Wood stripping process boosts bioplastics

Materials World magazine
,
29 Aug 2019

A process to leach lignin and cellulose from waste wood has been recognised for its potential in bioplastics production. Alex Brinded finds out more.

A bioplastics material company has been named as one to watch by Scientific American magazine. Chrysalix Technologies, a spin-out company from a project at Imperial College London, UK, has been listed as a 2019 top 10 emerging technology firm due to its innovative work in improving the bioplastics supply chain.

The company was founded in June 2017 by Dr Agnieszka Brandt-Talbot, Professor Jason Hallett and Dr Florence Gschwend, after their biomass research project at the university yielded promising results and led to the development of a process called BioFlex.

BioFlex breaks down biomass into cellulose and lignin, and can work with different wood types including waste wood or agricultural residues. ‘That’s the holy grail in the biomass or wood conditioning community – to find a low-cost process where you can put anything in and get lignin and cellulose out. We think we have got that holy grail, we just have to demonstrate that it works to scale,’ Brandt-Talbot said.

Currently, the plant-derived cellulose is being used for paper manufacturing, but it may have applications in bioplastics and biofuels, or as a replacement for petrochemicals. The lignin could be an ingredient for bio-adhesives. ‘We are interested in demonstrating the applications with partners who are experts in making bioplastics, we are not envisaging to make them ourselves,’ Brandt-Talbot said.

Wood gets flexible

BioFlex uses specific ionic solvents developed by the team. ‘The ionic liquid is basically the key aspect of our technology, the key invention. We have historically tested a few just out of interest and then we hit on this group that does the wood fractionation really well,’ Brandt-Talbot told Materials World. ‘We have got two or three that we are working with. One method is crystallised and is particularly good, as it works for the widest range of biomass.’

Another positive aspect is that BioFlex can be used for biomass contaminated with preservatives or paints, for example, waste wood previously treated with copper, chromium or arsenic. As well as fractionation, the ionic liquids strip the metals away so the cellulose can be separated without contamination. Electroplating is then used to collect the small amount of metals, which are sent to a refinery to avoid emitting toxic ashes.

On the product side, the team is in discussions with a bio-ethanol producer and cellulose manufacturers as well as companies using lignin for resins. ‘We are partnering on both sides – on the feedstock side that might have the wood or the waste wood or commercial waste. We have lots of people coming with feedstocks they are interested in testing,’ Brandt-Talbot said.

‘If our process works at scale, it will be quite a platform. It will be a process that can take different feedstocks that can then provide conditioned raw materials for bioplastics or bio-fuels.’

Alternative supply chains

Existing technologies that strip wood matter into cellulose and lignin using hot water or solvents, often fail with softwoods. In comparison, BioFlex works for softwoods, as well as hardwoods and grasses. The ionic liquid and the biomass are put into a reactor and heated to between 100°C–120°C to release the cellulose. The mixture is cooled and filtered as the cellulose stays solid, while the lignin is removed in an anti-solvent process, with some used as fuel, and the water then evaporated to isolate the ionic liquid.

The process has a high recovery rate, with several studies having demonstrated more than 99% at large scale. Although it has been proven to work with waste wood, Chrysalix aims to work with sustainably grown biomass, where possible. ‘My hope is that it will be used wherever it is suitable and depending on where we are geographically and the markets around it. Different things will be viable but in Britain, waste wood is probably the first point of call and the economics for that look really good because at the moment you have to pay to get rid of it,’ Brandt-Talbot said.

At present, the system does not produce enough fuel to substitute the petroleum it requires, but it may be possible to supply its own petrochemicals. ‘We can absolutely do that sustainably with the right legislation and the right education,’ Brandt-Talbot said.

‘There has been rapid growth but we are not quite there yet because there are quite a few technological bottlenecks and one of them is feedstock – providing cheap raw material so it can compete with matter made from petroleum. I think if we can make our economics work well, at that it will point take off.’