garbage truck dumping food waste in a landfill University of Minnesota

Recycled food waste in pig diets can reduce environmental footprint

U.S. EPA has suggested that converting food waste into animal feed is the preferred method to recycle food waste (after source reduction and feeding hungry people) compared with industrial uses (biofuels production), composting, and landfill or incineration.

By Jerry Shurson, Leonard Fung, Pedro Urriola and Jae-Cheol Jang, University of Minnesota Department of Animal Science; Larry Baker, University of Minnesota Bioproducts and Biosystems Engineering, and Jennifer Schmitt, University of Minnesota NorthStar Initiative at the Institute on the Environment
There is a tremendous need to evaluate opportunities to improve the environmental sustainability of pork production. Major food companies have initiated supply chain management programs to minimize their carbon footprint in response to consumer demands and societal concerns.

Feed is a major component of environmental sustainability of pork production systems, and the ingredients used in swine diets have important downstream environmental effects (i.e. manure composition, odor and greenhouse gas emissions) as well as upstream effects (i.e. water and land use, energy consumption and greenhouse gas emissions). In fact, Food and Agriculture Organization (2013) estimated that 45% of greenhouse gas emissions in livestock operations can be attributed to production, processing and transport of feed ingredients and feed. As a result, a demand is emerging to develop environmentally sustainable diets to minimize the environmental footprint of pork production. A recent study by Mackenzie et al. (2016) evaluated the environmental impact of several feed ingredients based on their acidification, eutrophication and global warming potential, as well as their non-renewable energy and resource use in Canadian pork production systems.

Historically, the small swine operations located near major cities served as significant users of food scraps and waste. Although its use faded into history as larger pork production systems were built, which have relied on using corn and soybean meal as the main ingredients in swine diets, the use of heat-processed food waste is re-emerging. The next phase of this evolution is now occurring. New food waste processing technologies have been developed, and efforts by organizations (e.g. Rethinking Food Waste Through Economics and Data; Food Waste Reduction Alliance) and companies (e.g. TUBS, Minneapolis, Minn.; California Safe Soil) are bringing heat processed, dehydrated food waste back into commercial reality. This emerging trend is driven by the fact that about 40% of the food produced in the United States is wasted annually at the retail and consumer portion of the food chain (Buzby and Hyman, 2012), which represents about 60 million metric tons and a tremendous economic loss of $165 billion to the U.S. economy (Gunders, 2012). Currently, most food waste is disposed in landfills, which has significant negative impacts on the environment, both upstream due to embedded land and other natural resource (i.e. water, crude oil) use in the waste, and downstream, with landfilling of food waste accounting for about 18% of total methane gas produced from landfills each year (U.S. Environmental Protection Agency, 2016).

The U.S. EPA has suggested that converting food waste into animal feed is the preferred method to recycle food waste (after source reduction and feeding hungry people) compared with industrial uses (biofuels production), composting, and landfill or incineration. While composting may be one of the most familiar alternative methods of food waste disposal compared with landfills, only about 1.5 million tons are composted in the United States annually. Therefore, there is an abundant supply and a tremendous opportunity to capture the potentially high nutritional and economic value of food waste sources by proper processing and use in animal feeds.

Our research team, in collaboration with TUBS Inc. (David Russick, Minneapolis), has been evaluating the nutritional composition and digestibility of several sources of food waste for swine. To begin, we collected and analyzed food waste samples from pre-consumer (supermarket) and post-consumer (University dining hall, municipal transfer station and household source separated organics) to compare their energy and nutrient composition with corn and soybean meal (Table 1). The calculated metabolizable and net energy content of supermarket and dining hall food waste was substantially greater, and the ME content of the source separated organics was also greater than these energy values in corn and soybean meal. This was likely a result of the relatively high crude fat and starch content, and comparable neutral detergent fiber content compared with corn and soybean meal. In addition, all food waste sources had greater lysine, methionine, threonine and tryptophan content than corn, but lower concentrations of these amino acids than soybean meal. All the food waste sources provided greater calcium and phosphorus content than corn, but also contained relatively high concentrations of sodium. These initial results suggest that food waste derived from all four sources evaluated would have significant nutritional and economic value to partially replace some of the corn and soybean meal in commercial swine diets.

University of Minnesota

Table 1: Comparison of energy and nutrient content (dry matter basis) of four sources of food waste with corn and soybean meal for use in swine diets.

The next step in determining the nutritional feasibility of various food waste sources in commercial swine diets is to determine actual metabolizable energy content and digestible amino acid and phosphorus content. We recently completed digestibility studies evaluating fish waste, supermarket food waste, and fruits and vegetable waste, and these results confirmed that multiple sources of food waste can provide significant nutritional value in commercial swine diets.

The next phase of research is to use the nutritional information already obtained on these food waste sources, to evaluate their effects on growth performance and carcass composition. We are also using this information to conduct a life cycle assessment of the environmental impacts of feeding food waste to swine. We are comparing the environmental impacts of using heat processed food waste sources as a feed ingredient in swine diets with other environmentally sustainable feed formulation practices such as supplementing diets with phytase or crystalline amino acids. This research is supported by the National Pork Board. We anticipate that the results from our life cycle analysis will show that using food waste as a feed ingredient in swine diets can have significant environmental benefits for reducing the carbon footprint of pork production.

References
Buzby, J.C., and J. Hyman. 2012. Total and per capita value of food loss in the United States. Food Policy, 37:561–570. 
FAO. (2013). Food Wastage Footprint: Impacts on Natural Resources — Summary Report. Rome. 
Gunders, D. 2012. Wasted: How America Is Losing Up to 40 Percent of Its Food from Farm to Fork to Landfill. Natural Resources Defense Council, August, 2012. 
Mackenzie, S.G., I. Leinonen, N. Ferguson, and I. Kyriazakis. 2016. Towards a methodology to formulate sustainable diets for livestock: accounting for environmental impact in diet formulation. British Journal of Nutrition 115:1860-1874. 
U.S. EPA, 2016. America’s Food Waste Problem.
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