Hemp, Flax Growing as Auto Plastics Building Blocks

OTTAWA – Auto-components researchers are developing the use of grasses such as hemp or flax to make tough but lightweight bioplastics that also help reduce a vehicle’s carbon footprint by using a renewable resource.

A key innovator is Bruce Dietzen, president of Renew Design, a Florida-based company that produces custom-ordered cars whose body parts are made from processing the outer stalk of hemp plants through combining it with a synthetic resin and placed in a mold.

“All the body panels are made of a woven hemp material which, since the 1950s, has been well understood to provide additional strength latitudinally and longitudinally as opposed to traditional materials like plastic, fiberglass or metal,” he explains.

Entry-level models of the car start at $40,000 and can reach $200,000 for a 525-hp motor, depending on the amount of power the customer wants. It also can be customized to work with an electric drivetrain and battery or biofuel, something Dietzen encourages.

He calls hemp the ideal material to use, saying car panels made of hemp are 10 times more dent-resistant than steel. It also is one of the strongest and most versatile fibers in nature and is carbon-negative, producing no carbon footprint due to its ability to absorb and store carbon while growing.

In the U.K., Kerry Kirwan, a professor at the University of Warwick’s manufacturing group, also has been developing sustainable and natural components for vehicles. His team first created the unwieldy-named “World F3rst Formula 3” racing car in 2009, which replaced traditional oil-based polymer parts with components such as bumpers and exterior trims made from natural and sustainable polymers. The car also can run on biodiesel manufactured from waste streams, such as cooking oil and chocolate.

“For the parts of the vehicle, we used a lot of natural fibers such as hemp and flax and recycled fibers, as well as biodegradable polymers such as polylactic acid, recycled polymers and biopolymers,” Kirwan says.

But he stresses using natural materials doesn’t necessarily mean something is more environmentally friendly.

“Not all polymers that come from natural sources are biodegradable, and not all fossil fuel-based polymers are not biodegradable,” he says. “It’s more complex than that. There’s actually biodegradable and not-biodegradable materials from both sources.”

Meant for Recycling, Destined for Incineration

However, the market for biodegradable car-component materials remains small because of how the car-disposal system actually works.

“Although decomposition is theoretically a great way to get rid of a part at the end of its life, which is generally what this research is all about, there’s no real mechanism for actually doing that,” Kirwan says.

“When a car is stripped, the material – plastic or metal – is either recycled or, more often than not, burned. While bio-based materials burn better, ultimately it doesn’t matter if it’s biodegradable or not, because it’s most likely just going to be incinerated.”

He sees natural fibers making headway in the automotive industry as part of polymer composites used in parts for door frames and underpanels because of their lightness, which can improve energy efficiency.

The idea of using grasses to make bioplastics that can be manufactured into car parts and components has a long history.

Henry Ford was a pioneer in developing auto-parts bioplastics, famously introducing the concept in 1940, when he used a sledgehammer to hit the hood of a car trunk made from a soybean-based material to demonstrate its strength.

More than 75 years later, Ford continues to innovate by tapping the strength of grass-based sourcing materials. Bioplastics containing 50% flax fiber is used in the armrest of the Ford B-Max in Europe, while the average Ford vehicle uses 20-40 lbs. (9-18 kg) of flax and other renewable materials, says Debbie Mielewski, senior technical leader of materials sustainability at Ford.

“In addition to flax, almost 300 parts used across Ford’s vehicles are derived from sources such as soybeans, cotton, wood, jute and natural rubber,” she tells WardsAuto.

“Since 2000, we are continuing to search for innovative and creative renewable material technologies that can reduce our dependence on petroleum, create new markets for agricultural products and generate additional revenue streams for farmers.”

Stronger Than Steel

Researchers in Australia have been experimenting with using hemp fiber for auto parts since 2000. A team led by Alan Crosky at the School of Material Science and Engineering at the University of New South Wales has developed tough material from hemp fibers that have a higher strength-to-weight ratio than steel.

A statement from the school about Crosky’s team and its work hails hemp fiber as a reinforcement and alternative to synthetic fibers such as glass. “The fibers are a renewable source, making natural fiber composites particularly attractive from an environmental standpoint,” the statement says.

On the other hand, there are ongoing challenges to be met. In addition to the inevitable quality and safety testing accompanying the introduction of any new material, research is being conducted into ways of evenly dispersing natural fibers to maximize strength and methods needed to control the molding process to ensure the fibers are not thermally degraded.

“Lastly, we need to ensure that the inclusion of the natural materials does not impart odor in the vehicle,” Ford’s Mielewski says.

Looking ahead, she expects to see the “more and more sustainable materials used not only in cars but in many other industries as well.”

Flax and similar natural materials “are lighter in weight, utilize waste products that would otherwise go to landfill or be burned, generate new material choices and, best of all, are better for our planet,” she notes. “Why wouldn’t we do this?”

-  with Ed Zwirn in New York and Barbara Barkhausen in Sydney