”Increased yield of biogas by post treatment of residual sludge” Energiforsk report 2016:312 Programkonferens Energigasteknik, Göteborg 8/9 juni 2017.

increased yield of biogas by post treatment of residual sludge REPORT 2016:312 Energy Gas Technology   Programkonferens Energigasteknik, Göteborg 8/9 juni 2017.

Feasibilty study on hydrothermal treatment of residual sludge and increased yield of biogas. Project duration 6 months. Final report October 2016. Funding: Samverkansprogram Energigasteknik Swedish Energy Agency and Swedish Energy Research Center Energiforsk. Partners: Biokol Sverige AB Käppala förbundet, Lidingö. Gästrike Vatten AB. Tekniska verken i Linköping AB. R&D partner: Leibniz-Institut für Agrartechnik und Bioökonomie (ATB), Potsdam   Programkonferens Energigasteknik, Göteborg 8/9 juni 2017.

Model of material flow: Biogas digester => HTC =>Biogas digester => Exit Programkonferens Energigasteknik, Göteborg 8/9 juni 2017

Result of digestion tests. Specific CH4 yield related to VS, Volative Solids, content for sewage sludge, two process waters and mixture in ratio 1:5 of sludge and process waters. SS: Sewage sludge, PW1: HTC process water; screw press, filter towel, pore size 100 micrometer PW2: HTC process water; vacuum filtred, filter paper, pore size 12 micrometer Programkonferens Energigasteknik, Göteborg 8/9 juni 2017.

Summary of the findings in the study: Set up: Effluent from aneorbic digester is concentrated to 10% DS and hydrothermal carbonized (HTC). HTC slurry is separated into hydrochar and process water. HTC process water is added to digistate precursor sludge by ratio 1:5. Summary of the findings in the study: a) Methane yield + 31% => Digestate mass +20% plus increased gas yield +11%. b) Thermal energy for HTC well covered by increased amount of gas. c) Phosporous in precursor sludge is concentrated in the hydrochar. d) Ammonia concentration after dilution 5 times is well below critical limit. e) Heavy metals are accumulated in the hydrochar. f) Side benefits: Hygenization and easy dewatering. Conclusion: It´s possible to achieve significant more biogas by hydrothermal treatment of the residues and recirculation of process water. Programkonferens Energigasteknik, Göteborg 8/9 juni 2017.

Mats Linder and Hans Simonsson, Gästrike vatten AB, Gävle. Acknowledgements: Reference group: Mats Linder and Hans Simonsson, Gästrike vatten AB, Gävle. Jan Moestedt Tekniska verken i Linköping AB. Devisa Karat, Käppalaförbundet Lidingö: Laboratory work: Benjamin Wirth and Maja Werner, ATB: HTC and aneorobic testing. Ignasi Puigdomenech: equilibrium calculations. Agnieszka Witkiewicz, Käppalaförbundet: Aneorobic testing. Project leader: Eva Björkman, Biokol Sverige AB. Programkonferens Energigasteknik, Göteborg 8/9 juni 2017.