The type of Gas Extraction system employed at any site will depend on many factors but, primarily, it will be based on the size of the landfill. There are no hard and fast rules to apply as to the threshold.
In our view, the landfill would need to service a population of 100,000 people before the generation of electricity would become economically viable. For smaller sites, it may be possible to generate electricity for internal use only, or to flare the gas, thereby reducing its environmental effect.
The landfill gas capture systems will be the same, irrespective of the method of burning of the gas. The system comprises the installation of a series of wells to collect the gas. The design of the grid is determined by the landfill’s characteristics, such as surface area, depth of waste, surface slopes, and type of final cover provided.
The size of the power station on larger landfills will depend on a number of factors. Gas is combusted in engines driving turbines which generate the electricity. The electricity is then delivered into the local grid for distribution to customers.
Generally, this type of installation will have a flare, which is available for use in the event of the power station being out of action, and ensures compliance with environmental requirements to dispose of the gas generated from the landfill in an acceptable manner.
With smaller landfills, the well field collection system will be the same as the system for large landfills. However, monitoring and tuning of the well field is not as intense as for electricity production, as the main purpose is to ensure the proper destruction of any gas generated via a flare system. Nevertheless, periodic checks are required to ensure there are no leaks in the well field pipe work, and that it is functioning as designed.
The flare construction can be of a similar standard as the standby flare at a power station. The flare would operate continuously and its size will be based on the peak gas production. Over time, and as gas production declines, the flare would be operated at lower volumes or for lesser hours each day.
Another option available at smaller landfills is the generation of electricity for internal consumption on the site. This could be in the range of 30 to 500kW. In this way, the combustion of the gas can be used to offset electricity charges for the operation of the site.
LGP is able to offer assistance with the gas extraction system at any sized landfill. We invite you to contact us for further information.