Greenhouse gas emissions from US household food choices
This paper estimates greenhouse gas emissions (GHGEs) associated with the food purchased by US households (based on survey data) and examines the links between food GHGEs and demographic factors. It suggests that education on the links between food and climate could be targeted at more educated and more affluent consumers, since their research shows (see below) that the these households have more GHGE-intensive dietary patterns.
The paper finds that average emissions per standard adult are 71.8 kg CO2 eq. per week, or 3.7 tonnes CO2 eq. per year, just for food. For comparison, note that under a contraction and convergence climate mitigation scenario, per capita ‘allowable’ emissions are no more than 2 tonnes CO2 eq. per year for everything (not just food), falling to 1.5 tonnes CO2 eq. by 2050. Meanwhile, O’Neill et al. (2018) estimate that per capita ‘allowable’ emissions would be 1.6 tonnes CO2 for every year between 2011 and 2100; this is based on a global population of 7 billion and doesn’t account for population growth.
Looking at GHGEs by food supply chain stage, the paper calculates that around two-thirds of GHGEs arise during the production and manufacturing stage, followed by retail (13%) and restaurants (12%), as shown below.
Image: Fig. 1 from Boehm et al. (2018)
By product type, beef, pork and other red meat accounts for the largest fraction of GHGEs (21%), followed by fresh vegetables and melons (11%), cheese (10%) and milk, milk products and butter (7%).
Households that have higher food GHGEs are found to spend, as a fraction of their food expenditure, more on protein foods, less on grains, less on beverages, and more on fats, oils, condiments and sugars, compared to households that had lower food GHGEs.
Households in the lowest quintile of food GHGEs have an average monthly income of $2020 per adult, compared to $3955 in the highest quintile of food GHGEs.
Changes in diet have been proposed as one way to reduce carbon emissions from the food system. But evidence on the implications of changing to low carbon food choices for both diet quality and food affordability are limited in the U.S. The objective of this study was to (a) estimate greenhouse gas emissions (GHGEs) from U.S. household food purchases; (b) examine the source of GHGEs across U.S. food production industries and stages of the supply chain; and (c) show the association between GHGEs and spending by food categories and household sociodemographics. GHGEs from food expenditures made by households participating in the National Household Food Acquisition and Purchase Survey were calculated using Economic Input-Output Life Cycle Assessment. Results indicate that food purchases accounted for 16% of U.S. GHGEs in 2013 and average weekly household GHGEs were 71.8 kg carbon dioxide equivalents per standard adult. 68% of average weekly household GHGEs from food spending came from agriculture and food manufacturing stages of the food supply chain. Industries that produce animal proteins accounted for 30% of average weekly household GHGEs, the largest share of any food industry. Households generating the highest levels of GHGEs spent a significantly larger share of their food budget on protein foods compared to households generating lower levels of GHGEs. White households and those with higher education levels generated more GHGEs from food spending compared to non-white and less educated households. Overall these findings inform the ongoing debate about which diets or food spending patterns in the U.S. are best for mitigating GHGEs in the food system and if they are feasible for consumers to purchase.
Boehm, R., Wilde, P.E., Ver Ploeg, M., Costello, C. and Cash, S.B., 2018. A Comprehensive Life Cycle Assessment of Greenhouse Gas Emissions from US Household Food Choices. Food Policy. In press, corrected proof.
Read the full paper here. See also the Foodsource chapter Environmental impacts of food: an introduction to Life Cycle Assessment.
North America is the northern subcontinent of the Americas covering about 16.5% of the Earth's land area. This large continent has a range of climates spanning Greenland’s permanent ice sheet and the dry deserts of Arizona. Both Canada and the USA are major food producers and some of the largest food exporters in the world. Industrial farms are the norm in North America, with high yields relative to other regions and only 2% of the population involved in agriculture.
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