Sicilian potential biogas production from Citrus industry by-product

In Europe, Italy is the second nation after Spain in Citrus production and 49% ca. of national fruit production is located in Sicily. The by-product obtained from the industrial processing of Citrus fruits into juice and essential oils is called “pastazzo” or Citrus Waste (CW). This study is aimed at evaluating the Sicilian potential biogas and energy production from the above “pastazzo” and verifying the possibility of using this by-product for Anaerobic Digestion (AD) process within 30 km from processing plants. The areas cultivated with Citrus species in Sicily and their distribution in the various municipal districts were mapped and analysed by means of QGIS software, together with the main Citrus processing plants and the three existing AD plants. The statistical data about the amounts of the by-product of Citrus processing industry were evaluated, in order to compute the Sicilian potential biogas and energy production. In Sicily it is possible to obtain, through the use of “pastazzo”, a yearly production of 12,916,800 m3 ca. of biogas, equal to 24,250,930 kWh of electric energy and 25,463,477 kWh of thermal energy or 6,200,064 m3 of biomethane. This high potential biogas and energy production is not be currently used in a sustainable way from the energetic and economic points of view, because the existing AD plants are farer than 30 km from Citrus processing plants. The CW produced in Sicily could be used inside a bio-reactor, together with other raw materials (e.g. pomace and wastewater from olive oil mills, cereal straw, poultry manure and Italian sainfoin or Hedysarum coronarium), for AD process.