Review Sources and mitigation of methane emissions by sectors: A critical review Izzet Karakurt, Gokhan Aydin * , Kerim Aydiner Karadeniz Technical University, Department of Mining Engineering, Trabzon, Turkey article info Article history: Received 25 September 2010 Accepted 6 September 2011 Available online 17 September 2011 Keywords: Global warming Methane Sectors Mitigation abstract The environmental community rightly recognizes global warming as one of the gravest threats to the planet. Methane (CH 4 ), one of the greenhouse gases causing global warming, is emitted from a variety of sources and its concentration in atmosphere has increased dramatically over the last few centuries. Therefore, the increasing concentrations of methane are of special concern because of its effects on climate and atmospheric chemistry. Anthropogenic sources of methane can be collected under the titles of agriculture, energy, waste and industry on the basis of sectors. This paper aims at examining the past trends in emissions, the sources and mitigation strategies of the methane. As a result of the study, it is determined that the agricultural sector is the biggest source of methane emissions among the sectors. The energy, waste and industry follow the agricultural sources respectively. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Greenhouse gases from burning of fossil fuels, production, trans- portation, conversion and using of energy result in climate changes by affecting the atmosphere chemically in the long term [1,2]. Methane, which is an important greenhouse gas, constitutes 16% of greenhouse gas emissions [3,4]. Although the methane concentration has remained stable for thousands of years, it has doubled in atmo- sphere recently [5]. Although the changing rate is less than the carbon dioxide has, it affects climate change at least as much as carbon dioxide due to its global warming potential (GWP) (Table 1) [5,6]. Methane is formed as a result of decomposition of organic materials in an environment without oxygen. It is released from natural and anthropogenic sources. 40% of global methane emis- sions come from natural sources, whereas 60% of global methane emissions is released from anthropogenic sources. Sources causing anthropogenic methane emissions grouped in Table 2 in sectoral bases [7]. These sectors include agriculture, energy, industry and waste. Fig. 1a shows the contribution of each sector to the total emissions. Additionally, methane release performances of the sectors between 1990 and 2010 respectively are depicted in Fig. 1b. In this study, methane emissions from sectors are analyzed. Emissions and percentage contribution values presented in this study are calculated based on the average emissions between 1990 and 2010 and methane emissions from industry are not dealt since it is highly low (6.30 MtCO 2 eq). The emissions raw data, used in this study, are taken from a report published by EPA (U.S. Environ- mental Protection Agency) [7]. Additionally, various strategies to mitigate methane emissions from each sector are mentioned. 2. Agriculture Methane emissions from agricultural sources are projected to be 3135.75 MtCO 2 eq annually. This value makes the agricultural sector to be the biggest emitter that is responsible for the majority of methane emissions from anthropogenic sources. In other words, 50.63% of anthropogenic methane emissions are released as a result of agricultural activities. Methane emissions from enteric fermen- tation constitute 59.84% of emissions, followed by the emissions from rice cultivation, other agricultural activities and manure management respectively. Fig. 2a illustrates the trend of methane emissions related to the agricultural activities between 1990 and 2010. Percentage change of emissions is at higher level for agri- cultural activities than the emissions from other activities. These emissions have increased significantly after the year of 2000. China is the country that constitutes 15.47% of total emissions in this category. India, Brazil, the United States and other countries given in Fig. 2b follow China respectively in terms of their methane emission release performance. The top ten emitters are responsible for 54.59% of emissions from this category. 2.1. Sources Sources causing methane emissions in agriculture sector can be ranged as enteric fermentation, manure management, rice culti- vation and other agricultures sources. * Corresponding author. Tel.: þ90 462 377 40 98; fax: þ90 462 325 74 05. E-mail address: gaydin@ktu.edu.tr (G. Aydin). Contents lists available at SciVerse ScienceDirect Renewable Energy journal homepage: www.elsevier.com/locate/renene 0960-1481/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.renene.2011.09.006 Renewable Energy 39 (2012) 40e48