Methane emissions are increasingly identified as a turbocharged driver of the climate crisis, catalyzing interest in how they can be mitigated in key agricultural sectors.
To bolster awareness of possible actions that can be taken, and support members with a menu of solutions, the Food and Agriculture Organization of the United Nations (FAO) published last September 25 “Methane emissions in livestock and rice systems. Sources, quantification, mitigation and metrics.”
The report was put together by a multidisciplinary team composed of 54 international scientists and experts of the Livestock Environmental Assessment and Performance (LEAP) Partnership hosted at FAO since 2012. It offers a comprehensive overview and analysis of methane emissions in livestock and rice systems.
It focuses on both the sources and sinks of methane gas, outlines how emissions can be measured, describes a broad sampling of mitigation strategies, and evaluates the kind of metrics that can be used to measure both emissions and their mitigation on the climate system.
“The results and recommendations of this report bolster the efforts of countries and stakeholders committed to reducing methane emissions and, in so doing, move us towards more efficient, inclusive, resilient, low-emission and sustainable agrifood systems,” said FAO Deputy Director-General Maria Helena Semedo in report’s foreword.
Methane accounts for about 20 percent of global greenhouse gas emissions and is more than 25 times as potent as carbon dioxide at trapping heat in the atmosphere.
Methane emissions from anthropogenic activities currently contribute about 0.5 degrees Celsius to observed global warming, making their reduction an important pathway to achieve the Paris Agreement.
The report aims to help enable agrifood systems to contribute their share to the Global Methane Pledge, a non-binding initiative endorsed by more than 150 countries to decrease methane emissions by 30 percent from 2020 levels by 2030, which would avoid more than 0.2 degrees Celsius of average global temperature increase by 2050.
FAO said the work is in line with its Strategy on Climate Change and the Strategic Framework 2022-2031, both of which aspire to reducing greenhouse gas emissions through a holistic mix of better production, better nutrition, a better environment and a better life—the Four Betters.
Besides agrifood systems, other human activities that generate methane emissions include landfills, oil and natural gas systems, coal mines and more. About 32 percent of global anthropogenic methane emissions result from microbial processes that occur during the enteric fermentation of ruminant livestock and manure management systems, while another 8 percent comes from rice paddies.
FAO said one of the trickiest issues with methane is how its emissions and inventories are measured, evidently a critical factor in determining the best mitigation pathways.
“Precise methods have been developed, often involving placing animals in respiration chambers, but they are expensive, labor-intensive, and difficult to apply to grazing animals. Sophisticated use of drones and satellites has been deployed, but this approach entails much modeling and research is lagging behind in validating these methods,” the report read.
“Moreover, enteric methane emissions can vary substantially between animals of the same species, opening a role for genetic selection as well as dietary innovation in livestock feed.”
Another key environmental factor is how local soils serve as a methane sink. Research summarized in the report indicates that upland forest soils are the most efficient at this, especially in temperate biomes, with storage rates four times as great as that of cropland, and that dry grazing lands have a notably higher uptake rate than moist grazing lands.
“Those findings could point to the merits of sylvopastoral approaches such as that deployed in a Globally Important Agricultural Heritage System in Portugal.”
FAO said more empirical data and systematic measurement standards will help craft better tailored local mitigation approaches.