Gas derived from Anerobic Digestion (AD) plants or landfill sites is usually fed to combined heat and power (CHP) engines to be converted to electricity for supply to the grid or for powering on site plant and equipment. When engines fail they can be expensive to fix and lead to significant loss of income for the operator. Biogas and Landfill gases can have significant levels of Siloxane contamination; this contamination is removed by carbon and regenerative filters. Over time the filters become saturated and let siloxane laden gas into the CHP engine, the build up of silica in the CHP engine will cause erratic running and may eventually lead to complete shutdown or failure.