was estimated at 85,450,000 t in 1996, exceeding human effluent and organic wastes in Japan. The issues which should be resolved are the development of various technologies for animal effluent management to control offensive odors and wastewater, exploitation of effluent energy use through anaerobic methane fermentation and feeding management to reduce the excretion of nitrogen and phosphorus. Promoting environmentally conscious agriculture which does not rely on the chemical fertilizer can be realized by effective use of liquid manure and compost. Many research projects have been carried out to extract the waste material energy as methane by processes related to animal and organic effluent management. The fuel cell which uses energy derived from animal effluents and organic wastes is being considered as an epoch-making technology.
