If landfill gas is only being flared, a blower and open-flame flare is enough. If it will run an engine, add a chiller and filter. In a budget enquiry for a 1 MW landfill gas project, the supplier priced both: a blower and flare unit, and a larger package with chiller and filter that cost roughly 75% more. The difference is what protects the engine.
The challenge: a project still at the study stage
An engineering contractor was working with a municipality on a landfill gas scheme of about 1 MWe. That needs roughly 500 to 750 Nm³/h of gas at 55 to 65% methane, but nobody yet knew the landfill’s real potential. The contractor asked for three things:
- A gas yield study to find the real resource.
- A budget for the gas extraction infrastructure for about 500 Nm³/h.
- A budget for a gas delivery unit (GDU) and flare in two versions.
The consultancy approach supplied alongside it set out the usual staged route: gas resource investigation (computer modelling and pumping trials), equipment specification (gas field layout, wells, pipework, condensate removal), installation and commissioning, then operation and maintenance. Pumping trials only happen after the model suggests the site is worth testing, and each stage can be a stand-alone contract so a project can stop if the gas is not there.
What a gas delivery unit does
The GDU draws gas out of the landfill and delivers it to the point of use at a controlled pressure. In this design:
- Flow range: 75 to 750 Nm³/h, a 10:1 turndown, which matters because landfill gas flow changes slowly over years and quickly with weather.
- Suction: about 20 mbar below atmospheric at the inlet.
- Blower: multi-stage centrifugal, stainless steel, with a pressure head of about 300 mbar. Around 200 mbar is needed at the user, and the rest allows for pipework and filter losses.
- Pressure control: a PID loop on the discharge line.
- Flare: elevated, open flame, with a flame tip designed for temperatures of 850°C.
Option one: blower and flare
This is the basic unit. It gets gas out of the ground, holds the pressure steady and burns any surplus. It is suitable where the aim is control and compliance rather than power.
Option two: add a chiller and filter
Landfill gas leaves the ground saturated with water. As it cools in pipework, condensate forms and carries contaminants including H₂S, which can damage an engine quickly. Fine particles also wear engine parts. The second option therefore added:
- A chiller that cools the gas so it leaves at no more than 80% relative humidity and under 40°C, with a dew point of about 20°C.
- A particulate filter of EN779 class F9, with an initial resistance of about 175 Pa and average efficiency over 95%.
Further additions, siloxane or H₂S removal, can be bolted on for engines that need cleaner gas. Adding carbon dioxide removal would take the gas towards use as compressed biomethane.
| Blower and flare | Blower, flare, chiller, filter | |
|---|---|---|
| Gets gas out and controls pressure | Yes | Yes |
| Burns surplus | Yes | Yes |
| Dries gas for an engine | No | Yes |
| Removes fine particles | No | Yes |
| Relative cost | Base | About 1.75 times base |
Why an open-flame flare here
The flare was an open, elevated type with a minimum design temperature of 850°C and manual air adjustment. That is fine for a budget stage or for sites with light controls, but UK regulators expect enclosed flares to reach at least 1,000°C, as set out in the Environment Agency’s LFTGN05. Check what your own permit requires before choosing. Delivery was estimated at 16 to 20 weeks from order to commissioning.
What to consider for your own project
- Know the end use before you order. Engines need dried, filtered gas.
- Confirm the resource first. Modelling and a pumping trial cost far less than building plant for gas that is not there.
- Specify turndown. A 10:1 range handles decline and weather swings.
- Allow for pressure drops. The blower needs head beyond what the engine demands.
- Check the flare against your permit. Temperature and monitoring requirements differ.
For a related example on temperature choice, see ground flare or elevated flare.
FAQ
How much gas does a 1 MW landfill gas engine need?
In this enquiry, roughly 500 to 750 Nm³/h, depending on methane content.
Why does landfill gas need drying?
It leaves the ground saturated, and condensate carries contaminants that damage engines.
Can I add a chiller later?
Often yes, but it is cheaper to plan for it from the start so the skid layout and pressure budget allow for it.
Planning a landfill gas project?
Tell us what you know about your site’s gas and we will outline a staged route from study to plant.