Animal Production: Reducing Greenhouse Gas Emissions

The raising of Livestock for human consumption produces a significant amount of greenhouse gases and contributes significantly to global warming. However, taking into account the latest projections from the Intergovernmental Panel on Climate Change (IPCC), a new study shows that the sector’s emissions intensity has been declining globally over the past two decades thanks to more efficient production methods. While adopting a vegetarian diet can reduce one’s carbon footprint, improving the efficiency of livestock farming is an even more effective strategy for reducing methane emissions on a global scale.   The livestock sector, which supplies the world with meat, eggs, and dairy products, has a significant environmental cost. In fact, it is the largest source of anthropogenic methane emissions worldwide, accounting for one-third of global emissions. And the growing demand for products of animal origin, particularly in developing countries, will only amplify its impact. Methane is thus the most abundant human-made greenhouse gas after carbon dioxide (CO₂) and has a warming potential 28 times greater per kilogram than that of CO₂ over a century. According to the FAO, methane emissions from livestock increased by more than 50% between 1961 and 2018 and are expected to continue rising along with demand. However, a new study challenges this assessment. Following the recent revision of the IPCC’s methodology and emission factors, 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, 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 examined the intensity of methane emissions from livestock 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 emission intensity actually decreased between 2000 and 2018. Advances in agriculture have made it possible to produce meat, eggs, and milk with an increasingly smaller methane footprint. A regional analysis, however, provided a more nuanced picture, showing that while emission intensities may be decreasing overall, regional differences persist. Some countries that lack access to advanced technologies continue to produce large quantities of greenhouse gases. Variations in emission intensity can be explained in particular by differences in productivity, linked, for example, to differences in animal diets, grazing intensity, or climate. A less nutritious or digestible diet (low in protein and high in fiber), combined with more extensive grazing (particularly 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 the researchers, reducing 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 adopting vegetarian diets or reducing human consumption of livestock products. According to projections for 2050, sustainable diets are expected to result in 190 to 206 tetragrams (Tg) fewer methane emissions, representing a 3 to 4 percent reduction in cumulative emissions from 2012 to 2050. In contrast, improving production systems would result in 821 to 1,077 Tg fewer methane emissions, representing a 15 to 16 percent decrease in total emissions. Working toward production systems with lower methane emissions would therefore have four times the mitigation potential compared to simply reducing meat consumption. These efforts should therefore be a priority, particularly in developing countries. In this regard, China, India, and South Africa emerged as the three countries with the highest mitigation potential. However, the researchers emphasize that this does not mean they support industrial livestock farming, which could be perceived as a solution to reducing methane emissions from livestock. In fact, intensive farming causes many other environmental problems, such as pollution resulting from poor manure management. There are other, more sustainable ways to improve current systems, in line with the natural conditions of the regions concerned and without causing a loss of biodiversity, environmental pollution, or climate impacts.