Methane has been found to be the primary contributor to the formation of ground-level ozone, a hazardous air pollutant and greenhouse gas, exposure to which causes 1 million premature deaths every year. Over a 20-year period, the methane gas has been predicted to be 80 times more potent at greenhouse warming than carbon dioxide. Researchers have now found that the adoption of 100 per cent of the most effective strategies for reducing methane emissions from cows and other ruminants can meet methane reduction targets by the year 2030 to help keep global warming to 1.5 degree Celsius above pre-industrial levels, but the same strategies are insufficient to reach methane reduction goals for 2050 due to projected increased demand in livestock products.
Claudia Arndt from the International Livestock Research Institute in Kenya’s Nairobi, along with her colleagues analyzed the effects of published strategies for mitigating methane emissions from ruminant livestock systems.
The authors found that three feed management practices could reduce methane emissions per unit of meat or milk on average by 12 per cent while increasing animal productivity.
In addition, the authors found that five mitigation strategies could reduce methane emissions per unit of meat or milk as well as absolute methane emissions on average by 21 per cent.
According to the study published in PNAS, disparities among high-income, middle-income, and low-income countries mean that high-income regions may be able to meet their methane reduction goals through the adoption of the effective mitigation strategies, whereas middle-income to low-income regions may not be able to do so.
Global food systems contribute up to 30 per cent of global greenhouse gas (GHG) emissions. The Paris Agreement’s goal of limiting global warming to 1.5°C above pre-industrial levels is unlikely to be achieved if food systems continue to operate under a business-as-usual (BAU) scenario.
Among food-related GHG emissions, methane (CH4) from livestock contributes 30 per cent of the global anthropogenic CH4 emissions, 17 per cent of the global food system GHG emissions, and 5 per cent of global GHG emissions. Of the global livestock CH4 emissions, 88 per cent are contributed by enteric fermentation.
Methane or CH4 is a short-lived climate pollutant. Given its perturbation lifetime in the atmosphere of around 12.5 years, it contributes significantly to near-term global warming.
Its global warming potential is 84 or 28 for 20- or 100-year time horizons, respectively.
When evaluating the contribution of global food systems to CH4 emissions over a 20-year period instead of the commonly used 100-year time period for national GHG inventories, the contribution of CH4 to food system GHG emissions more than doubles, from 17 to 36 per cent.
Achieving nationally determined contributions and climate-neutral targets in 2050 depends on reducing methane emissions.
In the context of sectoral reduction of methane emissions, technical solutions to reduce methane from agricultural production, especially strategies to reduce methane from enteric fermentation by ruminant livestock are an important part of achieving these climate goals. However, there is little quantitative data on the potential for reduction. Based on 2010 GHG emission levels and different mitigation scenarios to limit global warming to 1.5 °C, agricultural CH4 emissions need to be decreased by 11 to 30 per cent by 2030 and by 24 to 47 per cent by 2050.
The global population is projected to increase by 23 per cent between 2010 and 2030, with most of the increase occurring in low- and middle-income countries (LMIC).
Ruminants contribute about half of the animal protein produced by livestock. In LMIC, ruminants play an important role in food security. Ruminants can convert foods that are inedible to humans, such as pasture foods and cereal by-products produced on marginal lands or from subsistence agricultural production systems, into nutritionally dense human-edible foods.
Ruminants also provide other benefits, such as traction and manure for fuel and fertilizer. In addition, human population growth is generally high in LMIC, while consumption of animal source foods is often below dietary recommendations or reliant on ruminant meat and milk for livelihood and nutrition security.
Thus, from a feed-food competition perspective, ruminant production increases in LMIC should rely on human inedible feeds (i.e., forage and by-products). In contrast, in high-income countries (HIC) population growth is much lower and the consumption of animal protein is often above recommended dietary levels.
first published:May 12, 2022, 7:50 p.m.