Foodsource Building Block. 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 methane emissions from ruminant livestock and their impact on climate change. It provides an overview of the challenges in comparing different greenhouse gas emissions, with a specific focus on the Global Warming Potential (GWP) and its limitations, and introduces the concept of GWP*. The study examines the contribution of methane to global warming, the current trends in ruminant methane emissions, and the broader context of food system sustainability. The study aims to clarify how the impacts of different greenhouse gas emissions are often expressed using shorthand emission metrics, and why there can be considerable variation in how we report and think about different gases relative to each other using different metric concepts, and how methane should be thought about relative to CO2. The methodology involves a review of climate science, policy considerations, and practical implications related to emissions from livestock production.

Key Findings & Statistics

• The document indicates that livestock production accounts for approximately 14.5% of annual greenhouse gas emissions.
• Methane accounts for roughly 44% of livestock emissions.
• 39.1% of total livestock emissions are from enteric fermentation methane alone.
• To keep global warming to 1.5-2°C, the document suggests a rapid decrease of emissions from all sectors is needed.
• It notes that global CO2 emissions must reach net-zero to stop temperature increases.
• Reducing agricultural methane emissions by 24-47% below 2010 levels by 2050 is a goal from the IPCC Special Report.
• The document presents data indicating that the projections are for an increase in ruminant production, which translates into increases in methane (and other) emissions.
• Data from the FAO Global Livestock Environmental Assessment Model (GLEAM) is referenced.
• The document notes that organic livestock systems in the UK tend to be extensive.
• Conventional systems in the UK span a range of more extensive and intensive systems.
• The document highlights the fact that there is likely to be very considerable variation by specific production system and country.
• Table 1 indicates the emissions (kg) of methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) from production of 1kg of protein from average Global and Western European cattle, sheep, pig and chicken production (aggregated across all types of production system).
• Table 2 indicates the emissions (kg) of methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) from production of 1kg of protein from organic and conventional cattle, sheep, pig and chicken in the UK.

Other Important Findings

• The document emphasizes the importance of understanding the limitations of the GWP100 metric when assessing the impact of methane emissions.
• It highlights the differences between methane and CO2 in terms of their atmospheric lifespans and warming effects.
• It introduces GWP* as an alternative metric to represent how methane emissions affect global temperatures.
• The analysis suggests that the rate of methane emissions is more important than the total amount emitted in determining its impact on temperature.
• The document discusses the potential of reducing methane emissions to increase the amount of CO2 that can be emitted while remaining under temperature limits.
• It notes the link between livestock production, land use change, and biodiversity loss.
• The document suggests that in the context of food system methane emissions, misunderstanding the dynamics can sometimes lead to unhelpful framings of the food problem.
• It explores the potential of different production systems (intensive vs. extensive) and their associated emissions.
• It discusses the potential benefits of reducing methane emissions in terms of climate benefit, emphasizing that the climatic benefit of a sustained decrease in methane emissions is highlighted more sharply than from GWP100.

Limitations Noted in the Document

• The document acknowledges that concepts of ‘equivalent emissions,’ while derived from physical climate science, are not generally used in physical climate science itself.
• It recognizes that concepts of emission metrics, while derived from physical climate science, are not generally used in physical climate science itself.
• The document acknowledges that all metrics have shortcomings, and choices contain value judgments.
• The document does not elaborate further on the dynamics of N2O emissions.
• It is important to highlight the authors’ conclusion, particularly in light of the discussion below, that this 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 notes that the climate principles discussed below apply to any biogenic source of methane.
• The document notes that in this piece, they focus on ruminant livestock, as debates over the framing of methane have been especially prominent here.
• The document recognizes that the climate models mentioned above which are used to study and predict climate change are based either on emissions of individual gases with individual, distinct properties, or changes to total radiative forcing inferred from emission pathways.

Conclusion

The primary takeaway from this ‘Building Block’ is the nuanced understanding of methane emissions, and how they contribute to global warming and the importance of moving beyond GWP100 metrics to assess the impact of methane. The authors emphasize that simply using GWP100 can be misleading and may not accurately represent the true impact of different greenhouse gases. The study highlights that the rate of methane emissions, rather than just the total amount, is critical in determining its impact on global temperatures. This shift in perspective could reveal a potential for climatically sustainable space for ruminant production that might appear impossible under conventional ways of considering ‘equivalence’ between emissions and net-zero emissions targets. The document strongly emphasizes that global CO2 emissions must reach net-zero to stop temperature increases, and while some ongoing methane emissions may be able to give no further temperature increases, any emissions from the livestock sector will continue to contribute to our elevated temperatures. The document also calls for a reduction in consumption in high-consuming countries to make climate goals more attainable, suggesting a shift in dietary choices will have a positive impact. The document concludes with the idea that despite the harms of the livestock sector on climate change, this sector can also contribute to sustainable levels with reduced emission measures and also reducing consumption. The analysis also emphasizes the interconnectedness of various environmental concerns associated with ruminant production, including land-use change and biodiversity loss. The authors underscore that focusing solely on methane can lead to a narrow view, and a broader perspective is needed to address all environmental and societal concerns. In the context of food system sustainability, the document urges a move away from the traditional framing of the food problem and highlights the need to consider the complete picture, including the social and economic factors. The study ultimately recommends reductions in consumption of livestock products, in addition to technological and production-based strategies.