SUSTAINABILITY Valorization of harmful algal blooms and food waste as bio-methane Sara Plude 1 | Goksel N. Demirer 1,2 1 School of Engineering and Technology, Central Michigan University, Mt. Pleasant, Michigan, USA 2 Institute for Great Lakes Research, Central Michigan University, Mt. Pleasant, Michigan, USA Correspondence Goksel N. Demirer, School of Engineering and Technology, Central Michigan University, Mt. Pleasant, Michigan, USA. Email: demir1g@cmich.edu Funding information Central Michigan University Abstract This study evaluated anaerobic digestibility and biogas production potential of micro- algal biomass and food waste. Biochemical Methane Potential (BMP) assays were conducted to determine the biogas generation potential of microalgal biomass and food waste both separately and together. Results indicated that several algal species in the collected samples are among the major harmful algal bloom (HAB) taxa found in freshwaters in North America. Bio-methane yields for mono-digestion of micro- algal biomass and food waste were found to be 131–188 and 430–542 ml of bio- methane per gram of volatile solids (ml CH 4 /g VS), respectively; while bio-methane yield for co-digestion of microalgal biomass and food waste was 426–505 ml CH 4 /g VS. Co-digestion of microalgal biomass and food waste resulted in up to 12.3% increase in methane production relative to mono-digestion of these substrates. Statement of Industrial Relevance: Harmful algal blooms (HABs) have many adverse environmental impacts such as lowering dissolved oxygen concentrations, altering aquatic food webs, producing toxins, and taste-and-odor compounds. There has been a dramatic rise in the severity and geographical range of HABs with the increasing environmental degradation over the past century. This work provides a new insight in terms of integrating HABs disposal and valorization for bio-methane generation as a renewable energy. Bioenergy generation from mechanically harvested HABs along with its environmental and resource-conserving benefits are relevant to waste man- agement and biogas industries. Significance: The results indicate that integrating mechanical harvesting of HABs with valorization of the collected algal biomass will increase its economic feasibility. Moreover, anaerobic co-digestion of HABs and food wastes generate extra bio- methane relative to mono-digestion of these substrates by balancing the C:N ratio. KEYWORDS anaerobic digestion, biogas, co-digestion, food waste, microalgal biomass 1 | INTRODUCTION While algal communities are natural components of healthy aquatic eco- systems, under certain conditions (e.g., increased temperatures and nutri- ent concentrations), algae may grow excessively, or “bloom, ” and produce toxins that can harm human health, animals, aquatic ecosystems, and the economy. 1 There has been a dramatic rise in the severity and geographical range of harmful algal blooms (HABs) with the increasing environmental degradation over the past century. The most sustainable approach to man- age HABs is based on controlling nutrient inputs. However, this recovery can be delayed due to extensive sediment reserves that generate internal nutrient loading for many subsequent years. 2 Received: 10 February 2020 Revised: 17 September 2020 Accepted: 10 November 2020 DOI: 10.1002/ep.13561 Environ Prog Sustainable Energy. 2020;e13561. wileyonlinelibrary.com/journal/ep © 2020 American Institute of Chemical Engineers 1 of 7 https://doi.org/10.1002/ep.13561