Assessment of citrus pulp availability for biogas production by using a GIS-based model: The case study of an area in southern Italy

In literature, anaerobic digestion of biomasses is commonly considered an environmental friendly way to treat and revalorise large amounts of by-products from farm industries because it could ensure both pollution control and energy recovery. This process is defined as the biological conversion of organic material to a variety of end products including 'biogas', the main constituents of which are methane (65-70%) and carbon dioxide. Citrus pulp is the main by-product of citrus processing industries and is composed of variable quantities of peel, pulp, and seeds. Recently, citrus pulp has been object of research studies because of its possible conversion from an ordinary by-product to an energy resource through an anaerobic digestion process. This possibility is of relevant importance also for reducing the environmental burden caused by disposal processes of the residues of citrus processing industries. At present, the lack of official data related to citrus pulp availability and spatial localisation has limited the reuse, exploitation, and valorisation of this by-product. Therefore, with the aim to fill this gap the objective of this study was to analyse the spatial distribution of the citrus producing areas and the amount of processed citrus in order to quantify the availability of citrus pulp for biogas production at a provincial level. To this aim a GIS-based model, previously defined and applied to evaluate the amount of citrus pulp production at a regional level, was applied to the case study of Catania province (Sicily, Italy). The results obtained in this study could constitute a valuable support for providing potential solutions to issues related to the environmental burden of citrus pulp disposal. Moreover, they could contribute to build an information base aimed at improving the sustainability of biogas sector, by helping to identify the best location for new biogas plants through the optimization of the logistics of biomasses supply in geographical areas where biogas sector is still developing.