At the dry cleaners, clothes are washed in the chemical solvent PER (perchloroethylene). Although liquid CO2 would be an environmentally friendly alternative, the high pressure would require heavy machinery. In addition, CO2 does not remove stains easily, and it often leaves dirt behind elsewhere. Dr Stevia Sutanto, who has recently completed her PhD, reinforced the interaction of CO2 with textiles, thereby increasing its washing power. She also calculated that washing with CO2 would be less expensive than chemical cleaning using PER, as there are no disposal costs and the process requires no steam.