Technica1 assessment of mono-digestion and co-digestion systems for the production of biogas from anaerobic digestion in Brazil

摘要

AbstractThe use of dedicated energy crops (DEC) in anaerobic co-digestion systems becomes attractive, due to their high biogas yield per tonne of fresh matter; furthermore, when mixed with animal waste, they may reach adequate carbon to nitrogen ratios (C:N). This paper presents a performance evaluation of mono-digestion and co-digestion systems for the production of biogas using cattle manure, maize silage and grass silage as feedstock. Biogas plants of large, medium and small-scale, in the electric powers between 100 and 1000 kWe were evaluated. The results showed that the optimum percentage of maize silage and grass silage for co-digestion systems with cattle manure were in the ranges of 22–65% and 18–54%, respectively. The residual heat obtained from the co-digestion and mono-digestion systems was 87% and 75% from the total heat produced respectively, which can be used into processes that demand thermal energy. In all studied systems studied, the carbon dioxide released from the generation of electricity and the burning of methane represented 3% and 97% of the total carbon dioxide avoided, respectively. Finally, the co-digestion systems present better performance in terms of size, electricity consumption and heat consumption compared to mono-digestion systems.Graphical abstractDisplay OmittedHighlights•Dedicated energy crops can contribute to increase the specific biogas yield in anaerobic co-digestion plants (AcoD).•Maize and grass silage can be mixed with cattle manure in percentages of 18–65% for C:N ratios between 20:1-30:1.•CHP in the biogas plant provide electricity and heat for self-consumption, besides residual heat for other uses.•Co-digestion has better performance compared to the mono-digestion system, OLR of these systems are in values close to4.05kg VS/mBD3.d.•The use of DEC can help increase the amount of avoided CO2-eq, which in a context of CDM would be commercialized as CER.