Potential applications of protein-rich waste: Progress in energy management and material recovery

The protein-rich substrates (PRSs) are generated extensively as stated by the Food and Agriculture Organization (FAO) of the United Nations. Recently, enormous research data is available on the use of PRSs for biomethane and biogas production. However, the complete utilization of PRSs from energy and material recovery has not been comprehensively reviewed. Thus, this review emphasized a deep discussion on the appropriate use of PRSs for high biomethane and biogas production, based on the data obtained from the recent publications. This review also highlights the flow of nitrogen during PRSs utilizations for energy and material recovery, and challenges (such as high ammonia production and unbalanced C/N ratio) during anaerobic digestion (AD) of PRSs. The enhancement strategies (such as the addition of supplements, pretreatments, and co-digestion) have been suggested for the improvement of PRSs digestibility and biomethane production. The microbial interplay during AD of PRSs, shifts in the microbiome during co-digestion, and addition of supportive media have also been deliberated to provide a comprehensive framework. The applications of PRSs in material and value-added products recovery have also been deliberated. PRSs could potentially be used for energy recovery via AD in which hydrogenotrophic methanogens dominate under a high concentration of ammonia. PRSs and the digestate produced after AD of PRSs have high organic fertilizer application value. The comprehensive evaluation of the different applications of PRSs can act as a pillar in future PRSs-based research. [Display omitted]