Growing for a Drive: Researchers transform plant waste into carbon fibre for car parts

Researchers have found a way to transform plant waste left behind during industrial processes into carbon fibre that is strong enough to be used to make parts for cars or planes.

The plant waste, lignin, is left over in the form of a residue when plants and trees are used to make a variety of products, including paper and ethanol.

Conventionally it is considered a useless by-product, and often is burnt or finds its way to a landfill site, however scientists at Washington State University (WSU) have successfully developed a method to turn it into automobile-grade carbon fibre, giving it a valuable use.

“Lignin is a complex aromatic molecule that is mainly burned to make steam in a biorefinery plant, a relatively inefficient process that doesn’t create a lot of value,” said study lead investigator Dr Birgitte Ahring, a professor at The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, WSU.

“Finding better ways to use leftover lignin is really the driver here. We want to use biorefinery waste to create value. We want to use a low-value product to create a high-value product, which will make biorefineries sustainable.”

Lignin, the plant waste the researchers used, is left over from plants and trees used to make materials such as paper

The research, which is presented today at the 254th National Meeting & Exposition of the American Chemical Society, also presents a more affordable alternative to conventional carbon fibre, which is normally made from the expensive, non-renewable polymer polyarylonitrile (PAN).

“PAN can contribute about half of the total cost of making carbon fiber,” explained Dr Jinxue Jiang, a postdoctoral fellow in the Ahring laboratory at WSU. “Our idea is to reduce the cost for making carbon fiber by using renewable materials, like biorefinery lignin.”

However, while the lignin-based carbon fibre makes use of the previously ignored substance, it cannot be made entirely out of the waste material. Other researchers have attempted to make 100% lignin carbon fibre, but this is too weak to use in cars and planes.

As a result, this carbon fibre uses some PAN with the lignin to produce a strong yet affordable and more environmentally friendly product, finding that 20-30% lignin is acceptable before strength begins to reduce.

“We wanted to combine the high strength of PAN with the low cost of the lignin to produce an automobile-grade carbon fiber,” said Jiang.

The material could be used for a variety of car parts, including tyre frames

The researchers say their material could be used to make castings, tyre frames and internal car parts. However the next step will be to use it in a real-world setting within a car plant, in order to demonstrate its strength.

“If we can manage to get a fiber that can be used in the automobile industry, we will be in a good position to make biorefineries more economically viable, so they can sell what they usually would discard or burn,” said Ahring.

“And the products would be more sustainable and less expensive.”

Living artificial leaves: Solar panel-covered ‘cyborg’ bacteria to generate the renewable fuels of the future

Scientists have developed so-called ‘cyborg’ bacteria that mimic the natural photosynthesis of leaves to renewably generate food, fuels and plastics using only sunlight.

The bacteria, which are covered in minute semiconductors that serve as tiny solar panels, function in much the same way as natural leaves, but in a far more efficient manner.

“Rather than rely on inefficient chlorophyll to harvest sunlight, I’ve taught bacteria how to grow and cover their bodies with tiny semiconductor nanocrystals,” explained Dr Kelsey K Sakimoto, who undertook the research in Dr Peidong Yang’s lab at the University of California, Berkeley. “These nanocrystals are much more efficient than chlorophyll and can be grown at a fraction of the cost of manufactured solar panels.”

The research, which is being presented today at the 254th National Meeting & Exposition of the American Chemical Society has the potential to be developed into a valuable alternative to fossil fuels.

“Once covered with these tiny solar panels, the bacteria can synthesize food, fuels and plastics, all using solar energy,” said Sakimoto. “These bacteria outperform natural photosynthesis.”

The research involved taking a natural bacterium, Moorella thermoacetica, which is not conventionally capable of photosynthesis, and feeding it chemicals that it synthesised to augment its capabilities.

As the bacterium naturally produces acetic acid from CO₂, introducing other genetically engineered bacteria can enable it to produce fuels, polymers and even pharmaceuticals. In this case, Sakimoto fed it both cadmium and cysteine, an animo acid that contains sulphur, causing the bacteria to synthesis cadmium sulphide nanoparticles on its surface: the tiny solar panels that allow it to beat leaves in photosynthesising.

“The thrust of research in my lab is to essentially ‘supercharge’ nonphotosynthetic bacteria by providing them energy in the form of electrons from inorganic semiconductors, like cadmium sulfide, that are efficient light absorbers,” explained Dr Peidong Yang. “We are now looking for more benign light absorbers than cadmium sulfide to provide bacteria with energy from light.”

Image courtesy of Kelsey K Sakimoto

While the bacteria has only been developed in a lab setting, with an 80% efficiency, if it can be developed into a commercial product, it has the potential to be a hugely impactful technology in the transition away from fossil fuels.

“Synthetic biology and the ability to expand the product scope of CO₂ reduction will be crucial to poising this technology as a replacement, or one of many replacements, for the petrochemical industry,” said Sakimoto.

Other research has been previously undertaken to produce artificial leaves, which many hope could be used to form future decentralised power plants, however this research offers a significant improvement that could give it a much higher chance of being commercialised.

“Many current systems in artificial photosynthesis require solid electrodes, which is a huge cost,” explained Sakimoto. “Our algal biofuels are much more attractive, as the whole CO₂-to-chemical apparatus is self-contained and only requires a big vat out in the sun.”