Livestock production efficiency mitigates methane emissions

An international team of researchers examining global livestock methane emissions has found that, over the past two decades, the emission intensity per unit of animal protein produced from the livestock production sector has decreased due to greater production efficiency. The finding raises questions about how methane emissions will change in the future and how we can better manage their negative impacts.

The study — led by International Institute for Applied Systems Analysis (IIASA) guest researcher Jinfeng Chang and published in AGU Advances — applies the revised Intergovernmental Panel on Climate Change (IPCC) emission factors and methodology for livestock methane emissions, and assesses the resulting differences in future projections of methane emissions up to 2050.

The livestock sector is the world’s largest source of man-made methane emissions, and these emissions are projected to keep increasing along with the growing demand for livestock products. This is bad news for the planet as methane has a warming effect 28 times greater per kilogram than that of CO₂ over a 100-year period.

The study had three core aims:

1. Determine the range in estimates of livestock methane emissions and emission intensities using the different methodological tiers and versions of the IPCC guidelines (the 2006 version and the more recent 2019 refinement).
2. Find out how the intensity of livestock methane emissions has changed over the past few decades, and how these changes differ among countries/regions.
3. Explore the extent of future changes in methane emissions from the livestock sector — how much mitigation potential exists and what form it should take? Where might mitigation actions be most effective?

While total emissions for the sector continue to increase, the findings indicate that emission intensity actually decreased overall for most livestock categories globally between 2000 and 2018 per kilogram of protein (in products including milk and meat from cattle, buffaloes, goats and sheep; meat from pigs; and meat and eggs from poultry). A regional analysis provided a more nuanced picture, showing that while intensities may be decreasing across the board, regional differences remain.

These variations in intensity can mainly be attributed to differences in productivity, which can in turn be explained by differences in diet and/or grazing intensity, with a less nutritious/digestible diet (eg, low protein and high fibre) and/or more extensive grazing (for ruminants specifically) leading to higher emissions. For pigs and poultry, the management of manure accounted for the majority of methane emissions. Regional differences in emission intensities were also influenced by climate (with warmer climate enhancing emissions) and the manure management system employed.

According to the researchers, a continued overall downward trend in methane emissions from the livestock sector could provide a large potential to mitigate livestock emissions.

“The continuation of the past decreases in emission intensity provides a large potential to mitigate livestock emissions, especially in a number of developing countries in Africa, Asia and South America. Efforts on the demand-side to promote balanced, healthy and environmentally sustainable diets in most countries can mitigate future livestock methane emissions, but will not be sufficient for livestock methane emission mitigation without parallel efforts to improve production efficiency and decrease the emission intensity per unit of protein produced, Chang explained.

According to Chang, efforts to decrease emission intensity should be prioritised in developing countries with the largest mitigation potential, as improving production efficiency has a much greater mitigating effect than demand-side efforts. In this regard, China, India and South Africa emerged as the three countries with the highest mitigation potential.

“From our projections until 2050, sustainable diets are projected to result in 190–206 teragrams (Tg) less methane emissions in total (aggregated from 2012 to 2050) compared with a business-as-usual scenario, resulting in a 3–4% mitigation of accumulated emissions from 2012 to 2050. Improving efficiency, on the other hand, can result in 821–1077 Tg less methane emissions in total than business as usual under constant intensity — a four-fold larger mitigation potential — thus mitigating total emissions by 15–16%,” Chang added.

The researchers emphasised that their findings do not imply that they endorse the industrial livestock system for methane mitigation, as it causes many other environmental problems like pollution from failed manure management, and land-use change for grain and high-quality fodder cultivation. They suggested that there are many other, more sustainable ways to improve efficiency and that improvements to livestock production efficiency should take place in line with the natural circumstances in the respective regions. For example, in semi-arid regions where increasing crop production for feeding livestock is impossible due to water limitations, such as in Central Asia, improving grazing management to increase productivity should be prioritised as a sustainable solution rather than moving from low to industrialised systems.

“An optimal strategy should always consider other relevant sustainability goals like biodiversity, water pollution through nutrient runoff, and the potential implications for livelihoods and resilience to climate change impacts,” Chang concluded.

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