Marginal costs of abating greenhouse gases in the global ruminant livestock sector

Livestock [inclusive of ruminant species, namely cattle (Bos Taurus and Bos indicus), sheep (Ovis aries), goats (Capra hircus), and buffaloes (Bubalus bubalis), and non-ruminant species, namely pigs (Sus scrofa domesticus) and chickens (Gallus domesticus)] are both affected by climate change and contribute as much as 14.5% of global anthropogenic greenhouse gas (GHG) emissions,most of which is fromruminant animals (Gerber et al. 2013). This study aims to estimate themarginal costs of reducing GHG emissions for a selection of practices in the ruminant livestock sector (inclusive of the major ruminant species-cattle, sheep, and goats) globally. It advances on previous assessments by calculating marginal costs rather than commonly reported average costs of abatement and can thus provide insights about abatement responses at different carbon prices. We selected the most promising abatement options based on their effectiveness and feasibility. Improved grazing management and legume sowing are the main practices assessed in grazing systems. The urea (CO(NH₂)₂) treatment of crop straws is the main practice applied in mixed crop-livestock systems, while the feeding of dietary lipids and nitrates are confined tomore intensive production systems. These practices were estimated to reduce emissions by up to 379 metric megatons of carbon dioxide (CO₂) equivalent emissions per year (MtCO₂-eq yr⁻¹). Two thirds of this reduction was estimated to be possible at a carbon price of 20 US dollars per metric ton of CO₂ equivalent emissions ($20 tCO₂-eq⁻¹). This study also provides strategic guidance as to where abatement efforts could be most cost effectively targeted. For example, improved grazing management was particularly cost effective in Latin America and Sub-Saharan Africa, while legume sowing appeared to work best in Western Europe and Latin America.