Amid the often-distressing news about climate change, some good news: Existing strategies could mitigate livestock methane emissions by enough to help the sector limit its share of global warming to the 1.5°C target by 2030.
In a meta-analysis published in The Proceedings of the National Academy of Sciences (PNAS), Claudia Arndt, Leader of the Mazingira Centre at the International Livestock Research Institute in Kenya, and a score of experts from top-level institutes around the world reviewed hundreds of peer-reviewed studies for strategies designed to decrease product-based and absolute enteric methane emissions by ruminants. The research was initiated by Alexander N. Hristov at Penn State University. They found that livestock production could help meet the 1.5°C target by 2030—with the provision that the identified most effective product-based and the most effective absolute mitigation strategies be fully adopted, a goal that would require concerted action to identify and remove adoption barriers.
However, scientists caution that to stay on track by 2050, additional strategies will be needed due to a projected increased demand in livestock products. Thus, current strategies can meet short-term targets, but further research is needed to develop strategies sufficient to meet longer-run targets.
Microbes in the digestive tract of ruminants decompose and ferment feed, a process called enteric fermentation, producing methane as one of the by-products. The world’s >3 billion ruminants belch out the methane, contributing 30% of global anthropogenic methane emissions. Ruminants provide about half the animal protein produced by livestock. In low- and middle-income countries (where 84% of the world’s population live), consumption of animal-source foods is often below recommended dietary levels. In these countries, ruminant livestock play a critical role in food security and provide a host of other benefits such as traction and manure for fuel and fertiliser. In contrast, in high-income countries, the consumption of animal protein is often above recommended levels.
Because of ruminants’ multiple uses and their contribution to the Sustainable Development Goals, the authors focused on strategies that reduce enteric methane production without reducing animal productivity.
They identified three strategies that could reduce methane emission per unit of meat or milk on average by 12% while increasing animal productivity. The strategies were increasing feed intake level, having ruminants graze on less mature grass, and feeding increasing levels of concentrate. In addition, they identified five strategies that could reduce not only product-based on average by 17% but also absolute methane emissions on average by 21%, while maintaining animal productivity. The strategies include supplementing animals with methane inhibitors, oils and fats, oilseeds, or nitrate (electron acceptors) as well as feeding tanniferous forages.
The authors also looked at how the implementation of the identified strategies could help to reduce global, European and African methane emissions by livestock. They found that the full adoption of the most effective strategies could help meet the global 2030 but not the 2050 target. In Europe, they found multiple scenarios that did not require full adoption of the most effective strategies to meet the 2030 targets and that full adoption of the most effective strategies could meet the 2050 target. In Africa, by contrast, even though substantial reductions could be achieved, the identified strategies would not be sufficient to fully meet either the 2030 or 2050 target. This is because of Africa’s growing human population and per capita demand for animal products, which are expected to lead to a substantial increase in livestock production and greenhouse gas emissions. Still, its projected increase will be below European per capita demand.
‘The paper shows that there are effective strategies to reduce enteric methane emissions which can help meet the global 1.5°C target by 2030 but not 2050. As complete adoption of the most effective strategies by 2030 is unlikely and the target cannot be reached by 2050 with the identified strategies, other proposed means of decreasing methane emissions are necessary. Such strategies could be to remove emissions from the supply and demand side in the livestock sector’, said ILRI scientist Claudia Arndt.
The work was completed by the Feed and Nutrition Network of the Global Research Alliance on Agricultural Greenhouse Gases and started by funding through the GLOBAL NETWORK project, a multi-national initiative funded by the Joint Programming Initiative on Food Security, Agriculture, and Climate Change.
The International Livestock Research Institute (ILRI) is an international non-profit institution working to improve food and nutrition security and reduce poverty in low- and middle-income countries countries through research for efficient, safe and sustainable use of livestock. Co-hosted by Kenya and Ethiopia, ILRI has another dozen regional or country offices in East, South and Southeast Asia as well as Central, East, Southern and West Africa. ILRI is a part of ‘One CGIAR’, a newly reformulated global agricultural innovation network of 11 research centres working in close collaboration with hundreds of partners across the globe to achieve a food-secure future for all. Visit us at Ilri.org or follow us on Twitter at @ilri.org.
Penn State is one of the top educational institutions internationally, consisting of 24 campuses, 17,000 faculty and staff, 100,000 students, a teaching hospital, more than 500,000 active alumni and an online World Campus. Penn State’s interdisciplinary researchers solve problems that impact the world. Fifteen disciplines — from psychology to atmospheric science and materials engineering — rank nationally in the top 10 for research expenditures. Penn State is one of just two institutions in the U.S. accorded Land Grant, Sea Grant, Sun Grant and Space Grant status.
The research was performed by 24 scientists from 16 institutes:
International Livestock Research Institute (ILRI), Nairobi 00100, Kenya; The Pennsylvania State University, University Park, USA; University of Idaho, Moscow, USA; Colorado State University, Fort Collins, USA; Wageningen University and Research, Wageningen, The Netherlands; Natural Resources Institute Finland (Luke), Helsinki, Finland; University of Reading, Earley Gate, Reading, UK; INRAE, UCA-VAS, UMRH Centre ARA, Saint-Genès-Champanelle, France; University of California, Davis, USA; ETH Zurich, Zürich, Switzerland; Teagasc, AGRIC, Grange, Ireland; SRUC, Edinburgh, United Kingdom; Norwegian University of Life Sciences, Aas, Norway; De Heus Animal Nutrition, Ede, The Netherlands; Estación Experimental del Zaidín, CSIC, Granada, Spain; The Ohio State University, Columbus, USA.
Proceedings of the National Academy of Sciences
Method of Research
Subject of Research
Full adoption of the most effective strategies to mitigate methane emissions by ruminants can help meet the 1.5 °C target by 2030 but not 2050
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