Decentralized biogas produced through co-digestion of biomass can play an important role in our future renewable energy mix. However the optimal design, planning and use of a biogas production chain is a daunting process. When looking into a biogas production chain one must take into account, first, the biomass availability in quantity, quality and the location, second, the energy demand in energy type, quantity and location and finally the needed machinery and infrastructure to connect them. During this process there are social, legal and environmental issues to overcome, but overall the financial aspects will mostly dictate viability. Hence, the complexity involved in linking the aforementioned aspects is difficult at most.
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This study evaluated the performance of anaerobic co-digestion of cow manure (CM) and sheep manure (SM) in both batch and continuous digesters at 37 °C. Synergistic effects of co-digesting CM and SM at varying volatile solids (VS) ratios (1:0, 0:1, 3:1, 1:1, 1:3) were observed in the batch experiment, with the most effective degradation of cellulose (56%) and hemicellulose (55%), and thus, the highest cumulative methane yield (210 mL/gVSadded) obtained at a CM:SM ratio of 1:3. Co-digesting CM and SM improved the hydrolysis, as evidenced by the cellulase brought by SM and the increases of cellulolytic bacteria Clostridium. Besides, co-digestion enhanced the acidogenesis and methanogenesis, reflected by the enrichment of syntrophic bacteria Candidatus Cloacimonas and hydrogenotrophic archaea Methanoculleus (Coenzyme-B sulfoethylthiotransferase). When testing continuous digestion, the methane yield increased from 146 mL/gVS/d (CM alone) to 179 mL/gVS/d (CM:SM at 1:1) at a constant organic loading rate (OLR) of 1g VS/L/d and a hydraulic retention time (HRT) of 25 days. Furthermore, the anaerobic digestion process was enhanced when the daily feed changed back to CM alone, reflected by the improved daily methane yield (159 mL/VS/d). These results provided insights into the improvement of methane production during the anaerobic digestion of animal manure.
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Abstract written for an poster presentation at the EBA conference in Alkmaar. The flexibility of biogas makes it a very capable load balancer within decentralized smart energy systems. However, within this context the sustainability of biogas production is not fully understood. What is needed is a tool for analyzing the ustainability of biogas production pathways. The main goal, of this research is to design a transparent flexible planning tool capable determining the sustainability of decentralized biogas production chains. This insight will help in designing a tailor-made biogas production chain for a specific geographic location, increasing the effectiveness and sustainability of biogas as a renewable resource.
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