Researchers at the University of Milano, have reported acceptable margins to produce biogas from energy crops in Italy in a very recent publication released on Aug.2014.
The study, published on Waste Management Journal, observed and assessed the economic sustainability of three different biogas full scale plants in northern Italy, fed with different organic matrices: energy crops (EC), manure, agro-industrial and organic fraction of municipal solid waste.
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.
The total costs of the input mixtures were calculated by considering the prices and/or the production/transportation costs of all the organic material used, during the observation period. For dedicated crops, the production costs were considered, including soil preparation, seeding, costs of fertilizers, irrigation and plant harvesting.
The total investment cost, indicated by the plants owners, were of 4180 k€ for Municipal solid waste plant , and 3869 k€ and 2720 k€ for residues and crops. This cost included the design and authorization, the concrete structures, the pumping system, the mixers, the digesters heat-systems, the pre-treatment and post-treatment facilities and technologies, the combined heat and power (CHP) generation units, the start-up costs and the automation software/hardware. Plant using municipal wastes showed high management/maintenance cost for waste treatments (0.155 € Sm−3biogas, 45% of total cost), the plant using maize and sorghum suffered high cost for biomass supply (0.130 € Sm−3biogas, 49% of total cost) and the one with manure showed higher impact on the total costs because of the depreciation charge (0.146 € Sm−3biogas, 41% of total costs).
As main conclusion authors found that annua energy crops producing solage biomass (maize and sorghum) could be expensive at the current costs but there are several EU incentives, at least in Italy and some other countries. It is clear that perennial grasses could offer similar performance for biogas as we explained here. On the other hand, the high public incentive on EE, paid by Italian State and by many EU governments, could tend to sustain crop massive use, thereby demotivating the transformation of residues and waste into resources. There is space for a slight reduction of incentives and the tariffs should favor the use of by-product and waste. The trend of the market will be to stimulate smaller plants scale in order to replace energy crops with the use of agro-industrial waste.
The study can be accessed from here.
A video on arundo donax for biogas in Italy: