Edinburgh Instruments Ltd

Methane and Carbon Dioxide Sensing for Landfill Applications

Application: In March 1986 an explosion destroyed a bungalow adjacent to a landfill site in Loscoe, Derbyshire. Subsequent measurements showed that 150-200 cubic meters of gas per hour were being generated by landfill waste. This event triggered a change in the way the waste industry considered and regulated gas generated at landfill sites; resulting in the landfill regulations of 2002, and in particular LFTGN03: the Guidance on the Management of landfill Gas.

The regulations, which run to 128 pages, describe the management and control of landfill sites, and define landfill gas as being all the gas generated from landfill waste. This includes gases generated by biodegradation of waste and gas arising from chemical reactions and the volatilisation of chemicals from the waste.

These regulations require that for every landfill site, a gas management plan is put in place to ensure:

Landfill gas must be collected from all landfills receiving biodegradable waste and the landfill gas must be treated and, to the extent possible, used.
The collection, treatment and use of landfill gas is required; and must be achieved in a manner, which minimises damage to, or deterioration of, the environmental risk to human health.

Mature landfill gas is a mixture predominantly made up of Methane (CH4), and normally in the range of 40-60% and Carbon Dioxide (CO2). It may also contain varying amounts of nitrogen and oxygen derived from air that has been drawn into the landfill.

Because Methane is a greenhouse gas which is 21 times more harmful to the environment than Carbon Dioxide, by converting Methane to Carbon Dioxide through burning (and thereby generating Carbon Dioxide) this is considered more beneficial to the environment. In addition, by measuring the amount of Methane burnt, carbon credits are generated, which can then be traded, thus providing a useful revenue stream. Methane is also a useful fuel that can be used to power gas generators to produce electricity and heat.

Appendix F of the regulations describes infra-red measurement as the primary method of measuring Methane and Carbon Dioxide on landfill sites.

In 1956, the founder of Edinburgh Instruments published a paper on the design and fabrication of infrared band pass filters, which are a key component of modern IR bench sensors.

Edinburgh Sensors has actively commercialised this technology over the last 40 years, resulting in a reputation for reliable, accurate, long-term stability and low maintenance gas-sensing products, which have been used extensively over the last 10 years by many of the leading Landfill gas analyser developers, leading to installations worldwide on landfill sites.

Gascard NG is an ideal OEM sensing solution for measuring either methane (CH4) or Carbon Dioxide (CO2), having been designed for ease of integration.

Available with a 0-100% range for both CO2 and CH4, the sensor features on-board Barometric Pressure Correction, and extensive Temperature compensation, which allows installation worldwide in different climates

The Gascard NG has a range of different interface options, including analogue 4-20mA/0-20mA/0-5v, true RS232 communication, optional on board LAN support, and a serial interface for interfacing relay alarms. The on-board firmware supports either a traditional 4-segment LCD or a modern graphical display.

For OEM development, Edinburgh Sensors, can provide an evaluation kit consisting of a Gascard NG sensor, an advanced graphical display interface, and relay board allowing easy evaluation of the Gascard NG functions.

Technical support is available from our Engineers who are available to provide one-to-one customer service and technical support throughout the evaluation and system integration process

In addition to OEM Gas sensors, Edinburgh Sensors have been providing Gas Monitors based upon our proprietary infrared sensor technology for many years; with tens of thousands of our monitors in operation worldwide. It is hardly surprising, therefore, that these monitors have been put to widespread use in the Landfill applications.

The NEW Guardian NG Gas Monitor is already being evaluated by a number of our volume customers working within Landfill applications. Wall-mounted, in an IP54 enclosure, with an integral power supply and sample pump, allowing samples to be taken remotely from over 30 meters away, this Gas Monitor can be provided to measure 0-100% of Carbon Monoxide (CO) or 0-30% of Carbon Dioxide (CO2).

The Monitor features volt free relay alarm outputs, controlled by programmable alarm levels; an accurate temperature and pressure compensated measurement of the gas concentration via 4-20mA( or 0-20mA) and RS232 interface; and a graphical user interface with password protection - allowing not only display of the compensated gas measurement, but control of the Gas monitor calibration and alarm functions.