Greenhouse gas emissions from livestock: sources, estimation, and mitigation.

The increase in greenhouse gas (GHG) emissions has resulted in climate change and global warming. Human activities in many sectors, including agriculture, contribute to approximately 9.2% of total GHG emissions from Annex I countries. An argument on issues of livestock being the highest contributor to GHG emissions has grown since FAO's 2006 report Livestock's Long Shadow. The issue has continued growing, conflicting the importance of the industry in terms of food security and livelihoods, thus, monitoring GHG emission from this sector is vital. The most commonly used methods for calculating GHG emissions from the livestock sector are life cycle assessment (LCA) and the GHG inventory. Although the LCA presents information on the impacts of the livestock industry on the environment, the GHG inventory is the main tool used internationally for GHG reporting. This review comprehensively discusses the source of GHG emissions from the livestock industry and its estimation methodology, as well as the current strategies for mitigating these emissions.