#composites, #sustainability, #fibers, #bio-based, #natural_fiber, #plant-based, #sustainable_fiber, #plant_based, #recycle, #recycling, #sustainable_use
I’m going to go back to sustainable carbon fiber for my last post this calendar year because there is so much going on in this area that I just need to cover. There are some updates to things that I have covered fairly lightly in the past and new applications of bio-based or plant-based carbon fiber that are poised to take off in short order.
The first new application I found is from a European bicycle news outlet and it states that Bio-based carbon fiber may be the future of cycling. And Trek is one of the companies that is signing up for this now that they have released their report on the carbon footprint of both carbon fiber and aluminum bikes. This company is reporting on the use of a bio-based acrylonitrile made from lignin, something that I have written about previously (actually just 4 or 5 weeks ago). But this is a commercial enterprise reporting on what the bicycle industry is moving toward, so that is the biggest piece of this good news story.
Back to the plant or bio based carbon fiber. Most of the work that is being done uses wood waste material which has lignin, cellulose, and some shorter chain carbohydrates than cellulose like xylose and glucose (5 and 6 carbon chain hydrocarbons). Notable among these is the work being done by Trillium and Solvay which is the scale up of the Southern Research development of wood waste based acrylonitrile. Rather than being a lignin derived ACN, this group uses these short chain carbohydrates to make propylene glycol which they then expose to catalysts in a hydrocracking operation and a dehydration reaction to produce plant-based ACN. Their process looks like this.
This is the process that Trillium is scaling up with Solvay – one of the larger carbon fiber manufacturers – to develop a plant-based carbon fiber at an industrial scale. In late 2022 Trillium closed a funding round of $10.6M which they are working through now to scale up production of their BioACN plant-based acrylonitrile. And, since Solvay has signed a commercial agreement with them to use their BioACN to make carbon fiber, it appears that this is the latest very good news story on the industrial scale development of plant-based carbon fiber.
Another plant-based carbon fiber initiative was started by the Department of Energy in October of 2018. This initiative was intended to demonstrate cost effective production of carbon fiber using a plant-derived acrylonitrile. It was the National Renewable Energy Lab (NREL) in Golden, Colorado that was responsible for this initiative with minor participation from Oak Ridge National Lab in Tennessee. By the time the first year’s review of this project came around, they had already demonstrated production of carbon fiber from plant-based acrylonitrile at a “modeled” cost of less than $1 a pound. By modeled cost what they really mean is that if the project were to meet all of its goals and a commercial company was to scale this process up to hundreds of tons a year like the big players in the carbon fiber business already have with petroleum based carbon fiber, the production cost itself would be less than $1 a pound. This doesn’t include the cost of the plant-based acrylonitrile itself; it was just to demonstrate a process that was scalable up to industrial scale quantities of carbon fiber.
What they were banking on was a previously funded DOE project to demonstrate low cost plant-based acrylonitrile. It was the DOE that funded much of the work at Southern Research that is currently being scaled up by Trillium.
Another company that is using this same NREL developed plant-based acrylonitrile to make carbon fiber is a company called Mars. Mars makes water filtration systems using polyacrylamide as what is called a “flocculant”. Polyacrylamide is most commonly made using acrylonitrile and processing it into acrylamide which is then polymerized. Until the availability of bio-based acrylonitrile, these flocculants were exclusively made using petroleum based ACN. So, Mars obtained an exclusive license to scale up the production of their water filtration flocculant using BioACN from Trillium. They have also apparently signed a non-exclusive license to make carbon fiber using this bio-based feedstock, so there are two carbon fiber producers that are scaling up production of carbon fiber using plant-based ACN.
There is also a chemical supplier in the Netherlands, AnQore (1), that makes an acrylonitrile from plant waste based propylene and ammonia from biogas – the gasses that are liberated in the agricultural industry through fermentation of agricultural waste. The nasty smell that comes from your local dump, and from the sewer, is actually a fermentation product from decomposing plant matter in the garbage. These folks in the Netherlands harness that biogas and refine both ammonia and propylene from it, purify the gasses, and use them for feedstock in a normal ACN manufacturing process. They call their product Econitrile, and their process is certified to produce 60% less CO2 than the typical acrylonitrile made from petroleum feedstocks. It is, however, not entirely sustainable because AnQore uses existing petroleum fired processing equipment to make carbon fiber from the CAN that they produce from forest products industry waste. Their process uses lignin from the lignocellulose waste, and cracks it down to polypropylene and ammonia which are the petroleum based precursors for acrylonitrile today. They have been able to produce both of these compounds in high enough purity to make them work well as replacement feedstocks in the acrylonitrile manufacturing process. They also produce other chemistry that is useful in the materials industry directly from their forest products waste. So, this is a great step forward in the development of an entirely plant based carbon fiber.
Finally, I want to thank a researcher in Slovenia – Dr. Davide Benedetto Tiz – for sending me an article about work that he and his colleagues are doing at the National Institute of Chemistry in Ljubljana, Slovenia. This group has been working on the chemistry of lignin from the perspective of what they call “Covalent Adaptable Network” polymers as a replacement for typical thermoset plastics like epoxies. The Wikipedia definition of a Covalent Adaptable Network is a type of polymer that closely resembles a thermoset that has dynamic covalent chemistry incorporated into the polymer. What this means is that some of the functional groups of these polymers (mostly epoxies since they are the most abundant thermosets) are replaced with groups that will respond to something like heat, light, or even catalysts by breaking the thermoset polymer chains. This makes them inherently recyclable because what happens is that the cross-linking bonds that made the epoxy hard in the first place are broken and you can potentially get back the resin that you started with.
These researchers have been able to create epoxies with a broad range of properties, from typical Bisphenol-A based mechanical properties to even fire resistant epoxies. As you can imagine, this is pretty exciting stuff when it comes to how we recycle and reuse carbon/epoxy composites in the future. The authors of this paper present it as such in their paper title – Lignin-Based Covalent Adaptable Network Polymers ─ When Bio-Based Thermosets Meet Recyclable by Design. All of the variants that they have produced are recyclable and reusable which makes this one of the first truly sustainable epoxy formulations.
I wanted to remind everyone that this is my last post for the calendar year 2023. I will come back with my first 2024 post the Monday after New Year’s Day. Taking a break for the Holidays. And finally, and as usual, I need to sign off with the fact that my book is out and ready for anyone to purchase. The best place to get one is to go to my website and buy one. I will send you a signed copy for the same price you would get charged on Amazon, except that I charge $8 shipping. Anyway, here’s the link to get your signed copy: https://www.nedpatton.com/product-page/the-string-and-glue-of-our-world-signed-copy. And as usual, here’s a picture of the book, for those of you just tuning in.
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