Managing a landfill gas collection system successfully depends on one crucial factor: understanding how gas quality changes over time and with operating conditions. Without accurate, continuous monitoring, operators are essentially flying blind — and the consequences can look like sudden, unexplained equipment failures when in fact the root cause is a shift in the gas itself.
Feed gas analysis equipment exists to solve exactly this problem, providing on-line, real-time insight into the composition of the gas entering a collection or combustion system.
Why Landfill Gas Is So Difficult to Monitor
Landfill gas is notoriously challenging to measure reliably. It is typically saturated with moisture, which can condense inside sensitive instrument components and cause faults or false readings. It also contains a complex mixture of contaminant gases — some of which can interfere with sensor readings through cross-sensitivity, while others can actively damage sensors that aren’t designed to cope with the harsh landfill environment.
Landfill gas monitoring must contend with near-constant moisture saturation and a cocktail of contaminant gases — conditions that would quickly disable equipment not purpose-built for the task.
To operate reliably in this environment, feed gas analysis systems need more than just sensors — they need supporting infrastructure to protect those sensors from the conditions they’re measuring.
What On-Line Feed Gas Analysis Equipment Measures
On-line feed gas equipment typically monitors three core parameters:
- Methane (CH4)
- Carbon dioxide (CO2)
- Oxygen (O2)
On some installations, monitoring can be extended to include hydrogen sulphide (H2S) and carbon monoxide (CO), giving operators a fuller picture of gas composition and potential safety or process issues.
Supporting Systems
To keep these measurements accurate and the equipment functioning reliably, a complete feed gas analysis package generally includes:
- Feed gas filtration to remove particulates before they reach sensitive sensors
- Feed gas pre-heating to prevent condensate forming within the sample stream
- In-built dewatering systems to manage any moisture that does collect
- Water flood-protection measures with alarm notification, safeguarding the system against water ingress
Why Continuous Monitoring Matters
Methane production within a landfill is fundamentally a bacteriological process, influenced by a wide range of variables. As a result, the quantity and quality of methane at the point of use or disposal can vary significantly over time.
In some cases, particularly on well-managed sites with large gas production potential, these changes happen slowly. But in more finely balanced systems, changes can be dramatic and sudden.
It is not unknown for methane concentrations to drop from 60% to less than 20% within just half an hour of start-up — a shift that, without monitoring, looks like a sudden and inexplicable equipment failure.
This is precisely why continuous, on-line monitoring is so valuable: it gives operators the information they need to understand what’s actually happening in the gas collection system, rather than misdiagnosing gas quality issues as mechanical or combustion equipment faults.
Technical Specifications
Methane and Carbon Dioxide Analysers
| Parameter | Specification |
|---|---|
| Type | Infrared sensor |
| Aspiration | Pumped (0.2 to 3 l/min); diffusion feed option available |
| Output | 4-20 mA, 0.1 mA resolution, 500 Ohms maximum load (optional 0-20 mA or voltage output) |
| Controls | Zero and span adjust potentiometers |
| Accuracy | ±2% FSD |
| Repeatability | ±1% FSD |
| Response time | T90 = 5 secs from sample inlet (excl. aspiration time) |
| Temperature coefficient | 1000 ppm/K FSD at zero; 5000 ppm/K FSD at span |
| Stability | Better than ±2% FSD per month |
| Power consumption | 6 W |
| Alarms | Two operator-set digital alarms, optional rising or falling value |
| Operating temperature | 0–45°C |
| Humidity range | Unaffected by humidity, 0–100% non-condensing |
Oxygen Analyser
| Parameter | Specification |
|---|---|
| Type | Galvanic cell with acid electrolyte |
| Anode / Cathode | Lead / Gold |
| Detection range | 0–100% O2 |
| Accuracy | ±1% |
| Operating temperature | +5 to +40°C |
| Storage temperature | -20 to +60°C |
| Response time | T90 = approx. 12 secs |
| Lifetime | Approx. 900,000 %hours (O2% x hrs run) — approx. 5 years in 20°C air |
| Cross sensitivity | Virtually no influence from CO2, CO, H2S, NOx, SO2, and H2 |
| Warming-up time | Not required |
Extending the System’s Capability
Beyond core on-line composition monitoring, feed gas analysis equipment can be extended with a range of additional capabilities to suit different operational needs:
- Data-logging to build a time-based picture of fuel quality changes
- Alarm condition monitoring to give early warning of fuel quality deterioration
- Remote access to view real-time values and download logged data for offsite analysis
- Telemetric alarm transmission for sites where plant operation is considered critical
These extensions can be supplied as standard instrument packages or tailored to the specific requirements of a site, giving operators flexibility depending on the scale and criticality of their gas collection operations.
Typical Applications
This type of equipment is widely used across landfill sites and other gas-to-energy operations where understanding landfill gas composition is essential to safe, efficient operation — including gas collection network management, flare and engine feed monitoring, and sites integrating with SCADA systems for centralized process control. Multi-point monitoring options also allow a single analyser suite to cover several sampling locations across a site, reducing the need for multiple standalone units.
Key Takeaways
- Landfill gas is inherently difficult to monitor due to moisture saturation and contaminant gases that can damage or interfere with sensors.
- On-line feed gas analysis equipment typically monitors methane, CO2 and oxygen, with optional H2S and CO measurement.
- Supporting systems — filtration, pre-heating, dewatering, and flood protection — are essential to keep monitoring equipment reliable in harsh landfill conditions.
- Methane concentrations can shift dramatically and quickly (e.g. 60% to under 20% in half an hour), making continuous monitoring critical to avoid misdiagnosing equipment issues.
- Optional extensions like data-logging, remote access, and telemetric alarms add further operational value, especially on critical sites.
Understanding how your landfill gas quality changes over time is the foundation of a well-managed gas collection system. If you’d like to discuss feed gas analysis equipment for your site, or explore tailored monitoring solutions, get in touch with our Technical Sales Department today.