Nutrient Flow from Farm to Fork and Beyond

We study nutrient flow dynamics via the window of food waste. Globally, one-third of food produced for human consumption is never eaten but lost and wasted. Implicit in the losses is the waste of all the resources used to produce the food. Our research examines the "upstream" and "downstream" effects of nutrients and other resources embedded in the food supply, and the means to recapture the nutrients for economic and environmental benefits. Approximately 1.2 million metric tons (MMT) of nitrogen and 0.3 MMT phosphorus fertilizers were used to produce the 41 MMT of edible food wasted by U.S. consumers (2012 data), much of which can be potentially recovered through food waste treatment technologies (FWTT), then used for upcycling. Anaerobic digestion, a microbe-driven process that converts some of the organic compounds contained in food waste into biogas (a form of bioenergy), produces digestate. Composting aerobically degrades food waste, yielding compost. Both digestate and compost can be used as soil amendments, with a fertilizer equivalence of 35-45% for N and 70-90% for P. More recently, advanced technologies have emerged that help convert food waste into feed for non-ruminant animals. The new feed can substitute for traditional feed grains such as corn and soybeans, consequently 'sparing' fertilizers (and other resources) that would be otherwise required to produce the grain. Preliminary data show that up to 0.47 and 0.28 MMT of N and P chemical fertilizers could be spared if the consumption-stage food waste in the U.S. is recovered for upcycling through the new feed-making technologies. Our study will provide quantitative assessment and cross-comparison of different FWTTs for their respective capacities in recovering nutrients from wasted food for reuse in the food systems of the U.S. and China, along with other resource and environmental benefits.