Integrated anaerobic digestion and algae cultivation

Abstract

Anaerobic digestion is considered a versatile process that for years has been used to treat various types of waste. Besides being a low-cost technology applicable in rural and urban locations, anaerobic digestion produces multiple by-products that can be integrated into a biorefinery scenario. Similarly, microalgae biotechnology can adequately complement anaerobic digestion by improving resource recovery through a closed-loop process and contributing to a biobased green circular economy model. Therefore, this chapter aims to address current perspectives on the topic. It covers algae cultivation from anaerobic digestion residues as a post-treatment option and digestate as a potential medium for microalgae growth. Moreover, anaerobic digestion is presented as an energetic valorization route of algae biomass, including strategies to overcome main challenges, such as pre-treatment of microalgae biomass and anaerobic co-digestion. Biogas upgrading during algae cultivation is also discussed. Finally, it presents biorefinery models based on integrated microalgae and anaerobic digestion, reporting the technologies' sustainability and environmental impacts. Future perspectives on the subject are highlighted, encouraging further studies to improve microalgae biomass production, nutrient recovery, wastewater treatment, and biogas upgrading.