On-trend: Supercritical CO2 increasingly in the spotlight

Supercritical carbon dioxide (sCO2), carbon dioxide elevated in a fluid state at or above its critical temperature and critical pressure point, is the subject of increasing application across a range of once tired, less efficient or less than environmentally-friendly applications.

That’s according to a cover feature on the product in the upcoming CO2 Issue of gasworld magazine.
While often derided in mainstream media in the past for its harmful environmental impact, carbon dioxide is known to be a key product across a wide range of industries – from beverage carbonation to food chilling and freezing and even the medical sector – due to its invaluable properties.
Supercritical CO2 takes those characteristics to a whole new level. The very nature of supercritical CO2 means that it can adopt properties midway between a gas and liquid state and, therefore, unlock additional gains in efficiency and stability.

It’s at this state though that sCO2 demonstrates the unique properties that render it so useful to a growing range of applications – not least its incredible efficiency, stability, low toxicity and decreased environmental impact.

Environmentally beneficial and low-cost substitutes for rigid thermoplastics and fired ceramics are made using sCO2 as a chemical reagent, for example. Supercritical CO2 is also used as the working fluid in high efficiency water heat pumps, for domestic and business heating/cooling applications, and in vogue as an emerging natural refrigerant in new, low-carbon solutions. It could be used too as a working fluid in enhanced geothermal systems where the properties of its elevated state could provide many advantages to using water, not least higher energy yield.

Other ‘novel’ applications of late include the use of sCO2 as the extraction solvent for the creation of essential oils and other herbal distillates, as well as in the fast-growing cannabis market where it is often the preferred choice given its clean process of removing unwanted impurities.

Water and chemical-free textile dyeing is increasingly another avenue of application for sCO2. With as much as 28 billion kilos of textiles dyed annually, this is not only a huge market but also one with significant water and chemicals usage; it’s understood that the textile industry can use, on average, over 100 litres of water to process 1kg of textile material.

In its supercritical state, CO2’s high solvent power and permeability enables the dye to be absorbed easily and deeply into the fibres, creating vibrant colours resulting in a major environmental benefit: not only is there no dependence on water and process chemicals, meaning there is no waste water treatment required either.