Landfill Gas Capture

Introduction

Landfill gas (LFG) is a useful product of solid waste disposal. Landfills naturally generate methane and CO₂ as waste decomposes over time. This gas can be collected and, once it is purified, it can either be used to supplement natural gas, or it can be used as its own alternative fuel source.

The methane is generated through the process of anaerobic digestion. As solid waste is added to a landfill, it initially goes through an aerobic digestion stage where the available oxygen is used up. This step creates mostly CO₂ gas. Once the oxygen has been consumed, the process turns over to anaerobic digestion. At the beginning of this process, compounds are converted to acids and alcohols, releasing CO₂ and hydrogen. These acids are then consumed to produce acetate and organic acids, which leads to the growth of methane producing bacteria. Once the system has reached steady state, typically about 1 year after the material is added, the main products of the process are CO₂ and Methane. The concentrations generally remain steady at around 50% CH₄ and 45% CO₂. The production can last for 20 years before methane production level starts to drop off.

Often one of the most important parameters for landfill gas production is that it maintains compliance with the local municipality. Typically, this means controlling odors and emissions. This can be done by ensuring the system is always under a slight vacuum. The methane concentration can be used as an indicator that the system is under vacuum at this stage. Keeping the concentration under the known production output of the landfill indicates that some air is being pulled into the system, ensuring that leakage is minimized. The methane concentration is also an indicator of where the landfill is in its lifecycle. As the landfill nears the end of its production, the methane concentration will steadily drop off.

The MCP-200 process analyzer continuously measures 0-70% CH₄ in the landfill gas. The readings provide real-time control over the flow rates from the process and the methane content of the product. Using online control at this stage allows for the landfill parameters to be optimized to maintain a consistent vacuum on process and to monitor the product methane stream concentration.

System Benefits

• Continuously measures 0-70% methane in the effluent from the landfill.
• Totally solid-state build with no moving parts — modern design for low maintenance.
• Fast response time, analyzer updates reading in under 5 seconds.

Example MCP-200 Sample Conditioner

The system is built to monitor 70% methane in Landfill Gas. Key features for this application include:

• Stainless steel components/fittings & Viton gaskets for corrosion resistance.
• Particulate filtration to remove solids that could influence the measurement.
• Liquid filtration to remove entrained liquid that could influence the measurement.
• MCP-200 analyzer housed in an explosion-proof enclosure.

Installation and Product Photos

Further Reading