In alignment with the goal of the Paris Agreement, which aims to limit global warming below 1.5 or 2 °C, the United States is committed to achieving a 50-52% reduction in economy-wide net greenhouse gas (GHG) emissions from 2005 levels by 2030, and ultimately reaching net-zero emissions by 2050. The U.S. food supply chain (FSC) is widespread and has unique challenges that are not common across other industrial and commercial subsectors (e.g., direct crop and animal emissions, large waste streams, and low potential for electrification).
This study considers five reduced commodity groups: grain and oil; fruits, vegetables, and nuts; dairy; sugar; and animal products (meat, and poultry, seafood, and eggs). Impacts from food commodities grown for livestock feed were included, but food crops grown for non-livestock (i.e., pets, horses) were not. The U.S. FSC comprises five stages: on-farm production (including pre- and post-farm activities like agricultural chemical manufacturing and farm-to-manufacturing transportation), manufacturing, distribution, wholesale and retail (W&R), and consumption (i.e., food services and households). By adopting this supply chain management perspective, the study not only facilitates comparisons of the U.S. FSC with those in other sectors but also underscores the importance of efficient supply chain management in achieving a sustainable U.S. FSC. The energy consumption at each stage is quantified in terms of site energy (i.e., energy consumed at the site of use) and then converted into primary energy, defined as the energy required to produce the energy used on-site (e.g., electricity) plus any losses incurred through transmission and distribution; it is not true embodied energy as it does not include the energy required to refine fossil fuels or produce fertilizer or pesticide precursors and other starting materials and feedstocks.
According to the model created for this study, the entire U.S. FSC consumed 4,660 TBTU (4,910 PJ) of site energy, 7,130 TBTU (7,510 PJ) of primary energy, and originated 970 MMT CO2e of GHG emissions in 2016. This year was chosen for this modeling effort based on the large spread of date ranges of available data sources (2012 – 2020).
When broken down by stages, site energy consumed at on-farm production ranked the highest (1,920 TBTU, 2020 PJ, 41%) in the U.S. food system, followed by food consumption (i.e., food services and households) (1,130 TBTU, 1190 PJ, 24%), food manufacturing (1,080 TBTU, 1140 PJ, 23%), W&R (360 TBTU, 380 PJ, 7.8%), and food distribution (170 TBTU, 180 PJ, 3.7%).
Electricity was the largest site energy source (33%) and was mainly used at the W&R and consumption stages (96% and 66%), followed by food manufacturing (25%) and on-farm production (9.2%). Natural gas (23%) and petroleum products (22%) were also major site energy sources for the U.S. food system. On-farm production and food distribution accounted for most of the petroleum combustion, and natural gas was mainly consumed at food manufacturing and food services. Agricultural chemicals manufacturing (fertilizer and pesticides) and animal feed production contributed to 2.0% and 14% of the site energy usage. Only the on-farm production and manufacturing stages had reportable volumes of on-site renewable energy use, representing a small portion (3.6%) of the energy used in the U.S. food system.
