Making a Car With Potatoes

This is not an advertisement for a Formula 3 race car sponsored by a grocery store. Rather, those vegetables are amount the materials that are used in the production of that car. The work was performed by Kerry Kirwan and a team at the Warwick University Manufacturing Research Group, Sustainable Materials and Manufacturing. Potatoes for the body panels and carrots for the steering wheel—and a top speed of 125 mph.

The instrument panel for the BMW i3 plug-in hybrid features unpainted eucalyptus wood trim.

It is hard to imagine that the fabric used for these seats were once things like soda bottles, but Ford is using REPREVE on several of its models, and the material is a family of polyester and nylon fibers from recycled polyethylene terephthalate (PET) bottles.

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Things you may very well find in your next car: Steel, aluminum, chrome, hemp, orange peels, recycled plastic bottles, flaxseed and perhaps a dash of reclaimed timber.

Things you might find in the vehicle you get after that one: an instrument panel that could be composted instead of shredded and seat cushions made with waste CO₂ that makes those captains’ chairs in your minivan something closer to carbon neutral. 

A confluence of factors including enhanced performance benefits, lower technology barriers, green image-making and consumer interest (if not outright demand) are contributing to a surge of interior trim and functional part alternatives to petroleum-based polymers. Biocomposites (often natural fibers blended with traditional polymers), recycled post-consumer waste product materials and “grown” substitutes are finding their way into more vehicle programs. Economies of scale are increasing, albeit slowly, for biocomposites and recycled goods as well, moving from the premium to the affordable vehicle ranges. The trend, pushed in large part by OEMs, is creating some strange bedfellows between auto suppliers and nontraditional Tier 3 companies, some of which are developing automotive materials for the first time.

Biocomposites are nothing new to the industry. Henry Ford famously used them in enamels, paints and molded plastic parts. In 1941, Ford unveiled a demonstration car with soy-based plastic body panels. But biocomposites have remained typically hidden from the consumer’s view by their discrete placement in door liners and undertrays. But that’s changing, especially as eco-aware increasingly translates to premium trims. 

BMW’s 2017 i3 plug-in hybrid is a prime example. The vehicle literally places its eucalyptus wood fiber front and center on its dashboard as a lid for the glove box. According to the automaker, the wood is mainly grown in Europe and comes from “100 percent certified, responsible forestry management." No paint, no dye and no bleach products have prettied it up. There’s also liberal use of kenaf, of the hibiscus family, for large portions of the instrument and door trim panels; it’s spread across large surfaces within the i3, interwoven with naturally tanned leather. (The inner lining of the trunk lid and parts of the door trim in the 2016 BMW 7 Series also are made from kenaf).

The drive toward lightweighting vehicles also plays to the strengths of biocomposites, as natural fibers are essentially hollow and can be as much as 20 to 40 percent lighter, depending on the application. Natural fibers also have sound-deadening advantages and essentially act as humidity regulators. They absorb moisture during high humidity and release it in more arid conditions. Those qualities make natural fibers, especially hemp, popular as a filler material for insulation in large buildings.

The global natural fiber composites market is forecast to grow at a compounded annual rate of 8.2 percent from 2015 to 2020. This is driven, in large part, by the construction and automotive industries. Some notable advances and program developments that may be fueling that growth in years to come: 

  • In 2013 French supplier Faurecia SA created bio-injection molded structural parts, using its NAFILean (Natural Fibers for Lean Injection Design) process to produce door panel inserts for the Peugeot 308. The same year, it supplied panel inserts made of compressed spruce wood for Mercedes-Benz S-Class. Using that material, called LignoLite, Faurecia shaped portions of the vehicle’s instrument panel with weight savings of 45 percent, according to the company. In 2014, Faurecia premiered a BioMat plastic, a hemp/resin matrix containing 65 percent bio-based resin, which it will offer in 2018 for 2020 model year vehicles. And in 2018, Faurecia says it will offer BioMat made with 100 percent resin from agricultural waste. 
  • Toyota has been using bio-based plastics for more than a decade. They’re found in the seat cushions in the Toyota Prius, Corolla, Matrix and RAV4, and in the Lexus RX 350 and CT 200h. The company says it is assessing several bio-materials to determine if they’re good fits for global production, while meeting safety and performance standards. But the company is hoping to have more influence beyond its fleet. Toyota is working with SAE’s International Green Technology Systems Group to characterize and classify bio-based materials. 
  • Ford lays claim to being the first automaker to introduce soy-based foam in seat cushions and seat backs in 2007. Ford says soy foam is now in every vehicle it sells in North America. 
  • In 2014, timber giant Weyerhaeuser teamed up with Johnson Controls to create a tree-based alternative to fiberglass in the floor console armrest substrate for the Lincoln MKX. The collaboration was significant for two reasons. First, Weyerhaeuser’s Cellulose Reinforced Polypropylene, sold under the name THRIVE, is 6 percent lighter than fiberglass, according to the companies. The fiberglass part replaced with the timber substrate is used as a structural piece located within the center console armrest. If the technology can be transferred to larger parts, that means larger weight decreases. Secondly, unlike soy-based foam, CRP’s applications apply to exterior as well as interior uses, including under the hood in places requiring blow molded shapes, such as battery trays.

The Potential 
Seven years ago, Kerry Kirwan, head of Sustainable Materials and Manufacturing at the Warwick University Manufacturing Research Group, lead a team of researchers that created a Formula 3 racing car with non-traditional materials: body panels composed of potatoes; fueled with waste chocolate, beef fat and cheese factory residue; and a steering wheel made of carrots. Despite the veritable bounty on board, the car reached 125 mph.

That demonstration vehicle, which was 95 percent biodegradable, captured headlines and interest for what biomaterials could do in a punishing racetrack environment. However, today Kirwan is realistic about the feasibility of biomaterials in the mass market, particularly when it comes to their biodegradability. In other words, don’t expect to see compostable cars any time soon. 

“The truth of the matter is most cars will end up being shredded and there will be a mechanical recovery of metals through recycling, and then a lot of polymer stuff will be burned,” Kirwan comments. “Biodegradability doesn’t really come into it, because it just adds another layer of complexity. With biodegradable polymers, a lot of the challenge is to not inhibit or damage the existing recycling stream, because if you bring a biodegradable polymer into it, that can cause problems.”

And, that’s another of the attributes of biomaterials–one that doesn’t appear in the automotive marketing materials: They burn easily. Flammability over glass-fiber polymers is a feature, not a bug, when it comes to using hemp-filled, wood-filled, flax-filled or other composites. 

Nagging issues of scale and material consistency remain inhibitors to growth as well, Kirwan says. Production of natural materials are more susceptible to things like weather patterns impacting how crops are grown and harvested. Biodegradable thermoplastic polymers, such as polylactide (PLA) may forsake petroleum-based origins, but PLA still requires corn starch, sugarcane or other food-based feedstocks. The supply chains that enable synthetics like polypropylene and polyamide materials, for instance, are far more established and more stable. Add relatively cheap petroleum, and therefore relatively cheap petroleum-based polymers to the mix and the challenges to natural fibers really add up.

“If car manufacturers decided tomorrow it wanted a million tons of PLA for the umpteenth-million cars they wanted to produce, that would cause a massive potential issue,” Kirwan points out. “The focus needs to be second-generation feedstocks, waste feedstocks, to derive these polymers.”

Many suppliers are mindful of the food-versus-fuel debates of a few years ago that are inherent in biofuels like ethanol, and have focused on waste inputs like orange peels and coconut husks instead. But those feedstocks only go so far. 

Kirwan today is focusing on a new sustainable luxury project. Warwick researchers are considering what consumers truly comprehend as a luxurious material and how those expectations could be met with natural materials. For instance, consumers may want to see shiny carbon fiber, but can something be printed to look like carbon fiber? 

“It’s a more complex thing than just the performance. We’re trying to understand different material characteristics to human perception,” Kirwan says. “‘What is a luxurious material? What are its characteristics and how can manufacturers replace that with natural or recycled materials?’” 

The Ultimate Closed Loop
Beyond matters of what can be grown, the environmental trump card can be found in the closed loop of using strictly waste products. 

Ford is partnering with aluminum suppliers to recycle post-industrial waste from the aluminum used in the 2015 Ford F-150 into new aluminum that can then be reused for new vehicles. The same can be said of the seat fabric supplier for the F-150, Unifi (unifi.com), which makes the REPREVE family of polyester and nylon fibers formed through recycled polyethylene terephthalate (PET) bottles. The seat fabric is now found in several Ford vehicles. Ford estimates five-million plastic bottles, otherwise bound for landfills, will be reused to adorn the seats in the current generation F-150. 

Dearborn recently announced it’s working with alternative polymers firm Novomer (novomer.com) to develop and test materials derived, in large part, from the Holy Grail of waste materials: CO₂ itself. Novomer has created moldable foam, which goes by the tradename “Converge,” that harnesses carbon dioxide—as in the kind that carbonates soft drinks. Having shown promise in automotive testing, the company is now in talks with Tier 1 seating suppliers around its first would-be automotive product. Novomer sees potential in both hard- and soft-touch materials including seat backs, side panels and consoles, as well as floor mats and seat cushions. 

By weight, the material is made of 57 percent propylene oxide and 43 percent CO₂. By adding a proprietary catalyst and pressurizing the mixture, the reaction creates enough heat to create a polymer without any additional heat required. Stored in tanks, Converge has a shelf life of about a year. Once the supplier is ready to use it, an isocyanate is applied and the polymer may be fashioned into a mold. 

“If a company wants to substitute our polyols for the ones they’re using today, they will require different catalysts,” says Peter Shepard, Novomer’s chief business officer. “The recipe is different because it behaves differently than what is in use today, but doesn’t add costs.” 

Some 3.5 cubic pounds of CO₂ is produced for every pound of petroleum-based polymer, while Novomer’s foam creates one-third of that greenhouse gas material, Shepard says. The low carbon content similarly means it is less flammable than conventional materials, a plus for seat manufacturers.