**From the Dr. Jayson Lusk Blog: Beef, Chicken, and Carbon Emissions**

There seems to be rising attention paid to the environmental impacts of meat consumption. Some people see plant-based meat alternatives as one way to address this concern, and they question whether it is possible to see a big shift in the types of “meat” consumers buy. Such a shift, in fact, has occurred over the past fifty years – a period during which we’ve observed a remarkable change in meat consumption patterns.

The figure above shows US per-capita consumption (lbs/person/year) of beef and chicken from 1970 to 2020 based on **USDA data**. On a retail-weight basis, per capita consumption of beef fell from an annual average of 86 lbs/person in the 1970s to 56.7 lbs/person in 2010s (i.e., from 2010 to 2019) – a 34% reduction. At the same time, chicken consumption went from 38.9 lbs in the 1970s to 86.9 lbs in the 2010s – a 123% increase. Total consumption of these two meats has increased from an annual average of 124.8 lbs in the 1970s to 143.5 lbs in the 2010s.

Using the per-capita consumption data (expressed instead on a carcass rather than retail basis), coupled with additional **USDA data** on yield (lbs produced per animal) over time, one can infer the number of animals each person in the U.S. eats each year on average.

In the 1970s, the average American ate 14.5 chickens/year, a figure that increased to 22.3 chickens by the 2010s. In the 1970s, the average American ate 0.19 cows/year, a figure that fell to only 0.1 cows/year in the 2010s. Stated differently, it took about 5.3 years for the average American to eat one whole cow in the 1970s; at today’s consumption levels, it takes nearly a decade before the average American eats a whole cow.

What is the impact of this consumption pattern change from beef to chicken on one key environmental measure: greenhouse gas (GHG) emissions ?

One UN Food and Agricultural Organization **study** indicates that there are 5.4 kg of CO2 equivalent gasses emitted for every kg of carcass weight of chicken meat produced. USDA data indicate the average carcass weight of U.S. broilers over the past decade is about 4.53 lbs/bird (or 2.06 kg/bird). This means, each bird is associated with 11.1 kg of C02. Because consumers are now eating 22.3-14.5 = 7.9 more chickens each year than they were in the 1970s, this means they are also emitting 7.9*11.1 = 87.3 kg more CO2 than in the 1970s (assuming the per-head chicken emissions haven’t changed over time).

Has the reduction in beef consumption been enough to offset the increases in carbon emissions from the increased consumption of chicken? According to **one study**, roughly 22 kg of CO2 are emitted for every kg of carcass weight of beef produced. Cattle carcass weights have averaged about 804.7 lbs/head (or 365.8 kg/head) for the past decade, meaning each cow generates 8,047 kg of CO2 equivalent gasses. Because U.S. consumers are now eating 0.19-0.1 = 0.09 fewer cows each year than in the 1970s, they are emitting 0.09*8047 = 705.6 fewer kg of CO2 equivalent gasses from beef consumption (again, assuming the per-head beef emissions haven’t changed over time). Some of this reduction is because people are consuming less beef (per-capita consumption feel from 116 lbs to 81 lbs on a carcass weight basis), but also because cattle yields have substantially increased from about 617 lbs/cow in the 1970s to 804.7 in the 2010s) – we are getting more beef from each head of cattle.

So, the average American is emitting 87.3 more kg CO2 from extra chicken consumption but has cut 705 kg CO2 from less beef consumption since the 1970s. Looks like a net carbon win. And one that isn’t even close.

One pushback to this point may be that there are more people today than in the 1970s, so per-capita numbers may be misleading. Throughout the 1970s, the US population averaged 215 million, whereas in the 2010s, population averaged 319.6 million. Taking this into consideration, in aggregate, calculations suggest Americans are today consuming about 4 billion more chickens and 8.3 million fewer cattle than in the 1970s. Using the aforementioned per-head emissions implies we are, in aggregate, emitting 44.7 million metric tons (MMT) more CO2 from extra chickens but 67.1 less MMT CO2 from fewer cattle. Thus, on net, we are emitting 22.4 MMT fewer CO2 equivalent gasses from our aggregate beef and chicken consumption today than in the 1970s. Thus, it still appears a net carbon “win” even adjusting for population change.

While we’re at it, the data used in the above calculations can be used to ask a number of counter factional questions.

- What would today’s aggregate GHG emissions from chicken be if we hadn’t increased productivity (or yield) since the 1970s? Answer: 52.7 MMT more CO2.
- What would today’s aggregate GHG emissions from chicken be if population staid at 1970s levels? Answer: 25.9 MMT less CO2.
- What would today’s aggregate GHG emissions from chicken be if per-capita consumption staid at 1970’s levels? Answer: 48.4 MMT less CO2.

Now the same questions for beef.

- What would today’s aggregate GHG emissions from beef be if we hadn’t increased productivity (or yield) since the 1970s? Answer: 78.73 MMT more CO2.
- What would today’s aggregate GHG emissions from beef be if population staid at 1970s levels? Answer: 84.67 MMT less CO2.
- What would today’s aggregate GHG emissions from beef be if per-capita consumption staid at 1970’s levels? Answer: 112.57 MMT more CO2.

To give some sense of scale, the **EPA GHG inventory data** suggests all U.S. agriculture was responsible for 628 MMT CO2 equivalent emissions in 2019.

All in all, it seems meat consumption patterns have become much more carbon friendly since the 1970s – that’s not a headline one often sees.

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