54. Fermentation and Aerobic Stability of Ensiled Food Waste.

Abstract

Each year, millions of tonnes of fruits and vegetables never reach consumers as they fail quality standards. Although this waste can be repurposed as livestock feed, its high perishability limits its potential to contribute to a circular agri-food bioeconomy. The objective of this study was to compare the fermentation and aerobic stability dynamics of mixed food waste ensiled with either barley straw or oat hulls to corn silage, with or without an inoculant in a 3 × 2 factorial design. Food waste consisted of a mixture of potatoes, carrots, and apples chopped to 1 cm3 and mixed with chopped barley straw or oat hulls to achieve a target dry matter content of 38%. Corn silage was included as a control and the inoculant contained Lentilactobacillus hilgardii, Lactobacillus buchneri, and Pediococcus pentosaceus to improve aerobic stability. Three lots were prepared per treatment and packed to ∼240 kg/m3 in mini silos using a hydraulic press. One silo from each lot was opened after 3, 7, 14, and 60 d of ensiling to measure pH and enumerate lactic acid bacteria, moulds, and yeasts. After ensiling, silage was aerobically exposed for 3, 7, 14, and 21 d and pH, microbial abundance, and temperature was measured. Data were analyzed as a completely randomized block design with silage, inoculant, day, and their interactions as fixed effects and lot as a random blocking factor. There was a silage×day interaction (P < 0.001) for pH during ensiling, where pH differed across silage type from d 0 to 14, with the pH of food waste silage being higher than corn silage on d 60. There was a three-way interaction (P < 0.001) between silage, inoculum, and day on lactic acid bacteria abundance. Abundance of moulds and yeasts was affected by a silage×day interaction (P < 0.001) with greater abundance observed in straw silages on d 7 and 14. During aerobic exposure, pH was affected by silage×day and inoculant×day interactions (P ≤ 0.009) with higher pH in inoculated corn, and in hull treatments than straw treatments on d 7 and 14. Abundance of moulds and yeasts during aerobic exposure was affected by a silage×day interaction (P < 0.03) and an inoculant×day interaction (P < 0.007). Temperature during aerobic exposure was affected by a three-way interaction (P < 0.02), with lower temperatures observed in uninoculated straw, and inoculated corn, straw, and hulls at d 3, and uninoculated and inoculated straw and inoculated hulls at d 7 compared to other treatments. A terminal pH below 4 and minimal presence of moulds and yeasts after 60 days suggests that sufficient fermentation occurred across treatments regardless of inoculant use. Aerobic stability of food waste silage was improved with the use of the inoculant.