The way beef is farmed, and how we measure its emissions, produces dramatically variable greenhouse gas footprints, according to new research. Most striking is the difference in grass-fed beef, whose emissions were notably higher or lower, depending on how it was measured.
The researchers made this discovery by carrying out a meta-analysis on 32 studies that each did a life cycle assessment of different types of beef production. Collectively, these studies incorporated 115 beef production scenarios, on farms across the United States and Canada. These covered a range of production methods, from cattle farmed for beef and fed on grain in dense feedlots; to cattle raised for months on grassy pastures. Some of these studies factored in the carbon sequestration of different farming methods, while others did not.
When the researchers pooled the data, the most striking initial finding was that the greenhouse gas footprints across the different scenarios varied almost fourfold—from 10.2 to 37.6 CO2-equivalent per kilogram of beef. That reflected the huge diversity of farm types and methods employed.
The natural next step was to search for clues about which scenarios in the dataset produced lower emissions overall.
That revealed the first notable difference: studies that considered the carbon sequestration potential of the whole-lifecycle of cattle production (which were in the minority in the study sample) showed three to four times lower greenhouse gasses associated with beef, compared to studies that did not consider this factor.
The takeaway is that a more nuanced read of the life cycle could contribute to beef’s lower emissions profile. For instance, factoring in whether conservation agriculture was practiced on the croplands that produced maize for grain-fed cows, could tilt the greenhouse gas emissions downwards. That could also guide climate-concerned farmers on improved practices, like cover cropping, better manure management, and keeping the soil beneath pasturelands intact.
There was a second illuminating clue in the data. The researchers found that grass-fed beef had an altogether different emissions profile, depending on the metric used to measure it.
This is surprising because almost all studies find that grass-fed beef ranks high on emissions, when measured by weight, because these cows take longer to gain the mass needed to ready them for slaughter. Consequently, they spend more time belching out methane. But some studies that the researchers included in their analysis calculated emissions not by weight, but by economic value instead—i.e. emissions per dollar spent on beef.
Comparing the two metrics, the researchers found that under the cost measure, the emissions from grass-fed beef were several-fold lower than when measured by weight. This surprising difference could be explained by the huge 121% average increase in price applied to grass-finished beef, they say, because the large price premium dwarfs the greenhouse gas cost per dollar. (The emissions impact of beef will be much smaller per dollar if spread across $50 versus $5.)
A pragmatist might see the cost metric as a useful way to inflate the climate benefits of grass-fed beef. But perhaps the study’s real takeaway is concern over the huge diversity of greenhouse gas values that it reveals.
Beef production is one of the most carbon-intensive food sectors. To really grasp its climate impact we need consistent metrics. And to identify real opportunities to mitigate this impact, we need more thorough lifecycle analyses—like those in a minority of studies included the analysis—that reveal where carbon reduction is working, and what that looks like.
The results, say the study authors, “have implications for measuring and mitigating the carbon footprint of beef production, which is of interest to policymakers, producers, and researchers.”
Wang et. al. “Climate impacts of alternative beef production systems depend on the functional unit used: Weight or monetary value.” PNAS. 2024.
Image: © Anthropocene Magazine
