Biogas production from organic wastes in anaerobic digestion process

The dramatic rise in municipal solid waste (MSW), primarily driven by urbanization and population growth, presents significant environmental and management challenges globally. In Canada and specifically Quebec, landfilling remains a predominant practice, causing severe issues such as groundwater contamination from leachates and greenhouse gas emissions from decomposing organic fractions, significantly contributing to climate change. The organic fraction of municipal solid waste (OFMSW) represents a considerable portion of MSW, particularly rich in biodegradable materials like food and yard waste, offering substantial potential for renewable energy production through waste-to-energy technologies. Anaerobic digestion (AD) has emerged as a sustainable technology capable of biologically converting OFMSW into biogas thus significantly reducing environmental impact. However, conventional AD processes face critical operational limitations, particularly under high organic loading conditions where inhibitors such as ammonia and volatile fatty acids accumulate, adversely affecting microbial performance and reactor stability. This research investigates an innovative integration of microwave-assisted pyrolysis (MAP) and AD processes, exploring the beneficial role of biochar, a carbon-rich porous material, as an additive to enhance AD performance. Biochars synthesized via MAP from lignocellulosic biomass exhibit tailored physicochemical properties, including high surface area, excellent buffering capacity, enhanced electron transfer capability, and strong adsorption potential, attributes vital for mitigating inhibitory effects in AD systems. The study systematically explores how biochar dosage, particle size, and its physicochemical characteristics influence methane production and overall digestion stability and efficiency under high organic loading. Experimental findings reveal that biochar significantly reduces lag phases and stabilizes methane production, particularly in fresh OFMSW digestion scenarios, albeit without increasing the total biomethane potential of inherently stabilized substrates. It is shown that biochar properties produced at moderate to high microwave power provide optimal performance under varied operational conditions, demonstrating a practical approach to addressing high-loading operational challenges. Using real OFMSW samples from waste treatment plant (TRIOM en BEAUCE, QC, Canada), this study demonstrates that pretreatment (Bio-Dryer) and biochar supplementation in anaerobic digestion should be systematically evaluated and optimized. The effectiveness of biochar is strongly influenced by organic loading, with higher loads generally yielding greater improvements. In contrast, bio-drying can reduce methane yield despite potential benefits for process stability. The combination of biochar derived from MAP with AD offers a robust approach to maximize OFMSW diversion from landfills, advancing sustainability goals. This study contributes significantly to the field by introducing quantitative evidence supporting the use of MAP-derived biochar in AD systems, presenting a novel, integrative approach to municipal waste management, enhancing renewable energy recovery, and mitigating environmental pollution.