Biogas and biomethane production potential via anaerobic digestion of manure: A case study of Portugal

Anaerobic digestion is a promising technology that can be part of the solution to meet the increasing energy demand while reducing the harmful effects on the environment. The objective of this work is to assess Portugal's potential to produce biogas or biomethane via anaerobic digestion of manure. First, a spatial analysis of manure availability was done using ArcGIS. Then, a thermodynamic model of the production system was created in MATLAB, which includes three proposed production paths. The outputs of the thermodynamic model served as inputs for an economic analysis, also performed in MATLAB, and a life cycle assessment done using SimaPro software. Findings from the spatial analysis revealed that the centre and south areas (excluding Algarve) of Portugal have the highest manure availability, 73.6% of the national amount, and the Azores archipelago has high availability of cattle manure, 17.88% of the national amount. The total possible amount of production plants was estimated as 743. The thermodynamic model results show that the region of Leziria do Tejo has the highest biogas and biomethane production potential, at 557172 t/year and 352364 t/year. Furthermore, the total potential biogas and biomethane production in Portugal was estimated as 3561947.05 t/year and 1791402.48 t/year. Regarding energy, the calculated efficiencies of biogas and biomethane production were 62.96% and 51.82%. The economic analysis yielded national average selling prices of 0.8174 euro/kg and 1.290 euro/kg for biogas and biomethane. The life cycle assessment showed that the main concerns regarding this type of systems are toxicity impacts and resource consumption.