Bioenergy potential of paper waste: Fungal pretreatment and kinetics modelling

Abstract

Using the fungi Phanerochaete chrysosporium and Aspergillus niger as a biopretreatment agent to improve degradation of lignocellulosic paper with analogous increase in biogas production, anaerobic digestion (AD) was executed. Milled and hydrothermally-treated (HT) or steamed paper were separately inoculated for 360 hr at 28 °C with each fungal species, with an uninoculated treatment as control. AD experiment was conducted in bench-scale batch bioreactors for 48 days at 40°C. The initial characteristics of the feedstock and inoculum were examined in addition to biomethane yield, total and volatile solids degradation, and lignocellulosic content removal. The pretreatment of milled paper with P. chrysosporium resulted in the highest biogas yield of 1035 mL/gVS, followed by A. niger with a yield of 550 mL/gVS. These values represented a significant increase (p < 0.05) of 226 % and 73 % compared to the untreated feedstock, respectively. P. chrysosporium pretreatment achieved the highest total solids removal of 66.85 %, whereas A. niger pretreatment resulted in the maximum volatile solids removal of 64.63 % in HT-paper waste. P. chrysosporium also exhibited the highest lignin removal efficiency, with 84.31 % in milled feedstock and 79.17 % in the steamed state. A. niger showed 77.28 % and 67.09 % lignin removal in the milled and HT paper, respectively. The study demonstrated that pretreatment with P. chrysosporium and A. niger significantly (p<0.05) improved biogas production by facilitating the biodegradation of lignocellulosic components. All measured biomethane data from experiments fitted adequately to the modified Gompertz model with R² ranging from 0.97 to 0.99.