Landfill Gas Management Post Closure

In time and beyond the closure of the landfill, the amount of gas generated will be insufficient for viable electricity operations.  At this time, the power station would be removed and any remaining gas generated would be flared using the existing facility, or in some cases, where gas has declined considerably, with a new smaller flare.

The cycle of gas production varies during the life of the landfill with it increasing whilst land filling continues.  Should the life of the site be less than ten years, it will peak at closure and then decline steadily thereafter.  If the landfill operates for more than ten years the gas production will reach its maximum about ten years after opening and will remain at the same level until the closure of the landfill.

This is shown pictorially in Figure 1 below.

land_fill_gas_flow

Figure 1 – Landfill Gas Flow over the Life of the Landfill

Based on the gas flow from the landfill, it is possible to superimpose the generation potential of the site over its life.  Engine/gensets are added and later removed as the gas flow increases during active landfilling operations and then as gas flows decline post closure respectively.

This is shown pictorially in Figure 2 below.

electricity_generation

Figure 2 – Electricity Generation Potential over the Life of the Landfill

By following these principles, the site is not over-capitalised with equipment in the initial stages of the operations and later, as gas flows decline the engine/gensets can be utilised at other landfill sites. Thus, as the gas flows increase, extra engine/gensets are added to fully utilise the gas flow generated by the waste in-situ.

Landfill operators have an obligation to operate their landfills in an environmentally sustainable manner.  One key aspect of this is the collection and proper disposal of the landfill gas generated over the life of the landfill.

The generation of electricity, in addition to minimising the environmental effects of the gas generated by the landfill is producing renewable green electricity and is therefore offsetting the need for additional black electricity generated from fossil fuel products.  It therefore has a compounding benefit for the environment.

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