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

The 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. (C) 2017 Elsevier Ltd. All rights reserved.