Japanese researchers create flexible bio-based plastic that converts to urea fertilizer after use

Researchers at Chiba University in Japan have developed a bio-based plastic system that can be chemically converted into urea and isosorbide — both usable as fertilizer — after its service life ends. The study, published in Scientific Reports on August 18, addresses two environmental challenges at once: plastic waste accumulation and the high energy cost of synthetic fertilizer production.

The system is built around poly(isosorbide carbonate), or PIC, a polycarbonate derived from glucose. When treated with aqueous ammonia at 90°C, the polymer breaks down completely within about six hours to yield isosorbide and urea without any catalyst. The reaction products can be applied directly to soil without separation or purification.

From brittle laboratory plastic to flexible bio-based fertilizer material

Earlier work by the same team had demonstrated the basic ammonia-driven breakdown of PIC into fertilizer components. The new study overcomes a practical limitation: PIC in its pure form is hard and brittle, which restricted its potential applications. The researchers designed a dual-functional plasticizer — also derived from isosorbide — that increases the material’s flexibility more than tenfold while preserving its ability to convert into fertilizer. Critically, both the polymer and the plasticizer yield fertilizer components upon ammonia treatment, leaving no non-convertible residue.

Plant growth experiments confirm bio-based plastic fertilizer works

The team tested the unpurified decomposition products on two plant species: Arabidopsis thaliana, a standard model organism, and komatsuna, a leafy vegetable commonly grown in Japan. Plants treated with the plastic-derived fertilizer mixture grew comparably to those treated with commercial urea fertilizer, confirming the agricultural viability of the conversion products. Associate Professor Daisuke Aoki, who led the research, described the material as entering a phase where plastics offer “active environmental benefits” rather than merely being reduced or passively recycled.

What it means for the fertilizer industry

The concept remains at the laboratory stage and faces substantial hurdles before commercial adoption. Scaling the ammonia treatment process, competing with the low cost of conventional urea production, and integrating into existing plastic waste streams are among the challenges ahead. Global plastic use is projected to nearly triple to 1.2 billion metric tons by 2060 under current trends, according to the OECD, creating strong demand for alternatives to landfill and incineration.

For the fertilizer sector, the research contributes to a growing body of work on circular approaches to nutrient recovery. If the isosorbide-urea system can be commercialized, it would represent a novel pathway for producing nitrogen fertilizer from bio-based waste — though any meaningful impact on global urea supply, currently exceeding 180 million metric tons per year, would require adoption at a scale that is difficult to envision from present laboratory results.

Source: Phys.org