The International Information Center for Geotechnical Engineers

Landfill Gas Monitoring Systems - Introduction

 1. Introduction

 Landfill gas emissions can cause serious problems that are now widely known, especially when the gases, after escaping from the site, accumulate in enclosed spaces where they can present a latent hazard, giving rise to explosions under the certain conditions. Landfill gas monitoring is therefore a critical concern for landfill operators and has become part of the legal requirements for the design, operation, and closure.

Landfill gas, which has approximately 50 percent methane and 50 percent carbon dioxide with trace components, is produced through bacterial decomposition, volatilization and chemical reactions. In addition, a number of factors influence the quantity of gas that a MSW landfill generates and the components of that gas. However, adverse environmental effects of landfill gas are increasingly being felt today. In order to reduce risk from landfill gas hazards, engineers generally use two methods to quantify gas emissions from landfill: they either estimate the emissions or measure them. The former is landfill gas modeling while the latter is landfill gas monitoring.

The goal of landfill gas monitoring is to detect the presence of gas, and to predict the quantity of gas as well as location in which to expect high gas concentrations. In this context, there are lots of landfill gas monitoring methods. These methods vary for different landfills. To choose proper monitoring methods, many factors should be considered, such as landfill types, site conditions, regulatory requirements, costs, but most importantly, the objective of monitoring, or the parameters to be monitored.

Generally, all gas monitoring activities can be classified into five categories:

• Soil gas monitoring (Subsurface monitoring)

• Near surface gas monitoring

• Emissions monitoring

• Ambient air monitoring

• Indoor air monitoring

There are too many monitoring techniques of each category to discuss all of them in detail in this report. Also, there are “intersections” in these monitoring activities, for example, emissions monitoring, can be a surface monitoring or a subsurface monitoring, and the monitoring parameters and techniques for ambient air and indoor air are very similar.

Emissions monitoring focuses on the measurement of gas emission rate; flux chambers are usually used for emissions monitoring. Surface monitoring and subsurface monitoring focus on the concentration of landfill gas, such as methane.

In this report, soil gas monitoring is discussed in detail, including installation and sampling methods. And one or two techniques for near surface monitoring and emissions monitoring are introduced.

Finally, the Landfill Gas Monitoring Regulations are introduced at the end. It includes how to determine if a landfill gas need to be monitored, and guidelines or requirements for gas collection system, gas control device, and compliance schedule, and device removal.


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