Japan — Plastic pollution has proven stubbornly resistant to quick fixes. Even so-called biodegradable plastics often linger in the environment, breaking down into microplastics that spread through ecosystems and bodies alike. Now, researchers in Japan say they have created a plant-based plastic that sidesteps that trap. The material stays strong during use, yet breaks down rapidly in natural settings without leaving microscopic debris behind. …Cellulose-based plastics already exist, but most do not decompose quickly in marine environments. …The new plastic builds on that earlier concept. One polymer comes from carboxymethyl cellulose, a wood-pulp derivative that is already FDA-approved and biodegradable. The second component proved harder to identify. After extensive testing, the team selected a safe crosslinking agent made from positively charged polyethylene-imine guanidinium ions.