Composites recycling is gaining traction

Carbon fibers recovered from pyrolysis at ELG Carbon Fibre Ltd. are loaded into a chopping machine.

A key question facing the composites industry — What happens to manufacturing waste and end-of-life parts? — has been silently swept under the rug for years as companies resigned themselves to paying for landfill disposal while metals suppliers touted recyclability to industry. But at least three marketplace realities have converged to drive the growth of composites material recycling, particularly reclamation of carbon fiber:

• First, the European Union’s end-of-life-vehicle (ELV) directive requires that 85%, by weight, of the materials used in a car or light truck must be reusable or recyclable.
• Second, carbon fiber’s high manufacturing cost and high performance, even in chopped form, make it an attractive recycling target, which is creating market pull for recycled fiber products, most notably, from automotive.
• Finally, the newest generations of consumers were raised on environmental awareness, actively support recycling activities and closed-loop manufacturing, and seek out goods with recycled content.

Although CW’s coverage of composites recycling dates back over a decade, informal statistics still show that only ~2% of composites-related companies are active recyclers. That said, three years since our most recent feature on the subject, there is demonstrably greater interest and activity, and real applications of recycled fiber are growing. This blog summarizes the upcoming article which will appear in print in the July issue of CompositesWorld magazine.

The technologies: different approaches

One reason aluminum and steel remain formidable competitors to composites is their suppliers’ long track records in recycling, which has helped reduce their overall material production costs, says Ed Pilpel, senior technical advisor at Polyone Advanced Composites (Englewood, CO, US) and the current recycling committee chairman at the American Composites Manufacturers Assn. (ACMA, Arlington, VA, US). “But it took those industries 30-50 years to achieve their current success rate at recycling, which for aluminum is upward of 80%. The composites industry is much younger, and we have years to go,” he admits, “but we’ve got to jump into the deep end of the pool and get going.”

Those who have jumped in are employing several recycling strategies, separately or in combination. Most initial efforts have focused on reclamation and reuse of high-quality carbon fiber material waste streams, typically from aerospace manufacturing, because they are relatively easy to work with and yield high-quality carbon fibers with properties virtually undiminished, albeit in chopped form (continuous fiber can also be recovered, discussed below). Waste sources include off-spec material, cutting/trimming/kitting scraps (dry and prepreg) and bobbin ends, including thermoset and thermoplastic materials.

Current commercial methods for eliminating the resin from the carbon fibers are pyrolysis (thermal treatment) and solvolysis (chemical treatment). Although pyrolysis requires thermal energy to burn off the resin, and can cause fibers to char, the energy of pyrolysis represents only a fraction of the embodied energy of virgin carbon fiber. Some sources say solvolysis requires even more energy than thermal treatment, but it enables recovery of fiber and resin. In both processes, the recovered fibers transfer well to nonwoven mats or thermoplastic pellets for injection molding, and are a natural fit for automotive part applications.

More difficult is recycling of end-of-life (EOL) cured parts to complete a true “closed-loop” situation, where materials are recovered from scrapped products and reused in new iterations of those products. Pyrolysis and solvolysis can be applied to cured parts, as can mechanical crushing, typically used for fiberglass parts; the resulting crushed glass/resin material is either reused as a resin filler, burned for energy (waste to energy plants) or co-processed in cement kilns.

Alternatively, two companies offer recyclable resin products that can be un-crosslinked in a chemical solution that leaves the original fiber reinforcements intact (more on that below) for closed loop recycling in some sporting goods applications. And, a number of materials suppliers are investigating in-house, closed-loop recycling of scrap and parts, avoiding a recycling middleman.

Companies and groups included

 “Three years ago, it was a real push to get these materials out into the market. Now, there’s more ‘pull’ and we’re getting more inquiries on how to use recycled carbon. We are now designing products and developing them to meet specific customer requirements,” states Frazer Barnes, managing director at ELG Carbon Fibre Ltd. (ELG CF, Coseley, West Midlands, UK), a subsidiary of German metals recycler ELG Haniel (Duisburg, Germany). ELG CF processes more than 2,000 MT of waste material per year in its patented pyrolysis process, including manufacturing waste and cured parts.

In the US, Carbon Conversions (Lake City, SC, US) employs pyrolysis and can process “the entire composites waste stream,” claims Keith Graham, Carbon Conversions’ VP of business development. That includes continuous tow from various markets, intermediates — dry fiber waste (from fabrics, trimming, braiding) and “wet” uncured prepreg and pultrusion waste — and end-of-life parts from commercial aerospace, recreational and industrial sources. “We’ve built a robust business to take any industry’s waste stream and convert it into any one of our many products,” adds Graham. Hexcel (Stamford, CT, US) recently purchased a minority stake in the company. The company has successfully demonstrated automotive parts, including a floorboard part for an automotive OEM. Graham notes that Carbon Conversions will push the envelope to advance composites recycling: “We’re all in this together, and we need to produce repeatable, consistent quality materials to grow this industry.”

CFK Valley Recycling (Wischhafen, Germany), part of the Karl Meyer Group, is Europe’s largest composites recycler using pyrolysis, and takes in waste streams from automotive, aerospace and end-of-life sporting goods, says Tim Rademacker, a managing director at the company: “Due to the increasing use of wind turbine blades made with carbon fiber, the quantity of waste from the wind industry has risen significantly.”With a 1,000 MT per annum yield of recycled fibers, CFK Valley Recycling’s partner company within Karl Meyer AG, CarboNXT (Wischhafen, Germany), distributes the recovered fiber as chopped and milled products as well as wet-laid veils and air-laid nonwoven mats. Rademacker reports that milled recycled carbon fiber is used as a filler in polyurethane (PU) rear and front bumpers on the new Mercedes AMG GTC roadster.

Pilpel describes the ACMA’s ongoing collaboration with IACMI (Institute for Advanced Composites Manufacturing Innovation, Knoxville, TN, US) to bring a new thermal recycling solution to market: The trademarked Thermolyzer technology, from CHZ Technologies (a subsidiary of Aliquippa Holdings LLC, Austintown, OH, US), is a waste-to-energy reactor system, developed and originally envisioned in Germany to recycle discarded nylon carpeting. Thermolyzer processes shredded cured-part end-of-life waste — wind turbine blades, for example — and recovers all by-products by means of multiple reactors. Says Pilpel, “This technology creates a clean-fuel gas product from the resin residue that meets natural gas specifications, and it generates no harmful emissions, thanks to inline scrubbers.” With a long list of composites industry and wind energy partners, including Owens Corning (OC, Toledo, OH, US), ACMA and IACMI are evaluating a pilot process in Germany as a first phase, to prove the system and determine scalability, says OC’s Dave Hartman. See the Thermolyzer video here:

Adherent Technologies Inc. (ATI, Albuquerque, NM, US) started its recycling business at least 20 years ago. Company president Dr. Ron Allred and Dr. Jan-Michael Gosau, engineering and environmental project manager, chose a wet chemistry process they call chemolysis, also referred to as tertiary treatment, that uses a liquid transfer fluid and catalyst combined with low heat and pressure to recycle end-of-life parts and recover both carbon fibers as well as resin, without generating airborne emissions. The recovered resin can be reused as fuel or as process chemicals in other industries. ATI has recently formed a partnership with investment group DLC Capital (Melbourne, VC, Australia), owned by Damian Cessario, to commercialize the recycling technology. DLC Capital and ATI have collaborated for years and have now formed a composites company, V Carbon (London, UK), which will reclaim carbon fiber and then use the fibers to manufacture parts within the group.

A new entrant to the recycling community is Vartega (Golden, CO, US), headed by Andrew Maxey, an engineer whose interest in carbon fiber came from cycling: “We’re the new kids on the block, but things are accelerating and the opportunities for recycling are growing.” Vartega currently has a pilot-scale, proprietary and patent-pending low-energy solvolysis process, which treats uncured prepreg and towpreg scrap, from sources including Alchemy Bicycle Co. (Denver, CO, US). The company is developing a path whereby Vartega would eventually provide its process technology to licensees, who would lease modular equipment for in-house, closed-loop recycling on a regional basis, because, says Maxey, “It’s expensive to ship waste!” For now, Vartega is working with Technical Fibre Products (TFP, Schenectady, NY, US), which converts the recovered fibers (some of them continuous, from towpreg process waste), all with known pedigree and source, into nonwoven mat and veil products. The company has released testing data on its recovered fiber (see Learn More), where the tensile strength and modulus of recovered fiber are comparable to virgin fiber controls.

 “We’re an atypical company,” states CEO Bob Larsen of Composite Recycling Technology Center (CRTC, Port Angeles, WA, US). “We’re a nonprofit, and our mission is to inspire, grow and lead the recycling community.” Located in a region of concentrated composites manufacturing, in proximity to Boeing and many Boeing Tier companies Larsen says CRTC wants to drive economic redevelopment and help reduce Port Angeles’ unemployment, while modeling wise use of resources. CRTC combines recycled carbon fiber product development with production processes for high-volume, low-cost production. The company is co-located with Peninsula College and that school’s Composite Work Force Training program, to train future employees for planned growth. CRTC purchases “near first-quality” uncured aerospace prepreg scrap at a nominal rate from partner companies, including Toray Composites (America) Inc. (Tacoma, WA, US), and transforms it to make new, non-aerospace products, such as pickleball paddles. It has no plans to recycle cured composite parts: “We’re taking advantage of the chemistry that’s already there,” says Larsen. “We’re avoiding the need to add energy and cost to the material — carbon fiber already has more than twice the embodied energy of aluminum!”

Procotex oversized precision carbon fibers

Procotex (Dottignies, Belgium, a subsidiary of Dolintex NV) is another company that recycles only unprocessed fiber waste — primarily from weaving and cutting scraps, waste from carbon fiber producers, and, for now, only dry fibers. Begun in 1965, Procotex was originally a flax fiber processor, and in time began to recycle natural and synthetic fibers. The company entered the technical fiber space in 2011, when it acquired Apply Carbon SA (Lacuidic, France), an established specialist in the milling and precision cutting of carbon fiber, aramid and other technical fibers including basalt used in composites. Bruno Douchy, sales director at Procotex, says that the company recycles more than 1000 tonnes of carbon fiber waste per annum, to produce milled and chopped carbon. To address the issue of dust emitted from milled carbon, Procotex has developed a new milled carbon fiber in granulate form, which allows better dosing/dispersion into the extruder, without conductive dust, says Douchy. Other products include cut carbon fibers from 30ɲm to 120mm in length, with fiber quality comparable to virgin fiber; and new, oversized precision chopped or random cut carbon fibers, offered with sizings compatible with a number of matrices, that are designed to stay in bundle form for better dosing and dispersion. Says Douchy, “Recycled carbon fibers are attractive to the automotive industry, because good properties can be achieved at a much lower price. A challenge for auto industry projects is maintaining stable supply and quality. For this reason, we keep on hand a large stock of unprocessed material.” In addition to its technical fibers, says Douchy, Procotex processes 20,000 metric tonnes of recycled natural fibers, such as flax, and synthetic fibers including polypropylene — much of it from the carpet industry — and aramid. “We’re involved in the automotive, geotextile, compounding and concrete markets, and many more,” states Douchy. “We’re one of the biggest players with real industrial project experience in fiber recycling.”                                      

Adesso Advanced Materials (Wuhu, China; Cambridge, UK and Princeton, NJ, US) and Connora Technologies (Hayward, CA, US) are approaching recycling from the flip side: Through a strategic partnership, they have developed recyclable thermoset resins that, post cure, can be readily degraded and removed from the reinforcement, leaving fibers intact for reuse. Bo Liang, Adesso’s chairman and CEO, says its trademarked Cleavamine hardener and Recycloset resin enable the crosslinks in the cured part to be “cleaved” by a mild acid solution, such as vinegar. The recovered resin is neutralized and the thermoplastic precipitate can be reused as a toughening agent in adhesives or molding compounds, Adesso is currently involved in several major programs, including recyclable printed circuit boards (PCBs) for Shengyi Technology; a production carbon fiber bicycle by Pardus (a Taishan Sports brand, San Mateo, CA, US); automotive parts for Wuhu-based Chery Automobile Co. Ltd., in partnership with ELG CF; and research on recyclable wind blades, in cooperation with the University of Southern California. In a similar vein, Connora Technologies’ trademarked Recyclamine product is a hardener for epoxy resins that likewise enables polymer crosslinks in cured composites to be broken by an acid, leaving a thermoplastic epoxy residue. The reinforcing fibers originally used in the composite part can be recovered without chopping or shredding, in their original form and architecture, without damage. CW has written about Recyclamine’s use in a high-pressure resin transfer molding (HP-RTM) process (http://www.compositesworld.com/blog/post/recyclable-epoxy-proven-in-hp-rtm) in cooperation with Fraunhofer Project Center for Composites Research (FPC, London, Ontario, Canada) and Fraunhofer ICT (Pfinztal, Germany). The study showed that, after recycling, the properties of recovered reinforcements were the same as virgin carbon fiber. The company is continuing work on HP-RTM for the automotive industry via a Phase II SBIR project. More recently, Connora Technologies announced partnerships with Shred Optics (a company of Anomaly Action Sports USA, New Boston, NH, US), Future Fins (Huntington Beach, CA, US) and snowboard makers including Burton Snowboards (Burlington, VT, US), Niche Snowboards (Salt Lake City, UT, US) and The CAPiTA Mothership (Gail, Austria) to turn snowboard manufacturing waste into action sports accessories, says Connora CEO Dr. Rey Banatao.

Developing a business case

“Composites recycling efforts are a puzzle right now, with lots of pieces that include technology, government and industry groups, standards and education,” says Pilpel. “You have to start with a basic business case.” For example, a company’s simplest step is to convert its waste to energy at the plant site, avoiding the cost of landfill disposal and recouping a small portion of the original material cost. Greater return on material cost can be gained if waste can be converted to new, useable forms for sale, or returned internally to a company’s process: “We need to find the hidden applications for recycled material,” he adds, pointing to the success of used auto tire recycling in the US, where uses of shredded tire waste were eventually found, to keep tires out of landfills.

Clearly, if automotive manufacturers do adopt carbon fiber in production vehicles in a big way, supply challenges will follow. High-value recycled carbon fibers can help bridge the supply gap, at a lower price point. ACMA’s Recycling Committee is working with ISRI (Institute of Scrap Recycling Industries, Washington, DC, US) as well as IACMI to develop a recycling infrastructure with reliable logistics, and to develop standards for recycled fibers. The looming question is the far greater quantity of glass fiber parts that could, and should, be recycled — at this point, however, the lower value of glass makes it more difficult to address, says Pilpel.

“There’s no silver bullet, because composites are complicated structures. But we’re on the road to understanding this and getting the industry talking logically. It’s an exciting time, because a recycling infrastructure is growing,” says Vartega’s Maxey. Adds ELG CF’s Barnes, “The situation is getting better — by 2019, I think composites recyclers will start to see real volumes.”

For a great resource on recycling of composites, be sure to check out Composite UK's report "Composites Recycling - Where are we now?" found here: https://compositesuk.co.uk/industry-support/environmental/composites-recycling-report.