Landfill gas monitoring
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Landfill gas monitoring is the process by which gases that are released from landfill are electronically monitored.
Landfill gas production results from chemical reactions and microbes acting upon the waste as they begin to break down the putrescible materials.[1] in the landfill Due to the constant production of landfill gas, pressure increases within the landfill provoke its release into the atmosphere. Such emissions lead to important environmental, hygiene and security problems in the landfill. [2][3] Although there have been no deaths directly linked to landfill gas several accidents have occurred, for example at Loscoe, England in 1984.[4] Migrating landfill gas was allowed to build up and destroyed the property. Due to the risk presented by landfill gas there is a clear need to monitor gas produced by landfills.
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[edit] Techniques for the monitoring of landfill gas
- Surface monitoring
Used to check the integrity of caps on waste, check on borehole monitoring. May give preliminary indications of off-site gas migration. Typical regulatory limit is 500 parts per million (ppm) of methane (CH4) by volume. - Subsurface monitoring
Gas probes ~ used to enable point source monitoring of gas concentrations in the local environment around the probe. These may contain a single probe or multiple probes (at different depths) at a single point. Probes typically form a ring around a landfill. The distance between probes vary (based upon several factors) and rarely exceedes 1000'. Also known as migration or perimeter probes. Typical regulatory limit is 5% (CH4), which is 50,000 ppm. - Excavated trenches and pits backfilled around standpipes (provides means of measuring gas concentrations in shallow sites)
- Gas monitoring boreholes or wells (preferred method for measuring gas concentrations and sometimes flow rates both on and off site)
- Ambient air samplers.
Used to sample the air up-wind and down-wind of a landfill, over the period of several hours. Samples are taken in special plastic bags or steel canisters and analyzed at a laboratory. Where a landfill is situated in a location where the wind direction changes from day to night (like along a coastline), a 24 hour sampling period may be broken into day and night components. - The use of leachate wells (may be used for gas monitoring but are not comparable with, or substitutes for specially designed gas monitoring points)[5]
[edit] Types of landfill gas monitor
- Single reading monitors- these monitors give point readings for landfill gas composition
- Continuous gas monitors- these monitors remain in boreholes and give continuous readings over time for landfill gas composition and production
| Matter | % |
|---|---|
| Methane, CH4 | 54 |
| Carbon dioxide, CO2 | 42 |
| Oxygen, O2 | 0.8 |
| Fluor, F2 | 5 mg/m3 |
| Chlorine, Cl2 | 22 mg/m3 |
| Hydrogen sulphide, H2S | 88 mg/m3 |
[edit] See also
[edit] References
- ^ Burdekin, O. (2003) An investigation into the continuous monitoring of landfill gas and the commercial viability of the Intelysis landfill gas monitor, Manchester University, Unpublished thesis
- ^ Brosseau, J. (1994) Trace gas compound emissions from municipal landfill sanitary sites; Atmospheric-Environment 28 (2), 285-293
- ^ Christensen, T. H., Cossu, R. & Stegmann, R. (1999) Landfilling of waste: Biogas
- ^ Williams and Aitkenhead (1991) Lessons from Loscoe: The uncontrolled migration of landfill gas; The Quarterly Journal of Engineering Geology 24 (2), 191-207
- ^ Waste management paper 27 (1991)
- ^ Basic Information on Biogas
