Integration of algae cultivation to anaerobic digestion for biofuel and bioenergy production

Anaerobic digestion (AD) is a commonly used biowaste treatment technology. Biogas and digestate (also known as digestate) are two products. Digestate contains nutrients such as ammonia nitrogen. Recovering nutrients from digestate as marketable products are critical for AD plants to meet regulatory and market demands while generating additional revenue. Traditional digestate processing technologies, i.e., land application, require energy inputs and raise environmental risks. Alternatively, microalgae can remove various nutrients from digestate, particularly nitrogen and phosphorus, while generating biomass for biochemicals and biofuels production. Microalgae can biosynthesize both inorganic and organic carbons derived from AD and sequestrate atmospheric CO₂. Combining digestate treatment and microalgal cultivation has become a topic of interest in the past years, although the economic feasibility of such a project remains a challenge. This chapter covers the background, technology principles, and application schemes of integrating AD digestate treatment with microalgae cultivation.