Scientists Turn Flexible Plastic Waste Into Fertiliser That Helps Plants Grow

A Japanese research team has developed a way to turn waste plastic into fertiliser that actively benefits plant growth, rather than simply reducing environmental harm. The work, led by Associate Professor Daisuke Aoki at Chiba University, is described in an open-access paper in the journal Scientific Reports.

The approach builds on Aoki's earlier research using ammonolysis, a process that breaks down plastic polymers with ammonia. His team had shown that a plastic called poly(isosorbide carbonate), or PIC, could be converted through ammonolysis into isosorbide, urea and other fertilising agents. But PIC was hard and brittle, like many biodegradable plastics, which limited how it could be used and shortened its lifespan before it, too, became waste.

To fix this, the researchers created an isosorbide-based plasticiser — a chemical additive that increases flexibility — that made PIC far more bendable without sacrificing its ability to be converted into fertiliser through ammonolysis. The additive increased the plastic's elongation at its breaking point more than tenfold, from 4.3% to 45.2%. Even the plasticiser itself can be turned into fertiliser.

In experiments, the resulting fertilisers grew Arabidopsis thaliana and komatsuna, a leafy vegetable in the Brassica rapa family, as effectively as commercially available urea fertiliser. Aoki said the team wanted to move toward an "active" environmental contribution, designing materials that address plastic waste, resource depletion and sustainable agriculture at once.

The team envisions the flexible plastic being used in packaging, bags, seedling pots and agricultural mulch film before it is eventually converted into fertiliser. Aoki said he anticipates the work could lead to a shift in how plastic is viewed — "no longer... 'waste' but as a 'valuable resource for food production.'"