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The VORWERK Group is currently improving the world’s largest biogas plant (electrical output: 20 MW) with the construction of a biogas upgrading plant. In it, the excess gas from the 40 individual systems is transported into a membrane gas reservoir with a capacity of 3,200 m³. After a primary treatment stage where the water vapour is roughly separated from the gas, the gas is transported into the main compressor of the upgrading plant. The biogas is compressed to ca. 15 bar by means of a single-stage screw compressor. The gas then flows into one of 104 membrane modules in which the gas is fractionated into CO2 and CH4. These membranes are semi-permeable tubes with an outer diameter of 0.3 mm which are permeated by CO2 much quicker than by methane.

At the end of this three-stage membrane process, the bio-methane leaves the plant with a purity of 98 % and a pressure of almost 15 bar. The CO2 contains only 0.5 % methane and is subjected to a pressureless post-combustion treatment in a regenerative thermal oxidizer before it is released into the atmosphere. During full-load operation, the plant will consume 400 KW of electricity but in exchange will convert 1,300 m³/h biogas into 700 m³/h bio-methane, which equals a thermal output of 7,000 KW. This amount of gas can power 7,000 modern households or propel gas-powered vehicles up to 240,000 km per day.