CO2 Extraction Pressure and Temperature: A Plain-Language Guide for US Plant Operators
Most problems on a supercritical CO2 line trace back to two dials: CO2 extraction pressure and temperature. Operators inherit a recipe, copy a number off a spec sheet, or push the pressure higher hoping for more yield, and then wonder why the extract carries waxes it should not, or why a delicate aroma has flattened. Pressure and temperature are not settings to guess at. They are the levers that decide what comes out of your biomass and what stays behind. This guide explains, in plain language, what each one actually does, how to read the numbers on an equipment spec sheet correctly, and where to start for common botanical work.
Key takeaways:
- CO2 turns supercritical above 31.1 degrees C (88 F) and 73.8 bar (about 1,070 psi).
- Pressure is the main selectivity dial. Higher pressure means denser CO2, which dissolves heavier compounds.
- Temperature is mainly about protecting heat-sensitive actives, so keep it as low as your target compound allows.
- Spec-sheet ratings are maximum limits, not run settings.
What Is the Critical Point of CO2, and Why Does It Matter?
Supercritical CO2 is carbon dioxide held above its critical point of 31.1 degrees C (88 F) and 73.8 bar (about 1,070 psi). In this state it flows like a gas but dissolves compounds like a liquid, and its solvent strength rises or falls as you change pressure and temperature.
Carbon dioxide is a gas at room conditions. Raise it past a specific point of pressure and temperature and it enters a supercritical state, where it is neither a true gas nor a true liquid, flowing through a packed bed like a gas but dissolving compounds like a liquid. That crossover point, the critical point of CO2, is precise: CO2 becomes supercritical above roughly 31.1 degrees C (88 F) and 73.8 bar (about 1,070 psi). Below that, you are not doing supercritical extraction.
What makes CO2 valuable is that above this point it behaves as a tunable solvent. Change the pressure and temperature and you change how much the CO2 dissolves and which compounds it prefers. The same machine and the same carbon dioxide can pull a light, volatile aroma fraction at one setting and a heavy, colored oleoresin at another. That tunability is the whole point, and it is why understanding the two dials matters more here than in any solvent process. For the full range of materials this covers, see what a supercritical CO2 extraction system can extract, and for how the process works end to end, see our guide to the supercritical CO2 extraction process.
How Does Pressure Affect CO2 Extraction?
Higher extraction pressure makes the CO2 denser, so it dissolves more and heavier compounds. Low pressure (about 100 to 150 bar) favors light aromatics. Mid-range pressure pulls essential oils, and high pressure reaches oleoresins, pigments, and waxes.
CO2 extraction pressure is the lever you reach for first. Raising it increases the density of the supercritical CO2, and denser CO2 dissolves more, and heavier, material. Lower pressure keeps the CO2 lighter and more selective, so it lifts only the most soluble, most volatile compounds and leaves the rest in the biomass.
In practical terms this gives you a ladder. At the low end, around 100 to 150 bar, CO2 preferentially dissolves light, volatile fractions such as terpenes and top-note aromatics. As you climb into the mid-range, the CO2 begins pulling fuller essential-oil fractions and lighter resins. Push higher and it starts taking heavier oleoresins, color pigments, and eventually waxes and dense lipids. This is why pressure, not temperature, is the dial you move when you want to change what the extract actually contains.
The important operator lesson is that higher is not automatically better. More pressure means more solvating power, which means you also start co-extracting heavier material you may not want, such as waxes that then have to be removed in a downstream winterization and post-processing step. Published research points the same way: in one study on Schisandra chinensis, raising pressure from 350 to 400 bar gave practically no increase in yield. The goal is not maximum pressure. It is the pressure that captures your target compound while leaving the unwanted fraction behind.
How Does Temperature Affect CO2 Extraction?
The main job of temperature in CO2 extraction is protecting heat-sensitive actives. For most botanical work, keep it in the 35 to 60 degrees C (95 to 140 F) range, as low as your target compound allows.
CO2 extraction temperature is more subtle, and it works against itself. At a fixed pressure, raising the temperature reduces the density of the CO2, which lowers its solvating power. But higher temperature also raises the vapor pressure of the compounds you are trying to extract, which can help release them. These two effects pull in opposite directions, so temperature is rarely the lever you use to chase more yield. Pressure does that job more cleanly.
What temperature does control is the health of heat-sensitive actives. Many of the compounds that make CO2 extraction worth the investment, from delicate florals to nutraceutical actives, degrade when they get too hot. Set the temperature too high and you can flatten an aroma profile, darken a color, or reduce the potency of the very molecule you were trying to preserve. The discipline is simple: keep the temperature as low as your target compound and your chosen pressure will allow. Running cool is one of the core reasons manufacturers move to CO2 from steam distillation or hot-solvent methods in the first place.
Pressure and temperature are the two main dials, but CO2 flow rate, extraction time, particle size, and co-solvent also shape your results.
How to Read CO2 Extraction Pressure and Temperature Ratings on a Spec Sheet
A spec-sheet pressure and temperature rating is the maximum a system is engineered and certified to reach, not the setting you run. A 600-bar system offers a wider operating range than a 350-bar system, not automatically a better extract.
This is where many buyers misread the numbers. When an equipment spec sheet lists a pressure and a temperature, those are the maximum rated limits of the machine, the ceiling it is engineered and certified to reach safely. They are not the settings you dial in for every run.
Buffalo Extraction Systems' supercritical CO2 extraction systems are built to two pressure ratings, 350 bar (about 5,075 psi) and 600 bar (about 8,700 psi). The temperature ceiling is matched to the pressure rating: up to 70 degrees C (158 F) on a 350-bar system and up to 110 degrees C (230 F) on a 600-bar system. Read those as the outer envelope of what the equipment can do, not as a target.
In real botanical work you operate comfortably inside that envelope, and you would almost never run a heat-sensitive botanical anywhere near 110 degrees C, because the compound would not survive it. The 600-bar rating exists to give you headroom, the ability to reach dense, high-molecular-weight compounds when a specific product calls for it, not a number you are meant to push to on every batch.
One point for US buyers in particular: the pressure-vessel certification that matters most here is ASME, and along with PED, ATEX and CE it is configured to the system and declared at the order stage rather than being standard on every unit. So when you compare two systems, do not read a higher pressure rating as a higher-quality machine. Read it as a wider operating range, and confirm that the certifications your site and market require are part of the quote, since they also shape CO2 extraction machine cost.
CO2 Extraction Pressure and Temperature Chart for Common Botanicals
The CO2 extraction pressure chart below gives illustrative starting windows by the kind of output you want. Treat these as orientation, not prescriptions. Every biomass behaves differently, and the correct settings for your specific material and target compound are found by trial, not copied from a chart.
| Output you want | Typical pressure | Typical temperature | What is happening |
|---|---|---|---|
| Light aromatics and top-note fractions | ~100 to 150 bar (1,450 to 2,175 psi) | ~35 to 45 C (95 to 113 F) | Lowest solvating power; lifts volatile terpenes and light aromatics |
| Essential-oil fractions (e.g. spice essential oils) | ~150 to 250 bar (2,175 to 3,625 psi) | ~40 to 50 C (104 to 122 F) | Balanced capture of aroma and lighter resin compounds |
| Spice oleoresins (turmeric, black pepper, ginger, capsicum) | ~250 to 320 bar (3,625 to 4,640 psi) | ~50 to 60 C (122 to 140 F) | Higher density pulls color, pungency, and heavier resins (within a 350-bar system) |
| Dense compounds, waxes, certain lipids and pigments | up to 600 bar (8,700 psi) on a 600-bar system | kept as low as the compound allows | Maximum solvating power; may co-extract waxes that need winterization |
| More polar actives without adding heat | add ethanol co-solvent | unchanged | Raises polarity to reach more polar molecules; the co-solvent extract then needs ethanol removal |
Note on the envelope: a 350-bar system operates comfortably up to roughly 300 to 320 bar; sustained operation at or near 350 bar, or above, calls for a 600-bar-rated system. Match the envelope to the products you actually make, and see how CO2 extraction system levels pair capacity with each rating.
These windows are starting points for recipe development. Dialing them in for yield and purity is its own discipline, covered in our guide on how to optimize CO2 extraction parameters for higher yield and purity.
How Does a CO2 Extraction System Hold Pressure and Temperature Steady?
Setting a pressure and temperature is only useful if the system can hold them. Pressure that drifts mid-run changes what you extract from one minute to the next, which is why parameter control, not just parameter range, separates a research curiosity from a production asset.
On a Buffalo system, extraction pressure is held by a servo-controlled back-pressure regulating valve, which keeps the setpoint stable rather than letting it fluctuate. The extract is then separated across two independent separators running at lower pressures, so you can fractionate a single run by stepping the pressure down in stages and collecting different fractions in different vessels.
Parameter sets are stored and repeated through SCADA-based recipe control, with capacity for 100 recipes, so a validated setting for a given botanical can be recalled and run identically every time. For products that need more polarity, an optional ethanol co-solvent extends reach without forcing the temperature up. For strongly polar targets, compare when to choose CO2 over cryogenic ethanol extraction. Note that a co-solvent run leaves ethanol in the extract that must be removed downstream, so a no-residual-solvent claim does not apply to a co-solvent extraction on its own.
Why Should You Validate Settings With a Trial Before Buying?
No chart, including the one above, can tell you the exact CO2 extraction pressure and temperature for your material. Yield and quality depend on the specific compound you are chasing and on the raw material itself, its variety, its moisture content, how it was grown and stored, and how finely it is milled during pre-processing. Two batches of the same botanical from different suppliers can behave differently.
This is why serious buyers test their raw material before buying extraction equipment and validate settings on their own biomass before committing to a full system. You can run a physical trial on your specific raw material through BES Labs, which develops and confirms the working parameters for your material rather than leaving you to discover them in production. It is the difference between buying to a spec sheet and buying to a proven recipe.
How Buffalo Extraction Systems Helps You Get the Parameters Right
Buffalo Extraction Systems builds supercritical CO2 systems for exactly this kind of controlled, repeatable work. The 350-bar and 600-bar envelopes cover everything from light aromatics to dense compounds; servo-controlled back-pressure regulation holds your setpoint steady; dual-separator fractionation lets you split a run into cleaner fractions; and SCADA recipe control stores validated parameter sets so a proven recipe runs the same way every batch. The systems are engineered and manufactured with the depth of Cybernetik, the parent company behind BES, and are designed to run with a single operator on pilot-scale systems, with larger production systems typically adding a second operator.
If you are choosing a system, the practical starting point is to understand your target products and the pressure range they require, then match that to the right envelope. Our guide on how to choose the right supercritical CO2 extraction system walks through sizing and selection, and you can explore our supercritical CO2 extraction systems to see the range.
Conclusion
CO2 extraction pressure and temperature are not numbers to guess at or maximize. Pressure is your main dial for selecting what gets extracted; temperature is a lever to be kept low enough to protect heat-sensitive actives. Spec-sheet ratings describe the outer limits of a machine, not the settings you run every day, so read a higher rating as a wider operating range rather than a better machine. And because your raw material has the final say, the safest path to a reliable recipe is to validate it on your own biomass before you buy.
Ready to find the right parameters for your material? Request a Trial and validate your recipe on your own biomass.
Frequently Asked Questions
What pressure and temperature should I use for supercritical CO2 extraction?
The right supercritical CO2 extraction pressure and temperature depend on what you want to extract. Light, volatile aromatics come off at lower pressures of roughly 100 to 150 bar, essential-oil fractions in the mid-range, and heavier oleoresins at roughly 250 to 320 bar on a 350-bar system. Temperature is generally kept low, around 35 to 60 degrees C (95 to 140 F) for most botanical work, to protect heat-sensitive compounds. These are starting points; the exact settings for your material are confirmed by trial.
How does increasing CO2 extraction pressure affect what is extracted?
Raising pressure increases the density of the supercritical CO2, which increases its solvating power. Denser CO2 dissolves more, and heavier, compounds, so as you raise pressure you move from light aromatics up through essential oils to oleoresins, and eventually to waxes and dense lipids. Higher pressure is not automatically better, because you can start co-extracting heavier material you do not want.
What is the minimum pressure required for CO2 to become supercritical?
CO2 becomes supercritical above roughly 73.8 bar (about 1,070 psi) and 31.1 degrees C (88 F). Below that combined threshold it is not in the supercritical state. Practical botanical extraction runs well above this point, typically from around 100 bar upward.
How do I adjust CO2 extraction parameters to get a different compound selectivity?
Pressure is your main selectivity control. Lower pressure targets lighter, more volatile compounds; higher pressure reaches heavier ones. You can also fractionate a single run by stepping the pressure down across separators to collect different fractions, and add a small ethanol co-solvent to reach more polar molecules without raising temperature.
What happens to extract quality if CO2 temperature is set too high?
Excess temperature reduces CO2 density, which lowers solvating power, and more importantly it can thermally degrade heat-sensitive actives, flattening aromas, darkening colors, or reducing potency. Keeping temperature as low as the target compound allows is one of the main quality advantages of CO2 over hot-solvent or steam methods.
Is there a standard starting point for CO2 extraction pressure and temperature for botanicals?
There are useful starting windows by output type, for example roughly 100 to 150 bar for light aromatics and 250 to 320 bar for oleoresins, with temperatures generally in the 35 to 60 degrees C (95 to 140 F) range. These are orientation only. Because raw material variety, moisture, and milling all affect the result, the correct parameters for your specific material should be confirmed with a trial before production.
What is the difference between subcritical and supercritical CO2 extraction?
Subcritical extraction uses liquid CO2 below its critical temperature of 31.1 degrees C (88 F). It is gentler and very selective for volatile aromatics, but usually gives a lower yield. Supercritical extraction runs above the critical point, where higher solvent strength reaches a wider range of compounds.
How do I convert bar to psi for CO2 extraction?
Multiply bar by 14.5. For example, 100 bar is about 1,450 psi, 350 bar is about 5,075 psi, and 600 bar is about 8,700 psi.
