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Anaerobic Digesters as Biorefining Hubs: A look at sustainable resource recovery in Vermont
Summary
Vermont farmers can turn food scraps and manure into clean energy by feeding them together into biogas systems, which not only keeps waste out of landfills but also produces useful fertilizer without adding harmful phosphorus levels. The catch: researchers found tiny plastic particles (microplastics) in all the materials tested, including the manure, food waste, and soda waste—a reminder that as we recycle food waste, we may also be recycling plastic contamination back into farm soil and, potentially, our food supply.
Food waste entering landfills is a major global source of greenhouse gas emissions, highlighting the need for improved diversion and treatment strategies. In Vermont this issue is being addressed through ACT 148, enacted in July 2019, which bans the disposal of food waste in landfills and requires it be diverted to uses such as animal feed, composting or anaerobic digestion. This study explores the potential to increase food and beverage waste management through anaerobic co-digestion using manure on Vermont dairy farms. Digestate, pre-consumer beverage waste, and post-consumer food waste were collected locally and assessed by benchtop biomethane potential (BMP) assay over 30 days. Feedstocks and digestate were analyzed for nutrient composition before and after digestion to understand the potential impact of food waste co-digestion on farm nutrient management. Microplastic contamination was also assessed for each feedstock prior to BMP testing to better understand the implications of accepting food waste into existing digesters. Methane production was 401 � 141 mL CH4/g VS and 389 � 123 mL CH4/g VS with the addition of household food waste or de-packaged soda waste respectively to manure substrates. Food waste addition at levels resulting in desired methane production did not substantially alter the phosphorus content and availability in digestates. These findings demonstrate the potential benefits for farmers who incorporate post-consumer food waste into their AD systems, offering an economic incentive while supporting statewide sustainability efforts. However, microplastic contamination was detected in all materials tested (digested dairy manure, food waste and soda waste), underscoring an important consideration for system management. Farmer survey findings will also be presented to identify factors that may limit food waste intake on dairy farms.