Wastewater treatment process produces sewage sludge, which is dewatered and dried either mechanically or thermally. In certain cases the thickened sludge is digested. During the digestion process the sludge volume decreases and drying features improve. During digestion the sludge decomposes in anaerobic conditions into methane, water, carbon dioxide and mineral salts. This so called biogas (appr. 60% methane and the rest carbon dioxide) is utilized in the biogas engine plant, and the remaining components are dried in centrifuges. The dried sludge is taken to a land fill to be composted, and the resulting compost is used in landscaping. The sewage sludge generates approximately 400 dm3 of biogas per 1 kg of dry matter. The average heat value of biogas is 6.0 kWh/m3.
The biodegradable waste in a landfill creates methane and carbon dioxide. The gases damage the atmosphere and therefore according to the rules and regulations they must be collected. This also reduces the smell nuisance.
The landfill gas treatment plant provides the measurement and analysis of the gases, condensed water removal and at least a torch burner for the disposal of gases. The energy contained in the gas can also be utilized in many different ways.
During the biogas pretreatment process, moisture is separated and big-size impurities are filtered from the gas. Usually different kinds of gas analyzing and measuring devices are included in the supply.
The methane contained in biogas can be burned with an appropriate burner, thus producing hot water or steam. Up to approximately 90% of the energy contained in the gas can thereby be utilized. By using biogas as gas engine fuel, a generator attached to the engine can produce electricity utilizing up to 35% of the energy contained in the gas. In addition, by recovering the heat from the engine’s cooling water and from exhaust gas, approximately 50% of the biogas energy can be converted to heat energy, i.e. a total of approximately 85% of the biogas energy can be utilized.
We supply biogas boiler plants and biogas engine plants on a turnkey basis.