Public and regulatory scrutiny of landfill gas emissions has never been higher. Operators need combustion systems that not only destroy methane and trace contaminants effectively, but also do so at a realistic cost. The SC (Standard Combustor) Class of landfill gas flare stacks was developed precisely for this purpose — offering an enclosed, high-temperature flare solution that meets modern emissions standards without the price tag of more elaborate systems.
What Is an SC Class Flare Stack?
The SC Class is an enclosed (“shrouded”) ground flare design, as opposed to an open flame flare. Enclosing the combustion process allows the unit to control heat loss to the environment, hold the flame at a stable design temperature, and retain the combusted gases for a specified period — known as the retention time — before releasing them to atmosphere.
This is the current technologically preferred approach for landfill gas combustion, since it allows operators to reliably hit destruction efficiency targets for trace gas contaminants that are the primary cause of odour and environmental concern.
The core principle: raise combustion temperature to a minimum of 1,000°C and hold it there for at least 0.3 seconds, using well-mixed fuel gas and combustion air within a controlled combustion zone.
The Science: Balancing Time and Temperature
Destruction of trace contaminants in landfill gas is governed by the Destruction Efficiency Rating (DER) — a trade-off between combustion temperature and residence time. The hotter the flame, the shorter the residence time needed to achieve a given destruction efficiency.
For comparison, municipal waste incinerators typically require temperatures above 850°C sustained for 2 seconds. Landfill gas flares, however, can achieve significantly higher combustion temperatures, allowing for a much shorter residence time.
There is, however, a ceiling: above approximately 1,200°C, thermal NOx formation begins to increase sharply. Any gain in destruction efficiency at these higher temperatures is offset by the environmental cost of increased NOx emissions — which is why the SC Class is engineered to hold temperatures at the practical, efficient minimum of 1,000°C rather than pushing higher.
Above ~1,200°C, thermal NOx formation rises sharply — negating the benefit of any additional destruction efficiency gained from a hotter flame.
How the SC Class Achieves Reliable Combustion
Achieving consistent, compliant combustion depends on tightly controlled combustion air. The SC Class design ensures homogeneous conditions within the shroud, achieved through effective mixing of fuel gas and combustion air in the combustion zone, producing a non-visible, partially pre-aerated, turbulent diffusion flame.
Key operational features include:
- Automatic flame temperature control
- Booster turn-down to zero flow without surging, allowing the system to respond smoothly to varying gas flows
- High-reliability landfill gas pilot for consistent re-ignition
- Self-checking UV flame detection sensor
- Flame arrestors fitted on both the gas booster inlet and outlet
Control Panel and Instrumentation
The SC Class control system is built around a fully programmable PLC (Programmable Logic Controller), giving operators flexibility to configure:
- Delay times
- Re-ignition sequences
- Dual-stage trigger levels for alarm or shutdown, based on methane and oxygen analyser inputs
Control panels are built with a 20% expansion factor as standard, allowing for future retrofit of additional equipment — such as a telemetry unit — without needing a full panel replacement. This means alarm conditions can be isolated within the PLC logic and reported remotely, for example via telephone line.
Optional instrumentation includes:
- Flow rate measurement
- Gas concentration measurement
- Remote access and datalogging
Construction and Materials
Durability and site practicality were clearly design priorities. The SC Class flare stack is:
- Skid-mounted for ease of movement around site
- Finished with hot dip galvanised pipework to industry standard
- Fitted with a burner made from high-temperature stainless steel
- Available in Battleship Grey or a custom colour to match site branding or preference
- Optionally available in fully stainless steel construction, extending life-cycle and improving visual appearance
The ground flare shroud itself is either galvanised or finished with high-temperature paint, depending on flow rate and the resulting shroud size.
Technical Specifications
| Parameter | Specification |
|---|---|
| Flow rate range | 100 to 15,000 m³/hour |
| Pressure rise across gas booster | 150 mbar |
| Minimum flame temperature | 1,000°C |
| Minimum retention time | 0.3 seconds |
| Minimum methane concentration for combustion | 25% |
| Standard number of inlets | 2 flanged inlets (additional available on request) |
| Flow control | Chemical duty butterfly valves |
| Pipework finish | Hot dip galvanised to industry standard |
| Burner material | High temperature stainless steel |
| Flame arrestor location | Gas booster inlet and outlet |
| Flame detection | Self-checking UV sensor |
| Standard colour | Battleship Grey (custom colours available) |
| Optional construction | Fully stainless steel |
Meeting Emissions Standards
The SC Class is designed to meet UK, European, and US emissions standards, making it suitable for landfill sites operating under varying regulatory regimes. For sites and jurisdictions such as the US EPA and UK Environment Agency frameworks for landfill gas management, the 1,000°C / 0.3-second retention specification represents the practical minimum needed to achieve compliant destruction efficiency without excessive NOx formation.
When to Consider a Higher Specification
The SC Class provides the minimum specification required to meet DRE requirements — a 1,000°C flame temperature sustained for a 0.3 second retention time. For applications requiring higher combustion temperatures or performance beyond this baseline, the MC Class of flare units offers a step up in specification.
Key Takeaways
- The SC Class is an enclosed, ground-mounted landfill gas flare designed to control emissions cost-effectively.
- Combustion is held at a minimum of 1,000°C for a minimum retention time of 0.3 seconds — the practical balance point between destruction efficiency and NOx formation.
- The system handles flow rates from 100 to 15,000 m³/hour and is compliant with UK, European, and US emissions standards.
- Flexible PLC-based control panels, optional gas analysis instrumentation, and remote monitoring support long-term compliance and ease of operation.
- Skid-mounted, galvanised, and available in stainless steel, the SC Class is built for practical deployment and durability on active landfill sites.
Get in Touch
If you’re evaluating flare options for a landfill gas management project and want to understand whether the SC Class — or the higher-specification MC Class — is the right fit for your site, get in touch with our team. We can help you match flow rates, emissions requirements, and site conditions to the right flare stack solution.