Estimation of Energy and Nutrient Composition of Food Waste from Different Sources As Potential Use in Swine Diets

In the United States, approximately 40% of the food produced is wasted annually, representing about 60 million t, and valued at $165 billion dollars. The objective of this study was to investigate nutrient and energy variability in food waste sources collected in the Minneapolis-St. Paul, MN metropolitan area, and their potential for use in swine diets. A total of 3 food waste sources were selected and included a supermarket (SM; retail to consumer), university residential dining hall (RH; consumer to post-consumer), and a waste recycling and transfer station (TS; post-consumer to municipal waste disposal). Samples were collected directly from each site during 12 visits throughout 2015. After collection, samples were oven dried for 72 h at 60°C and ground. Samples were analyzed for inputs to NRC (2012) DE, ME, and NE equations (GE, DM, CP, ether extract, starch, ADF, NDF, and ash). Samples were also analyzed for fatty acid profile and thiobarbituric reactive substances (TBARS). Reference values were obtained from NRC (2012). Data were analyzed using 1-way ANOVA with waste sources as fixed effect. Samples of SM contained the highest (P < 0.05) amount of calculated DE (5,016 kcal/kg), ME (4,832 kcal/kg), and NE (3,740 kcal/kg) among the three sources. Samples from SM and RH, but not TS, had greater DE, ME, and NE than corn and soybean meal. Samples of SM contained the most Lys (1.82%) and Met (0.53%) among the sources (P < 0.05), but less than soybean meal (Lys 2.79%, Met 0.60%). Samples of TS contained the highest amount of linoleic acid (7.05% DM) among the three sources (P < 0.05) and all three sources were greater than corn and soybean meal. Likewise, samples of SM contained greater (P < 0.05) iodine value product (211) compared with RH (95) and TS (71). All samples contained low TBARS (SM: 0.17; RH: 0.16; and TS: 0.18 mg MDA eq/g oil). Although the concentrations of nutrients and calculated energy values of SM, RH, and TS were comparatively high compared with corn and soybean meal, their composition was highly variable (SD > 300 kcal/kg for GE, DE, ME and NE; SD > 3% for CP, ether extract, NDF and ADF). Pre-consumer food waste (SM) appears to have greater nutritional value than post-consumer food waste (RH and TS), but all sources are suitable for use in commercial swine diets provided that iodine value product and TBARS are properly managed.