Strategies to mitigate enteric methane emissions by ruminants - a way to approach the 2.0°C target.
Claudia Arndt, A.N. Hristov, William J. Price, Shelby C. McClelland, Amalia Mejia Pelaez, S.F. Cueva, J. Oh, A. Bannink, A.R. Bayat, L.A. Crompton, J. Dijkstra, Maguy Eugène, E. Kebreab, Michael Kreuzer, Mark McGee, Cécile Martin, C. J. Newbold, C.K. Reynolds, Angela Schwarm, K.J. Shingfield, Jolien B. Veneman, David R. Yáñez-Ruíz, Zhong-tang Yu
Abstract
Abstract Ruminant livestock enteric fermentation contributes approximately one-third of the global anthropogenic methane (CH 4 ) emissions and is projected to increase significantly to meet the increasing demand for animal-sourced protein. Methane, a short-lived greenhouse gas, needs to be reduced -24 to -47% by 2050 relative to 2010 to meet the 2.0°C target. This study describes the results of a comprehensive meta-analysis to determine effective mitigation strategies. The database included findings from 425 peer-reviewed studies (1963 to 2018). Mitigation strategies were classified into three main categories [animal and feed management, diet formulation, and rumen manipulation (additives and methods used to modify the rumen)] and up to five subcategories (98 total mitigation strategy combinations). A random-effects meta-analysis weighted by inverse variance was carried out (Comprehensive Meta-Analysis, V3.3.070). Five feeding strategies, namely CH 4 inhibitors, oils and fats, oilseeds, electron sinks, and tanniferous forages, decreased absolute CH 4 emissions by on average -21% (range -12 to -35%) and CH 4 emissions per unit of product (CH 4 I; meat or milk) by on average -17% (range -12 to -32%) without negatively affecting animal production (weight gain or milk yield). Furthermore, three strategies, namely decreasing dietary forage-to-concentrate ratio, increasing feeding level, and decreasing grass maturity, decreased CH 4 I by on average -12% (range -9 to -17%) and increased animal production by on average 45% (range 9 to 162%). The latter strategies are central to meeting the increasing demand for animal-sourced food. All strategies, but CH 4 inhibitors, can be implemented now and offer immediate approaches for combating global warming.