Biodegradable plastics made from sugar and carbon dioxide

Scientists have developed low-cost biodegradable plastics using sugar and carbon dioxide, an advance that may spell the end for unsustainable products that choke the environment.

Polycarbonate is used to make drinks bottles, lenses for glasses and in scratch-resistant coatings for phones, CDs and DVDs. Current manufacture processes for polycarbonate use BPA (banned from use in baby bottles) and highly toxic phosgene, used as a chemical weapon in the First World War.

Scientists at the University of Bath in the UK have made alternative polycarbonates from sugars and carbon dioxide in a new process that also uses low pressures and room temperature, making it cheaper and safer to produce.

These polycarbonates can be biodegraded back into carbon dioxide and sugar using enzymes from soil bacteria. This new plastic is bio-compatible so could in the future be used for medical implants or as scaffolds for growing replacement organs for transplant, researchers said.

Polycarbonates from sugars offer a more sustainable alternative to traditional polycarbonate from BPA, however the process uses a highly toxic chemical called phosgene.

Scientists developed a much safer, even more sustainable alternative which adds carbon dioxide to the sugar at low pressures and at room temperature.

The resulting plastic has similar physical properties to those derived from petrochemicals, being strong, transparent and scratch-resistant. The crucial difference is that they can be degraded back into carbon dioxide and sugar using the enzymes found in soil bacteria.

The new BPA-free plastic could potentially replace current polycarbonates in items such as baby bottles and food containers, and since the plastic is bio-compatible, it could also be used for medical implants or as scaffolds for growing tissues or organs for transplant.

"With an ever-growing population, there is an increasing demand for plastics. This new plastic is a renewable alternative to fossil-fuel based polymers, potentially inexpensive, and, because it is biodegradable, will not contribute to growing ocean and landfill waste," said Antoine Buchard, from the university's Department of Chemistry.

"Our process uses carbon dioxide instead of the highly toxic chemical phosgene, and produces a plastic that is free from BPA, so not only is the plastic safer, but the manufacture process is cleaner too," said Buchard.

Researchers used nature as inspiration for the process, using the sugar found in DNA called thymidine as a building block to make a novel polycarbonate plastic with a lot of potential.

"Thymidine is one of the units that makes up DNA. Because it is already present in the body, it means this plastic will be bio-compatible and can be used safely for tissue engineering applications," said Georgina Gregory, PhD student at Bath.

"The properties of this new plastic can be fine-tuned by tweaking the chemical structure - for example we can make the plastic positively charged so that cells can stick to it, making it useful as a scaffold for tissue engineering," Gregory said.

The study was published in the journals Polymer Chemistry and Macromolecules.