National food waste recycling promises major climate gains but comes with microplastic risks Sadie Harley Scientific Editor Robert Egan Senior Editor Keeping food waste out of landfills provides climate and other environmental benefits, and Vermont requires residents to divert these materials to better management pathways. With other states considering similar policies, UVM researchers studied the potential outcomes of bringing these efforts to a national scale. The findings, published in the journal Nature Food, indicate a need to plan not just for channeling food waste into landfill alternatives—but also for managing the microplastics that can remain in the resulting compost and other organic materials, says study co-author Eric Roy, a professor in the Rubenstein School of Environment and Natural Resources.

Solutions to keep food waste out of landfills include turning it into compost for agricultural use and using anaerobic digestion to produce biogas for renewable energy. While researchers have looked at these disposal options before, none had taken microplastic contamination into consideration at scale, says Roy. Big climate gains, new plastic risks Key findings include that diverting food waste from landfills to composting and anaerobic digestion at a national scale in the U.S.

would reduce the current climate impacts of these wastes by 89% to 99%. Environmental nutrient pollution from food waste management, which can contribute to summer blue-green algae blooms in lakes, could drop by 49% to 54% for nitrogen and 78% to 98% for phosphorus. But if the organics resulting from composting and anaerobic digestion were spread on agricultural fields, they could also carry around 20,000 tons of microplastics into the soil annually, the researchers found.

"If you don't intentionally intervene and have a plan for how you're going to minimize plastic in your recovered soil amendments, there will probably be plastic there based on just how pervasive it is in our food system right now," says lead author Kate Porterfield, a Gund Institute for Environment postdoctoral researcher. "It's literally everywhere." The work points to the need for better planning at every step of the food recycling process—including the design of packaging before the food is ever in it, Porterfield says. Tracking waste through the system Using a combination of data from across the U.S., the team created life cycle assessment models to inspect the potential effects of nationwide composting, anaerobic digestion or landfill disposal of food waste.

The approach takes into account every step of food waste's journey, from the moment it arrives at a waste transfer station to its fate as compost in a field, methane gas converted to electricity or a slimy pile with plastic slowly releasing greenhouse gases in a landfill. The researchers also considered a potential drop in the need for synthetic fertilizers in agriculture resulting from recovered nutrients in organic wastes replacing them—but found that nutrients recovered from food waste would offset only about 2% of annual U.S. demand.

Policy momentum meets practical limits Dealing with food waste is becoming increasingly top of mind among some policymakers, with up to 40% of U.S.