Towards sustainable methane supply from local bioresources: Anaerobic digestion, gasification, and gas upgrading

Abstract

Methane is a versatile and storable energy carrier, which is likely to play an important role in the European transition towards a low fossil carbon energy sector. We investigate the potentials for meeting regional methane demands through conversion of local residual bioresources for supply of bio-based CH4. We have developed a tiered assessment framework involving i) allocation of residual and constrained bioresources to conversion pathways based on physical and biochemical properties, ii) life cycle assessment (LCA) of technology conversion pathways through process-oriented parameterisation of the LCA model, and iii) LCA modelling of system-level technology implementation scenarios for quantification of regional potentials for bio-based CH4 supply and environmental savings, in view of current uses of the same bioresources. Two main technology conversion pathways are included: gasification and anaerobic digestion, both with hydrogen enhancement. The latter was also considered with water scrubbing upgrading. The framework is implemented for the French region, Occitania, with a residual bioresource potential of 48 TWh·y−1 (distributed on 41 different bioresources), and an annual methane demand of 17.5 TWh·y−1, currently supplied by natural gas. The assessment results clearly demonstrate that utilisation of available residual bioresources has tremendous potential both for covering current gas demands in the region (up to about seven times in some scenarios) but also for a reduction in climate change impacts from the region (up to about 37%).