How They Differ from Classic Essential Oils
Not everything aromatic can be easily captured by steam.
Some flowers and resins are so delicate — or so rich in heavy, non-volatile components — that standard distillation yields disappointing results. That’s where solvent extraction and CO₂ extraction come in.
These methods can pull out a broader range of molecules, but they also produce products that are not identical to classic steam-distilled essential oils.
Solvent Extraction: Concretes and Absolutes
In traditional solvent extraction, an organic solvent (such as hexane or ethanol) is used to dissolve aromatic compounds from plant material.
Simplified process
- Plant material is soaked in a solvent.
- Aromatic compounds, pigments, and waxes dissolve.
- The solvent is evaporated, leaving a waxy, aromatic mass called a concrete.
- The concrete can be further extracted with alcohol and processed into an absolute — a more refined, liquid aromatic product.
Pros
- Can capture delicate floral notes that don’t survive distillation well (e.g., jasmine, some roses).
- Extracts a wider range of components, including heavier molecules that don’t readily distill with steam.
Cons
- Risk of residual solvent if not properly removed.
- The composition is richer in non-volatile substances (waxes, pigments), so the product behaves differently from an essential oil.
- Not always suitable for applications where the cleanest possible profile is needed (e.g., internal use, very sensitive individuals).
In perfumery, absolutes are prized for their complexity. In aromatherapy, they are often used more cautiously and in small amounts.
Supercritical CO₂ Extraction: A Modern Middle Ground
Supercritical CO₂ extraction uses carbon dioxide in a special state — neither a typical gas nor a typical liquid, but something in between, achieved at specific temperature and pressure.
In this state, CO₂:
- Diffuses like a gas
- Dissolves substances like a liquid
This can make it a very effective, tunable solvent.
How it works
- CO₂ is brought to its supercritical state using pressure and temperature.
- Supercritical CO₂ flows through plant material, dissolving target compounds.
- Pressure is lowered; CO₂ returns to a gaseous state and separates from the extract.
- The resulting product is collected as a CO₂ extract.
Pros
- Leaves no solvent residue if properly handled — CO₂ simply evaporates.
- Can operate at relatively low temperatures, which helps protect heat-sensitive molecules.
- Composition can sometimes be tuned by adjusting pressure and temperature.
Cons
- Requires specialized, expensive equipment.
- The resulting extract can still be quite different from a steam-distilled oil — often richer, heavier, and more “complete”.
Are These Products “Better” or Just Different?
There isn’t a universal “better”.
Instead, ask:
- What is the plant?
Some botanicals shine as CO₂ extracts; others do very well with simple steam distillation. - What is the intended use?
For perfumery, complexity and richness might be desirable.
For very sensitive skin or internal use (where allowed), simplicity and purity may matter more. - What are your values around processing?
Some people are comfortable with absolutes in very low doses. Others prefer to stick to hydro- or steam-distilled oils whenever possible.
In our view, solvent and CO₂ extracts are useful tools — not automatically superior, not inherently suspicious. They just need to be understood and used with the right expectations.
In the final article of this series, we’ll explore some of the modern “assisted” techniques, especially microwave-assisted water distillation, which aims to make distillation faster, gentler, and more energy-efficient.