January 2022

Special Focus: Sustainability

Taking a measured approach to climate change through continuous emissions monitoring systems

The need to reduce emissions has never been greater.

The need to reduce emissions has never been greater. A report1 published by the Inter-governmental Panel on Climate Change (IPCC) has been labeled a “code red for humanity” by the United Nations (UN). The report highlights that the Earth’s surface temperature was 1.09°C higher in the decade between 2011–2020 than between 1850–1900, that the past 5 yr have been the hottest on record since 1850, and that the recent rate of sea level rise has nearly tripled compared with 1901–1971. The report indicates that human influence is very likely the main driver of the global retreat of glaciers since the 1990s and the decrease in Arctic sea ice.

As a heavily industrialized sector with a global impact, the oil and gas industry has a major role in tackling climate change. According to a report by McKinsey, the oil and gas sector must reduce its emissions by at least 3.4 gigatons of carbon-dioxide equivalent per year (GtCO2e/yr) by 2050 compared to a business-as-usual approach.2

Initiatives such as the Oil and Gas Methane Partnership (OGMP) will play an important role in reaching these reduction targets. The OGMP is part of the Climate and Clean Air Coalition to Reduce Short-Lived Climate Pollutants (CCAC) initiative led by the UN Environment Program (UNEP), the European Commission (EC) and the Environmental Defense Fund (EDF). Sixty-two companies with assets on five continents, representing 30% of the world’s oil and gas production, have joined this partnership. The new OGMP 2.0 framework is now the gold-standard reporting framework that will improve the reporting accuracy and transparency of anthropogenic methane emissions in the oil and gas sector.

The need for measurement

For targets to be met, emissions must be measured and monitored. Continuous emissions monitoring systems (CEMS) are available to monitor a wide array of emissions. Available options range from standard systems for natural-gas-fired boilers to measure emissions such as carbon monoxide, carbon dioxide and nitrogen oxides to highly sophisticated, multi-component systems for waste-incineration plants measuring water soluble pollutants such as hydrogen fluoride, hydrogen chloride and ammonia.

The combination of environmental pressure, tightening regulations and a broader range of technology options is seeing a rising uptake of CEMS in industrial applications. The ARC Advisory Group forecasts a 4.8% growth in CEMS adoption between 2018–2023, with most of it being driven by Asia, as key players such as China, Southeast Asia and India increase their levels of industrial activity.3 Growth is also expected to be generated by operators involved in electric power generation, incineration and chemicals manufacturing, which collectively represent the world’s largest markets for emissions monitoring systems.

Different types of CEMS

When it comes to CEMS solutions, users can select from a diverse choice of technologies that allow emissions to be accurately measured in a wide variety of refinery, petrochemical and chemicals applications. This includes the use in both production processes to measure gases and volatile organic compounds and for monitoring emissions from plants, such as from fired heaters, steam methane reformers and steam boilers. When it comes to measuring stack emissions, operators have a choice of techniques.

Extractive techniques. Commonly used for measuring gases, extractive techniques consist of two primary methods. Heated extraction involves extracting the sample gas from the stack by using a sample probe, heated line, gas conditioning equipment and a heated sample pump. Before analysis, condensate is usually removed from the sample and the temperature is reduced to protect the analyzers, commonly referred to as “cold/dry” measurement. The author’s company’s continuous gas analyzersa work on this principle. As a modular gas analysis solution, it can combine up to four analyzer modules handling a total of six sample components. With ATEX 3G protection, the complete system can be designed without a purge, thus cutting maintenance time and costs, and increasing system availability by allowing maintenance operations or repairs at any time.

The alternative is to keep the gas hot all the way through the system, which is known as a “hot/wet” process. The sample must arrive at the analyzer inlet in a representative state that reflects conditions in the stack. The design of the sampling system must also protect against any sample loss or degradation. The author’s company provides an alternative Fourier-transform infrared spectroscopy (FTIR) solutionb to simultaneously measure multiple components. The system even allows the addition of further new components in the future by modifying the FTIR spectroscopy model.

In-situ measurement. In-situ “probe” analyzers are directly connected to the probe installed at the measurement point. Most in-situ systems use infrared measurement techniques.

Another popular technique is cross-duct analyzers. These analyzers project infrared (IR) or ultraviolet (UV) energy across the stack and detect the change in the energy state of the gas molecules as they absorb this energy at characteristic wavelengths.

Most cross-duct systems measure 1–2 gases over a range of wavelengths. Furthermore, as there is no contact with the target gases, they can require less maintenance and operator involvement. One drawback is that cross-duct systems can be more complicated to calibrate, although this can sometimes be overcome using an automatic calibration system.

The author’s company’s in-situ cross-duct analyzerc for measuring gas component concentrations applies a highly selective, optical measuring principle of tuneable diode laser (TDL) absorption spectroscopy. The laser is selected for a single wavelength in the sample gas absorption spectrum, where no cross sensitivity from other gases occurs. The absorption line is scanned, and the receiver detects the absorption caused by the measuring component and calculates the gas concentration.

While in-situ analyzers can be installed directly on the stack with no sample handling, around 80%–90% of plants worldwide have a strong preference for extractive methods that tend to offer a lower cost of ownership.

In comparison to in-situ measurement, extracting a sample means only that the probe is in contact with the gas and not with any delicate optical components. After conditioning, a clean and dry sample is presented to the analyzer. The system can then be installed in an air-conditioned cabinet or shelter, protecting it against potentially harsh ambient conditions.

Whereas in-situ devices are usually limited to 1–2 components, multiple components can be measured simultaneously by using a sequence of sensors in an extractive system, requiring fewer holes in the stack.

With the analyzer system usually installed at ground level in a clean and accessible environment, maintenance is much more convenient, components are easy to work on and test gas cylinders are available nearby to easily calibrate the devices.

A measured future

While addressing climate change is going to take a combined effort by governments, organizations and individuals worldwide, measurement systems are going to play a crucial role in helping the world to reduce emissions. As the value of these systems becomes more widely understood and the technologies become easier to implement, CEMSs will certainly be set to play an increasingly central role in ensuring that all industries play their part in finding ways to limit their emissions. HP


a ABB’s AO2000 and EL3000 continuous gas analyzers
b ABB’s ACF5000 FTIR analyzer
c ABB LS25 analyzer


  1. McGrath, M., “Climate Change: IPCC Report is ‘Code Red for Humanity’,” BBC, August 2021, online: https://www.bbc.com/news/science-environment-58130705
  2. Beck, C., S. Rashidbeigi, O. Roelofsen and E. Speelman, “The Future is Now: How Oil and Gas Companies can Decarbonize,” McKinsey & Co., January 2020, online: https://www.mckinsey.com/industries/oil-and-gas/our-insights/the-future-is-now-how-oil-and-gas-companies-can-decarbonize
  3. ARC Advisory Board, “Emission Monitoring Systems,” online: https://www.arcweb.com/market-studies/emission-monitoring-systems

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