A variety of polymers-from polyolefins to nylon-can now be made commercially from sugar and starch, rather than crude oil. The main user of these new materials, at least in the short term, is the packaging sector.
Bio-sourced plastics account for less than 1% of all consumption. And most of this is derived from corn or sugar. But a wealth of potential starting materials-from meat to mushrooms-is also being investigated.
These new bio-sourced plastics have become available because of research into renewable precursors – the chemicals that are polymerised to make plastics.
New ways of making chemicals like succinic acid could transform the way in which plastics are produced.
"The bio-based chemicals sector is poised to transform the production of industrial chemicals," says Marifaith Hackett, chemical analyst at consultancy IHS, and author of a recent report on bio-based building blocks.
She cites Coca Cola's 'Plant Bottle' (bio-sourced PET) as a material that is beginning to be made from renewable sources.
New sources
PET is made from two precursors that are traditionally derived from crude oil: mono ethylene glycol (MEG) and purified terephthalic acid (PTA). Coca-Cola's 'Plant Bottle' uses sustainably-sourced MEG - and the drinks giant wants to source its PTA in the same way.
It will take the technology forward with help from three biotechnology partners: Virent, Gevo and Avantium.
Virent is scaling up a plant to make bio-based paraxylene, a precursor of bio-PTA; Gevo will also supply plant-based paraxylene for a similar purpose; and Avantium is using its YXY technology to produce polyethylene furanoate (PEF), a sustainably sourced variant of PET. It currently operates a 40 tonnes/year pilot plant, but has plans to scale this up in order to supply PEF to Coca-Cola in future.
"This is the next step towards our vision of creating all of our plastic packaging from responsibly sourced plant-based materials," says Rick Frazier, vice president of commercial product supply at Coca-Cola.
By 2020, the company intends to make all of its bottles using renewable technology - making them 100% sustainable.
At the same time, new corporate sustainability goals by companies like Coca-Cola and Procter & Gamble are helping to push green packaging design up the agenda. P&G, for example, aims to replace 25% of its petroleum-based packaging with sustainable alternatives by 2020.
And consumer giant Unilever has launched a new search for Open Innovation partners, which includes a focus on sustainable packaging.
The company is inviting potential collaborators to work with its research teams to create "lighter, more sustainable packaging that will cut the weight, quantity and waste of our product packaging". It has a particular interest in ideas for food packaging.
Some of the areas it is considering include: stronger materials; thin-walling and downgauging; multi-purpose films; novel design, which might borrow ideas from fields like architecture or building construction; and material solutions including new polymers, fillers, additives, fibres or micro-bubbles.
Other feedstocks
Many bioplastic monomers are made from common crops - but researchers are trying ever more unlikely sources as starting points for 'green' polymers.
Corn, sugar, beans and potatoes are all used as raw materials to make plastics as diverse as nylon and PLA. But the emerging challenge is to use 'non-food' sources - including algae, cellulose and food industry 'waste', such as shells and husks - to make environmentally-friendly plastics.
Cereplast already offers bioplastics made from algae, while US start-up company Myriant has devised a process to make both lactic acid and succinic acid from cellulosic feedstocks; the main use of lactic acid is as the precursor for PLA. And one of the first ever commercial polymers, cellophane, is based on cellulose.
The emergence of these new monomers could lead to the creation of new polymers. An example is PBS, a biodegradable plastic made from (bio-based) succinic acid. PTT-MCC Biochem will use bio-succinic acid from US-based BioAmber to produce 20,000 tonnes a year of PBS, at a plant in Thailand, due to open in 2014.
Other suppliers are also focusing on succinic acid: BASF and Purac have used a specially designed microorganism to produce it from renewable feedstocks, for example.
Hackett says that PBS would not have been economical before, as succinic acid was not a cheap enough feedstock. The advent of ready supplies of succinic acid now makes its production a commercial reality, she says.
A meaty solution
But it's not just plants that might form the basis of future bioplastics. In a paper presented at the recent Antec plastics technical conference, researchers from Clemson University in the US revealed details of how to make a bioplastic from waste meat proteins.
Sam Lukubira and Amod Ogale, of the Department of Chemical and Biomolecular Engineering, used meat- and bone-meal (MBM) to produce bioplastic sheets. They believe that the sheets have potential use in geo-structural applications.
Process conditions had to be set carefully. When the relative humidity of the MBM powder was above 55%, excessive denaturation produced a dark, glue-like material. Glycerol (around 30% by weight) was used as a plasticiser and the pressed sheets were tested for mechanical properties. Those made with finely ground particles (less than 250 microns) were twice as strong as those made from larger particles.
A similar technique, using blood meal, has already been commercialised by New Zealand-based Novatein. The bioplastic made in the process has similar mechanical properties to low density polyethylene (LDPE), says the company, and is made using a "scalable process".
Novatein was spun out of Waikato University, where the original research was carried out by senior lecturer Johan Verbeek. The company expects to have developed a commercial product within the next few years.
The company has high hopes for the technology: it says that around 1.5kg of bioplastic can be made from 1kg of blood meal - and New Zealand's meat industry produces around 80,000 tonnes a year of bovine blood.
Packaging designers are under ever-increasing pressure to incorporate sustainability into their thinking. When down-gauging has gone as far as it can go, this emerging breed of bio-sourced materials will help them in their aims – whether they have come from blood, mushrooms or corn.
