Review Methane capture from livestock manure S.M. Tauseef, M. Premalatha, Tasneem Abbasi * , S.A. Abbasi 1 Centre for Pollution Control and Environmental Engineering, Pondicherry University, Chinnakalapet, Puducherry 605 014, India article info Article history: Received 12 January 2012 Received in revised form 3 November 2012 Accepted 24 December 2012 Available online 30 January 2013 Keywords: Livestock manure Anaerobic digesters Methane capture Global warming abstract It has been estimated that livestock manure contributes about 240 million metric tons of carbon dioxide equivalent of methane to the atmosphere and represents one of the biggest anthropogenic sources of methane. Considering that methane is the second biggest contributor to global warming after carbon dioxide, it is imperative that ways and means are developed to capture as much of the anthropogenic methane as possible. There is a major associated advantage of methane capture: its use as a source of energy which is comparable in ‘cleanness’ to natural gas. The present review dwells upon the traditional ways of methane capture used in India, China, and other developing countries for providing energy to the rural poor. It then reviews the present status of methane capture from livestock manure in developed countries and touches upon the prevalent trends. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction: generation of methane by the ruminant animals Ruminant animals (cattle, buffalo, sheep, goat, and camel) produce significant amounts of methane as part of their normal digestive process. In the rumen (large fore-stomach) of these animals, microbial fermentation converts their feed into products that can be digested and utilized by the animal. This microbial fermentation process (enteric fermentation) produces methane as a by-product, which is exhaled by the animal. The other major manure-related contribution to global warming is by swine droppings. The demand of pork products is expected to increase by 28% over the next decade (FAPRI, 2010), with proportionate increase in the swine population e consequently, in the quan- tities of their manure. Methane is also produced in smaller quantities by the digestive processes of other animals, including humans, but emissions from these sources are insignificant (USEPA, 2011a). Whereas the methane that is exhaled by the ruminant animals is impossible to capture, a large proportion of methane produced by the manure of these animals can be captured. Livestock manure keeps releasing methane due to the anaerobic decomposition of organic material contained in the manure by bacteria exited along with the manure from the animal (Chhabra et al., 2009). Manure deposited on fields and pastures also produces significant amounts of methane. Manure lagoons and holding tanks, which are com- monly used at larger dairy and swine operations, also release sig- nificant quantities of methane (Wiedemann et al., 2010; Aneja et al., 2009). Manure-based methane has been estimated to contribute 4% of all anthropogenic methane that is presently being added up to other natural and anthropogenic sources of global warming (USEPA, 2006). The world’s livestock population has been rising (Fig. 1); the rate of increase is particularly sharp in the two most populous countries of the world e China and India (Fig. 2). The overall livestock-based methane emissions are projected to increase to the extent of 16.5% by 2030 from their 2005 level (Fig. 3). The increase is expected to be particularly high in Africa, Central and South America and the Middle East. Even as, historically, the largest portion of GHG emissions from manure management have been from the countries belonging to the Organization for Economic Cooperation and Development (OECD), which accounted for 43% of all emissions in 2005, these emissions are projected to increase by just 1% between 2005 and 2030. In contrast, the expected growth rates are significantly higher in Africa (43%), non-OECD Asia (39%), Middle East (10%), and Central and South America (30%). Interestingly, despite the rapidly increasing methane con- tribution from these countries, the OECD would remain the top emitting region even in 2030. The 2.3% decrease seen between * Corresponding author. Tel.: þ91 97514 68491; fax: þ91 413 2655263. E-mail addresses: tasneem.abbasi@gmail.com (T. Abbasi), prof.s.a.abbasi@ gmail.com (S.A. Abbasi). 1 Tel.: þ91 94432 65262; fax: þ91 413 2655263. Contents lists available at SciVerse ScienceDirect Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman 0301-4797/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jenvman.2012.12.022 Journal of Environmental Management 117 (2013) 187e207