Two recent peer-reviewed articles in the Journal Nature Food show that previous measures of the food-system’s contributions to greenhouse gas (GHG) emissions had been underestimated.
(https://www.nature.com/articles/s43016-021-00225-9; https://www.nature.com/articles/s43016-021-00358-x)
One study finds that, in 2015, food-system emissions amounted to 18 Gt CO2 equivalent per year globally, representing 34% of total emissions. Within the food system, the largest proportion came from agriculture and land use/land-use change activities (71%), with the remaining from supply chain activities: retail, transport, consumption, fuel production, waste management, industrial processes and packaging.
The other study estimates that out of the global food-system emissions, 57% is from the production of animal-based food (including livestock feed), 29% from plant-based foods, and 14% from other utilizations. Rice alone contributes to 12% and beef alone 25% of the entire food-system emissions. These figures are based on the entire life-cycle of food production. In short, the production of beef, pork, poultry, and other meat products is responsible for a good part of global GHG emissions.
Rice feeds more than half of the world’s population, but growing rice produces methane, which has a global warming potential (GWP) of more than 30 times that of carbon dioxide. In a rice field, the water blocks oxygen from penetrating the soil, creating ideal conditions for anaerobic bacteria that emit methane. Cows are “ruminants” because the largest pouch of the stomach is called the rumen. Many large hoofed carnivorous grazing mammals (e.g., cattle, sheep, goat, bison, and deer) are ruminants. In these animals, the process of swallowing, “un-swallowing”, re-chewing, and re-swallowing feed is called “rumination,” which produces methane. Methane is released in belching through the mouth.
A recent issue of the Economist magazine summarizes the findings from these two articles in a few excellent infographics. The first graphics below shows that beef is uniquely carbon intensive. This is because cattle emit methane. Beef production produces 7 times as much GHG emission per calorie as pork, 12 times as much as eggs, and 31 times as much as tofu (a soy bean product). The second graphics below shows that emission from global beef production is 3.5 times that of Japan and 5 times that of the entire air travel industry.
