Energy Potential of Digestate Produced by Anaerobic Digestion in Biogas Power Plants: The Case Study of Croatia

摘要

The number of biogas power plants increased significantly in the recent years. A lot of countries developed competitive national biogas markets after decades of intensive research and technology innovation. Biogas power plants make use of advanced anaerobic digestion processes to increase the production of biogas as a principal source of income. On the other hand, digestate is still considered a by-product and usually disposed of in landfills. This article proposes energy generation from digestate as a financially viable alternative. Before energy generation, digestate is separated into solid and liquid fractions and dried by thermal energy. Calorimetric measurements showed that the heating value of digestate is 13 MJ/kg, which favors its energy generation potential, especially if the excess heat from cogeneration is used for the drying. The digestate produced in biogas power plants can be used as a low-cost alternative fuel for electricity generation in biomass power plants. It is estimated that digestate-generated electricity could contribute with 4.2% of the total electricity generation in Croatia. The economic analysis revealed that the price of electricity generated from digestate, under the present feed-in tariff system in Croatia, is two to three times higher than the total cost of digestate.