Biogas is a growing source of renewable energy for clean-water plants, whether for on-site heating or combined heat and power, for vehicle fuel, or for renewable natural gas fed into natural gas utility pipelines.

But what’s the content of that gas? How much methane? Knowing the answers can help facility staff optimize gas production and consistently meet vehicle fuel or renewable natural gas specifications.

QED Environmental Systems now offers a fixed analyzer designed for high-accuracy methane, carbon dioxide and oxygen readings for biomethane applications. Users can select a fourth gas reading for hydrogen sulfide at various levels to optimize accuracy.

The BIOMETHANE 3000 analyzer helps clean-water plants achieve high biogas operation efficiency by optimizing the anaerobic digestion process. It provides reliable readings above the 95% methane level and below the 1% oxygen level at first-stage production.

The unit is customizable to site requirements. With an IP65-rated enclosure, it is certified for use in potentially-explosive atmospheres. The device is easy to install and operate and has a color visual display. Its fully automated calibration function maintains methane testing accuracy. Belinda Shuler, biogas product manager with QED, talked about the technology in an interview with Treatment Plant Operator.

What was the reason for bringing this technology to the wastewater treatment market?

Shuler: Our methane measurement technology was first used in landfill gas applications to manage methane, CO2, oxygen, carbon monoxide and H2S. With growth in anaerobic digesters for biogas production, it fits perfectly into that market. 

Why is it important to measure methane concentration accurately?

Shuler: The main reason for monitoring the concentration of methane is to document that the methane content meets a specification for renewable natural gas. The developer or facility owners get paid by the volume of methane that is sent through the line. Another reason is that the facility or developer can get carbon credits for capturing and using the gas or flaring it.

 Are there other applications where it is beneficial to monitor methane content?

Shuler: Yes. We use our analyzers at food processing plants, slaughter houses, breweries, and paper mill water treatment plant digesters. The importance is to be able to track what is happening inside the digesters. The concentrations of methane, CO2 and oxygen all are intertwined. If the oxygen content starts going up in an anaerobic digester, the methane content will go down, and the anaerobic process will not perform optimally. If they have oxygen intrusion, they may have a crack in a pipe connection, or a valve has been left open. It’s an indication of some damage that needs repair.

Is it valuable to know the precise methane content in a process like combined heat and power?

Shuler: Yes. Generator sets require a certain percentage of methane in the fuel. If the methane content falls too low, it may be necessary to pipe in supplemental natural gas to keep the engines running at peak output.

Can this device measure digester gas impurities like siloxanes or acids?

Shuler: We don’t measure those, although with our portable biogas instruments we can measure ammonia.

What methods do these devices use to measure the different gases?

Shuler: For methane and CO2 we use nondispersive infrared technology. For oxygen and for H2S or one of the other additional gases, we use electrochemical cells.

How is the information captured and reported to the end users?

Shuler: Our communications can be a 4-20 mA output or Modbus RTU. Facilities can also choose Ethernet communication, Profinet or Profibus. Most clean-water facilities have a SCADA system, and they will see the actual percentages of gases on their screens as numeric displays. Sometimes they have the entire process laid out on the screen showing the different points where the gas concentrations are being read. In that way they can see how the concentrations are changing throughout the process.

At what points in the process are these analyzers typically installed?

Shuler: Many facilities will deploy them before an H2S scrubber. That way they can see how much H2S is going in and how much is coming out. If they see the H2S readings after the scrubber increasing, they know it’s time to change the scrubber media. We can measure H2S at levels as low as zero to 50 ppm, or as high as zero to 40,000 ppm.

Where else in the process are the analyzers beneficial?

Shuler: A critical point is before the pipeline, engine or boiler, so they can see the result of their processes and methane production. We also see users connect them to a flare, so they know how much methane is being burned off. For some facilities, that is for air emission reporting regulations. In other cases, utilities receive credits for methane destruction.

How does this technology provide a return on investment?

Shuler: The most significant way is in prevention of unplanned downtime. To that end, we offer a hot swap, where if an analyzer fails, we can overnight ship them a new module that they can switch out. We hear time and again how many thousands of dollars are lost because of lost readings. The methane is what pays their bills, and if they can’t prove the methane content, they are not getting paid.

Do any facilities keep extra modules on hand as essential spares?

Shuler: Some facilities do buy their own spare analyzer to have on site, especially if they have multiple units.

How much operator attention does this technology

Shuler: The BIOMETHANE 3000 has auto-calibration, so it’s very user-friendly. Users don’t need to have someone on site to watch it because it sends the data constantly to their SCADA system.

How flexible is this technology to meet individual user needs?

Shuler: We don’t have units sitting on a shelf. We send the users a form to complete to tell us what they need. If they don’t need all the bells and whistles, they don’t have to buy them. If they want to measure from four different points within their system, we can do that. If they want to measure continuously and have over-the-top accuracy, we can do that. We build our units specifically to suit each project.