Landfill Gas Collection Systems Defined – UK Facts and Myths
Go no further to read all about landfill gas collection systems. LFG collection systems are defined in the next section, followed by a UK landfill gas collection history. Those are the facts, now for the myths!
If you scroll further down on this page we explain some myths about Landfill Gas Collection Systems, and a truth.
A Definition of Landfill Gas Collection Systems
A Landfill Gas Collection System is a network of landfill gas extraction wells, a suction pump or pumps, pipework, valves and gas flow control,
Image by US EPA – LMOP (US EPA – LMOP) [Public domain], via Wikimedia Commons
condensate drainage, and monitoring devices installed in a landfill for the purpose of sucking landfill gas out of landfilled waste under a slight vacuum. These system invariably deliver the landfill gas (LFG) to one point, a secure “Flare” compound area which may also include landfill gas utilization equipment. In the compound the suction pump (known as the “blower”) expels the LFG into the flaring system or the LFG utilization plant.
The blower is an essential component of LFG collection, and needs to be carefully specified to be suitable to perform the function of delivering the LFG to the flare. However, it's purchase and installation is commonly part of the flare and/ or utilization equipment, to which it must also be closely matched by careful selection of the correct specification. via Wikipedia.
A History of Landfill Gas Collection in the UK
In the UK Landfill Licencing was introduced in 1974, when the government placed a responsibility on all local authorities to issue Waste Management Licences (WMLs). WMLs were issued to suitable applicants on the basis of landfill management guidance contained in documents which were progressively updated from the original “Brown Book” to the “Blue Book” according the the colour of their binding.
At the start guidance was minimal, but by the time that the document; “Waste Management Paper No. 27: Landfill Gas: A Technical Memorandum Providing Guidance on the Monitoring and Control of Landfill Gas”, was published in 1991, the principle that all landfills should including an extraction and collection system was well established in the UK. This included as a minimum, landfill gas flaring. See Waste Management Paper Nr 27 UK Landfill Gas eBook
In addition the UK regulations have for more than 15 years required shrouded flares, and very few candle flares were ever used.
It was very soon accepted in the UK that it was essential that the flare flue gas be held for long enough to ensure full combustion. Candle flares with their unconfined flame, are unable to comply with the requirement for the set temperature to be held for a set time period.
As a result of these regulations, which are now also instilled in EU Directives, the UK's landfill gas has been collected and at least flared from all licensed landfills since the late 1980s.
Once all landfill operators were required to spend the necessary money to install and operate the collection systems, the step to LFG utilization became much easier to justify on economic grounds.
The fact was that the collection systems were then, and still are, seen as a landfill cost. As such, any profit made from LFG became justifiable without the burden of the payback for the investment in the gas collection system needing to be shown on the utiliser's balance sheet.
More Facts and Some Myths About Landfill Gas Collection Systems
“Landfill gas collection systems are implemented to prevent explosions from methane accumulation inside the landfill.”
No landfill has ever exploded due to gas build-up, nor is likely to. Gas pressure in landfills only rises to the point where the methane inhibits further gas production. Generally, as gas pressure inside a landfill increases more leaks out through cracks in the lining due to imperfections present. In addition for a landfill to explode it would be necessary for a large quantity of air to be present to put the gas-air mixture within the “explosive limit”. As soon as air enters a landfill the production of methane tails off. Methane generating organisms cease making it.
“The wetter the landfill, the higher the generation, however, landfill gas collection is more difficult.”
This is generally correct as long as introducing water doesn't also introduce excessive oxygen, or physically cool the waste to a significant degree.
“There is no need to remove organic materials from household, and commercial waste, and bio-digest it expensively now that landfill gas is being collected and used”.
The idea of using landfills as a method for the efficient production of biogas (LFG) will always be rejected. The proportion of LFG that can feasibly be collected from landfilling is too low, and emissions too high. That's due to the fact that LFG systems are not installed until several months to years after waste emplacement ( EPA, 1996). By this time much of the readily biodegradable waste has already been degraded. It is only the slowly biodegradable waste which remains and continues to degrade (Fei et al) once the LFG collection systems are in-place.
Then also at the end of the closed landfill maintenance period LFG production only tails off very gradually after the methane present in the LFG falls below a level at which it can be combusted.
“Landfill gas flares should always be ready, on stand-by should any of the landfill gas engines shut down.”
This is no myth, the gas flow once collected in a LFG collection system must always be either utilised or combusted in a flare. Allowing the gas to escape to atmosphere, even for short periods, is unsafe.
“Landfill Gas Flare Stack Monitoring Can be Done on Any Flare”
Landfill Gas Flare Stack Monitoring or more correctly landfill gas flare monitoring, can only be carried out on enclosed flares. Only enclosed flares hold all the LFG for a set period. Candle flare emissions vary according to the path length of the LFG through the flame and temperature profile as they pass. Enclosed flares are the only landfill gas where the flue gas is of a consistent quality which can be monitored.
Landfill gas collection systems are how modern landfills deal with gases created within the waste.
Landfill gas collection systems are becoming increasingly sophisticated, and are being implemented all over the world to prevent the loss of methane, a very strong greenhouse gas, into the atmosphere.
Landfill Systems is the Suffolk UK based company which designs, manufactures, installs and commissions complete landfill gas extraction and collection systems. These include pumping, venting* and flaring systems.
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