Anaerobic treatment of sugarcane bagasse. An opportunity for sustainability in rural environments?

Junin is a town in Ecuador known for producing alcohol on an artisanal scale, with around 45 distilleries. The artisanal alcohol production process uses firewood as fuel, dumping sugarcane bagasse (SB) outdoors, affecting the environment. The research aimed to assess the techno-economic feasibility of SB treatment for energy generation in artisanal distilleries. The alternatives for the energy use of SB were anaerobic digestion (AD) and combustion. AD evaluation used 5 inoculum-to-substrate ratios (ISR) in biomethanation potential (BMP) assays. The 2:1 ISR presented the highest methane yield for SB (195.54 NLCH4 kgVS−1). Likewise, the estimation of the energy potential by combustion was through thermogravimetric analysis (TGA), resulting in a higher heating value of 16.62 MJ/kg DM. The results of the BMP assays and TGA contributed to the formulation of three SB use scenarios: (i) AD + biogas combustion (S1), (ii) biogas for heat and power generation (S2), and (iii) SB combustion (S3). The evaluation of the techno-economic viability used the financial indicators Net Present Value (NPV) and Internal Rate of Return (IRR), among others. Some variables analyzed were the gross energy generated and the greenhouse gas emissions avoided. The financial indicators associated with S1 and S3 were the most satisfactory compared to S2, which had the highest investment recovery period (11.01 years), and the lowest IRR (13.05 %). All scenarios were feasible, with NPVs positive and IRRs higher than annual interest rate (8 %). Only S3 supplies the energy required in the distillation of ethanol (3,959.702 MJ d−1). However, S1 and S2 offer the highest GHG decreases, 16.96 tCO2e per year. These results are an initial reference for implementing biomass recovery technologies in rural areas of Ecuador as an opportunity for sustainability.