WP6 – Anaerobic digestion of KOD biopulp, optimization and upgrading of biogas

The aim of this work package is the use of the outbound product, originated from the digestion of biopulp, for ecological farming. In addition, process conditions for the maximum biogas production and the biological upgrading of biogas, maximum TS % in the digester, dilution of incoming material, anaerobic turnover rates, etc. will be tested and analysed. The fertilizer quality is determined by analyzes and in situ field trials (WP3). Bioaugmentation will be performed to overcome the inhibition effect due to high salt content in the digester. A bacterial culture acclimated at salt content will be applied that will enable the digester to be operated at a high solids content and dilution by recycling without inhibiting the methane production.

The produced biogas is upgraded with a new technology using the biological conversion of carbon dioxide by hydrogen addition to methane. All previous experiments with biological upgrading of biogas (conversion of carbon dioxide to methane) have been challenged primarily on the transfer of hydrogen from the gas to the liquid phase. The project will demonstrate the usage og a system with a separate biological reactor with a special hydrogen transferring unit on a recycled liquid stream supplied to the biological reactor. The upgraded biogas will be of the quality enabling its deployment on the natural gas network. The pilot trials will be used as part of the assessment basis for full-scale demonstration. Full-scale demonstration will also be dependent on adequate amounts of hygienized biopulp, so in case of insufficient amount of hygienized biopulp, a new prototype of the pilot plant will be developed for continued large-scale tests.