Most bioplastics are made with some oil-derived chemicals as well as ones from renewable biomass, and they tend to be more expensive and less useful than traditional polymers.
Now a team from Warwick University and Southampton-based Biome Bioplastics is launching a study of how 100 per cent renewable bioplastics could be made using chemicals derived from the breakdown of the paper manufacturing waste product lignin, which could also improve the bioplastics’ cost and performance.
‘The key element of it is [asking] can we use bugs to do things that chemical plants do?,’ Biome CEO Paul Mines told The Engineer. ‘And in doing so can we do it in a less capital-intensive way than a chemical plant with a very low cost for material?’
Lignin, which is a key component of plant structures and one of the most abundant organic compounds on Earth, is formed from “aromatic” rings of carbon atoms that are chemically very useful because they can be bonded with different functional molecular groups.
‘Aromatic chemicals tend to provide higher functionality than long, straight chains in polymer,’ said Mines. ‘But lignin is a horrendous molecule to get things out of.’
Scientists at Warwick’s Centre for Biotechnology and Biorefining led by Prof Tim Bugg have identified an enzyme produced by certain bacteria that can break down lignin more cost-effectively than traditional methods.
They now plan to work with Biome Bioplastics, supported by a £150,000 grant from the Technology Strategy Board (TSB), to study whether it might be possible to scale up this process to a commercial level by examining the different pathways by which the enzyme breaks down the lignin.
‘What we’re trying to do is get some intermediate chemicals out,’ said Mines. ‘As the bug breaks down the lignin, you’re trying to either stop that breakdown process part way through, either chemically or by switching off genes in the bug, or pulling the chemical out so the reaction never completes.’
‘What industrial biotechnology offers is a cheaper means of production using a waste product. The interest is can it help us to drag the two to four times cost of bioplastics down much closer to the cost of petrochemical plastics.’
The aromatic chemicals could also improve the properties of bioplastics including their flexibility, strength and performance at high temperatures, allowing them to break into new applications.
‘At the moment we’ve got bioplastics that function at up to 100ºC,’ said Mines. ‘That prevents things like automotive work because when you make a car you want to make sure the plastics are good for high temperatures as well.’
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