Green House Gas Emissions Monitoring

GHG Emissions Monitoring Application: Flare Gas Monitoring
Like the Mandatory Reporting of Greenhouse Gases Rule, strict regulations require operations to measure and record flare gas consumption.

Facilities emitting 25,000 metric tons of CO2 annually are required by the EPA to report annual GHG emissions per EPA mandate 40 CFR Part 98. There are many operations or applications where waste gas is flared into the atmosphere. Flare stacks are typically seen at oil and gas wells, refineries, well-drilling rigs, natural gas plants, wastewater treatment plants, chemical plants, and landfills. Like the Mandatory Reporting of Greenhouse Gases Rule (40 CFR 98), strict regulations require operations to measure and record flare gas consumption.

EPA 40 CFR part 98 requires reporting by 41 industrial categories. The categories are divided into subparts. Since flaring gas is common in many industries, the following subparts apply:

Subpart Q – Iron and Steel Production

  • Flaring blast furnace gas and coke oven gas

Subpart Y – Petroleum Refineries

  • Flaring waste gas

Subpart W – Petroleum and Natural Gas Systems

  • Flaring natural gas
  • Flaring various gases created during the processing of natural gas

Subpart X – Petrochemical Production

  • Flaring various gases during petrochemical production

Subpart II – Industrial Wastewater Treatment

  • Flaring biogas (rather than using it for fuel at a combustion source)

Subpart JJ – Manure Management

  • Flaring biogas (rather than using it for fuel at a combustion source)

Subpart HH – Municipal Solid Waste Landfills

  • Flaring LFG at a municipal landfill

Subpart TT – Industrial Waste Landfills

  • Flaring LFG at an industrial waste landfill


Flare Gas Monitoring

flare gas application guideMeasuring flare gas becomes a challenge for most flow meters. Ultrasonic flow meters are useful to measure flare gas. They tolerate some condensed liquid, are not affected by gas composition, and endure fluctuations in pressure and temperature. With this type of performance, however, come high costs ranging from $50,000-$100,000 per installation.

When flaring known gas composition, and water vapor isn’t condensing, thermal mass flow meters make an attractive alternative for flare gas metering. The SAGE meter has wide turndown or up to 1000:1 rangeability, which means it accommodates extreme flow conditions and large flow swings. Low velocities are associated with flare gas under normal venting situations, yet high flow rates typical in upset conditions. Additionally, their fast response to flow changes, low-pressure loss, accuracy (1% of reading plus 0.5% of full scale over a 100 to1 turndown), and reproducibility make the meter a contender in flare applications.

Companies are taking advantage of the cost savings associated with thermal flow meters, which are $5000 or less, versus the $50K to $100K for an ultrasonic application. When operations determine the flare gas composition, SAGE can adjust the meter to measure the known flare gas. This works for applications where compositional changes are known or are seasonal. While a bit more inconvenient than an ultrasonic meter, the savings warrant the minor difficulty in many cases.

It is clear that while thermal mass flowmeters are not the perfect choice to measure flare gas in many flare applications. However, the meter makes good sense when the composition is known, and there is no condensation. Also, when there are known variations in gas composition, SAGE can estimate variations in accuracy based on the gas composition analysis.

How Sage Can Help

SAGE Insertion Style flow meters provide the wide turndown required to cover both the extremely low flows (low velocities) associated with standard venting and the extremely high flow (high rates) associated with an upset condition. Their fast response to flow changes, low-pressure drop, and reproducibility are essential characteristics for a flare application. Also, SAGE products provide the customer with a unique in-situ calibration Check at a “No Flow” (0 SCFM) condition. This vital procedure assures that the meter has retained the original NIST Traceable calibration, verifies the meter’s accuracy, confirms that the sensors are clean and that the flow meter hasn’t drifted or shifted. This procedure is a tremendous benefit since it eliminates the cost and inconvenience of annual calibrations on the flow meter and provides the data needed to comply with several environmental protocols.


With EPA now requiring emitters to report annual GHG emissions, flow meters are scrutinized to find the best ways to measure and report data. Thermal mass flow meters are becoming the preferred choice to monitor and measure GHG emissions in applications such as biogas, digester gas, landfill gas, and flare gas. One of the primary advantages of thermal flow meters (over volumetric meters) is that they measure mass flow. The SAGE products are state-of-the-art as the manufacturer is the first to bring to market a digitally-driven sensor, a graphic display, and onsite calibration verification. The SAGE meter is the only TMFM which provides a convenient, in-situ, and in-line calibration check that assures the flow meter retains the original NIST traceable calibration and is accurate.

Learn More

To read the Sage Metering white paper “Greenhouse Gas Emissions Monitoring Using Thermal Mass Flow Meters,” visit Sage GHG Emissions White Paper.