Summary: The *Cowspiracy* fact sheet claims that a vegan diet can reduce dietary emissions by 20 lbs CO2e per day. This figure is higher than recently published estimates and arises because (i) the authors do not replace animal products with vegan alternatives (and include their associated emissions) and (ii) the authors apply the emission factor for cheese, a GHG-intensive product, to all dairy products.

Although I haven’t seen *Cowspiracy*, coverage of the documentary on the blogosphere made it clear that Goodland and Anhang’s claim that livestock accounts for 51 percent of anthropogenic greenhouse gases (GHGs) emissions is highlighted in the documentary. I have documented problems with this analysis elsewhere. There is a website associated with the documentary that includes a page entitled “The Facts”. In addition to repeating the Goodland and Anhang claim, the page also makes the claim

Each day, a person who eats a vegan diet saves 1,100 gallons of water, 45 pounds of grain, 30 sq ft of forested land, 20 lbs CO2 equivalent, and one animal’s life.

I was interested in where the claim of 20 lbs CO2-equivalent (CO2e) came from, since this number is higher than what has been reported in a number of studies that have been highlighted in the media recently. The Cowspiracy site even cites Scarborough et al.(2014), which looks at UK emissions for different dietary types and concludes that the daily *dietary* emissions for heavy meat eaters are 7.19 kg CO2e (and 5.63 kg CO2e for medium meat eaters), while for vegans, the corresponding figures is 2.89 kg CO2e. Converting the difference into pounds yields a figure of 9.5 lbs (for medium meat eaters, the difference is 6 lbs). [The site also links to analysis by the Shrink that Footprint site, which uses US consumption data and concludes that compared to a vegan diet, the average American diet results in an extra 1 Ton CO2e/year, or 6.1 lb (2.74 kg) CO2/day and a “meat lover” diet results in an extra 1.8 tCO2e/year, or 10.9 lb (4.9 kg) CO2e/day.] Why is the figure on Cowspiracy twice the figure for heavy meat eaters (and over three times the figure for medium meat eaters)?

It turns out that the figure is not from a peer-reviewed source, but is instead a calculation based on dietary emissions by food type from the Environmental Working Group (EWG) and average consumption figures for the United States. Indeed, in footnote [xiv], the Cowspiracy fact sheet notes:

– CO2 based of feed conversion ratios and the average US meat consumption of 209lbs per year, per person.

Beef is at 22-27 kg CO2 Eq per kg produced/consumed X 2.5 ounces/day=1.75 kg or 3.85 pounds

Cheese/milk is 13.5 kg per kg product X 2 pounds/day=12.15 kg or 12.5 pounds

Pork is 12 kg per kg product X 2 ounces/day=.68 kg or 1.5 pounds

Combination chicken and turkey is 7 kg per kg product X 4.48 ounces/day= .89 kg or 1.96 pounds minimally (using only chicken)

{turkey, for instance, is 11 kg per kg product}

Eggs are at 5 kg per kg product X 2/3 egg per day= (50 g/egg) .55 pounds

— which equals 20.36 pounds of CO2 Eq saved per day.

There are two problems with this analysis. First, they don’t replace the animal products with vegan alternatives (which would have lower carbon emissions), which means even taking their analysis at face value, the saving would be less than they are claiming. A bigger problem has to do with their treatment of dairy products. The EWG provides emissions estimates for four different dairy products, measured in kg of CO2e per kg of product (reported in parentheses following each product) – cheese (13.5), butter (2.5), yogurt (2.2), and 2 percent milk (1.9). The Cowspiracy analysis elects to treat the entire 2 lb of dairy as cheese, which has the highest emission factor. The page doesn’t appear to provide an attribution for where the dairy figures are from, but it’s straightforward to find per capita annual figures on U.S. dairy consumption from the USDA. Figures are available on consumption for individual categories (milk and cream, yogurt, butter, cheese, etc.) and an aggregate measure based on “milk equivalent, milk fat basis”), which was 614 lb in 2012 (close to the 2 lb per day reported on the Cowspiracy fact sheet). In comparison, cheese consumption (American, Other and Cottage) was 35.6 lb (or about a tenth of a pound per day). There doesn’t seem to be any justification for using the emission factor for cheese, other than to inflate the figure. Indeed, the dairy category accounts for over 60 percent of the 20 lbs that they suggest can be saved, which is why their number is double that provided by Scarborough et al.

Edited Sept. 27, 2015 – a short summary was added to the article.

Edited Feb. 17, 2016 – added the emission figures from Shrink That Footprint.