Bioenergy production from nopal cladodes and dairy cow manure on a farm-scale level: Challenges for its economic feasibility in Mexico

Abstract

Anaerobic digestion of agricultural biomass is recognized as a good option for generating affordable and environmentally sustainable renewable energy. This study evaluated the economic feasibility of biogas production through nopal-manure co-digestion on a farm-scale under Mexican conditions. Three utilization pathways were analyzed: biogas production, electricity production and methane production. The potential for greenhouse gas mitigation and digestate utilization were included in the total benefits. Electricity production had the greatest potential for greenhouse gas mitigation, reducing 0.334 kg of CO2-eq per MJ of electricity generated, whereas the results for biogas and biomethane production were much lower (0.057 and 0.058 kgCO2-eq·per MJ respectively). The financial analysis showed that biogas production does not recoup the initial investment layout. Electricity and biomethane production had an Internal Rate of Return of 7.5% and 7.2% respectively. The value of displaced energy and digestate are the factors that contribute most to profitability, while the market value of mitigation is negligible. The challenges to improving profitability are: reducing biomass production costs, properly valorizing the digestate, improving carbon credits and promoting the production and use of bioenergies on a farm-scale level.