Thermophilic self-fermentation of chicken manure for enhanced soluble metabolite products and bio‑hydrogen production

Treating chicken manure (CM) through anaerobic digestion encounters a hurdle due to its high nitrogen content, leading to volatile fatty acid accumulation and methanogenesis disruption. To overcome this, redirecting the process to yield soluble metabolite products (SMPs) and hydrogen is proposed. Mesophilic (30 °C) and thermophilic (55 °C) acidogenesis were employed, utilizing self-fermentation and sludge augmentation at various total solids (TS) concentrations ranging from 2.5 % to 20 %. SMP production showed direct proportionality to TS concentration. Optimal conditions were observed in thermophilic self-fermentation at 15 % TS, yielding 0.20 ± 0.01 g SMPs/g volatile solid. Moreover, the mass balance analysis revealed 46.68 g of SMPs, equivalent to 53.82 g of soluble chemical oxygen demand (SCOD) solubilized in the total SCOD of 63.56 g in the effluent. Although thermophilic bioaugmentation enhanced hydrogen production, its impact on SMPs was insignificant. This study underscores the potential of CM self-fermentation, highlighting its organic matter and microorganism-rich characteristics.