A Self-sustaining Biorefining Concept to Convert Agricultural Residues into High-Value Chemicals

Farm-based agricultural and food residues represent an underutilized reservoir of biomass rich in carbon and other nutrients. These residues have a great potential as feedstocks for the production of high-value chemicals. However, conversion technologies along with high energy and water demand hinder the utilization of these residues. This study presented a new concept of integrating anaerobic digestion (AD), electrocoagulation (EC), and aerobic fungal cultivation to self-sustain the conversion of animal manure and food wastes into a high-value product - chitin/chitosan as a bio-pesticide for agricultural applications. The manure and food wastes are first anaerobically digested to produce methane energy, liquid digestate, and solid digestate (treated digested fiber). Liquid digestate is treated by an EC process to reclaim the water for the use of fungal cultivation. The treated solid digestate is mixed with the EC water to carry out Rhizopus oryzae cultivation of chitin/chitosan accumulation. The methane energy is used as the power source to support the entire biorefining process. A detailed mass and energy balance on the studied biorefining concept concluded that integration of anaerobic digestion, EC, and aerobic fungal fermentation could be a truly green process of high-value chemical production with neutral (or positive) energy and water balance.