In my earlier post on the energy intensity of meat versus vegetables, I noted by work on energy use in food systems. It’s worth exploring energy use in the US food system a little more thoroughly, partly because I find it an interesting subject but also because there are plenty of misconceptions out there about the energy intensity of different sub-sectors within the food system and how they stack up relative to one another.
The US Department of Agriculture, which offers the most authoritative analysis of energy use in the US food system, divides this sector of the US economy into seven sub-sectors: agriculture, processing, packaging, freight, wholesale and retail, food services and household use [1, 2]. Based on USDA’s data, in 2002 the US food system invested just over 12 calories of energy into each calorie of food consumed once waste and spoilage were accounted for. Of these, 1.6 calories were used within the agricultural sector, although this also includes fisheries and some other production ventures, and another 2.7 calories were used to process and package food. Distribution, which includes long distance freight, wholesale and retail sales and food service enterprises such as restaurants and caterers, used another 4.4 calories. The energy use associated with long distance transport of food only makes up 0.4 calories of this figure, with the bulk of food distribution energy used in the wholesale, retail and food service segments. Household energy use, which includes that associated with driving to and from grocery stores and restaurants as well as energy used within the home to refrigerate, freeze, process and cook food, added the final 3.4 calories to the tab. According to USDA data, the energy intensity of the US food system has been increasing; it took just under 11 calories to deliver one calorie of loss-adjusted food in 1997, 12 in 2002 and just over 14 in 2007, and if we extrapolate this trend forwards the US food system requires about 15 calories of energy to yield one of consumed food in 2014.
As high as this 15 calorie figure might seem, it’s surely an underestimate. The USDA report from which these data were drawn left out a number of areas within the US food system that use energy in their operations, including research and development within food enterprises, waste disposal, water provision, food-related wastewater treatment, food waste disposal, food system governance, and the energy costs of providing healthcare to those who suffer from food and diet-related ailments, among others. A more expansive assessment of energy use in the US food system, one that attempted to account for food’s entire life cycle from soil to consumers and back to soil, would likely estimate total energy demand higher than 15 input calories per consumed food calorie.
All living organisms face a constant energetic arms race against their environments, always scheming to derive more food calories from their surroundings than they need to burn metabolically to acquire them. Organisms who are successful, whose life ways yield a positive energy return on investment with respect to consumed calories versus those burned for energy, live to reproduce and raise successful offspring. They enjoy a certain ecological staying power, if you will. Those that fail to eat more calories than they burn eventually starve, and their genetic lineage ends.
The US food system, along with those of most countries in the world today, operates at a steep energy deficit. As a species, Homo industrialis remains successful because we subsidize our food system with nonrenewable energy sources, including coal, oil, natural gas and, to a lesser degree, fissionable uranium. As long as these resources remain readily available and inexpensive – and the environmental and social consequences of relying on them are bearable – we’re fine. If any of the above changes however, the energy deficit our food system runs will become a serious thorn in our sides, or more aptly a thorn in our bellies. It behooves us, I think, to ponder the implications of relying on such an energy intensive food system, and to reflect on how we might steer its development down a more resilient and adaptive path.
- Patrick Canning, et al. (2010) Energy Use in the US Food System. Report by the US Department of Agriculture’s Economic Research Service.
- Food Availability (Per Capita) Data System. United States Department of Agriculture’s Economic Research Service. Estimates of food availability corrected for waste and spoilage are called ‘loss-adjusted’ by the USDA, and are used as a proxy for food that’s eaten by a person.