Abstract
Food waste (FW), a major part of the US waste stream, causes greenhouse gases within landfills, but there is an opportunity to divert FW to anaerobic digestion (AD) facilities that produce biogas and digestate fertilizer. The composition of FW inputs to AD determines the value of these products. This study provides insight into the effect of waste composition on the quality of AD products by first characterizing the biogas and digestate quality of anaerobically digested FW from four diets (paleolithic, ketogenic, vegetarian, and omnivorous), and then estimating the difference in biogas produced from codigested FW and brewery waste (BW). Waste feedstock mixtures were incubated in lab-scale bioreactors for 21 days with live inoculum. Biogas quality was monitored for 21–30 days in four trials. Samples were analyzed using a gas chromatograph for detection of methane (CH4) and carbon dioxide (CO2). The composition of the waste inputs had a significant impact on the quality of biogas but not on the quality of the digestate, which has implications for the value of post-AD fertilizer products. Wastes with higher proportions of proteins and fats enhanced biogas quality, unlike wastes that were rich in soluble carbohydrates. Codigestion of omnivorous food waste with carbon-rich agricultural wastes (AW) improved biogas quality, but biogas produced from BW does not necessarily improve with increasing amounts of AW in codigestion.
Highlights
Anaerobic digestion (AD) technology used to manage organic wastes can provide benefits to the waste, energy, and agriculture sectors
This study evaluates the effect of codigesting agricultural residues with food waste (FW) and brewery waste (BW) using agricultural waste (AW) from Miscanthus × giganteus, an emerging advanced bioenergy crop
Codigestion of FW and BW with agriculture residues produced some of the highest quality biogas, but the quality was not sustained over time as it was in the case of FW-K
Summary
Anaerobic digestion (AD) technology used to manage organic wastes can provide benefits to the waste, energy, and agriculture sectors. Wastes are digested by microbes and converted into two marketable products: renewable natural gas (RNG) and digestate fertilizers. Of the 292 million US tons of waste entering landfills, 24% is comprised of food waste (FW) that can be diverted for use in AD systems [1]. The composition of feedstock waste greatly influences AD system performance and the quality of output products [2]. Large industrial AD systems consistently monitor and adjust both waste inputs and system conditions to ensure the productivity and health of the microbial community during digestion. Small-scale systems are more vulnerable to instability caused by variable feedstocks [3]. It is essential to understand how FW from different sources will affect AD products, regardless of the scale of application
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