Landfill gas flaring and utilisation facilities play a critical role in reducing methane emissions and generating renewable energy, but they also need to demonstrate that their exhaust gases are clean and compliant. As environmental awareness grows and statutory controls tighten, on-line monitoring of exhaust gas quality has become an essential part of running a well-managed site.
This post looks at what exhaust gas analysis equipment does, why it matters, the regulatory standards it needs to satisfy, and the recommended monitoring regimes used across the UK landfill gas sector.
Why Exhaust Gas Monitoring Matters
Combustion of landfill gas — whether in an enclosed flare or a utilisation engine — produces a mix of by-products. Left unchecked, these can include harmful pollutants such as carbon monoxide, oxides of nitrogen, and unburned hydrocarbons. Regulatory bodies, including the UK Environment Agency, have set clear limits on these emissions to protect air quality and public health.
The UK Environment Agency sets strict compliance limits: 50 mg/Nm³ for carbon monoxide, 150 mg/Nm³ for oxides of nitrogen, and 10 mg/Nm³ for unburned hydrocarbons — all normalised to 3% oxygen.
Because emission concentrations are always quoted relative to a standard oxygen content (typically 3% in the UK), any monitoring system must also track oxygen levels alongside the target pollutants. Other gases — such as hydrogen sulphide, sulphur dioxide and carbon dioxide — can also be monitored, although they are of more limited relevance in the exhaust from landfill gas combustion equipment.
What Exhaust Gas Analysis Equipment Does
Exhaust gas analysis systems are designed to give site operators continuous, reliable visibility of combustion performance and emissions quality. Core capabilities include:
- On-line monitoring of exhaust gas quality in real time
- Datalogging of results to support trend analysis over time
- Remote access options, including web-based viewing of results, so site managers and regulators can review data without being on-site
- Sequential sampling systems designed specifically for multi-point installations
- Multi-point sampling systems supplied on a design-and-build basis to suit individual site layouts
- Field-proven systems with a track record across operational landfill gas sites
This combination of continuous monitoring and remote reporting makes it far easier for operators to demonstrate ongoing compliance and to react quickly if performance drifts outside acceptable limits.
Environment Agency Compliance Limits
To confirm that flare systems are operating correctly, emission concentrations — referenced to Normal Temperature and Pressure (NTP = 0°C and 1013 mbar) and 3% oxygen — should not exceed the following:
| Pollutant | Compliance Limit |
|---|---|
| Carbon monoxide (CO) | 50 mg/Nm³ |
| Oxides of nitrogen (NOx) | 150 mg/Nm³ |
| Unburned hydrocarbons | 10 mg/Nm³ |
CO and NOx can be measured relatively easily with current technology. Unburned hydrocarbon monitoring at the ranges required is not yet available at a realistic price point, which is an important practical consideration when designing a monitoring package.
Recommended Monitoring Regimes
Guidance exists on the level of monitoring that should be applied to enclosed flares, along with the acceptable methods to be employed. Monitoring/sampling points should be easily accessible, safe, and functional, and retrofitted where currently absent. Trace gas concentrations should be analysed annually.
Level 1 — Continuous Operational Monitoring
Inlet Gas (pre-combustion)
– CH₄, CO₂, O₂
– Continuous monitoring
Outlet Gas (emission)
– Upper chamber temperature
– Gas flow rate into chamber
– Continuous monitoring
Level 1 monitoring verifies effective plant operation and should be carried out continually, ideally with telemetry, since it provides the basic information needed for controlling the flare.
Level 2 — Periodic Characterisation and Compliance Verification
Inlet Gas (pre-combustion)
– Bulk gases (O₂, CO, NOx, CO₂, THC) via GCMS Suite
– Annual monitoring
Outlet Gas (emission)
– CO, NOx, CH₄, trace species
– Six-monthly/annual monitoring
Level 2 monitoring supports gas characterisation, compliance verification, assessment of potential health impacts, and commissioning activities. It should be carried out periodically, or whenever there is a significant change in landfill gas composition or flare operation — for example, when a new phase of a site is brought online, or when plant is newly commissioned or re-commissioned after relocation.
Second level monitoring frequency should typically be annual, but this depends on proximity to population centres or environmentally sensitive areas, and on findings from environmental impact assessments.
During commissioning, Level 2 monitoring should be used to demonstrate both initial effectiveness and the ongoing capability to continuously meet emission standards.
Recording and Reporting
Good data collection is only half the job — it also needs to be properly interpreted and reported. All results obtained by flare-system managers should be subject to formal interpretation. This interpretation, together with a copy of the flare maintenance log, must accompany results and reports when communicated to regulatory officers, on at least a monthly basis.
This reporting discipline is where remote access and web-based data viewing genuinely pay off, allowing operators to compile and share results efficiently without manual data extraction from on-site equipment.
Key Takeaways
- Landfill gas flaring and utilisation sites must monitor CO, NOx, and unburned hydrocarbons, normalised to 3% oxygen, to meet UK Environment Agency standards.
- Compliance limits are 50 mg/Nm³ (CO), 150 mg/Nm³ (NOx), and 10 mg/Nm³ (unburned hydrocarbons).
- A two-tier monitoring approach — continuous Level 1 monitoring for operational control, and periodic Level 2 monitoring for compliance and characterisation — is recommended.
- Modern exhaust gas analysis equipment offers on-line monitoring, datalogging, remote/web-based access, and multi-point or sequential sampling designed around individual site needs.
- Formal interpretation of results, alongside flare maintenance logs, should be reported to regulators at least monthly.
Get in Touch
Reliable exhaust gas analysis is central to running a compliant, well-managed landfill gas flaring or utilisation facility. If you’d like to discuss fixed instrumentation, manual monitoring regimes, or a design-and-build multi-point sampling system tailored to your site, get in touch with our technical sales team to find the right solution for your monitoring requirements.