Envision being able to throw an empty plastic water bottle into a household composting bin that breaks down the plastic and creates biogas to help power the home. Currently, scientists have taken the initial step toward this futuristic setup by demonstrating that some blends of bioplastics can decompose under varied conditions. They publish their results in the ACS journal Environmental Science & Technology.

Plastic waste pollution is a universal environmental problem, predominantly in oceans, where plastic debris can kill or harm marine animals and birds that ingest or become ensnared in it. Despite greater levels of recycling in a number of countries, the majority of plastic waste still ends up in landfills or the environment. Researchers have created biodegradable plastics, but they repeatedly lack the flexibility, toughness, or strength of conventional plastics. Blends of different bioplastics can offer better characteristics, but their environmental fate is undefined. Tanja Narancic, Kevin O’Connor, Ramesh Babu Padamati and colleagues were keen on analyzing the degradation of specific bioplastics and their blends under different conditions.

The scientists examined the fates of 15 different plastics or blends under managed scenarios, such as anaerobic digestion and composting, as well as unmanaged environments, including soil and marine or fresh water. Polylactic acid (PLA) is one of the best-selling commercial biodegradable plastics, but it needs high temperatures for breakdown and is not home-compostable. Unexpectedly, a blend of PLA and polycaprolactone (PCL) degraded totally to carbon dioxide, water, and biomass under usual home-composting environments.

A number of the individual plastics and blends that were examined, decomposed under conditions of anaerobic digestion, a process that can create biogas, and all degraded with industrial composting. The scientists say that biodegradable plastic blends could offer new possibilities for handling plastic waste. However, only two plastics, thermoplastic starch (TPS) and polyhydroxybutyrate (PHB) broke down totally under all water and soil conditions. Thus, biodegradable plastics are not a complete solution for plastic pollution, and they must be managed prudently after they are disposed of by the consumer, the scientists say.

The researchers were funded by the European Commission Horizon 2020 Program, the European Commission Seventh Framework Program for Research and the Science Foundation Ireland.

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