A framework for evaluating energy embedded in the United States' food system, including trade-offs between refrigeration and food waste

Recent legislative proposals and publications focus on combating climate change, calling for a reduction of greenhouse gas emissions (GHG) in the United States (US) and worldwide (1-3). Research examining the relationship between energy use and the food system has found that for the last 40 years, the food system accounted for 10-14% of all US energy use, contributing to 14% of national CO₂ emissions (4-6). In 2002, the US food system required the same amount of energy as India's annual consumption (6). Because the food system is resource intensive, it is worth exploring the environmental impact of our consumption habits. In particular, the role refrigeration plays in our food system is worth exploring because it is energy intensive but helps avoid food waste. This body of work assesses the environmental impacts of the average American's diet and food loss and waste (FLW) habits through an analysis of energy, water, land, and fertilizer requirements (inputs) and GHG emissions (outputs). Existing datasets were synthesized to determine the ramifications of the typical American adult's food habits, as well as the environmental impact associated with shifting diets to meet US Department of Agriculture (USDA) dietary guideline recommendations. Results for 2010 indicate that FLW accounted for 35% of energy use, 34% of blue water use (groundwater and surface water), 34% of GHG emissions, 31% of land use, and 35% of fertilizer use related to an individual's food-related resource consumption, i.e., their foodprint. A shift in consumption towards a healthier diet, combined with meeting the USDA and Environmental Protection Agency's (EPA) 2030 food loss and waste reduction goal could increase per capita food related energy use 12%, decrease blue water consumption 4%, decrease green water use 23% (water stored in soil), decrease GHG emissions from food production 11%, decrease GHG emissions from landfills 20%, decrease land use 32%, and increase fertilizer use 12%. Food-related energy use is expected to increase, even with the reduction in FLW, because fruits and vegetables are less calorie dense than meat products. So although produce has a lower energy intensity per gram, consumers need to consume larger quantities of produce than meat to reach the same caloric intake. Refrigeration infrastructure can help prevent food waste, but there are few studies that holistically examine the energy embedded in the US food system. The food cold chain is the temperature-controlled supply chain for refrigerated and frozen foods, beginning after harvesting crops and slaughtering animals and ending at consumption. The cold chain is integral to extending the shelf life of food and preventing food waste. This study estimates the energy consumption and carbon footprint of refrigeration along the US food cold chain using an environmental input-output (EIO) analysis from the USDA. Cold chain energy consumption is calculated by food group, food chain stage, industry, and fuel type. In 2007, food refrigeration accounted for 30% of the 13.17 exajoules (EJ) that the US used to produce and move food from farm to plate. This energy use equates to 3.4% of total US energy use, and 2.6% of total US GHG emissions. Results from this study are extrapolated to assess energy use from 1993-2012 and find that over these 20 years, refrigeration was consistent, accounting for 27-30% of annual food-related energy. This steady energy demand reflects that we increasingly rely on the food cold chain, as over the last 20 years, refrigeration effciency has significantly improved (7). The third component of this dissertation is to create a framework for assessing the energy-intensities for food and FLW at different stages of the supply chain. This project builds on existing analysis to provide an updated assessment of energy embedded in FLW, by capturing both direct and indirect energy inputs through use of an EIO analysis. In 2007, approximately 4.38 EJ of energy were embedded in US food waste, totaling to 33% of food system energy use, or 4% of US energy. Of the energy embedded in FLW, 27% is generated at the household and 20% at the processing stage. Energy from packaging waste contributes 8% of embedded energy, indicating that despite recent media attention, FLW interventions might prove more impactful at the household or processing stages. Taken together, these analyses can be used as a framework for assessing the environmental impact of consumer habits and the technological trade-offs of increased energy for refrigeration compared with the energy savings of avoided food waste.