Four kinds of CO₂ get discussed as sustainable sourcing options, and they are not interchangeable. Direct air capture (DAC) CO₂ is pulled from ambient air, where CO₂ sits at roughly 420 parts per million, the most energy-intensive route per ton. Point-source captured CO₂ is recovered from a concentrated industrial stream before it vents. Biogenic CO₂ is defined by origin rather than method: carbon that was recently in the atmosphere, absorbed by plants, and released again through fermentation or digestion. Fossil-byproduct CO₂ comes from ammonia plants, natural gas processing, and underground wells, carbon that was locked away until industry released it.
A single ton can be two of these at once. CO₂ captured at a biogas upgrader is both biogenic and point-source, and that combination carries the lowest carbon-accounting burden a buyer can get. The molecule is identical across all four categories. The accounting is not, and buyers increasingly care about the difference.
What Makes CO₂ Biogenic
Biogenic CO₂ comes from the natural carbon cycle. Plants absorb CO₂ from the atmosphere as they grow. When that plant material decomposes or is processed through anaerobic digestion, it releases CO₂ back into the atmosphere. Capturing that CO₂ before it is released does not add new carbon to the system. It is carbon that was recently in the atmosphere and will return to it regardless.
CO₂ from renewable natural gas upgraders is biogenic. The biogas comes from organic waste, dairy manure, food scraps, wastewater, or landfill decomposition. All of these feedstocks were recently living material that absorbed atmospheric CO₂.
Fossil-Derived CO₂ Is Different
Most merchant CO₂ in the United States comes from fossil sources. Ammonia plants, hydrogen reformers, natural gas processing, and natural underground wells like Jackson Dome in Mississippi are the primary producers. When this CO₂ is eventually released to atmosphere, either during use or after, it adds carbon that was previously locked underground back into the active carbon cycle.
This does not make fossil-derived CO₂ bad. The CO₂ market exists because there are real industrial needs for the product, and these sources have supplied it reliably for decades. But from a carbon-accounting perspective, the two origins are fundamentally different. Even ethanol-derived CO₂, which starts as biogenic carbon absorbed by corn, gets complicated once the fossil energy inputs of farming, transport, and distillation are counted.
Direct Air Capture Is Not What You Are Buying
When people hear carbon capture, many picture direct air capture: machines pulling CO₂ out of the sky. DAC is real, but it works from a feed concentration of about 0.04%, which makes it the most expensive and energy-hungry route to a ton of CO₂. Its economics point at carbon-removal credits, not commodity gas supply.
Point-source capture starts from streams that are already 30 to 99% CO₂, biogas upgrading tail gas, fermentation off-gas, flue gas. Recovering CO₂ from a concentrated stream takes a fraction of the energy per ton, which is why essentially every ton of captured CO₂ sold into the commercial market today is point-source. A buyer evaluating suppliers that use carbon capture instead of fossil sources is, in practice, choosing among point-source operators and asking whether the source stream is biogenic.
Where Purchased CO₂ Lands in the GHG Protocol
For a beverage company, purchased CO₂ is a Scope 3 emission. It falls under Category 1, purchased goods and services, which captures the cradle-to-gate emissions of producing the gas. The trucks that deliver it fall under Category 4, upstream transportation and distribution. Neither shows up in the company's direct Scope 1 figure, because the company did not produce the CO₂ itself.
That sounds tidy, but it hides a problem. The emissions embedded in a ton of CO₂ depend entirely on how it was made and how far it traveled. CO₂ pulled off an ammonia plant that burns natural gas as a feedstock carries a different footprint than CO₂ recovered from a renewable natural gas upgrader. A 500 mile haul from the Gulf Coast carries a different footprint than a 120 mile run from a regional facility. The scope category is identical. The actual number is not.
And there is a line most procurement teams have never seen. Under the Greenhouse Gas Protocol, CO₂ released from biomass does not go into Scope 1, 2, or 3 at all. It is reported outside the scopes as a separate biogenic figure. For a company that separates biogenic and fossil emissions in its reporting, switching from ammonia-derived CO₂ to RNG-derived CO₂ moves the line item from one column to the other. The volume of gas does not change. The carbon accounting does.
A Database Average Is Not Primary Data
Most companies never get this far, because most companies use a generic emissions factor. They take the tonnage of CO₂ they bought, multiply it by an industry average pulled from a database, and call it done. That is secondary data, and it is the accounting equivalent of guessing. It assumes every ton of CO₂ in the country carries the same footprint, which is not remotely true.
The frameworks that matter are moving away from that. The Science Based Targets initiative and CDP both reward supplier-specific primary data over database averages, because primary data reflects what actually happened rather than a national mean. A company that can show where its CO₂ was captured, how it was purified, and how far it traveled is reporting a real number. A company applying a default factor is reporting a placeholder and hoping it holds.
What Makes the Claim Defensible
Primary data is only as good as the documentation behind it. To put a credible CO₂ figure in a sustainability report, a buyer needs a handful of things from the supplier: where the CO₂ originated, whether the source is biogenic or fossil, the capture and purification method, and the transport distance and mode. A chain-of-custody or mass-balance record that ties a delivered load back to its source closes the loop.
Most merchant CO₂ cannot offer that. It is aggregated, blended across sources, and moved through layered distribution, so the original source is effectively lost by the time it reaches the customer. CO₂ produced at a single known facility, from a single known feedstock, with a documented purification process, can. That traceability is the difference between a reportable number and an estimate.
Clean Is Not the Same as Pure
Purity and carbon profile are two separate attributes, and the conversation gets confused when they blur. A natural CO₂ well can produce extremely pure CO₂ that is entirely fossil-derived. A landfill gas capture system can produce biogenic CO₂ that is full of contaminants and unusable for food contact applications.
A CO₂ buyer in the beverage industry needs both. The CO₂ has to meet the ISBT purity specification for food safety: benzene, hydrogen sulfide, total sulfur, and acetaldehyde all measured down to parts per billion. And increasingly, procurement teams want the source to align with their company's sustainability commitments. Clean carbon that fails purity specs is worthless to a bottling plant. Pure carbon from a fossil source is becoming harder to justify in a Scope 3 report.
How Cryogenic Purification Bridges the Gap
The challenge with biogenic sources is contamination. Raw gas from an RNG upgrader or digester contains hydrogen sulfide, siloxanes, volatile organic compounds, and moisture. Getting that stream to beverage grade means removing contaminants down to parts per billion, at the smaller scales typical of distributed biogenic sources, where most purification technologies struggle.
Cryogenic purification handles it. By cooling the gas stream and exploiting the different phase transition temperatures of CO₂ and its contaminants, a cryogenic system separates impurities through physics rather than chemistry. No solvents to degrade. No media to replace. At our Lewiston, North Carolina facility, we take the CO₂ stream from an adjacent RNG upgrader and produce FDA-registered, ISBT-compliant, beverage grade liquid CO₂. At CleanCycleCarbon, every ton of CO₂ we produce is biogenic.
What to Ask Your Supplier
If sustainable sourcing matters to your procurement process, four questions do most of the work. What is the original source of the CO₂? Is it biogenic or fossil-derived? What is the carbon intensity of the capture and purification process? And can the supplier provide documentation that supports those claims under your Scope 3 methodology?
Most conventional suppliers will not have good answers to the last two questions. That is not a criticism; the industry was not built around carbon accounting. But buyers who used to ask one question, does it meet spec, are now asking two: does it meet spec, and where does it come from? Clean carbon is a measurable attribute of how CO₂ is sourced, captured, and delivered, and the buyers who understand the distinction now will be better positioned when it stops being optional.
