Valorization of pretreated sawdust and poultry manure for biogas and digestate organic fertilizer production

Abstract

This study evaluated the effect of alkaline and biological pretreatment on the co-digestion of sawdust (SD) and poultry manure (PM) for enhanced biogas production and digestate nutrient recovery. Sawdust was divided into two portions and pretreated either with sodium hydroxide (NaOH) (Sample A) or biologically using cattle rumen inoculum (Sample B) prior to anaerobic digestion under mesophilic conditions (35 days) in a 6-L batch reactor. The alkaline-pretreated substrate (Sample A) produced significantly higher cumulative biogas yield (9.37 L; average 0.52 L/day) compared to the biologically pretreated substrate (Sample B) (5.38 L; average 0.30 L/day), representing a 42% increase. Methane content was also higher in Sample A (69.08%) than in Sample B (62.13%). Structural analysis showed substantial lignin and cellulose reduction after pretreatment, particularly under alkaline conditions, which enhanced substrate digestibility. The resulting digestates were rich in macro- and micronutrients, indicating strong potential for agricultural application as biofertilizers. The findings demonstrate that alkaline pretreatment significantly improves lignocellulosic biodegradability and biogas yield, supporting sustainable waste-to-energy and nutrient recovery strategies in developing regions.