Compostable plastics have a sweet ending

The degradable polymer is made from sugars known as lignocellulosic biomass, which come from non-food crops such as fast-growing trees and grasses, or renewable biomass from agricultural or food waste.

It is being developed at Imperial College London by a team of Engineering and Physical Sciences Research Council scientists led by Dr Charlotte Williams.

The search for greener plastics, especially for single use items such as food packaging, is the subject of significant research worldwide. “It's spurred on not only from an environmental perspective, but also for economic and supply reasons,” explains Dr Williams.

Around 7% of worldwide oil and gas resources are consumed in plastics manufacture, with worldwide production exceeding 150 million tons per year. Almost 99% of plastics are formed from fossil fuels.

“Our key breakthrough was in finding a way of using a non-food crop to form a polymer, as there are ethical issues around using food sources in this way,” said Williams. Current biorenewable* plastics use crops such as corn or sugar beet.

“For the plastic to be useful it had to be manufactured in large volumes, which was technically challenging. It took three-and-a-half years for us to hit a yield of around 80% in a low energy, low water use process,” explains Dr Williams.

This is significant as the leading biorenewable plastic, polylactide, is formed in a high energy process requiring large volumes of water. In addition, when it reaches the end of its life polylactide must be degraded in a high-temperature industrial facility.

In contrast, the oxygen-rich sugars in the new polymer allow it to absorb water and degrade to harmless products – meaning it can be tossed on the home compost heap and used to feed the garden.

Because the new polymer can be made from cheap materials or waste products it also stacks up economically compared to petrochemical-based plastics.

The polymer has a wide range of properties, laying the field open for a larger number of applications other than biorenewable plastic packaging. Its degradable properties make it ideal for specialised medical applications such tissue regeneration, stitches and drug delivery. The polymer has been shown to be non-toxic to cells and decomposes in the body creating harmless by-products.

The team – including commercial partner BioCeramic Therapeutics, which was set up by Professor Molly Stevens and colleagues at Imperial – are investigating ways of using the material as artificial scaffolds for tissue regeneration. They are also focusing on exploiting the degradable properties of the material to release drugs into the body in a controlled way.

Now the team is focused on developing the specific material characteristics needed for the packaging and medical areas.

“The development of the material is very promising and I'm optimistic that the technology could be in use within two to five years,” says Williams, who is already working with a number of commercial partners and is keen to engage others interested in the material.

Notes for Editors:

Biorenewable plastics are materials whose feedstock material (monomer) comes from renewable resources. The leading example is poly(lactic acid) which derives from lactic acid, produced by fermentation of corn or sugar beet. These biorenewable plastics are different to biopolymers, which are naturally occurring polymers such as starch or cellulose (note that these are not plastic materials).

The chemical name for the compostable polymer is Poly(acetic acid-5-acetoxy-6-oxo-tetrahydro-pyran-2-yl-methyl ester) and copoly(lactic acid-ran-acetic acid-5-acetoxy-6-oxo-tetrahydro-pyran-2-yl-methyl ester).

Research leader Dr Charlotte Williams is a champion of the widespread application of biomass to make fuels and materials. She has published a highly cited article in science magazine highlighting the challenges associated with converting plants to fuels and products. She won a 2009 Royal Society of Chemistry Early Career Award for her work in this area. The research is being carried out in collaboration with Prof. Molly Stevens, an expert in the application of degradable plastics in medicine. Her research has recently been recognised by the IUPAC creativity in polymer science prize.

The polymer was discovered and developed by Dr Min Tang and Dr Anita Haider in their doctoral research. Dr Tang continues to develop the materials.

Engineering and Physical Sciences Research Council (EPSRC)

EPSRC is the main UK government agency for funding research and training in engineering and the physical sciences, investing more than £850 million a year in a broad range of subjects – from mathematics to materials science, and from information technology to structural engineering. www.epsrc.ac.uk

BioCeramic Therapeutics Limited

BioCeramic Therapeutics Limited is a pioneer in the exciting new field of regenerative medicine, bringing together some of the world's best materials scientists, doctors, biologists and chemists in both private and public sectors. BCT is developing two families of implants designed to promote tissue regeneration. Initial applications are in orthopaedics and oral care, with plans to extend this to a wide range of other tissues important in human diseases. www.bioceramictherapeutics.com

Imperial College London

Consistently rated amongst the world's best universities, Imperial College London is a science-based institution with a reputation for excellence in teaching and research that attracts 14,000 students and 6,000 staff of the highest international quality.

Innovative research at the College explores the interface between science, medicine, engineering and business, delivering practical solutions that improve quality of life and the environment – underpinned by a dynamic enterprise culture.

Since its foundation in 1907, Imperial's contributions to society have included the discovery of penicillin, the development of holography and the foundations of fibre optics. This commitment to the application of research for the benefit of all continues today, with current focuses including interdisciplinary collaborations to improve health in the UK and globally, tackle climate change and develop clean and sustainable sources of energy. www.imperial.ac.uk

For further information, contact:
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Image details
Image: PN 09-10 ready meal packaging
Credit: iStockPhoto
Suggested caption: Food packaging is just one of the potential applications of the compostable sugar-based polymer.
Image: PN 09-10 polymer team
Credit: Imperial College London
Suggested caption: The compostable polymer was developed by (left to right) Professor Molly Stevens, Dr Min Tang (holding the new polymer) and Dr Charlotte Williams at Imperial College London.