US scientists turn old plastic into soap after fireside inspiration

Guoliang Liu and his colleagues built an oven-like reactor that could burn plastic safely. The residue from the process was short-chain polyethylene, a type of wax. Photograph: vintagerobot/Getty Images

Scientists have discovered a method to give new life to old plastic – by converting it into soap.

Plastics are chemically similar to fatty acids, which are one of the main ingredients in soap. For Guoliang Liu, an associate professor of chemistry at Virginia Tech and author of the paper published in the journal Science, this similarity suggested it should be possible to convert polyethylene into fatty acids, and then into soap. The problem was size: molecularly, plastics are very large, about 3,000 carbon atoms long, whereas fatty acids are much smaller.