Energy Generation Potential in Greece From Agricultural Residues and Livestock Manure by Anaerobic Digestion Technology

Greece is an agricultural country producing a significant amount of crop residues as well as livestock manure. The use of agricultural waste as a major component of renewable energy is suitable for improving energy security. Thus, studying the energy generation potential of these wastes is important. The theoretical annual potential of agro-industrial residues (such as wheat products, industrial plants, potatoes, vegetables, olives, fruits, nuts, dairy products etc.) was estimated equal to 19,005,490 t/y, taking into consideration their annual production and their respective residue production in Greece. Accordingly, the theoretical annual potential of livestock manure, including the residues from animal husbandry in Greece (cattle, chicken, goats, pigs, sheep etc.) was estimated equal to 26,952,500 t/y. In this study, the possibility of energy production through anaerobic digestion was investigated. Taking into account the biodegradability of the residues, it was estimated that the total 45,957,990 t/y residues may produce 330,000 t/y fertilizer and 1.97 x 10(9) m(3)/y methane. Taking advantage of the energy content of biogas by co-generation of energy and heat, 4.9-7.9 Icurrency signWh/y of electrical energy and 6.9-12.8 Icurrency signWh/y of thermal energy could be produced. Given the annual electrical energy consumption in Greece, about 39 % of this energy need could be replaced by electrical energy produced from agricultural residues and livestock manure. Conclusively, crop residues and livestock manure may stand as an energy source with significant contribution to the Greek energy balance.