Climate: Livestock accounts for one-third of global methane emissions

Raising animals for human consumption produces a significant amount of greenhouse gases and contributes significantly to global warming. However, based on the latest report from the Intergovernmental Panel on Climate Change (IPCC), a new study shows that the emissions intensity of the livestock sector has been decreasing globally over the past two decades thanks to more efficient production methods. While adopting vegetarianism can reduce one’s carbon footprint, mitigating the impact of animal production would be a far more effective strategy for reducing anthropogenic methane emissions on a global scale.   Livestock farming, which meets global demand for meat, eggs, and dairy products, takes a significant toll on the environment. In fact, this sector is the world’s largest source of anthropogenic methane emissions. And the growing demand for products of animal origin, particularly from developing countries, will only amplify its impact on the climate. In fact, methane is the most abundant human-caused greenhouse gas after carbon dioxide (CO2) and contributes to global warming 28 times more per kilogram than CO2 does over a 100-year period. According to the FAO, the Food and Agriculture Organization of the United Nations, methane emissions from livestock farming increased by more than 50% between 1961 and 2018 and are expected to continue rising as demand for products of animal origin grows. Using the methodology and emission factors from the IPCC guidelines, an international team of researchers, led by Jinfeng Chang, set out to reassess global methane emissions from Livestock over the past two decades and to develop projections for 2050. Their study, which was recently published in AGU Advances, is the first to apply the IPCC’s revised guidelines on a global scale and to assess the resulting differences. In particular, the study estimated the methane emission intensity from livestock farming worldwide—that is, the amount of methane released per kilogram of animal proteins produced. The authors found that over the past two decades, the sector’s emissions intensity actually decreased between 2000 and 2018.

Progress and efforts made by the livestock sector have made it possible to produce meat, eggs, and milk with an increasingly smaller methane footprint

However, a regional analysis provided a more nuanced picture, showing that while emissions may be decreasing overall, regional differences persist. Some countries that lack access to advanced technologies continue to produce significant amounts of greenhouse gases. Variations in emission intensity can be explained in particular by differences in productivity, which stem from differences in feed rations and/or grazing intensity, or even climate. A less nutritious or digestible diet (for example, low in protein and high in fiber) combined with greater access to grazing (especially for ruminants) and a warmer climate will lead to higher emissions. For pigs and poultry, manure management accounts for the majority of methane emissions. According to researchers, reducing methane emissions in the livestock sector is a priority for mitigating global greenhouse gas emissions, particularly in a number of countries in Africa, Asia, and South America. Addressing the sources of emissions and optimizing production systems to reduce emissions intensity per unit of protein produced would be even more effective than reducing consumption of livestock products. According to projections for 2050, sustainable diets (balanced, healthy, and environmentally friendly) are expected to result in 190 to 206 teragrams (Tg) in reduced methane emissions, representing a 3–4% reduction in cumulative emissions from 2012 to 2050. In contrast, improving livestock farming practices would result in 821 to 1,077 Tg fewer methane emissions, representing a 15 to 16 percent reduction in total emissions. Working toward cleaner methane-emitting production systems would therefore have four times greater mitigation potential than reducing demand for meat. Efforts to reduce the methane emission intensity of livestock should therefore be a priority, particularly in developing countries such as China, India, and South Africa, which have the highest mitigation potential. Changes in livestock farming practices and productivity gains require sustainable solutions, such as increasing the proportion of grains and/or higher-quality forage in animal feed and optimizing grazing management. According to the authors, improving the efficiency of animal production must always be consistent with the natural conditions of the region where animal production takes place. The optimal strategy must also take into account other relevant sustainability objectives, such as biodiversity, water pollution from manure runoff, and potential implications for the environment and resilience to climate change.