What Carbon Capture Storage And Utilization Projects Need to Model for Air Quality

Carbon Capture Storage and Utilization (CCUS) can dramatically reduce CO₂ emissions from power generation, oil sands, petrochemicals, cement, steel and other hard-to-decarbonize sectors. But capturing carbon does not eliminate air-quality concerns. It simply changes them.

The environmental assessment doesn't end when CO₂ capture begins. In some cases, the modelling problem becomes more complicated.

Amine-based capture can introduce new emission sources and contaminants (including amines, ammonia and solvent degradation products) and some compounds can undergo atmospheric transformation after release.

Traditional assessments focus on pollutants such as NOₓ, SO₂, particulate matter and VOCs. Amine-based carbon capture systems introduce additional contaminants that may require detailed modelling and health-risk evaluation, including unreacted amines, ammonia, nitrosamines, nitramines, VOCs and other solvent degradation products.

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What makes CCUS different is that some of these compounds do not remain unchanged after release. They can react in the atmosphere, form new contaminants, deposit onto soil and vegetation and create potential human-health and environmental concerns that conventional industrial assessments may not fully address.

As a result, regulators increasingly expect more than a standard dispersion model. They may require evaluation of atmospheric chemistry, deposition, sensitive receptors and potential health impacts, particularly where amine capture systems are involved.

The key question is no longer simply, "How much CO₂ is being captured?" It becomes: Can the project reduce emissions while protecting people, ecosystems and nearby communities?

What Regulators Need Demonstrated

For a carbon capture storage and utilization project, the regulator's question is simple: Can the project operate while protecting human health and the environment?

In Alberta, that typically means demonstrating compliance with applicable Alberta Ambient Air Quality Objectives (AAAQOs), protection of human health through Human Health Risk Assessments (HHRAs) where required, protection of ecological receptors, use of Best Available Technology Economically Achievable (BATEA) and effective mitigation of significant emissions.

Importantly, the absence of an Alberta air-quality objective does not automatically remove the need for assessment. Where provincial standards do not exist, regulators may require risk evaluations using Health Canada, international or other recognized toxicity benchmarks.

Ultimately, the assessment must provide defensible evidence that the project can operate safely, manage its emissions responsibly and avoid unacceptable effects on people, ecosystems and the surrounding environment.

Here is a quick carbon capture storage and utilization modelling roadmap:

Carbon Capture Storage and Utilization and Why Amines Need Special Attention

Modern carbon-capture systems often use amines to absorb CO₂. While highly effective, they can release small amounts of solvent and degradation products, some of which may transform in the atmosphere into nitrosamines and nitramines.

Carbon Capture systems - schematic

Because some of these compounds have significant toxicological concerns, including potential carcinogenic and mutagenic effects, regulators may require more than conventional dispersion modelling. Depending on the project, the assessment may need to model amine emissions, predict atmospheric chemical transformations, estimate nitrosamine and nitramine formation and evaluate potential health risks using recognized toxicity benchmarks.

Although Alberta does not currently have ambient air-quality objectives for many of these compounds, their assessment may become an important part of the air-quality evaluation, particularly for amine-based capture systems where atmospheric transformation and health-based criteria are relevant.

What Makes CCUS Modelling Different?

Carbon capture storage and utilization projects often require more than standard air-quality modelling. In addition to predicting what leaves the stack, assessments may need to evaluate how contaminants behave after release, including atmospheric chemistry, deposition to soil and water and exposure to nearby communities and ecological receptors.

Amine-based systems can introduce complex chemistry, while multiple source types, such as stacks, vents, fugitives and process releases, may all contribute to the overall impact. Regulators also expect consideration of non-routine scenarios, including startup, shutdown, maintenance, upset conditions and emergency releases.

The goal is not simply to estimate emissions, but to understand what forms in the atmosphere, where it goes and who or what could be affected.

When Is ADMS 6 Useful?

ADMS 6 is often used when a project requires more than conventional dispersion modelling. It can address complex terrain, building downwash, multiple interacting sources, wet and dry deposition, time-varying emissions, detailed meteorology and atmospheric chemistry.

Not exactly beautiful, but trying to improve...

Where amine chemistry, atmospheric transformation or deposition are important, ADMS 6 can provide capabilities that may not be available in a conventional dispersion-only assessment. Rather than simply modelling dilution, ADMS can evaluate the atmospheric reactions that may form nitrosamines and nitramines, compounds that often drive regulatory and health-risk assessments.

The result is a more complete picture of what happens after emissions leave the facility, including where contaminants travel, how they transform and what concentrations may ultimately reach nearby receptors.

Do You Actually Need More Modelling?

Not necessarily.

Before starting a new CCUS assessment, the first question should be: What does the regulator actually need demonstrated? Sometimes additional modelling is required. Sometimes an existing assessment already answers the regulatory question. Sometimes the issue is simply an emission scenario, source characterization or operating assumption that needs refinement.

Have a look at this chart: Do You Need Another Study?

The goal is not to run more models. The goal is to provide defensible evidence that the project can operate safely and meet environmental requirements.

A surprising number of assessments go wrong by answering the wrong question. Common pitfalls include using unrealistic solvent emissions, treating amines as conventional pollutants, modelling the wrong operating scenario, relying on unrepresentative meteorology, overlooking vents or fugitive sources or ignoring deposition when environmental receptors are the real concern.

The most expensive modelling mistake is rarely a software error. It's answering the wrong question correctly.

A CCUS Example: When the Regulatory Question Changes

Imagine a natural-gas processing plant with an approved air-quality assessment. The facility's existing model already addresses traditional pollutants such as NOₓ, SO₂, H₂S and particulate matter.

Now the company adds a major amine-based carbon-capture expansion. New absorber towers, blower systems and CO₂ compression equipment are installed. At first glance, it may seem that the existing air-quality model simply needs to be rerun.

But the project has changed.

The new capture system introduces additional emission sources and contaminants, including amines, ammonia, formaldehyde and solvent degradation products. More importantly, some of these compounds can react in the atmosphere after release. Amines may combine with ozone, NOₓ and sunlight to form nitrosamines and nitramines, compounds that can require special health-risk evaluation.

The assessment therefore shifts from a traditional dispersion problem to a dispersion-and-chemistry problem. Instead of asking:

"Do stack emissions meet air-quality objectives?"

the regulator is asking:

Could atmospheric chemistry, meteorology, terrain and facility emissions combine to create nitrosamine or nitramine concentrations that affect human health?

Answering that question may require advanced tools such as ADMS 6, five years of meteorological data, terrain and building-downwash analysis, background air-quality monitoring data and specialized chemistry calculations.

In one such assessment, predicted concentrations of nitrosamines, nitramines, amines, ammonia, SO₂, H₂S, formaldehyde and other contaminants all met the applicable Alberta, Ontario and international criteria. The proposed CCUS expansion was therefore not expected to significantly affect regional air quality.

The broader lesson is simple: when carbon capture is added to an existing facility, the environmental question often changes. Before rerunning an old model, determine whether the existing assessment still represents the emissions, chemistry, receptors and health risks associated with the modified facility. For modern amine-based carbon capture storage and utilization projects, the answer is often no.

The Bottom Line

Carbon capture storage and utilization can significantly reduce greenhouse-gas emissions while supporting industrial growth, but reducing CO₂ is only part of the regulatory story. For amine-based capture systems, regulators increasingly expect assessment of solvent emissions, atmospheric chemistry, nitrosamine and nitramine formation, deposition and potential health impacts.

A successful CCUS air-quality assessment demonstrates more than carbon reduction. It shows that the project can operate safely while protecting people, ecosystems and nearby communities. The best assessments start early, helping identify risks, support approvals and confirm that the project can perform as designed while meeting environmental requirements.

CCUS, Air Quality Modelling and The Questions Regulators Actually Ask

Carbon capture storage and utilization can dramatically reduce CO₂ emissions, but it can also introduce new air-quality challenges. For amine-based capture systems, the regulatory focus often shifts from traditional pollutants to amines, ammonia, nitrosamines, nitramines and other solvent degradation products.

From an AEPA and AER perspective, the key question is simple: Can the project operate without causing unacceptable impacts to air quality, human health or the environment?

That means more than modelling stack emissions. Regulators want to know what happens after release. Can amines react in the atmosphere? Could nitrosamines or nitramines form? Are deposition impacts important? Are there nearby communities, water bodies, agricultural lands or sensitive ecological receptors that change the assessment?

For many CCUS projects, conventional dispersion modelling alone is not enough. Advanced chemistry and deposition modelling may be required, particularly when amine capture systems are involved. Alberta commonly uses ADMS 6 for these assessments because it can evaluate plume chemistry, nitrosamine and nitramine formation, deposition, complex terrain, building downwash and multiple interacting sources.

A successful carbon capture storage and utilization assessment typically demonstrates:

• Compliance AAAQOs
• Acceptable human-health risk
• Protection of environmental receptors
• Appropriate use of Best Available Technology Economically Achievable (BATEA)
• Effective mitigation and monitoring plans

Just as important is determining what actually needs to be modelled. Sometimes a full new assessment is required. Sometimes existing studies already answer part of the regulatory question. Sometimes the critical issue is a revised emission scenario, source characterization or operating assumption.

At Calvin Consulting Group Ltd., we help clients answer those questions before they spend money on unnecessary modelling. Our team includes industry-leading air quality specialists who have previously trained personnel from AEPA, AER and Environment Canada. Using five-year site-specific meteorology, terrain integration, ADMS 6, AERMET and CALMET, we prepare defensible, regulator-ready assessments that help keep projects moving.

Before you commission another modelling study

Ask three questions first:

1. What changed at the facility?
2. What new environmental question does that create?
3. Does the existing assessment answer it?

Calvin Consulting can review the existing assessment, identify the regulatory question and determine what additional modelling (if any) is actually justified. Reach us at...

...now. Together, let's protect the air, win approvals and lead the way forward.

​Clean air is our Passion...Regulatory Compliance is our Business.

Before commissioning CCUS air-quality modelling, confirm:

□ Capture technology
□ Solvent chemistry
□ New emission sources
□ Amine emission rates
□ Ammonia emissions
□ Degradation products
□ Stack/vent characteristics
□ Normal operating scenario
□ Maximum operating scenario
□ Startup/shutdown
□ Maintenance
□ Upsets/emergency conditions
□ Meteorological dataset
□ Terrain
□ Building geometry
□ Background concentrations
□ Human receptors
□ Ecological receptors
□ Deposition requirements
□ Atmospheric chemistry requirements
□ Applicable criteria/benchmarks
□ Existing modelling
□ Regulator's specific question

Before choosing an air quality model, I ask six questions:

• What changed at the facility?
• What new emissions are possible?
• What operating scenarios matter?
• What receptors need to be protected?
• What criteria or health benchmarks apply?
• Does existing modelling already answer part of the question?

Do you have concerns about air pollution in your area??

Perhaps modelling air pollution will provide the answers to your question.

That is what I do on a full-time basis.  Find out if it is necessary for your project.

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Thank you to my research and writing assistants, and the author remains responsible for the content.

Not every compound of interest necessarily has a provincial ambient air-quality objective.

Where a specific regulatory criterion is unavailable, the assessment may instead require appropriate health-based benchmarks or other recognized toxicity information.