Thermal stabilization of digesters biogas plants by means of optimization of the surface radiative properties of the gasometer domes

New incentivation schemes for power generation from biogas favor in Italy the construction of small plants. These ones, however, have poorer financial viability and biological stability than larger plants. For small plants it is therefore essential that every aspect of their operations is carefully designed to ensure maximum performance and a reasonable payback period. In this respect, summer overheating of anaerobic digesters due to solar gains through the gasometer domes must be prevented as it can undermine the profitability of biogas plants. A solution relies upon the implementation of a ‘cool’ gasometer, that is a gasometer dome with properly chosen radiative surface properties. The study presented here allowed assessing the effectiveness of the proposed approach with a standard biogas plant with 250 kWe power through the use of either commercial software or a calculation code specifically built and validated on the basis of experimental data. More specifically, it was found that the adoption of coatings with proper solar reflectance and thermal emittance for the membranes of the gasometer dome permits to significantly reduce summer overheating in the digesters, with appreciable economic benefits in the face of a modest investment