Value Addition of Anaerobic Digestate From Biowaste: Thinking Beyond Agriculture

Purpose of Review: This article aims to shed light on the various value-added opportunities arising from the valorization of digestate nutrients. As opposed to the conventional applications of digestate for land/soil applications, this review discusses the key bioconversion routes to microalgae, biofuels, biochemicals, and enzymes production in which digestate is utilized as a feedstock for microorganisms to produce high-value bio-based products. Recent Findings: A comprehensive analysis of key digestate valorization schemes in this review showed that microalgal cultivation and biopesticide production results obtained using digestate provide new directions to optimally utilize this resource. Pilot scale and long-term performance, and environmental assessment of these digestate-based productions will govern their success within the bioeconomy scheme in the near future. Summary: Recovery of nutrients from digestate of anaerobic digestion (AD) and its use as a feedstock in biotechnological processes is an environmentally benign and socially responsible method to treat the waste digestate appearing from digestion plants. The replacement of cost-intensive pure nutrients by digestate could improve the economic feasibility of bioprocesses. This fits in the advanced biorefinery model within the circular bioeconomy scheme by providing new and alternative markets for digestate while increasing the economic incentives for AD.