Ex-post Evaluation of Geomembrane Biodigesters to Treat Organic Residuals in Mountain Ecosystems

Abstract

The economic and financial efficiency of two 10 m3 geomembrane biodigesters to treat swine and cattle residuals was evaluated. The study took place at the Cooperative of Credits and Services (CCS) of the municipality of Cumanayagua, Cienfuegos, Cuba. Its aim was to apply a procedure to evaluate investment projects management, based on the logical framework approach. The indicators for evaluation and the indexes of component and management were determined in two moments within the life cycle of the biodigesters: preparation and evaluation. The biodigester for swine residues had +185% economic efficiency, totally corresponding to the results from physical and financial efficacy, along with 69% undervalued operational costs. On the other hand, the biodigester for cattle residues had -90%, -87% periodic efficiencies, along with decreased relative physical, financial and cost efficacies, as well as a reduction of operational costs to 37 and 67%, respectively. In general terms, the economic efficiency had the greatest difficulties during the first three years of the application, caused by unbalances between the planned income and the real expenses. To conclude, biodigesters ranged from low to moderate operation, according to the values preset for the research. Technology proved feasibility, but the economic and financial variables were monitored permanently.

Keywords

• impact assessment
• monitoring
• management
• anaerobic digestion
• renewable energy
• cattle raising
• methane
• biogas