Methane And The Sustainability Of Ruminant Livestock

Generated Summary

This document, a building block from the Food Climate Research Network (FCRN), explores the complex relationship between ruminant livestock, methane emissions, and climate change. It delves into the challenges of comparing different greenhouse gas emissions, particularly the limitations of the Global Warming Potential (GWP) 100 metric, and introduces the alternative GWP* metric. The document aims to provide a nuanced understanding of how methane emissions from ruminant livestock contribute to global warming, the implications of different emission metrics, and the potential for climatically sustainable food systems. It emphasizes the need to consider various factors beyond methane, including other greenhouse gas emissions (CO2 and N2O), land use, and societal concerns. The document further examines the current and projected trends in ruminant methane emissions and the broader context of livestock production and sustainability, highlighting the need for a holistic approach to address climate change and ensure food system resilience.

Key Findings & Statistics

• The document refers to a study where in the UK, across both production methods, ruminant systems had lower CO2 emissions per kg protein than monogastric systems, but greater emissions of N2O.
• Globally, livestock production contributes to about 14.5% of annual greenhouse gas emissions, with methane accounting for about 44% of this.
• 39.1% of total livestock emissions are from enteric fermentation methane alone.
• Reducing CH4 emissions by less than 24-47% below 2010 levels by 2050 would mean that global CO2 emissions will have to decline even faster to meet this temperature objective.
• The GWP100 of methane is 28.
• The document cites a study where it was found that the emission from cattle is 6.54, sheep is 4.82, pigs is 0.68 and chicken is 0.02
• In the study, the CO2 emission from cattle is 65, sheep is 21, pigs is 25 and chicken is 26.
• Also in the study, N20 emission from cattle is 0.22, sheep is 0.20, pigs is 0.04 and chicken is 0.03.
• In Western Europe, the data shows that in cattle, methane is 2.59, sheep is 2.50, pigs is 0.46 and chicken is 0.02.
• CO2 emissions in Western Europe for cattle is 26, for sheep is 20, for pigs is 27 and for chicken is 24.
• N2O emissions in Western Europe for cattle is 0.12, for sheep is 0.09, for pigs is 0.04 and for chicken is 0.02.
• In the UK, the methane emission from conventional cattle is 1.67, sheep is 3.57, pigs is 0.22 and chicken is 0.02.
• CO2 emissions in the UK from conventional cattle is 11.55, sheep is 15.32, pigs is 16.89 and chicken is 21.52.
• N2O emissions in the UK from conventional cattle is 0.12, sheep is 0.11, pigs is 0.04 and chicken is 0.04.
• The methane emission from organic cattle is 1.91, sheep is 3.69, pigs is 0.08 and chicken is 0.02.
• CO2 emissions from organic cattle is 10.35, sheep is 11.51, pigs is 10.51 and chicken is 20.19.
• N2O emissions from organic cattle is 0.08, sheep is 0.09, pigs is 0.05 and chicken is 0.05.

Other Important Findings

• The document highlights that methane has a shorter lifespan than CO2, and its climate impacts are primarily dependent on the ongoing emissions rate.
• The GWP100 metric does not fully capture the complexities of different emissions, and it can sometimes fail to represent certain dynamics.
• The GWP* is based on the observation that the overall dynamics of how sustained emissions of different gases contribute to global temperature change cannot be represented by any simple means of weighting individual emissions.
• The study suggests that organic production could provide lower emission footprints than conventional systems, and the lower CO2 emissions for organic ruminant systems is particularly notable.
• The document also mentions the potential opportunity cost in not using land for other climate mitigation purposes, including for carbon capture and/or bioenergy, or for other reasons such as biodiversity conservation.
• The impacts of ruminant production also extend beyond climate change.
• The document suggests that halting land expansion, especially in sensitive ecoregions is imperative in order to halt the decline of biodiversity.

Limitations Noted in the Document

• The document acknowledges limitations in emission metrics, including the GWP100.
• The impact of different production methods are highly variable and dependent on the specific management of individual systems, with large ranges in relative performance between organic and conventional systems.
• The study highlights that the emission reduction would be negated by the CO2 generated by additional land-use change required if we wanted to maintain the same meat output.
• The document states that some stakeholders conflate emission metrics with climate science and may mistakenly believe that new metrics completely overturn our understanding of atmospheric physics.
• The document highlights that the climate principles discussed below apply to any biogenic source of methane, however, and for food system sustainability could also be considered in the context of rice production and consumption.

Conclusion

The document emphasizes the need to consider methane emissions within a broader context that includes other greenhouse gases, land use, and societal concerns to address climate change and ensure food system sustainability. The document underscores the importance of reducing emissions from all sectors and the need to recognize that different emission reduction strategies may be required. The study suggests that organic production could provide lower emission footprints than conventional systems, and the lower CO2 emissions for organic ruminant systems is particularly notable. The document also mentions the potential opportunity cost in not using land for other climate mitigation purposes, including for carbon capture and/or bioenergy, or for other reasons such as biodiversity conservation. It stresses that achieving ‘net zero’ emissions is the ultimate requirement, but the speed with which we get there is also key. The sooner we start reducing CO2 emissions, and the faster we reach net zero, the lesser the long-term warming we will have from CO2 that has accumulated in the atmosphere. The document recognizes that a sustained rate of methane from an activity such as ruminant production may be compatible with our 1.5-2°C temperature goals. However, the study stresses that this may not be enough and that global ruminant methane emissions at today’s levels would require those of us in, for example, Europe, the Americas and Oceania who already eat much more than the global average to reduce our consumption. Furthermore, current trends indicate that stabilization is in any case not on the cards. Therefore, it is critical to prioritize the reduction of emissions from both agriculture and transport. It concludes by suggesting that a more nuanced perspective could reveal a potential climatically sustainable space for ruminant production that may appear impossible under conventional ways of considering ‘equivalence’ between different emissions and net-zero emissions targets. The document makes it clear that this space is still limited, and not compatible with ever-increasing demand for ruminant products.