Although attracted initially by environmental benefits, car makers and their suppliers are also asking what added functionality they can get from non-compostable, bio-based materials. One advantage is of course lighter, more cost-effective vehicles. A rule-of-thumb is that 5% less weight means average fuel savings of 3%, according to industry association Plastics Europe.
However, weight advantages are not assured. Some 'classic' bioplastics such as polylactic acid (PLA) have a higher density than their petroleum-based counterparts, the Belgium-based European Automobile Manufacturers' Association (ACEA) told European Plastics News.
ACEA said soy-based seat foams and upholstery can also be heavier. Ford and Fiat say soy-based seats in their vehicles weigh as much as if made with traditional materials. Natural fibre-reinforced plastic, on the other hand, offers 5% to 15% weight saving, depending on what it replaces.
Bioplastics are not as affected by oil price volatility as petroleum-based materials, an advantage over traditional plastics. "The importance [of bioplastics] will certainly continuously grow with crude oil shortage," said an ACEA spokesperson.
Still, environmental benefits remain important. "Plastics, regardless of the raw material used, are lightweight and cost-efficient materials," said Thomas Bauwens, a spokesman for Plastics Europe. "If, on top of this, bioplastics can further reduce the environmental burden...then car manufacturers will be interested in choosing bioplastics."
And manufacturers certainly interested are interested. Reduced dependence on volatile energy markets is one of the benefits of bioplastics, said John Viera, Ford Motor Company's director of sustainable business strategies.
Ford's use of soy-foam seat cushions has allowed its supply chain to reduce petroleum usage in production by more than 2,300 tonnes annually while lowering carbon dioxide emissions by some 9,000 tonnes, said Viera.
Where Ford cannot save weight through soy-based seats, it uses honeycomb-structured traditional plastics for a 20% weight reduction, which leads to better fuel economy and reduced carbon emissions. These foam seat backs and cushions with up to 24% renewable material appear in all Ford vehicles. Also, 75% of Ford vehicles produced annually contain soy-based foam in headrests, including the 2013 Fusion, F-150, Taurus, and Explorer.
The company is also researching natural fibres, such as rice hulls and coconut reinforcement, for moulded plastic parts. These would reduce petroleum use in manufacturing and make parts lighter and more natural-looking as the long fibres are visible in the plastic.
"The team is researching formulations using up to 30% natural fibres, which would typically replace talc or glass in traditional automotive plastic composite formulations," Viera said.
He hailed the 2010 Ford Flex for the first ever application of wheat straw-reinforced plastic, used for third-row interior storage bins, which offers annual savings of some 9 tonnes in petroleum.
Bioplastics feature in some Ford doors. A 50:50 polyethylene composite with fibre from kenaf, a tropical plant, is replacing oil-based materials for door bolsters in the new Escape. Lignotock - 15% phenol formaldehyde thermoset and 85% wood fibre - provides lighter, better sound-deadening than conventional glass-reinforced thermoplastics.
Toyota Motor Group, another car giant, has reduced CO2 emissions from parts manufacturing by 20% thanks to bioplastics, said its subsidiary Toyota Canada.
Carbon neutrality is achieved over the cycle from raw material to end-of-use, bioplastic car part. Living plants remove CO2 from air while expired parts are recycled in a thermal process re-releasing that CO2.
Toyota claims to have been the first to use sugar cane-based PET in vehicle liners and other interior surfaces. In North America, it combines PLA derived from sweet potato, corn, and sugar beet with other polymers.
Processing methods for bioplastic depend on the car part. For upholstery material on door and luggage area trims, PLA is mixed with PET. For injection moulded parts such as scuff plates and interior trims, finely ground PLA is dispersed in polypropylene (PP).
Many Toyota vehicles have soy-based seat cushions, including the Prius, Corolla, Matrix, RAV4, and Lexus RX 350. The Lexus HS 250 is packed with bio-based parts, including the luggage trim upholstery, cowl side trim, seat cushions, door scuff plate and tool box area. Toyota aims to have 20% of all plastic components in its vehicles made of bioplastics by 2015.
Italian car maker Fiat is also becoming a convert. A spokesperson for Centro Ricerche Fiat, its research company, said: "Use of bioplastics allows us to increase the ecofriendly profile of our products, assuring same or better performances, possibly at same costs."
The company has used castor oil-derived polyamides and soya-derived polyurethanes to replace their crude-oil-derived equivalents in more than one million vehicles and plans to continue this. For context, Fiat Group Automobiles shipped nearly 2.2 million vehicles world-wide in 2011.
Fiat cars for Brazil contain polyurethane seat foams with about 5% soy polyol. It is still seeking improvements; for example, the foam seats cannot contain more than 5% bio-based material or they lose performance in elasticity.
Fiat is also looking to increase the amount of bio-fillers it uses to reinforce some vehicles' plastics and elastomers. In 2011, its use of DuPont's castor oil-based Zytel RS polyamide 1010 in some fuel lines won the Automotive Innovation award in the environmental category from the United States and Europe-based Society of Plastics Engineers.
DuPont's technology and strategic partnerships to create novel methods of manufacturing high-performance materials from renewable resources have featured big name car manufacturers in recent years.
The company's Zytel RS line of bioplastics is a renewably sourced long chain of nylon products, between 60% and 100% bio-material, that can be adapted for temperature resistance. It also provides the Sorona EP line of 20-37% starch-based polymer resins as well as the Hytrel RS line of 20% and 60% non-food biomass based thermoplastic polyester elastomers. Toyota in Japan launched the Prius 'A' alpha car featuring Dupont's Sorona EP in the instrument-panel air-conditioning system outlet.
Japan-based Mazda claims two car industry firsts: a plant-derived content above 80%, for interior fittings in its Premacy Hydrogen RE Hybrid car; and a 100% plant-derived biofabric for seat covers.
US-based Johnson Controls will meanwhile provide Germany's BMW with door panels combining wood fibres and plastics making them 20% lighter than with traditional materials. These will feature in the new BMW 3 Series of cars, making them more fuel efficient.
Daimler, for the same reasons, mixes kenaf, flax, and sisal in plastics for its door linings. Mercedes-Benz's Biome concept car is envisaged as a vehicle that would be 'grown in a lab' from organic biofibres, stronger than steel but lighter than metal and compostable at the end of its life.
Bioplastics have not yet been used to make external car components. Price is one obstacle, because such external parts cannot yet be manufactured on the same scale as interior components, said John Williams, head of materials for energy and industry at the UK's non-profit National Non-Food Crops Centre (NNFCC).
"[Also] you have the requirements of strength that you don't necessarily have with bioplastics," said Frederic Scheer, CEO and chairman of Cereplast, a US and European based provider of starch-based resin pellets that can be processed in existing equipment to create bonding agents in car manufacturing.
Williams expects more durable bioplastics soon, though. "I've seen mainstream developments not yet launched where these things can be, ultimately, the outside panel," he said.
Williams also expects cost disparities between renewable and traditional plastics to decrease, spurred by continued development and, possibly, rising oil prices.
Thomas Bauwens at Plastics Europe predicts the market for fuel-efficient, lighter vehicles in general will grow as European car manufacturing recovers.
"With the present focus of the European automotive industry on 'green vehicles' the need for plastic materials in cars will probably grow," he added.
Cereplast likewise sees Europe as a growth market. Some 80% of its sales are in European continental markets where it continues to expand, with a new headquarters in Germany and a manufacturing plant in Italy purchased last year.
"We look at Europe as one of our top priorities for 2012, 2013, and going beyond," said Cereplast's Scheer. "Bioplastics will become so sophisticated that they will basically substitute plastics as we see it today."