Biogas plant upgrading with a thermochemical- and biological-integrated solution

Offentlig prosjektsammendrag

Biogas is produced in anaerobic digester (AD) where microorganisms convert organic materials to methane and carbon dioxide. Biogas from waste is renewable energy and can significantly contribute to greenhouse gas (GHG) emission reduction. Compressed biomethane (CBM) and liquified biomethane (LBM) will play key roles in the transport sector in the Norwegian scheme of phasing out fossil fuels. It is expected that the biogas fuel market will grow from 300 GWh in 2016 to 3000 GWh in 2025. The typical organic conversion rates in AD are ranged 30-50%, which means over 50% of organics in waste end up in digestate. Digestate can be used as organic fertilizer. However, issues, such as microplastics and pharmaceutical residues in digestate, GHG emission during digestate storage and transportation and high transportation costs for diluted digestate, are still associated with current digestate handling practises. On the other hand, lignocellulosic wastes, such as garden waste, sawdust, agricultural wastes and forest wastes, has enormous potential as bioenergy. However, these waste streams are not considered as primary feedstocks to AD due to existence of lignin and its strong interaction with cellulose and hemicellulose which is the main hurdle to the conversion of lignocellulosic materials to biogas. In this study a thermochemical- and biological-integrated solution will be developed and tested to recover energy in the form of biogas by converting non-biodegradable organic in digestate and lignocellulosic materials to biodegradable feedstock to AD, and meantime to produce biochar and eliminate most of microplastics and pharmaceutical residues in digestate. The proposed solution would empower biogas plants to maximize biogas production via treating digestate and lignocellulosic wastes in existing facilities to meet growing demands from the transport sector and become more sustainable when facing stringent government regulations in the future.