Summary

Hong Kong is extracting gas from landfill sites to help reduce the use of fossil fuels in town gas production process.  There will be an annual reduction of use of up to 43,000 tonnes of naphtha in the process, which will lead to a reduction of up to 135,000 tonnes of carbon dioxide emission per year. 

What is it?

The North East New Territories (NENT) Landfill Gas Utilisation Scheme is one of the largest off-site landfill gas utilisation schemes in the world.  The scheme is a successful case in turning waste into energy.  It helps to minimise the use of fossil fuel in the town gas production process and reduce the release of methane, a greenhouse gas from the natural degradation of waste, into the environment.

How does it work?

Landfill gas recovered at NENT Landfill and has been used to meet on-site energy demands such as electricity for site facilities and heat for wastewater treatment process.  As the waste volume grows, the rate of landfill gas generation at NENT Landfill is anticipated to increase from its current value of 6,000 m3/hr to a peak value of around 15,000 – 20,000 m3/hr.  The LFG export scheme will help to make best use of the large volume of landfill gas that would be generated at the NENT Landfill in the coming years. Without this scheme, the surplus landfill gas not utilised on site will have to be flared for safety reason. 

A LFG treatment plant has been installed at NENT Landfill to remove carbon dioxide, hydrogen sulphide and non-methane hydrocarbons from the raw landfill gas.  The product gas, known as synthetic natural gas (SNG), contains over 80% methane.  The SNG is delivered to Towngas production plant through a 19-km underground pipelines

Application

The NENT LFG Utilisation Scheme not only provides a new source of energy to reduce the use of fossil fuel in town gas production, but also cuts the emission of greenhouse gases, thus helping improve the air quality of Hong Kong.

Results

During the first year of operation of the landfill gas export scheme, treated landfill gas with energy equivalent 143 x 106 MJ were exported to Towngas production plant for beneficial uses. The export of treated landfill gas will continue in the next fifteen years.

CO2 Emissions Reductions

The landfill gas which originally flared off is now used as substitute heating fuel for the Towngas production process.  There will be an annual reduction of use of up to 43,000 tonnes of naphtha in the Towngas production process, which will lead to a reduction of up to 135,000 tonnes of carbon dioxide emission per year.

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