Compostable plastics breakthrough sounds sweet
By Jeff Salton
February 18, 2010
Traditional environmental enemies food packaging and other disposable plastic items could soon be composted at home along with organic waste and not collected for landfill thanks to a new sugar-based polymer being developed at Imperial College London. The degradable polymer is made from sugars known as lignocellulosic biomass, which come from non-food crops like fast-growing trees and grasses, or renewable biomass from agricultural or food waste.
A team of Engineering and Physical Sciences Research Council (EPSRC) scientists, led by Dr Charlotte Williams says 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.
EPSRC’s research shows around seven percent of the world's oil and gas resources are used to manufacture plastics, with worldwide production more than 150 million tons annually. Almost 99 percent of plastics are made 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 bio-renewable plastics use crops such as corn or sugar beet. Bio-renewable plastics are materials whose feedstock material (monomer) comes from renewable resources.
“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 percent in a low energy, low water use process,” explains Dr Williams.
Until now, the leading bio-renewable plastic, polylactide, has been 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 thrown on the home compost heap and eventually used to feed the garden.
Adding to its appeal, the new polymer can be made from cheap materials or waste products which makes it economically sustainable compared to petrochemical-based plastics.
Other possible uses
The team says the polymer may also have applications in specialized medical applications such as tissue regeneration, stitches and drug delivery as 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 hopeful that the degradable properties of the material may be used to release drugs into the body in a controlled way.
“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.
Images courtesy Imperial College London