Landfill sites don’t stop producing gas just because methane concentrations decline. As landfills mature, gas quality naturally falls, and many operators are left with a difficult problem: how do you safely and legally destroy gas that is too weak to burn with conventional equipment? The LHC (Low Heat Content) Range of flare stacks was developed specifically to answer that question, enabling safe combustion of landfill gas containing as little as 5% methane.
The Problem with Low Calorific Value Gas
Standard landfill gas flares are typically only able to sustain combustion down to around 20% methane by volume. Below this threshold, most codes of practice actually require operators to halt flaring altogether, because incomplete combustion and flame instability create a real risk of explosion.
This creates an operational headache for aging or depleting landfill sites, where methane concentrations gradually decline over the site’s lifetime. Gas that can no longer be reliably flared with conventional burners still needs to be managed responsibly — both for odour and emissions control, and to comply with environmental permits.
In practice, if methane concentration drops below approximately 20%, it is almost impossible to sustain combustion with conventional burners — yet the LHC flare is designed to operate reliably down to just 5% methane in air.
Why Low-Methane Gas Is So Hard to Burn
Two physical challenges make low-calorific gas combustion difficult:
Dilution at the burner tip. Conventional burners rely on rapid mixing of fuel gas with air to achieve complete combustion. A typical 500 m³/hr biogas flow at 50% methane needs to mix intimately with roughly 3,750 m³/hr of air. When methane content is already as low as 5%, any further dilution with air can be enough to prevent combustion from occurring at all.
Flame cooling. To sustain combustion, the ignition temperature of approximately 450°C must be maintained. In an open, uninsulated burner, heat escapes into the surrounding environment faster than the low-energy fuel can replace it, and the flame is simply extinguished by cooling.
Solving both of these problems simultaneously — insufficient mixing and excessive heat loss — is exactly what the LHC Range flare has been engineered to do.
How the LHC Flare Works
The LHC flare tackles the twin challenges of heat loss and poor mixing through a combination of insulation, precise air control, and turbulent combustion chamber design.
Minimising Heat Loss
The flare is lined with high-density ceramic insulation to keep as much thermal energy as possible inside the combustion chamber. This is a critical design feature: the system is engineered so that outside casing temperatures stay below 30°C even while the internal combustion chamber runs at 1,000°C, with an ambient temperature assumption of 15°C.
For particularly low calorific value gas, incoming feed gas (including combustion air) is routed counter-current to the outgoing exhaust gas, pre-warming the fuel mixture before combustion. This has to be carefully controlled, however, since if the feed mixture gets too hot, auto-ignition could occur in the wrong part of the unit.
Fine Control of Combustion Air
Getting the air-to-fuel ratio right is essential when working with such lean gas mixtures. The LHC flare continuously measures combustion chamber temperature and automatically adjusts a venturi-nozzle arrangement on the inlet gas feed train to fine-tune the air supply. Where additional cooling is needed, extra air can be introduced at the base of the burner using natural draft.
High-Turbulence Mixing
To achieve the intimate gas/air mixing that low-methane combustion demands, Organics uses a cyclone-burner arrangement paired with high-turbulence refractories. This produces homogeneous combustion conditions throughout the chamber, avoiding the cool spots that would otherwise allow the flame to fail.
The result is a flare that combines built-in explosion protection with quiet, stable operation and minimal combustion noise.
Key Features at a Glance
- Heat loss from the combustion process minimised to maintain high temperatures
- Fine control of combustion air
- High-turbulence mixing of fuel gas and air
- Built-in explosion protection
- High-turbulence refractories
- Homogeneous combustion avoiding cool spots
- Minimum combustion noise
- A wide range of automation options available
Technical Specifications
| Parameter | Value |
|---|---|
| Thermal capacity | 125 – 500 kW |
| Equivalent flow rate at 5% methane | 250 – 1,000 Nm³/hr |
| Equivalent flow rate at 20% methane | 50 – 250 Nm³/hr |
| Pressure rise across gas booster | 150 mbar |
| Combustion chamber temperature | 1,000°C |
| Minimum methane concentration for sustained combustion | 5% |
| Maximum methane concentration for sustained combustion | 60% (flow rate = 80 Nm³/hr) |
| Pipework finish | Hot dip galvanised or stainless steel |
| Burner material | High temperature stainless steel |
| Flame detection | UV sensor or thermocouple |
Theoretically, 5–15% methane by volume can burn in air — but achieving this reliably and safely in the field requires the kind of insulation, air control, and turbulent mixing built into the LHC Range.
Typical Applications
The LHC Range is particularly well suited to:
- Aging or closed landfill sites where methane concentration has declined below the level conventional flares can handle
- Sites approaching the end of their gas extraction life, where continued destruction of residual gas is still required for regulatory or environmental compliance
- Situations where variable gas quality (including higher CO₂ or air content) makes reliable combustion difficult with standard equipment
Because the system offers a wide range of automation options, it can also be integrated into existing landfill gas management infrastructure with minimal disruption.
Key Takeaways
- Conventional landfill gas flares generally cannot sustain combustion below ~20% methane, creating a compliance and safety gap for maturing landfill sites.
- The LHC Range flare is purpose-built to burn gas down to as little as 5% methane, using ceramic insulation, counter-current preheating, and precise venturi-controlled air metering.
- A cyclone-burner arrangement with high-turbulence refractories ensures homogeneous combustion and avoids the cool spots that cause flame failure in low-calorific gas.
- The system includes built-in explosion protection and is available with a range of automation options, with thermal capacities from 125 to 500 kW.
Get in Touch
If your landfill site is producing gas with declining methane content and you need a safe, compliant way to manage it, our team can help you assess whether the LHC Range flare is the right fit for your operation. Contact us today to discuss your site’s specific gas composition and flow requirements.