Protein nanofiber additives improve biogas yield, kinetics, and digestate dewaterability in anaerobic digestion

Anaerobic digestion (AD) plays a key role in wastewater treatment, converting organic waste into biogas and biofertilizers. Yet, the efficiency of AD processes are often constrained by slow microbial kinetics, long digestion times, and poor digestate dewaterability. In this study, we introduce bovine serum albumin (BSA)-derived protein nanofibers (PNFs) as a novel multifunctional bio-additive designed to mimic extracellular polymeric substances (EPS). Biochemical methane potential (BMP) assays were conducted under mesophilic conditions to investigate impacts of BSA PNFs on biogas production, whereby incorporation of 900 mg/L (relative to inoculum) led to a synergistic 16 ± 4 % increase in cumulative biogas production ( p < 0.05). Under high organic loading, BSA PNFs reduced the lag phase and improved microbial activity, shortening ultimate digestion time by 40 % from 35 to 20 days. These improvements were linked to enhanced microbial granulation and community stability: BSA PNFs altered the EPS profile, increasing tightly bound protein content and promoting microbial aggregation. Microscopy revealed improved floc morphology and granule formation in PNF-treated samples. PNF integration also enhanced digestate dewaterability, with a 20 ± 2 % reduction in sludge volume index (SVI) and a 2 ± 0.5 % increase in total solids. These findings demonstrate the potential of BSA PNFs to greatly enhance AD performance and sustainability in wastewater treatment. • Bovine serum albumin (BSA) protein nanofibers (PNFs) enhanced biogas yield by 16 ± 4 %. • BSA PNFs cut ultimate digestion times from 35 to 20 days under high load. • PNFs promoted granulation and the stabilization of microbial aggregates by increasing tightly bound protein concentration. • BSA PNFs improved digestate dewaterability by 20 ± 2 %, reducing sludge volume index.