Christiane Herrmann1, Navajyoti Kalita2, David Wall3, Ao Xia4, Jerry D Murphy5. 1. The MaREI Centre, Environmental Research Institute, University College Cork, Ireland; Leibniz Institute for Agricultural Engineering Potsdam-Bornim, Department of Bioengineering, Max-Eyth-Allee 100, 14469 Potsdam, Germany. 2. The MaREI Centre, Environmental Research Institute, University College Cork, Ireland. 3. The MaREI Centre, Environmental Research Institute, University College Cork, Ireland; School of Engineering, University College Cork, Cork, Ireland. 4. The MaREI Centre, Environmental Research Institute, University College Cork, Ireland; Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Chongqing University, Chongqing 400044, China. 5. The MaREI Centre, Environmental Research Institute, University College Cork, Ireland; School of Engineering, University College Cork, Cork, Ireland. Electronic address: jerry.murphy@ucc.ie.
Abstract
Microalgae can be used to upgrade biogas to biomethane and subsequently be digested for biogas production. However, the low C:N ratio of species such as Arthrospira platensis may cause ammonia inhibition and low process stability during anaerobic digestion. This study investigates co-fermentation of A. platensis with carbon-rich co-substrates (barley straw, beet silage and brown seaweed) at a C:N ratio of 25 to enhance biomass conversion. No synergistic effects on biomethane potential could be proven in batch fermentation tests. However continuous digestion trials showed significantly improved process stability. Mono-digestion of A. platensis was stable only at an organic loading of 1.0gVSL(-1)d(-1). The optimum process co-digested A. platensis with seaweed and achieved stable operation at an organic loading of 4.0gVSL(-1)d(-1). Co-digestion of microalgae and seaweed can be effectively applied to integrated coastal biomethane systems.
Microalgae can be used to upgrade biogas to biomethane and subsequently be digested for biogas production. However, the low C:N ratio of species such as n class="Species">Arthrospira platensis may cause ammonia inhibition and low process stability during anaerobic digestion. This study investigates co-fermentation of A. platensis with carbon-rich co-substrates (barley straw, beet silage and brown seaweed) at a C:N ratio of 25 to enhance biomass conversion. No synergistic effects on biomethane potential could be proven in batch fermentation tests. However continuous digestion trials showed significantly improved process stability. Mono-digestion of A. platensis was stable only at an organic loading of 1.0gVSL(-1)d(-1). The optimum process co-digested A. platensis with seaweed and achieved stable operation at an organic loading of 4.0gVSL(-1)d(-1). Co-digestion of microalgae and seaweed can be effectively applied to integrated coastal biomethane systems.