When methane is used as a fuel in a gas engine it is burnt and converted to carbon dioxide and other trace elements. This carbon dioxide is released as a hot gas in the CHP plant exhaust.
The recovery of this gas would open up to the potential of its utilisation for beneficial purposes including:
- As a growth promoter in plants - See greenhouse cogeneration
- As an ingredient in drinks - See quadgeneration
- As a gas in industrial processes - See quadgeneration
- For carbon sequestration in order to negate carbon emissions
Although the utilisation of gas is one of the cleanest types of fuel during combustion there are some trace contaminants in the raw exhaust which would make it unsuitable for the above applications. Typically selective catalysts can be utilised in order to remove different contaminants from the raw exhaust gas. In order to concentrate and recover cleaned carbon dioxide different systems are required such as absorption based fluids and technologies such as pressure swing absorption.