Landfill Methane Mitigation
A landfill site (also known as a rubbish dump) is a site for the disposal of waste materials by burial and is the oldest form of waste treatment. Historically, landfills have been the most common method of organized waste disposal and remain so in many places around the world. Decomposition of waste produces combustible and toxic gases that move from higher pressure areas (areas deep within the landfill) to lower pressure areas (areas such as ground surface and off-site areas). These gases easily move through loose sand or gravel soils and are released into the air through any available crack or opening. While wind dilutes the gas with fresh air, it can also move hazardous gas into neighboring communities. Many people find the odors emitted from a landfill to be unpleasant and may suffer temporary symptoms such as nausea and headache. Many landfill sites are also subsequently repurposed and used as sites to construct large residential, commercial, or industrial facilities. When buildings are constructed on top of a closed landfill or situated next to a closed or open landfill, a buildup of toxic and combustible gases is possible. It is therefore essential that all buildings in the vicinity of an active or repurposed landfill implement continuous and accurate gas monitoring to ensure the health and safety of the occupants.
Gas and Fire Detection
Hazardous gases that emit from landfill sites include:
- Combustible gases such as Methane
- Hydrogen Sulfide
- Carbon Dioxide
Gas must be monitored in the subsurface, near the surface, and above the surface (in the air) of a landfill. Gas detection may take place in monitoring wells, ventilation systems, and/or buildings on or off-site. Gas sample locations and sampling methods vary from landfill to landfill, depending on monitoring concerns or regulatory requirements.
In extreme circumstances, a landfill fire can occur if methane was not properly detected. Therefore fire detectors must be placed near sources of ignition.
Placing industrial-grade gas detectors within the buildings that are proximal to the landfills is also common.
The gas and flame detectors provide their measurements to a controller that can trigger the appropriate alarming or mitigation response. The controller also stores the data for subsequent diligence analysis.
Automation and Integration Strategies
Buildup of combustible gases can cause a hazard to a building built on a landfill site, particularly in enclosed areas such as basements and crawlspaces that might contain heating, ventilating, and air conditioning (HVAC) or electrical equipment. Smaller buildings without a centralized Building Automation System (BAS) should program the controller in the gas detection system to trigger a series of visual or audio alarms, to turn off any ignition source near the location of the discharge of gas, and to remotely notify a central monitoring center. The controller could also implement strategies such as texting or e-mailing notifications to appropriate health and safety responders. In the case of a large facility with a centralized BAS, the gas detection system should integrate with the BAS and fit within its management and workflow framework.
Automated safety systems such as those described in this section should be “performance approved” and checked on a periodic basis.