Carbon capture, utilisation, and storage (CCUS) is progressing rapidly from pilot-scale demonstrations to full-scale industrial deployment across waste to energy, power generation, cement, refining, and other energy-intensive industries.
As capture rates increase and regulatory monitoring becomes mandatory, as with any other type of treatment/abatement, the reliability, resolution, and transparency of process monitoring will become essential for both operational and environmental performances.
Gas composition analysis is a central part of carbon capture processes. Whether monitoring combustion gases entering an absorber (solid, membrane, or solvent), detecting solvent breakthrough at the outlet, tracking degradation byproducts, or checking gas quality before compression and transport, analytical data directly influences the control, efficiency, safety, and environmental compliance of the carbon capture process (post-combustion carbon capture).
Gas chromatography (GC) has traditionally been the preferred analytical technology in many applications (such as hydrogen, carbon capture, and petrochemicals) where it is necessary to measure several gas parameters (impurities) with high precision. However, GC systems are inherently periodic, typically providing a measurement every 10 - 20 min. They are also complex to maintain and operate, with high to very high operating costs (OPEX). In contrast, Fourier transform infrared (FTIR) spectroscopy allows for continuous online monitoring, providing analysis of numerous parameters with excellent accuracy in near real-time. This technology can also be widely deployed in plants where post-combustion carbon capture units are or will be deployed in the future. With reduced OPEX, their deployment is also a way to optimise maintenance processes and the costs associated with adding new multi-gas analysis equipment to CCS/CCUS units.
This article examines the advantages of monitoring gas parameters using FTIR, compared to using GC and periodic analysis of these same parameters (with a few exceptions in both directions) in carbon capture processes. It focuses on operational understanding, process optimisation, and environmental compliance.
Carbon capture processes: dynamic systems
Post-combustion carbon capture processes do not always benefit from a stable input flow. The composition of the feed gas to the carbon capture unit can vary rapidly due to upstream disturbances, load changes, fuel variability, or transient operating modes such as startup, shutdown, or source plant abatement failures.
In post-combustion capture, the composition of combustion gases can change within minutes after a burner adjustment or fuel change. Oxygen concentration, CO2 content, humidity, and traces of elements such as SO2, NOX, NH3, and organic compounds can fluctuate significantly.
These variations have a direct impact on the efficiency of the absorber depending on its type, solvent degradation rates, corrosion risk, captured CO2 quality, compression requirements, and overall capture performance. Therefore, representative and timely measurement of gas composition is essential for efficient operation.
GC: periodic monitoring
GC remains a robust and widely used analytical method in industry, but not specifically in industries targeted for CCU implementation. In impurity measurements (hydrogen production for mobility/air separation/food-grade CO2), GC technology is widely used to measure CO2, O2, N2, H2, CO, CH4, VOCs, mercaptans, and other permanent gases with high accuracy.
However, in the context of continuous process monitoring, GC has several fundamental limitations related to its analytical principle, sampling method, and industrial integration.
Discrete measurements
CG is based on spot analyses. Each measurement provides information at a given moment, often integrated over the sampling period. Between two successive analyses – which may be spaced several minutes to several tens of minutes apart – no information is available on the evolution of the process. This discontinuity limits the ability to quickly detect transient variations or rapid drifts.
Performance limits depending on compounds
While GC is well suited to a wide range of compounds, it is less effective for reactive or polar compounds such as ammonia, aldehydes, or amines (compounds found in solvent-based post-combustion carbon capture systems). Measuring these species generally requires additional equipment, specialised columns, or even more frequent maintenance.
OPEX
In addition to high investment cost (CAPEX), GC involves:
- Regular maintenance with high cost (columns, detectors, and carrier gases).
- Periodic calibration and validation requirements.
- Expertise of maintenance technicians.
These constraints may limit its large scale deployment as a primary monitoring tool for real-time applications in measuring CO2 impurities in carbon capture processes.
FTIR spectroscopy: continuous measurement
FTIR spectroscopy analyses gas composition by measuring infrared absorption across a broad spectral range. Because each molecule exhibits a characteristic absorption fingerprint, multiple components (300+ according to gas library) can be identified and quantified simultaneously, and FTIR systems operate continuously.
FTIR is based on direct spectroscopic measurement, without any chromatographic separation steps. This significantly reduces the time required for sample transport and analytical processing. This allows for better correlation between the measurement and the instantaneous state of the process, which is essential for controlling and optimising capture units (absorber, regenerator).
In carbon capture applications, FTIR systems can measure:
- Major components such as CO2, CO, and H2O.
- Acid gases including SO2, total sulfur, NOX.
- Reactive or polar species such as NH3, HCl, HF, HCN, and organic compounds.
- Amines (MEA/MDEA/AMP) and PZ in certain conditions.
In comparison, GC requires either multiple columns/detectors or multiple successive analyses. The main benefits of FTIR technology compared to GC in post-combustion CC are:
Detecting transient events
One advantage of continuous monitoring is its ability to capture transient events that are invisible to periodic systems and can avoid long-term consequences that short-duration excursions in gas composition can have especially in solvent-base carbon capture technology, such as:
- Brief solvent breakthrough events at the absorber outlet.
- Short spikes in SO2 or NOX accelerating solvent degradation.
- Temporary oxygen ingress increasing corrosion risk.
- Amine slips during regeneration transitions.
A measuring cycle of 10 - 15 min. may miss such events entirely or report only an average and therefore underestimate the event, whereas continuous monitoring by FTIR captures the full-time profile, revealing the exact onset, duration, and magnitude of the event. This level of detail enables operators to understand not just that an issue occurred, but why it occurred, supporting effective root cause analysis and long-term process improvement.
Enhancing process control and optimisation
Carbon capture processes are an energy-intensive operation, and optimisation is critical to economic performance and so they require high-resolution data for advanced control strategies.
With real-time measurements, operators can:
- Adjust solvent circulation rates based on actual inlet conditions.
- Optimise absorber and stripper temperatures.
- Detect early signs of solvent degradation.
- Respond immediately to feed gas disturbances.
Continuous data also supports tighter control limits. Instead of operating conservatively to compensate for limited measurement resolution, plants can run closer to optimal conditions with greater confidence. From a control perspective, true on-line measurements can be integrated into dynamic control loops.
Operational robustness for long-term monitoring
In the context of continuous industrial operation, FTIR technology offers better operational stability for long-term monitoring and has already proven itself through its large scale deployment in continuous emissions monitoring systems (CEMS) used in all major industries targeted for the addition of carbon capture units to achieve decarbonisation.
GC, although more accurate for certain analyses, is more sensitive to instrumental drifts related to column and detector wear.
Acceptance by operators
As mentioned previously in this article, FTIR technology is widely adopted in sectors targeted for the implementation of carbon capture units to decarbonise unavoidable emissions (waste-to-energy, power generation, cement, refining, and other energy-intensive industries).
Operators who are trained in this technology are familiar with maintenance operations, have a good understanding of the costs of these operations, and have the experience necessary to monitor these systems effectively. The inherently lower OPEX of FTIR compared to GC is thus optimised by adding similar analysers to existing CEMS on carbon capture units. Acceptance from operators will also be easier, as no new complex analytical systems will be added to those already in operation at the ‘parent’ plant.
Supporting environmental compliance and transparency
Although comprehensive environmental regulations specific to carbon capture processes are not yet fully established – primarily because most carbon capture technologies remain at an early stage of industrial maturity, with solvent-based capture currently being the most advanced – environmental compliance is expected to become a major driver for the large scale deployment and adoption of carbon capture systems in the near future.
Regulatory frameworks increasingly emphasise the availability of continuous, traceable, and high-quality data capable of capturing both average operating conditions and short-term process deviations. From this perspective, continuous monitoring using FTIR spectroscopy is well aligned with emerging regulatory expectations. FTIR-based systems have already been widely adopted under some of the most stringent environmental regulations and in highly regulated industrial sectors for emissions-to-air monitoring, notably within the framework of the European Industrial Emissions Directive (IED) and the Waste Incineration Directive.
Building on this regulatory heritage, ENVEA’s experience in the deployment and operation of continuous emissions monitoring systems (CEMS) provides a robust basis for extending FTIR technology to carbon capture processes, where similar requirements for transparency, traceability, and regulatory compliance are anticipated.
Improving safety, asset protection, and decision-making
Carbon capture technologies are still undergoing significant development, and operational experience continues to expand. Nevertheless, it is already well established that several gas-phase species relevant to carbon capture processes can pose safety, operational, or asset integrity risks, even at low concentrations. For instance, oxygen ingress may accelerate corrosion phenomena, acid gases can degrade downstream equipment, and trace contaminants such as ammonia, mercury, or organic compounds may adversely affect compressors and CO2 transport infrastructure.
In this context, real-time or near-real-time continuous monitoring enables the early detection of abnormal operating conditions, allowing timely corrective actions before irreversible damage or safety incidents occur. By contrast, periodic or non-real-time measurements may lead to delayed detection, whereby deviations are identified only after adverse impacts on equipment or process performance have already materialised.
Beyond immediate risk mitigation, the availability of continuous datasets throughout the operational learning curve enables systematic correlation with inspection, maintenance, and failure records. This data-driven approach supports the development of predictive maintenance strategies, contributing to reduced unplanned downtime and improved asset availability.
Continuous measurements further enhance confidence in the reliability and interpretability of the data. Temporal trends become more clearly defined, correlations between process variables are more readily identified, and true anomalies can be more effectively distinguished from measurement noise or instrumental artefacts. This improved data clarity supports more informed operational decision-making and enables robust long-term analyses, including performance benchmarking and advanced process diagnostics.
Finally, continuous, high-resolution datasets are particularly well suited to emerging digital tools, including advanced analytics and machine learning techniques, which rely on dense, high-quality data to extract actionable insights and support process optimisation.
Complementary roles
FTIR spectroscopy and GC should not be regarded as competing technologies, but rather as complementary analytical tools addressing different measurement needs within carbon capture processes.
GC remains highly relevant in applications requiring very high analytical precision for selected components, ultra-trace detection limits, or compliance with established standards and reference methods if any.
However, when applied as the sole source of process information in inherently dynamic systems, periodic GC measurements introduce temporal blind spots that limit process visibility. The discrete and delayed nature of chromatographic analysis constrains the detection of short-term deviations and transient events that can significantly impact process performance, solvent integrity, and asset protection.
In this context, continuous FTIR monitoring provides a complementary layer of real-time process insight. By delivering high-frequency, multi-component measurements with low analytical latency, FTIR enhances situational awareness and supports timely operational decision-making. The combined use of continuous FTIR monitoring for dynamic process supervision and GC analysis for high-precision or confirmatory measurements offers a robust and balanced analytical strategy for post-combustion carbon capture systems.
Conclusion
Post-combustion carbon capture is intrinsically continuous and dynamically evolving, and its effective operation cannot be fully characterised through periodic analytical snapshots alone. As carbon capture projects scale toward industrial deployment and operate under increasingly stringent economic, operational, and regulatory constraints, the availability of continuous, high-quality gas composition data becomes a critical requirement rather than an optional enhancement.
True online FTIR monitoring provides a fundamentally different level of process insight by enabling real-time, multi-component analysis with high temporal resolution. This capability supports faster detection of process disturbances, improved operational control, enhanced environmental compliance, and more effective protection of equipment and infrastructure. In contrast, while periodic GC measurements remain valuable for specific analytical objectives, their inherent limitations in temporal resolution and latency restrict their suitability as primary monitoring tools for dynamic capture processes.
Overall, integrating continuous FTIR monitoring with targeted GC analysis reflects the operational realities of modern carbon capture facilities. Such an approach aligns measurement strategies with process dynamics, supports data-driven optimisation and decision-making, and contributes to the reliable and transparent operation of large scale carbon capture systems. In an industrial context where performance margins are narrow and process stability is paramount, continuous insight is essential to the long-term success of carbon capture deployment.