Available online at www.sciencedirect.com Greenhouse gas mitigation in animal production: towards an integrated life cycle sustainability assessment IJM de Boer 1 , C Cederberg 2 , S Eady 3 , S Gollnow 4 , T Kristensen 5 , M Macleod 6 , M Meul 7 , T Nemecek 8 , LT Phong 9 , G Thoma 10 , HMG van der Werf 11 , AG Williams 12 and MA Zonderland-Thomassen 13 The animal food chain contributes significantly to emission of greenhouse gases (GHGs). We explored studies that addressed options to mitigate GHG emissions in the animal production chain and concluded that most studies focused on production systems in developed countries and on a single GHG. They did not account for the complex interrelated effects on other GHGs or their relation with other aspects of sustainability, such as eutrophication, animal welfare, land use or food security. Current decisions on GHG mitigation in animal production, therefore, are hindered by the complexity and uncertainty of the combined effect of GHG mitigation options on climate change and their relation with other aspects of sustainability. There is an urgent need to integrate simulation models at animal, crop and farm level with a consequential life cycle sustainability assessment to gain insight into the multidimensional and sometimes conflicting consequences of GHG mitigation options. Addresses 1 Animal Production Systems Group, Wageningen University, P.O. Box 338, 6700 AH, Wageningen, The Netherlands 2 SIK, The Swedish Institute of Food and Biotechnology, P.O. Box 5401, 402 29 Gothenburg, Sweden 3 CSIRO Livestock Industries, Locked Bag 1, Armidale, NSW 2350, Australia 4 University of Hohenheim, Institute of Agricultural Farm Management (410b), D-70593 Stuttgart, Germany 5 Dept. of Agroecology and Environment, University of Aarhus, Faculty of Agricultural Sciences, PO Box 50, DK-8830 Tjele, Denmark 6 Animal Production and Health Division, Food and Agriculture Organization, Viale delle Terme di Caracalla, 00100 Rome, Italy 7 Department of Animal Production, University College Gent, Valentin Vaerwyckweg 1, B-9000 Gent, Belgium 8 Agroscope Reckenholz-Ta¨ nikon, Research Station ART, CH-8046 Zurich, Switzerland 9 Crop Sciences Department, Can Tho University, 3-2 Street, Cantho City, Viet Nam 10 Department of Chemical Engineering, University of Arkansas, WCOB 475, Fayetteville, AR 7270, USA 11 INRA, UMR 1069, Sol Agro et HydroSyste` me, 350000 Rennes, France 12 Natural Resource Department, Cranfield University, Bedfordshire MK43 0AL, United Kingdom 13 Agresearch Limited, Ruakura Research Centre, Hamilton, New Zealand Corresponding author: de Boer, IJM (Imke.deBoer@wur.nl) Current Opinion in Environmental Sustainability 2011, 3:423–431 This review comes from a themed issue on Carbon and nitrogen cycles Edited by Carolien Kroeze and Lex Bouwman Received 16 May 2011; Accepted 15 August 2011 Available online 9th September 2011 1877-3435/$ – see front matter # 2011 Elsevier B.V. All rights reserved. DOI 10.1016/j.cosust.2011.08.007 Introduction Livestock production is recognized to contribute signifi- cantly to emission of greenhouse gases (GHGs, Figure 1), mainly through emission of carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O) [1  ]. CO 2 is released from combustion of fossil fuels to power machin- ery, from burning of biomass, and from microbial decay related to, for example, changes in land use or in crop management [2]. CO 2 can be sequestered also by trans- forming arable land into permanent grassland. CH 4 is produced when organic matter decomposes in oxygen- deprived conditions, for example, during enteric fermen- tation (especially in ruminants) and storage of manure [3]. CH 4 is also inadvertently released during fossil fuel extraction and refining. N 2 O is released during microbial transformation of nitrogen in the soil or in manure (i.e. nitrification of NH 4 + into NO 3  , and incomplete deni- trification of NO 3  into N 2 ; [4]) as well as during nitrate fertilizer production. Policy makers across the world are increasingly aware of the need to tackle livestock-related GHG emissions. The Global Research Alliance on agricultural GHGs was launched in December 2009 alongside the UN climate conference in Copenhagen. It brings together more than 30 countries to find ways to grow more food without increasing GHG emissions from agriculture (www.globalresearchalliance.org). To reach this goal, the Alliance promotes active exchange of data, people and research across member countries, of which this paper is an example in the field of live- stock production. The research literature on GHG mitigation in livestock production can be broadly classified in the following, partly overlapping, categories: first, improving efficiency in crop or animal production; second, reducing enteric CH 4 emissions; third, reducing emissions from manure management; fourth, sequestering of soil carbon; fifth, changing human consumption of animal-source food (ASF) [5,6  ,7]. www.sciencedirect.com Current Opinion in Environmental Sustainability 2011, 3:423–431