Agriculture plays a well-established role both in the production of food and feed and in the production of renewable energy. This latter aspect is represented by the possibility of using biomasses coming from waste and by-products of the food industry, livestock sewage, agricultural residues, and dedicated bio-energy crops, as sources that can be converted in thermal and electrical energy, primarily by means of anaerobic digestion processes. Sicily has a great potential in terms of biomass availability, and then the production of bioenergy from renewable sources could be significantly increased. This study focuses on waste and by-products coming from citrus industry in Sicily and it wishes to give, on the basis of direct investigations and laboratory analyses, a cognitive contribution to the assessment of biogas and bio-methane quantities that could be obtained.