Anaerobic co‐digestion of food waste and microalgae in an integrated treatment plant

Abstract

BACKGROUND Anaerobic co‐digestion has been considered for improving anaerobic digesters’ stability and methane production, particularly for residues with low biodegradability or lack of alkalinity. Food waste was identified as a biomass with macro and micronutrients unbalance and low alkalinity content, both of which hamper its anaerobic digestion. The present study focused on evaluating the anaerobic co‐digestion of food waste and microalgal biomass harvested from an open pond treating food waste digestate. RESULTS According to BMP tests results, mono‐digestion of food waste showed low methane yield (~35–68 mL CH4·g VS−1), most likely due to acid accumulation, as was observed by the low pH and low methane content in biogas. Process stabilisation was further attested through anaerobic co‐digestion with microalgae at different proportions in terms of volatile solids (VS). The highest methane yield was obtained at 75:25 of food waste and microalgae (514 mL CH4·g VS−1), with the highest synergy between substrates (28% higher compared to theoretical value). Moreover, estimates for real scenarios of co‐digestion in an integrated treatment system composed of an anaerobic reactor and microalgae‐based ponds revealed that, due to low microalgae production, proportions of 99:1 would be more realistic. CONCLUSION Research showed how a higher proportion of food waste was preferable, although a minimum amount of microalgae seemed important for maintaining process stability and increasing methane production. In the demonstration‐scale plant, co‐digestion and co‐disposal was estimated to be more sustainable when carried out in solid‐state or with recirculation of treated effluent. © 2021 Society of Chemical Industry (SCI).

Anaerobic Digestion of Food Waste—A Short Review

“…These changes led to a decrease in the acidity of the environment, leading to an increase in the activity of methanogenic bacteria, which in turn allowed biogas production to be higher by 258.16 mL•g −1 VS and by 359.74 mL•g −1 VS, compared to the mono-digestion of FW and WH. Ferreira et al (2021) showed that a mixture of food waste and microalgae (MA) increased methane yields, compared to the separate digestion of FW and MA, by 21% and 55%, respectively [103]. Based on the results, it was concluded that the increase in the production of the gas in question was due to an increase in the buffer capacity of the ferment in the digester and a decrease in the accumulation of organic acids through the addition of microalgae.…”

Emerging Sustainability in Carbon Capture and Use Strategies for V4 Countries via Biochemical Pathways: A Review

“…Co-digestion of two or more substrates has a beneficial effect on increasing biogas production yield by up to 200% and improving the stability of the anaerobic digestion process [57]. Ferreira et al [58] achieved the highest methane yield using a mixture of 75% food waste and 25% microalgae. This resulted in a methane yield of 514 mL/gVS and a synergy between the substrates that was 28% higher than the theoretical value.…”

Microalgae Technology in Aquaculture Applications: A Comprehensive Literature Review

“…Microalgae aid in removing organic pollutants from wastewater, demonstrating promise in waste management and water quality improvement (Mulbry et al, 2008). Additionally, the integration of microalgae cultivation with waste anaerobic digestion enhances system stability and methane production, highlighting the potential for sustainable waste treatment and biomass generation (Ferreira et al, 2022).…”