This guide outlines the basic principles of all landfill gas extraction pipework, focusing on condensate management, valve selection, and system redundancy to ensure maximum methane recovery and environmental safety.
Key Takeaways on the Landfill Gas Extraction Pipework Basics
- Condensate Management: Efficiently removing moisture is the primary challenge in maintaining gas flow.
- Valve Superiority: Sleeve valves are highly recommended over butterfly valves for finer control and better drainage.
- Future-Proofing: Pipe gradients must account for ground settlement to prevent water logging.
- System Redundancy: Using parallel pipe runs ensures operational flexibility during repairs or site expansion.
The Role of the Gas Collection System
The fundamental purpose of any collection system is to extract the maximum possible volume of gas while leaving the condensate behind. Landfill gas is naturally warm and saturated with water; as it leaves the waste and passes through cooler ground or surface-laid pipes, it produces significant volumes of liquid that can obstruct gas flow if not managed correctly.
The condensate is drained back into the waste. It is not normal to pump condensate into a leachate treatment plant. The contaminants in the landfill gas condensate differ from the leachate and make it difficult to treat in a landfill leachate treatment facility.
Well Head Technology and Flow Regulation
The proprietary well head is a critical component used to monitor and regulate gas flow from individual wells. These units typically include a barometric leg designed specifically for draining condensate away from the main flow.
When selecting a gas flow regulation device, a sleeve valve type is far superior to a standard butterfly valve. The sleeve valve allows for much finer adjustment, particularly at low flows. Most importantly, this design does not restrict condensate, a common failure point in butterfly valve installations.
Pipe Sizing, Velocity, and Ground Settlement
Choosing the correct pipe diameter is of prime importance. The velocity of the gas flow relative to the pipe gradient is the critical factor in successful de-watering. Designers often use flow modelling and site experience to ensure the pipework can handle the volume without “holding up” the water.
Furthermore, pipelines must be carefully laid to falls. Because landfills are prone to settlement, the initial fall must comfortably exceed the anticipated loss of height. A residual fall is necessary to ensure condensate continues to flow toward knock-out pots (condensate collection points) throughout the design life of the system.
Redundancy and Sectionalized Networks
It is often a false economy to use a single large-diameter pipe for an entire field. Instead, installing duplicate parallel pipe runs provides essential flexibility. If a section is damaged by machinery or shifted by settlement, the system remains partially operational.
By dividing the collection system into sections, operators can re-site or repair specific lengths of the landfill gas extraction pipework without a total system shutdown, ensuring continuous methane recovery.
Expert Design Consultation
Given the technical complexities involved, it is highly recommended that operators engage an experienced designer or a design and build contractor to oversee the installation of any landfill gas collection network.
Frequently Asked Questions (FAQs)
What is a knock-out pot?
A knock-out pot is a specialised collection point in the pipework designed to trap and remove condensate from the gas stream before it reaches the pumping station.
Why does landfill gas produce so much water?
The gas is generated in a warm, moist environment. As it travels through cooler pipework, the temperature drop causes the water vapour to condense into liquid form.
Why is ground settlement a risk for pipework?
As waste decomposes, the landfill surface sinks. If the pipe gradient is too shallow, this settlement can create “bellies” or low spots in the pipe where water collects, eventually causing a complete gas blockage.
For a more detailed guide to landfill gas extraction pipework design, click here.
[Published November 2012. Updated March 2026.]
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Which is the best extraction pipe to use?
Can I get a complete drawings of a landfill gas extraction system for reference of an existing gas to energy project.Am an engineer from India.
Naveen
It would not be ethical for me as a professional landfill consultant to provide you with the drawings produced for another client. I am surprised that you ask such a question. Drawings are provided for each client and not publically available.
However, our “Introduction to Landfill Gas Extraction” ebook is available to buy from this website. If you buy it, the design requirements to enable you to design an LFG Extraction System are included. When you have bought it you can email me and ask further questions and I’ll reply with assistance, or if would like a 30-minute consultancy session to talk about the design on Skype or a similar platform I will provide that at no additional cost.
It’s a shame Algea cultivated in Photo Bio Reactors (PBR) isn’t employed to capture CO2 released by methane producers on a permanent basis. The carbon from the garbage will then be returned to the planet via fertiliser, compostable products, and other means.