Abstract
The aim of this work is to evaluate the potential production of biogas and, indirectly, biomethane or electric and thermal energy, from prinkly pear (Opuntia ficus-indica L.), to be grown in a part of Sicilian uncultivated areas and co-digested together with the available livestock manure and slurry.
In order to increase the Renewable Energy Sources (RES) and reduce the dependency from fossil ones, the conversion of biomass into biogas through Anaerobic Digestion (AD) process is paramount for producing biomethane, to be used as fuel for means of transport and agricultural machines or heating, or electric and thermal energy through Combined Heat and Power (CHP) plants. Moreover, the digestate produced through AD process can be applied to soils as organic fertiliser in the place of chemical ones.
Prinkly pear was supposed to be grown, by mechanising the harvest of cladods (modified stems), in a part of the Sicilian Used Agricultural Area that is currently uncultivated (totally 600,000 ha ca.), identified by means of a GIS software. Thus it was possible to compute the potential production of biogas and, indirectly, biomethane or electric and thermal energy.
The results show that the Sicilian potential production of biogas is 612,115 103 m3, from which 342,784 103 m3 of biomethane could be extracted or 67,038 MWh of electric energy and 70,390 MWh MWh of thermal energy could be generated. Moreover the obtained digestate would be used as biofertiliser, within both conventional and organic farming.
This work demonstrates that the production of RES, such as biogas from prinkly pear, represents a very profitable way of using the uncultivated areas: the income of the farmer would include not only that deriving from the sale of biomethane or electric and thermal energy but also the saving for replacing chemical fertilisers with digestate and the subsidy for producing biomethane as fuel for means of transport or electric and thermal energy from biogas.
