Anaerobic co-digestion of agro-industrial wastes: A systematic review focused on feedstock physicochemical parameter optimization Academic Article in Scopus uri icon

abstract

  • Agro-industrial waste (AIW) valorization is crucial in transitioning the agro-industry towards a circular bioeconomy. The high nutrient content that characterizes AIW poses significant environmental threats but also offers an opportunity for bioenergy generation through anaerobic digestion (AD). Most AIW have imbalanced nutrient compositions that cause a poor performance when traded by AD. Thus, Anaerobic codigestion (AcoD) of complementary AIW has been used to avoid inhibition and enhance process performance. This systematic review investigated optimization of physicochemical parameters in AIW AcoD systems reported in the last decade. Three databases were searched, obtaining 237 articles. After removing duplicates, out-of-scope studies and exploratory AcoD without optimization, 61 studies were included. Data regarding operating parameters, feedstock characteristics, optimization parameters, and the coproducts (biogas, digestate and energy generation) were extracted. The technical analysis revealed that optimized AcoD enhanced process performance, increasing CH4 yields up to 20-fold compared to monodigestion, shortening lag phases by up to 7 days, and reaching 60 % VS removal. Optimization of C/N ratios was found to lower TAN and VFA accumulation, buffer acidic wastes and improve microbial adaptability. Beyond energy, AcoD optimization highlights opportunities for valorization of by-products such as VFAs and high stability digestates. Nonetheless, seasonal and compositional AIW variability remains one of the most significant barriers to achieving stable operation that could be mitigated with strategies such as pretreatment and batch characterization. Moreover, feedstock transport costs remain the most significant limitation for large-scale applications, highlighting the importance of GIS-based models for plant location planning. © 2025

publication date

  • March 1, 2026