Albion’s ABC of Waste Management – G GAS (LANDFILL GAS) SITES

Landfill gas is a complex mix of different gases created by the action of microorganisms within a landfill. Landfill gas is approximately forty to sixty percent methane, with the remainder being mostly carbon dioxide. Trace amounts of other volatile organic compounds (VOCs) comprise the remainder (<1%). These trace gases include a large array of species, mainly simple hydrocarbons.

Landfill gases have an influence on climate change. The major components are carbon dioxide and methane, both of which are greenhouse gases. Methane in the atmosphere is a far more potent greenhouse gas, with each molecule having twenty-five times the effect of a molecule of carbon dioxide. Methane itself however accounts for less composition of the atmosphere than carbon dioxide.

Production

The main source of landfill gas is from a microbial process called methanogenesis. This is a process where anaerobic bacteria decompose organic waste to produce biogas, which consists of methane and carbon dioxide together with traces of other compounds. Formation of methane and carbon dioxide commences about six months after initial depositing of the landfill material. The evolution of gas reaches a maximum at about 20 years, then declines over the course of decades.

Landfill Gas Utilisation

The landfill sector has developed landfill gas extraction systems to remove the methane gas from site and either burn it in a landfill gas flare or more likely in a generator to produce electricity. Until recently landfill sites were the biggest producer of renewable energy in the UK, only recently being over taken by electricity generated from wind power.

Odour

One of the biggest cause of complaints from landfill sites is odour. Often the odour is caused by the trace components of landfill gas rather than the waste itself. Careful management of landfill gas is required to manage odour from landfill sites. This can prove problematic if infilling is still ongoing when methanogenesis commences as the landfill gas infrastructure cannot easily be installed at this stage.

As waste quantities going to landfill reduce (as more waste is being recycled, landfill ban comes into force in Scotland) the rate of filling of cells also declines, so the current practice is to develop smaller cells, which can be filled quickly, capped and restored and then landfill gas extraction equipment can be installed.

Safety

In addition to managing landfill gas above the ground to minimise odours, landfill operators are also concerned about migration of landfill gas underground. Legislation in this area in the UK is comprehensive and dates back to the Loscoe Gas Explosion in 1986 where a bungalow was destroyed. This has been further improved by improvements to the landfill lining standards which helps prevent landfill gas migrating laterally from the site. Operators will also routinely monitor boreholes and gas monitoring points between the landfill site and any sensitive receptors i.e. houses or offices.

Carbon Dating

One common issue with landfill site monitoring is whether you are detecting landfill gas or methane gas from former mine workings. Albion staff were involved in one of the first cases in the UK back in early 1990’s where a carbon dating technique was used to determine whether it was landfill gas or mine gas. It turned out it was landfill gas and improvements to the site extraction system prevented landfill gas migrating from the site.

Albion Landfill Gas Services

Do you need support with landfill gas management on site? In addition to routine landfill gas monitoring we can also review the integrity of your landfill gas field, proposed improvements to improve the quality and reduce emissions and odours from your site(s).

If you need further information or wish to have a chat about your requirements please contact Alasdair Meldrum or call us directly on 01292 610428.