Q.

Carbon dioxide is a greenhouse gas. If you use carbon dioxide as a solvent, are you releasing it into the atmosphere?

A.

The carbon dioxide that we use is mainly captured from the fertilizer manufacturing process. So we are not putting extra carbon dioxide into the atmosphere, but instead we are re-using carbon dioxide that would otherwise have been released. When we extract natural products from plant material, the carbon dioxide that we use is recycled several times in the process before being eventually released. 

Q.

Why do you use carbon dioxide?

A.

We use carbon dioxide as a solvent to extract valuable natural products, mainly from plant material. Carbon dioxide is a clean, non-flammable solvent and its use does not release volatile organic compounds (VOCs). It does not react easily with other chemicals, so it is safe to use. Carbon dioxide has many advantages as a solvent when used as a liquid or a supercritical fluid. It can be “tuned” to selectively extract different kinds of molecules by varying its temperature and pressure. The mild extraction conditions cause minimum damage to the complex, sensitive molecules that we are extracting.

Since carbon dioxide is a gas at ambient temperatures and pressures, products obtained from carbon dioxide extraction will have little or no solvent residue. There is no concern with human exposure to residual carbon dioxide, whereas this is not the case for many other natural and synthetic solvents.¹

Q.

What are the extraction conditions?

A.

Liquid carbon dioxide can be used to extract many natural products, including oils, flavours and fragrances from spices, and oils and resins from hops for brewing. Liquid carbon dioxide does not require high temperatures or pressures – typical extraction conditions are 60 bars and 10 ^oC. For more demanding applications, we routinely use supercritical carbon dioxide at pressures of up to 300 bars and temperatures of up to 60 ^oC, although higher pressures can be used in specialised cases. For further details see our technical overview document Clean and Green Technology.