Wherever landfill gas, biogas, or other waste gases are generated, safe and effective disposal is essential – both for environmental compliance and public safety. Flare systems remain one of the most trusted and widely used technologies for combusting these gases, and the right choice of flare depends heavily on local regulations, gas composition, and site constraints.
This guide walks through the full range of flare technologies available, from simple open-flame stacks through to ultra-low emission systems engineered to minimise NOx formation, based on more than 15 years of proven design and manufacturing experience.
Flare technology has evolved from simple open combustion to sophisticated systems capable of Destruction and Removal Efficiencies in excess of 95% for toxic trace gases.
Why Flaring Still Matters
Landfill sites and biogas facilities generate gas streams rich in methane – a potent greenhouse gas – along with trace contaminants. Flaring converts these gases into carbon dioxide and water vapour through controlled combustion, dramatically reducing their environmental impact compared to uncontrolled release. Depending on regional standards and site-specific goals, operators can choose from a spectrum of flare designs offering different levels of environmental control, cost, and complexity.
The Flare Product Range at a Glance
| Range | Type | Key Characteristics |
|---|---|---|
| AC Range / US AC Range | Open elevated flame | Pre-aerated combustion, 800-1,000°C flame temperature |
| SC Class / US SC Class | Enclosed high-temperature | 0.3 sec retention (0.6 sec for US variant), ≥1,000°C (1,800°F) |
| MC Class | Enclosed high-temperature | 0.6 sec retention time, 1,200°C |
| RB Class | Low height | Extended diameter shroud, meets height-restricted sites |
| SMART Low NOx | Ultra-low emission | Exhaust gas recycle and fuel-staging |
| LHC Range | Low calorific value gas | For declining or low-methane gas streams |
| Industrial Flares | Petro-chemical | Heavy-duty industrial applications |
| Mobile Ground Flares | Portable | Temporary or relocatable duties |
| Machine Range | Base-load | Basic, cost-effective units |
| Solar Powered (BCW / ACE) | Off-grid | Powered entirely by solar energy |
Open Flame Systems: The AC Range
The AC Range provides a no-frills combustion tool for locations where stringent environmental controls don’t apply, or where relatively clean gases need to be safely disposed of. These open, elevated flame burners use a pre-aerated combustion principle, giving a short, sharp, non-luminous flame rather than the long, lazy, yellow-tipped flame typical of diffusion burners.
Flame temperatures are controlled in the range of 800 to 1,000°C, depending on methane concentration, flow rate, and prevailing wind conditions. Because increased aeration reduces flame yellowing and radiant heat, these flares can be built shorter without raising ground-level temperatures.
US AC Range Flares
The US AC series (also called candle or utility flares) is designed specifically for the North American market, where taller burner stacks are preferred. It shares the same pre-aerated combustion principle, with flame temperatures controlled between 800-1,000°C (1,500-1,800°F).
Enclosed Combustion: SC and MC Class Flares
Where public concern about visible emissions is a factor, enclosed “shrouded” flares provide a substantially more controlled solution.
SC Class Flares
The SC (Standard Combustor) Class raises combustion temperatures to at least 1,000°C and holds the gases at that temperature for a defined retention time – a minimum of 0.3 seconds. This is achieved by controlling heat loss to the environment and ensuring homogeneous mixing of fuel gas and combustion air within the enclosed shroud.
The US SC Class variant increases retention time to a minimum of 0.6 seconds at temperatures of at least 1,800°F, with lower flame temperatures used where ultra-low emissions are required.
MC Class Flares
The MC Class pushes this approach further, holding combustion gases at 1,200°C for the specified retention time – effectively the practical ceiling for this emissions-control method, since NOx formation increases sharply above this temperature due to thermal NOx mechanisms.
Achieving this reliably requires very tight control of combustion air. The stoichiometric (ideal) ratio of air to methane is approximately 10:1, but in practice, imperfect mixing typically pushes the real-world ratio closer to 25:1 – the additional air cools the flame and prevents excessive temperatures.
Above 1,200°C, NOx levels increase dramatically due to thermal NOx formation – which is why MC Class flares are engineered to hold this exact temperature ceiling.
Low-Height and Low-Heat-Content Solutions
RB Class Flares
Where planning restrictions limit stack height, the RB Class offers a low-height, environmentally sound alternative. It uses an extended-diameter flare shroud and wider flame distribution across the shroud’s cross-section, allowing elevated temperatures and extended retention times within a shorter combustion chamber.
To avoid the “lazy diffusion flame” problems that can arise from a shorter shroud (which reduces the head available for air inspiration), the design uses higher burner pressure to maintain turbulent diffusion flame combustion.
As with all Organics landfill gas flaring equipment, the RB Class is designed for open-air use, with hazardous area zoning available to Intrinsically Safe (IS) or Zone II standards as standard, and Zone I on request. Control panels include a 20% expansion factor for future control equipment additions.
Low Heat Content (LHC) Flares
Low heat content flares address a specific challenge: landfill sites where gas production is declining, or where collection efficiency is low – for example, where migration control takes priority over methane concentration. This technology, first developed in the mid-1990s with support from the UK Department of Trade and Industry, has since been widely replicated across the landfill gas industry.
Ultra-Low Emissions: SMART Flare Technology
For sites where NOx and toxic trace gas emissions are a major concern, the SMART flare range represents the top end of the technology spectrum. It combines high-temperature, extended-retention-time combustion with exhaust gas recycling to actively suppress NOx formation mechanisms.
The core technical principles are:
- Exhaust gas recycle – reduces the intensity and heat of combustion
- Fuel-staging – separates combustion into two zones, minimising peak flame temperatures
- Thorough air/fuel-gas mixing – reduces free oxygen available for NOx formation and minimises carbon monoxide
By separating combustion into two zones, peak flame temperatures are minimised, which directly reduces the rate of Thermal NOx formation – the primary source of nitrogen oxides in landfill gas flares.
When combined with extended retention times, SMART flare technology can achieve Destruction and Removal Efficiencies in excess of 95% for most toxic trace compounds – including large-scale ammonia destruction without an increased NOx burden.
Solar-Powered Flares: Off-Grid Solutions
Not every site has grid power available, and not every situation permits an open flame. The solar range addresses both scenarios:
- BCW Range – solar, wellhead-mounted flares for sites where an active landfill gas extraction system isn’t practical.
- ACE Range – solar-powered flaring systems for situations where open flames are unacceptable and no power is available to drive active gas extraction. The ACE flare uses solar power to maintain charge in an onboard battery pack.
Technical Specifications
| Parameter | Value |
|---|---|
| Flow rates available | 50 to 15,000 m³ per day |
| Materials | Carbon steel, stainless steel, stainless steel alloys |
| Pressure rise across gas booster | 60″ WG (150 mbar) |
| Flame temperatures | 1,500-1,800°F (800-1,000°C) |
| Retention time | Up to 0.6 seconds |
| Minimum methane concentration for sustained combustion | 12% |
| Pipework finish | Hot-dip galvanised, 304 SS, 316 SS |
| Burner material | High-temperature stainless steel |
| Flame arrestor | Fitted on gas booster inlet and outlet |
| Flame detection | Self-checking UV sensor |
From Specification to Handover: The Project Route
Every flare project follows a structured delivery process designed to maintain quality and schedule control:
- Specification – design parameters are formalised in an Order Confirmation, drafted by the Operations Department.
- Design – each project is treated as a one-off, with full manufacturing drawings produced.
- Procurement – components are sourced and tracked through to final fit-out.
- Manufacture – completed to good engineering practice, or under Third Party Inspection (e.g. Lloyds) where required, using coded welders.
- Fit-out – carried out in-factory or on-site for larger installations, supervised by an Operations Department engineer.
- Commissioning and handover – performed on-site by the Technical Manager or their staff, following established procedures.
- Service support – ongoing spare parts supply, advice, servicing, or complete operational management after handover.
Key Features Summary
- Proven flare design experience spanning more than 15 years across landfill gas, biogas, and standard fuel gas applications
- Equipment delivering more than 99% availability for combustion facilities, and 99% for gas pumping/processing equipment
- Turnkey design, manufacture, and installation services – or component supply only
- Finance available through affiliated companies for finance-and-operate projects
- Full operation and maintenance services available
- A one-stop solution for waste and surplus gas combustion
Summary
Flare technology spans a wide spectrum – from simple open-flame AC Range stacks suitable for relatively clean gas disposal, through enclosed SC and MC Class systems delivering controlled high-temperature combustion with defined retention times, to ultra-low emission SMART flares engineered specifically to minimise NOx and destroy toxic trace gases. Additional solutions such as RB Class low-height flares, LHC low-calorific-value gas systems, and solar-powered BCW/ACE flares extend coverage to virtually any site constraint, from height restrictions to off-grid locations.
Choosing the right flare depends on your gas composition, flow rates, local emissions standards, and site conditions. With flow rates handled from 50 up to 15,000 m³ per day and flame temperatures engineered between 800-1,200°C depending on the class selected, there’s a proven solution for almost every landfill gas or biogas combustion challenge.
Whether you need a straightforward candle flare, a fully enclosed low-emission system, or a complete turnkey combustion facility with ongoing service support, get in touch with our team to discuss the right flare specification for your site.