CO₂ quality verification across the carbon-capture value chain

Q: Why is CO2 source no longer a reliable indicator of quality?

Each capture route carries its own contaminant signature: siloxanes and sulfur from biogas, halogenated hydrocarbons from waste-to-energy, amine degradation products from post-combustion capture, and atmospheric contaminants from direct air capture. Quality must be shown with data, not assumed from origin.

In the late 1980s a major beverage producer accepted carbon dioxide on supplier certification, only to discover it carried benzene that routine testing had missed. The recall that followed reshaped how the industry treats CO₂ quality, and the lesson still holds: CO₂ is not inherently pure, so it has to be verified. That lesson is now urgent for a different reason. The CO₂ supply base is diversifying fast, and source type no longer tells you what is in the gas.

Biogas upgrading, waste-to-energy, post-combustion capture, biomass processing and direct air capture each bring their own contaminant signature. ASTG verifies CO₂ quality continuously across the value chain, from capture through transport to end use, so quality is demonstrated with data rather than assumed from origin.

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Why source no longer guarantees quality

Traditional CO₂ came from a handful of predictable processes, so purity standards grew up around predictable risks. The new sources break that assumption, and each carries a distinct profile that has to be screened for directly.

CO₂ source	Characteristic contaminants to screen for
Biogas upgrading	Siloxanes and sulfur compounds
Waste-to-energy	Halogenated hydrocarbons
Post-combustion capture	Amine degradation products
Direct air capture	Atmospheric contaminants

Across every source, the safety-critical impurities still apply: aromatic hydrocarbons measured as benzene with full BTEX speciation, total sulfur, moisture, oxygen and carbon monoxide. Multiple capture points, liquefaction, long-distance transport and the blending of supply streams each add further opportunities for contamination.

What the standards now expect

The ISBT, EIGA and CGA frameworks are aligning on consistent purity limits and shared analytical methods, which is what makes alternative sources usable at scale. ISBT's alternative-source qualification guidance sets the direction: detailed source risk assessment, expanded analytical screening beyond the traditional contaminants, validation of purification processes, and ongoing monitoring to prove continuous compliance.

From periodic certificates to continuous verification

Periodic laboratory testing and a certificate of analysis describe one batch; they cannot see the dynamic changes in composition that a diversified, blended supply produces. Continuous, high-sensitivity analysis closes that gap. The AirBreather platform measures more than 40 impurities at once, resolves aromatics on a dedicated GC-PID and total sulfur to sub-ppb, and issues a secure Certificate of Analysis with 21 CFR Part 11 records, across capture, transport and use. ASTG's decarbonization qualification systems apply the same discipline to qualifying new feedstocks.

Frequently asked questions

Why is CO₂ source no longer a reliable indicator of quality?
Because each capture route carries its own contaminant signature: siloxanes and sulfur from biogas, halogenated hydrocarbons from waste-to-energy, amine degradation products from post-combustion capture, and atmospheric contaminants from direct air capture. Quality has to be shown with data, not assumed from origin.

What should alternative CO₂ sources be screened for?
Beyond the traditional panel, expanded screening covers siloxanes, sulfur compounds, halogenated hydrocarbons and amine degradation products, alongside the safety-critical aromatics (benzene and BTEX), total sulfur, moisture and oxygen.

How does ASTG verify CO₂ quality across the value chain?
With continuous, high-sensitivity analysis across capture, transport and use: speciated aromatics, sub-ppb total sulfur, and secure certificates of analysis with 21 CFR Part 11 records, rather than periodic laboratory certificates.

ASTG continuous CO2 quality verification across the carbon-capture value chain