Production costs and operative margins in electric energy generation from biogas. Full-scale case studies in Italy

• Case studies for economic feasibility of electric power from biogas in Italy are presented.
• Electric energy production costs depend on biomass supply, management and investment.
• Strong dependence on substrate type and plant size was observed.
• Margins with present tariffs in Italy were acceptable.
• Public incentives to renewable energy from biogas should be better calibrated.

The purpose of this study was to observe the economic sustainability of three different biogas full scale plants, fed with different organic matrices: energy crops (EC), manure, agro-industrial (Plants B and C) and organic fraction of municipal solid waste (OFMSW) (Plant A). The plants were observed for one year and total annual biomass feeding, biomass composition and biomass cost (€ Mg−1), initial investment cost and plant electric power production were registered. The unit costs of biogas and electric energy (€ Sm−3biogas, € kW h−1EE) were differently distributed, depending on the type of feed and plant. Plant A showed high management/maintenance cost for OFMSW treatment (0.155 € Sm−3biogas, 45% of total cost), Plant B suffered high cost for EC supply (0.130 € Sm−3biogas, 49% of total cost) and Plant C showed higher impact on the total costs because of the depreciation charge (0.146 € Sm−3biogas, 41% of total costs). The breakeven point for the tariff of electric energy, calculated for the different cases, resulted in the range 120–170 € MW h−1EE, depending on fed materials and plant scale. EC had great impact on biomass supply costs and should be reduced, in favor of organic waste and residues; plant scale still heavily influences the production costs. The EU States should drive incentives in dependence of these factors, to further develop this still promising sector.