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Upcycled animal feed: Sustainable solution to food waste problem

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Shurson says feeding value of several food waste sources is equal to, or exceeds, traditional ingredients like corn and soybean meal for pigs.

Up to 40% of the American food supply goes to waste each year, with heavy loss occurring between Thanksgiving and New Year's Day. 

Throughout the winter holidays, the amount of trash produced increases by 25%, with food making up the largest category of that waste in the United States, according to the Ecology Center. 

Across the country, animal scientists and entrepreneurs are searching for solutions to address this issue by turning food waste into animal feed using thermal processing.

Gerald Shurson, an animal science professor in the University of Minnesota College of Food, Agricultural and Natural Resource Sciences, says upcycling valuable nutrients from byproducts produced by the grain milling, meat packing and milk processing industries in order to create pig feed is safe and the public health risks are minimal.

"If we're going to feed a growing population of people, we must first do a better job at preventing food waste and ultimately the food waste that can't be prevented must be recycled to the highest possible value, which is feeding it to animals," Shurson says.

In the June 2021 Council for Agricultural Science and Technology (CAST) paper, "The Role of Agricultural Science and Technology in Climate 21 Project Implementation," Shurson suggests a national framework is needed to create/expand the commercialization of food waste recycling options — that are not only appropriate for specific waste streams, but also for optimal nutient recovery and reduced climate impact.

"When you invest so many resources, including energy (carbon), protein (nitrogen), phosphorus, and water into producing a pig that's at market weight, and it doesn't go for human consumption, that's a tremendous loss of not only income and revenue for farmers, but also valuable nutrients that could have been consumed by hungry people," Shurson says.

While aerobic composting and anaerobic digestion are viable alternatives to landfilling food waste, Shurson and co-authors Zhengia Dou, David Gallagan and Allison Thomson say a preferred approach is to upcycle food waste by re-purposing into animal feeds ( Re-Feed) through thermal processing. "With Re-Feed, species-specific feeding strategies allow matching food waste types/sources with animal species to support maximal extraction of the biological value of nutrients while minimizing animal and public health risks. For example, plant-based food discards such as unsalable fruits and vegetables [roughly 13%–14% of supermarket inventories (Buzby et al. 2016)] are relatively high in dietary fiber content and thus most suitable for ruminants, given the animals' ability to use fiber as an energy source," the authors note.

According to the CAST paper, about 45% of consumer food waste in South Korea is converted into feeds for livestock. Treatment processes include sorting, screening, grinding, dewatering, heating and drying  — modern safety protocols rather than the former practices of "swill feeding"or "garbage feeding" pigs.

The authors note that several studies have demonstrated Re-Feed is a "robust solution for addressing multiple objectives" and that the "substitution of conventional feedstuffs (e.g., corn, soybean meal, forages) with food-waste-derived feeds will reduce land, fertilizer, pesticides, energy, water that are otherwise needed for producing the conventional feedstuffs, thereby 'sparing' relevant climate, resource and environmental burdens."

"We obtained great results showing that the feeding value of several food waste sources is equal to, or exceeds, traditional ingredients like corn and soybean meal for pigs, which could repurpose food waste from being an enormous environmental burden into a valuable resource in pig diets," Shurson says.

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