From plastic trash into sudsy cleansers.

Science News reports on a system for “upcycling” plastic trash by converting the non-recycled waste destined for the landfill into surfactants, the chemicals that make soap, um, soapy:

“To me, plastic waste basically [is] aboveground crude oil,” says chemist Guoliang Liu of Viginia Tech in Blacksburg. “We don’t have to go deep into the ocean or underground to mine [it] anymore” to make valuable chemicals.

Surfactants and the two most used kinds of plastic, polyethylene and polypropylene, are made of molecular chains of carbon atoms. But surfactants’ chains are far shorter than those of plastics and are capped with groups of water-attracting atoms.

To turn plastic into surfactants, Liu and colleagues developed a special reactor that carefully heats and condenses plastic into a wax with short carbon chains. By capping the wax’s chains with groups of oxygen atoms and treating them with an alkaline solution, the researchers turned the wax into surfactant. Combining the surfactant with a bit of dye and fragrance produced tiny bars of soap.