This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ Preprints) and either DOI or URL of the article must be cited.
Anaerobic co-digestion of dairy manure and food wastes is increasing in the New England region of the United States because of policy measures intended to divert organic materials from landfills, reduce greenhouse gas emissions, and increase renewable biogas energy production. The sustainability of this approach depends on the management and valorization of remaining solid and liquid residues (i.e., digestates) after anaerobic digestion. Few studies have characterized digestates derived from combined dairy manure and food waste feedstocks. In this study, we analyzed screw-press separated liquid and solid digestates from 6 of 26 (23%) operational full-scale facilities in New England. We quantified multiple pools of nitrogen and phosphorus in these materials, with results suggesting that in most cases these nutrients largely exist in forms that can be recycled via slow-release fertilization, with smaller fractions in forms more easily lost to the environment. Furthermore, we found that solid digestates can inhibit mycelial growth of a common soilborne fungal pathogen, Rhizoctonia solani, suggesting potential to manage resident soil pathogens. Capitalizing on both nutrient recycling and pathogen suppression co-benefits will likely be useful in digestate valorization efforts.
Version 1 has been submitted to a peer reviewed journal.