Anaerobic digestion in global bio-energy production for sustainable bioeconomy: Potential and research challenges

Wastes are unceasingly generated in the world, and most of them can be recycled, reused, or recovered to promote a circular economy. Among waste treatment approaches, the anaerobic digestion (AD) process has been considered as an ideal process due to its ecological benefits (reduction of unpleasant odor, pathogens accumulation, or greenhouse gas emission), social and economic advantages, and energy saving. In addition to biogas production, this process can be used to produce various bioproducts, such as biopolymers, bioplastics, biomass, biofertilizers, and biolipids. Interestingly, the AD process residue or digestate is a nutrient-rich by-product that can be used as a biofertilizer for agronomical purposes to balance N-P cycle in the soils. Despite of numerous benefits of AD, less than 1 % of waste is treated by this process. This process has the potential to be integrated with other waste treatment approaches to increase waste treatment efficiency. Therefore, it is essential to focus on each advantage and clarify ambiguity in order to satisfy more countries for employing AD for waste treatment. In this review, various benefits of AD are evaluated; and its potential impacts on particularly agriculture are examined in detail. Additionally, potential biomass and wastes that can be used for anaerobic digestion worldwide are deliberated. Besides, a critical perspective has been developed on the economic, environmental, and social evaluation of the benefits of AD and, as a final point, focused on an integrated circular cascading approach.