Availability of disaggregated greenhouse gas emissions from beef cattle production: A systematic review

Abstract

Agriculture is a significant source of anthropogenic greenhouse gas (GHG) emissions, and beef cattle are particularly emissions intensive. GHG emissions are typically expressed as a carbon dioxide equivalent (CO 2 e) ‘carbon footprint’ per unit output. The 100-year Global Warming Potential (GWP 100 ) is the most commonly used CO 2 e metric, but others have also been proposed, and there is no universal reason to prefer GWP 100 over alternative metrics. The weightings assigned to non-CO 2 GHGs can differ significantly depending on the metric used, and relying upon a single metric can obscure important differences in the climate impacts of different GHGs. This loss of detail is especially relevant to beef production systems, as the majority of GHG emissions (as conventionally reported) are in the form of methane (CH 4 ) and nitrous oxide (N 2 O), rather than CO 2 . This paper presents a systematic literature review of harmonised cradle to farm-gate beef carbon footprints from bottom-up studies on individual or representative systems, collecting the emissions data for each separate GHG, rather than a single CO 2 e value. Disaggregated GHG emissions could not be obtained for the majority of studies, highlighting the loss of information resulting from the standard reporting of total GWP 100 CO 2 e alone. Where individual GHG compositions were available, significant variation was found for all gases. A comparison of grass fed and non-grass fed beef production systems was used to illustrate dynamics that are not sufficiently captured through a single CO 2 e footprint. Few clear trends emerged between the two dietary groups, but there was a non-significant indication that under GWP 100 non-grass fed systems generally appear more emissions efficient, but under an alternative metric, the 100-year global temperature potential (GTP 100 ), grass-fed beef had lower footprints. Despite recent focus on agricultural emissions, this review concludes there are insufficient data available to fully address important questions regarding the climate impacts of agricultural production, and calls for researchers to include separate GHG emissions in addition to aggregated CO 2 e footprints.

Global food system emissions could preclude achieving the 1.5° and 2°C climate change targets

“…As such, we did not make further assumptions over the ratio of CH 4 : N 2 O from manure emissions (e.g., potential changes over time). Given the importance of separating out CH 4 emissions, we acknowledge that this represents a limitation to our approach, and call for studies to publish emissions as separate gases in the future to facilitate the use of alternative metrics and climate models (38).…”

Plant-Based Meats, Human Health, and Climate Change

“…It must be noted though that not all pasture-based (grass-fed) operations are per se regenerative or neutral, and depending on management practices, grass-fed beef systems can have a higher carbon footprint than some feedlot systems (Pierrehumbert and Eshel, 2015;Lynch, 2019). It is also important to highlight that the amount of carbon sequestered with well-managed grazing of livestock on carbon-depleted soils is initially more rapid and diminishes over time as soil health is restored (Godde et al, 2020), which is not surprising once equilibrium of ecological systems are reached.…”

“…Greenhouse gasses are often lumped together under the umbrella of CO 2 -eq, which equates different GHGs to carbon dioxide (CO 2 ) (Allen et al, 2018). However, different gasses have different global warming potentials (GWP) and their exact values depend on the CO 2 -eq metrics and the timescale (e.g., 20 or 100 years) that is used to express its GHGE contribution (Lynch, 2019). While livestock production also includes significant emissions of CH 4 (methane), plant based-meat emissions mostly consist of CO 2 from energy generation (Heller and Keoleian, 2018).…”

“…While methane is a potent GHG, it is also temporary one; it lasts a decade before it breaks down into CO 2 that can be sequestered in soil. With a stable or slightly decreasing population of cattle in the US, though not globally, the methane belched from cattle is not likely to add new carbon to the atmosphere (Lynch, 2019). On the other hand, once we put carbon dioxide in the atmosphere from burning fossil fuel-whether from transportation or food production-it persists for thousands of years.…”

Metabolic Regulations by lncRNA, miRNA, and ceRNA Under Grass-Fed and Grain-Fed Regimens in Angus Beef Cattle

“…Meat intake from grass-fed cattle for an adult will significantly increase consumers' long-chain omega-3 PUFA content of plasma and platelet (McAfee et al, 2011 ), which will reduce the risk of coronary heart disease and resist thrombotic and inflammatory diseases (Mozaffarian et al, 2005 ). Besides, the grass-fed regimen can also improve animal welfare, eliminate risks of bovine spongiform encephalopathy (Lobato et al, 2014 ), and decrease carbon footprints (Lynch, 2019 ).…”