Sustainable Plant Plastics

Replacing food packaging made from fossil oil

James Elliott, a professor of Macromolecular Materials Science, gave an interesting overview of a project to create sustainable plastic packaging from plants. The talk was held at the Maxwell Centre at the University of Cambridge. We got to see an overview of the science behind the new material as well as handle some sample plant materials and see some prototype plastic film.

In essence the aim is to replace single use fossil oil plastics, used for food packaging, with a similar plastic made from plants. The new material would be ideally suited to food packaging that is often contaminated with food residue that would otherwise make it tricky to recycle. The new plant based plastic would degrade successfully in modern industrial composting facilities. Since the raw materials are plant based, and the material is composted after use, the process with respect to the raw materials is carbon neutral.

The new material is principally made of cellulose. Plastics have been made from cellulose for over a hundred years (things like rayon, acetate movie reels and cellophane film) but the process is quite energy expensive and chemically messy. The new process improves on that. At the moment they have been experimenting with genetically engineered plants, but for commercial applications would expect sources such as waste wood from forestry operations, or straw from rape seed oil production to be used. The key point here is that there needs to be enough of the raw material already available in order to produce the 2 million tonnes of plastic that is used in the UK for food packaging each year. If you have to grow extra crops just to produce the plastic then it would be a less attractive option.

Technical barriers to be overcome include making the plastic slightly less brittle and to have a lower permeability to water. This seemed to be one of the trickier aspects and involves modifiying the natural crystal structure to produce the required characteristics. This would make the material comparable with current plastics and would mean that manufacturers could use it as a like for like replacement without changing their food packaging machinery.

It is hoped that the first industrial production would start in October 2023 with an initial 10 thousand tonnes being produced in the first year. By 2028 this could increase to 100 thousand tonnes per year with a view to then scale up and license the technology. If the plastic works, then this sounds like rather a long time to replace single use food packaging and you wonder why the government would not be able to drive change at a quicker rate.

Initially there could be several problems. In Cambridgeshire the industrial composting used at the Materials Recycling Facilities, such as at Waterbeach, don’t appear to handle compostable bio-plastics labelled as PLA. Polyactide (PLA) plastics are made from plants such as corn or sugarcane from which the basic ingredient of lactic acid is extracted. This is a problem for consumers who follow the recycling labels and put PLA items in the “green” wheelie bin for food and garden waste. Similarly, if they put bioplastic cups, bottles and packaging in the single “blue” wheelie bin for recyclables then attempts to recycle PET bottles made from fossil oil will be hampered due to contamination with incompatible plant plastics. Traditionally much of the “single bin” approach to separating materials has relied on a mixture of mechanical sorting and manual sorting, with robotic sorting also now being introduced. Hence, there will be a considerable challenge in educating the public about a new plastic and deciding how to collect and sort the new material.

Making plastics fantastic (again!): From discovery science to industrial application
Thursday May 26th, 2022
Maxwell Centre, University of Cambridge


Cambridge Network

Cambridge Circular Plastics Centre

Resource Efficiency Collective – Plastics in the UK
A good summary of plastic usage in the UK.

Recap : Cambridgeshire and Peterborough Recycle
What happens to waste in Cambridgeshire and Peterborough

YouTube – Making Plastics Fantastic (Again!)
An earlier talk from 4 Feb 2021 explaining the proposed technology.