Abstract:

The consumption of thermal energy for heating the substrate in the process of biogas production represents a significant loss in the total energy balance that can be obtained from the biogas plant and further used as a produced energy. In addition, production process requires considerable additional energy spent for transport and biomass preparation as raw materials for biogas production. Thus, it is very important, among many concepts of biogas energy production, to choose the most convenient one. In practice, the plant for the biogas production is often integrated with a Combined Heat and Power Plant (CHP) for providing energy from biogas into a unique plant. The advantage of such a concept is the possibility of waste heat utilization, inevitably occurring in the drive heat engines, to meet the needs of heat consumption for the substrate heating. However, the energy efficiency of such a process is necessary to compare with the other processes efficiency of biogas energy utilization. For example, the use of solar energy to heat the substrate in conjunction with modern high efficient biogas boiler has been considered as an alternative CHP. Aiming to solve the aforesaid assignment adequate analytical expressions have been derived. A method application has been illustrated on the example of a small farm possessing manure from the pig farm and unused maize stalks residues from agricultural production. Analytical expressions were derived to determine the main biogas plant parameters such as the size and shape of the digester, the plant capacity, biogas yield, generated power strength and others. These features are necessary to determine the heat loss through the digester walls and thermal energy required for heating the substrate. It finally determines the energy utilization of biogas plant with CHP.

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