Monitoring And Analysis of Landfill Gases
CoGDEM is the trade association representing manufacturers and service providers who are active in the field of gas detection instrumentation and environmental monitoring apparatus. Crowcon Detection Instruments Ltd was one of the founding members of CoGDEM, and in this article their Product Manager of Fixed Systems, Andy Avenell, gives an update on Landfill Gas.
Landfill is by far the most common method of waste disposal in the United Kingdom. Despite the increase in recycling, data from the latest Defra* Municipal Management Survey (2003- 2004) shows the amount of waste going into landfill still represents 72% of all waste and totals 20.9 million tonnes. In England and Wales, landfill is regulated under The Landfill (England and Wales) Regulations 2002. In Scotland, they are regulated through the Landfill (Scotland) Regulations 2003. These regulations set out a pollution control regime as part of their implementation of the EU Landfill Directive (Council Directive 1999/31/EC), which aims to prevent, or to reduce as far as possible, the negative environmental effects of landfill. Landfill site operators must carry out control and monitoring procedures during the life of the site and for a period after closing, as specified by the Environment Agency in England and Wales or SEPA in Scotland.
Hazards Associated with Landfill
There are two primary hazards associated with landfill. One is the production of leachate, which is formed when water passes through the waste in the landfill, picking up organic and inorganic compounds. This toxic liquid then collects at the base of the landfill cell. If not properly controlled, it can contaminate the surrounding soil, groundwater and nearby water courses.
The other main hazard is gas caused by the breakdown of organic materials, producing methane, carbon dioxide, hydrogen sulphide and other gases, depending on the landfill's content. This mixture is known as landfill gas. The majority of the gas is produced during the working life of a landfill and for about 20 years after a site has been sealed and capped. However low levels of residual generation will occur for much longer than the main period of gas production, possibly in excess of 100 years. Methane poses a severe explosion risk, is damaging to plant life and is also a greenhouse gas. Carbon dioxide, also a greenhouse gas, is toxic and an asphyxiant, as it depletes local oxygen levels. Hydrogen sulphide is highly toxic, even at very low concentrations.
Schedule 2, paragraph (4) of The Landfill (England and Wales) Regulations 2002 requires the following gas control measures:
- Appropriate measures must be taken in order to control the accumulation and migration of landfill gas
- Landfill gas must be collected from all landfills receiving biodegradable waste and the land fill gas must be treated and, to the extent possible, used
- The collection, treatment and use of landfill gas under sub-paragraph (2) must be carried on in a manner which minimises damage to, or deterioration of, the environment and risk to human health
- Landfill gas which cannot be used to produce energy must be flared