Gasification is a process that can take non-inert materials such as wood, plastics and food – basically, anything that will rot down – and converts the solid material to a gas that can be used in the same way as gas in the home for heating and hot water. Gasification has been used since the late 1800s for the production of town gas for street lighting and cooking in the home, so this is a tried and tested process over many, many years.

Gasification is a highly efficient process whereby virtually all the energy in the material being gasified is released into the gas and, therefore, a very efficient method of generating steam and electricity from waste materials. Waste types accepted for energy generation will be along the lines of packaging that is too contaminated for recycling, treated wood wastes, damaged and/or out of date food from supermarkets and other wastes that are too low in value to recycle.

The process starts in a primary chamber where the waste materials are reacted under high temperature with only a very small amount of air. The amount of air is carefully controlled and monitored so that the waste volatilises but doesn’t burn in an uncontrolled manner as a bonfire might. By volatilising the waste it does not burn, but instead generates a gas referred to as a synthesis gas, or syngas, that is principally made up of hydrogen, methane and carbon monoxide. There are no emissions of any kind from this gasification stage.

The syngas from the primary chamber is piped off into a second chamber where the gases are combusted in the same way as a gas central heating boiler in a house. The heat generated by these combusted gases is then passed through a boiler where the heat is rapidly exchanged to heat water and produce steam. This steam can then be used in industrial processing such as bottling plants or used to generate renewable electricity using steam turbines. Steam turbines are how many power stations in the UK create electricity for the National Grid.

The combusted and, by now, cool gases finally go through flue gas treatment with bicarbonate of soda to neutralise any acids, urea to remove nitrogen oxides and finally bag filters to capture dust. Once the gas has gone through this phase it is then passed through the flue and into the atmosphere in the same way as a central heating boiler.

 

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