Lemon peels and flax fibers hold the key to eco-cars

Products of biological origin make cars more sustainable and environmentally friendly
(photo: CC0 Public Domain)

Helen Massey-Beresford

If you think of the automotive or construction industries, you’re unlikely to associate them with lemon peels, cornstarch, and almond shells. Yet manufacturers may increasingly rely on such raw materials as Europe looks for ways to reduce waste — both agricultural and plastic.

New high-performance industrial materials derived from agricultural waste have been created by the BARBARA project, which shows the way to boost innovation in the European bioeconomy.

Towards a circular economy

Funded by an EU-private sector partnership, the project uses agricultural residues, including lemon peels, cornstarch, almond shells and pomegranate peels, as additives for biopolymers that are found in living organisms, such as plants, and can be used in the production.

The result: prototypes of car parts and building formwork, made with the help of the specialized expertise in 3D printing of the Spanish Technology Center Aitiip.

“The most exciting thing from our point of view is that there are no residues, only resources,” says Berta Gonzavo, director of research at Aitiip, which coordinated the three-and-a-half-year project. “Parts for the automotive and construction industries have been successfully approved, showing that a circular economy is possible and contributing to reducing environmental impact.”

The EU is promoting the development of products derived from materials of biological origin, part of the drive to reduce not only waste but also carbon dioxide emissions and make industrial goods safer.

The EU’s bioeconomy has been growing for a decade, reaching €2.4 trillion in 2019 and with prospects for further growth, according to a study conducted in October 2022.

In confirmation of the high expectations for the biotechnology industries, in 2014 the EU created a joint venture with them for 3.7 billion euros, with the aim of stimulating scientific research in this area. In 2022, it was followed by a €2 billion initiative, whose participants range from farmers to scientists, and which aims to overcome technical, regulatory and market barriers to bio-based products.

Every year, the EU generates around 60 million tonnes of food waste and 26 million tonnes of plastic waste.

The production of materials for industry from renewable sources, including waste, is becoming increasingly important, and according to Gonzavo, projects like BARBARA are just the beginning.

When the BARBARA project began in 2017, there was only one biopolymer available for 3D printing. The project increased the number of bio-based materials using a combination of industrial biotechnology, nanotechnology and advanced manufacturing technologies.

New processes were discovered for the extraction and use of such compounds as natural dyes, fixatives for natural dyes, antimicrobial agents, and essential oils of pomegranate, lemon, almond shells, and corn.

Bring back the board

The BARBARA project created eight materials containing pomegranate and lemon pigments, pomegranate fixatives, lemon flavor and almond shells that could be used instead of existing plastics. The new materials led to different colors, scents, textures and antimicrobial properties.

The eleven partners also printed prototypes of door trims and dashboard panels for the automotive industry, as well as fasteners for the construction industry.

The new materials have better mechanical, thermal and even aesthetic properties.

Therefore, they can be used to improve the quality of the final material, even just by adding color or flavor.

Although the project has ended, the participants hope that the technologies can move to the demonstration stage in the next four to five years. This will show whether there are opportunities for large volume production.

With the global biopolymer industry growing by 6% per year and the European sector growing by 30% per year, Gonzavo says the EU is in an excellent position to take the lead.

“We are one step closer to the circular economy,” she says. “Waste can be a resource, not just waste.”

Substitutes for plastics

Regarding plastics, the research outlook also looks promising.

In 2020, only 14% of plastic waste in Europe was recycled in the EU according to the European Commission. The remaining 86% was incinerated, landfilled, dumped or exported, highlighting the need to create a more sustainable system.

With the expected increase in the production of plastics in the medium term, reducing their impact on the environment becomes even more important.

The ECOXY project, funded by the same public-private partnership as BARBARA, is looking at alternatives to bio-based plastics known as “fiber-reinforced thermoset composites,” or FRTCs.

Although these types of materials are light and strong, they do not have environmentally friendly characteristics. In addition to being derived from fossil fuels, they are not recyclable and are often made from toxic materials that include an endocrine-disrupting compound called bisphenol A.

“Fiber-reinforced composite materials are coming into use more and more, so these bio-based composite materials should be able to replace them in all the fields in which they are used,” says Arac Genua, a researcher at CIDETEC, the Spanish institute that coordinates the project ECOXY.

The three requirements

The project, which runs parallel to BARBARA, involves a consortium of 12 partners from industry and research sectors from across Europe.

As a starting point, they take materials that meet three requirements: they can be recycled, reshaped and repaired. Although already patented by CIDETEC, these materials have a drawback.

“We’ve made them more sustainable, but we’re still working with products derived from petroleum, and the most commonly used one is derived from bisphenol A,” Genoa says. “We had the opportunity to go one step further and make them more sustainable by using bio-waste to create a bio-based FRTC.”

The consortium studies lignin, which is derived from wood and plant fibers. It uses lignin bioresin with flax fiber as a reinforcing component to produce a demonstration product, in this case a car back seat panel.

“It was really good to be able to scale up and produce a demonstration product,” says Genoa. “We started with small amounts of materials and showed that they can be used on a medium scale.”

The real challenge was to make the characteristics of the new material comparable to those currently used.

Bioresins showed very good characteristics equal to those derived from fossil fuels according to Genoa. In terms of the strength of linen fibers, however, there is still much to be desired.

The future focus

Future research may include exploring the use of bio-based carbon fibers also derived from lignin.

“We will continue to work on developing and optimizing bioresins that meet all three requirements for different applications,” says Genoa.

The EU-funded BIO-UPTAKE project, for example, is working on the development of ceiling panels for construction.

“In these cases, not only linen, but also bio-based carbon fiber will be used,” says Genoa.

In the short term, the new materials are better for the health of the workers who come into contact with them during production.

In the long run, the environment will benefit in no small measure thanks to the resulting reduction in waste.

The research in this article was funded by the Biotechnology Industries Joint Undertaking (BBI JU), which in 2022 was succeeded by the Circular Biotechnology Europe Joint Undertaking (CBE JU). This article was first published inHorizonthe EU research and innovation journal.

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