Abstract:
Pakistan is critically leading towards amplified air, water and soil pollution caused due to open dumping of municipal solid waste. Organic fraction of biodegradable wastes may be converted into renewable bioenergy by the process of anaerobic digestion. Biological conversion of wastes may be one solution to many environmental problems and bioenergy is a virtuous, greenhouse friendly substitute for fossil fuels and way forward to sustainable development. Organic content of municipal solid waste generated in Pakistan comprises of 53-58 per cent kitchen waste and 6-8 per cent paper waste. Presence of 50-56 per cent cellulose content in paperboard waste makes it a potential feedstock for anaerobic digestion but the major limitation is the presence of lignin: 17-23 per cent , that hinders and elongates the hydrolytic phase of anaerobic digestion, therefore, leads to lesser biogas production. Pretreatment of lignocellulosic substrates prior to digestion may enhance the biogas yield and quality by minimizing the time required for the initial hydrolysis of the feedstock. The study was aimed to investigate the synergistic effect of anaerobic co-digestion of paperboard waste with organic kitchen residues at mesophilic temperature of 35±2°C and pretreatment of paperboard waste with alkali (NaOH), hydrothermal and ultrasonic on the rate of hydrolysis and biogas production. Paperboard waste undergoes 76, 68 and 42 per cent delignification for alkali, hydrothermal and ultrasonic pretreatments, respectively. Whereas the biogas yields increased up to: Alkali (70 per cent ) > hydrothermal (61 per cent ) > ultrasonication (45 per cent ) as compared to the control (untreated paperboard waste only), with methane content ranged between 43.6-68 per cent . Organic loading rate for stable digestion process was optimized at 5 g VS/l, which resulted in 25 and 33.9 per cent more biogas production as compared to escalated loading rates of 10 and 15 g VS/l, respectively
