Livestock sector has a history of decreasing emissions

Science Notes: The intensity of emissions is decreasing, but regional differences remain

Variations in methane-producing intensity are mainly attributed to differences in productivity, including the nutrition and digestibility of livestock diet.

A new study shows that emission intensity per unit of animal protein produced has decreased globally over the past two decades due to greater production efficiency.

Despite concerns about the environmental cost of livestock production, the global appetite for animal products such as meat, eggs and dairy continues to grow. 

Following the recent revision of the Intergovernmental Panel on Climate Change (IPCC)’s emission factors and methodology for livestock methane emissions, an international team of researchers, led by International Institute for Applied Systems Analysis guest researcher Jinfeng Chang, set out to reassess global livestock methane emissions over the past two decades and project emissions to 2050. 

Their study, published in AGU Advances, is the first to apply the revised IPCC guidelines globally and assess the resulting differences in future projections of methane emissions.

The study’s investigation covered three questions. First, the team wanted to determine the range of 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). 

They also wanted to find out how the intensity of livestock methane emissions has changed over the past few decades, and how these changes differ among countries and regions. 

Third, researchers explored to what extent methane emissions from the livestock sector will change in the future, how much mitigation potential exists and what form it should take, as well as where such mitigation actions might be most effective.

While total emissions for the sector continue to increase, the findings indicate that emission intensity decreased overall for most livestock categories globally between 2000 and 2018 per kilogram of protein in products including milk and meat from cattle, buffalo, 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 include the nutrition and digestibility of the diet. Lower protein and higher fibre, including extensive grazing, resulted in higher emissions.

“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,” said Chang.

“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 to a business-as-usual scenario, resulting in a three to four per cent mitigation of accumulated emissions from 2012 to 2050. Improving efficiency, on the other hand, can result in 821-1,077 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 to 16 per cent.”

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