New sugar-based polymer makes composting of disposable plastics possible at home

18-Feb-10

Food packaging and other disposable plastic items could soon be composted at home along with organic waste thanks to a new sugar-based polymer, being developed at Imperial College London by a team of Engineering and Physical Sciences Research Council scientists led by Dr Charlotte Williams. 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. The 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. 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.