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R&D efforts and partnerships are keeping pace with the clamour for renewable-sourced rubber for tyres, says Angelica Buan in this report.
From guayule to soy beans
Increasing environmental and energy concerns are prompting tyre makers to partner with materials science experts in discovering the alchemy of biobased rubber alternatives.
Perhaps the most prominent and much anticipated green rubber breakthrough is that of the desert shrub guayule rubber. The high-yield renewable feedstock is expected to unchain the industry from the supply and price volatility of Hevea-sourced natural rubbers.
The five-year US$6.9 million-Biomass Research and Development Initiative (BRDI) grant for guayule rubber research has been completed. The study consortium led by Cooper Tire & Rubber and partners (Clemson University, Cornell University, PanAridus and the Agricultural Research Service – USDA) has announced that the 100% guayule-based concept tyres have “overall performance at least equal to tyres made with Hevea and synthetic rubber.”
Performance is only half the good news. The guayule rubber tyre is environmentally-friendly too. It has been found to chalk up between 6% to 30% lower emissions in ten different life cycle environmental and energy impact categories, compared with a conventional tyre.
For Goodyear Tire & Rubber Company, soybeans are magic seeds for its new rubber tyres. With support from the Missouri-based farmers-producers organisation, the United Soybean Board (USB), the US tyre maker created a tread compound, or formulation, using soybean oil, which is naturally derived, cost-effective, carbon-neutral and renewable. The soybean oil in tyres enables Goodyear to keep the rubber compound pliable in changing temperatures – such as in dry, wet and winter conditions – a key performance achievement in maintaining and enhancing the vehicle’s grip on the road surface.
Goodyear’s tests have shown rubber made with soybean oil mixes more easily in the silica-reinforced compounds used in manufacturing certain tyres. This also improves manufacturing efficiency and reduces energy consumption.
USB shared in an earlier report that soybean oil in tyres can potentially increase tread life by 10% while reducing the use of petroleum-based oil. Moreover, rubber compounds made with soybean oil blend more easily with the silica used in building tyres, thus helping to improve plant efficiency and reduce energy consumption and greenhouse gas emissions.
In 2012, Japanese tyre maker Bridgestone also unrolled its Firebrand concept tyre containing 10% or almost 41 l of soybean oil. It explained that one bushel, or an equivalent of 35 kg, of soybeans yields almost 5 l of soy oil.
It can be recalled that Goodyear also incorporated other biobased materials into its tyres. In 2015, the Ohiobased company forged a supply agreement with Yihai Food and Oil Industry in China for silica derived from rice husk ash, for use in a consumer tyre it produces and sells in China.
Green tyres take a leap forward
Back in 2013, guayule was also the centrepiece of a biobased rubber project led by Italy-headquartered Versalis, the chemicals subsidiary of ENI, and US-based Yulex, a company producing agriculture-based biomaterials. Both companies were exploring guayule for consumer, medical and industrial applications, with Versalis constructing an industrial production complex in Southern Europe. Based on the partnership with Yulex, Versalis also went on to sign an agreement with Italian tyre maker Pirelli for a joint research project on the use of guayule in the production of tyres.
Another partnership was forged by Versalis two years after with Ecombine Advanced Materials and EVE Rubber Institute, both companies are under Chinese rubber and tyre machinery company Mesnac, to develop a technology for green tyres.
The partnership integrates Versalis’s elastomers technologies with EVE’s Advanced Technology for Compound Manufacturing (ATCM) for the production of advanced elastomer compounds that possess enhanced mechanical performances and environment-friendly features.
Bio-based butadiene a success
Meanwhile, Versalis has also achieved a new milestone with US technology firm Genomatica having successfully advanced to pilot-scale production, of bio-butadiene (bio-BDE) from fully renewable feedstock.
The project started with the establishment of a technology joint venture between both the firms in 2013. The joint venture – with Versalis having the majority stake – has developed a complete process to make bio- BDE and plans to license the resulting technology.
Versalis and Genomatica together determined that 1.3-butanediol (1.3-BDO) was the most suitable intermediate to produce bio-BDE.
Genomatica applied its ‘whole-process’ systems approach to bioengineering to develop a microorganism that produces 1.3-BDO in a way that enables cost-efficient, scalable fermentation, recovery and subsequent process operations. Versalis leverages its industrial process engineering and catalysis capabilities, plus expertise in overall polymer production, to purify the 1.3-BDO, dehydrate it and then purify the resulting butadiene.
Versalis said it produced several kg of butadiene from 1.3-BDO made in 200 l fermenters at its research centre at Novara and Mantova, and then made bio-polybutadiene, at the Ravenna R&D centre, using both anionic and Ziegler-Natta catalysis.
Initial testing of the bio-BDE and bio-BR demonstrates good compatibility with industry standards. Versalis is continuing to test the bio-BDE within its other proprietary rubber and plastics downstream technologies such as SBR (styrene butadiene rubber), SBS (styrene butadiene styrene rubber) and ABS (acrylonitrile butadiene styrene).
Plant-based processes for butadiene/feedstock
Meanwhile, a team of scientists from the Catalysis Centre for Energy Innovation have developed a process to convert plant matter into a chemical used to make rubber as well as plastics. The team, which includes Professors from the University of Delaware, University of Minnesota, and the University of Massachusetts, is able to convert sugars extracted from switch grass, wood chips and other biomass into butadiene.
“Butadiene is the chief chemical component in a broad range of materials found throughout society. When this four-carbon molecule undergoes a chemical reaction to form long chains called polymers, SBR is formed, which is used to make abrasive-resistant automobile tyres. When blended to make nitrile butadiene rubber (NBR), it becomes the key component in hoses, seals and the rubber gloves ubiquitous to medical settings,” they explained.
The technique was published in the American Chemical Society (ACS) scientific journal Sustainable Chemistry and Engineering. With the process, butadiene may be produced from high yield feedstock with lowcost manufacturing; and could bring particular value to major tyre makers, including Goodyear, Bridgestone and Michelin, the authors said.
The three-step process developed converts the sugars from woody plants into one compound and then another. The new substance is then mixed with a catalyst called phosphorous all-silica zeolite, also invented by the centre, to create butadiene. Fine-tuning the process is ongoing to make it economically viable for commercial-scale production.
Elsewhere, researchers from the College of Food, Agricultural, and Environmental Sciences (CFAES) – Animal Sciences of the Ohio State University, led by Dr Thaddeus Ezeji, have developed a process for producing butadiene (2.3-butanediol) from cellulosic materials such as leaves, stems and stalks of plant; sugar, and starch. The invention involves metabolic engineering of a non-pathogenic organism for efficient 2.3-butadiene production and the elimination of interfering exopolysaccharides (EPS) production.
According to the researchers, the technology includes low cost media components for the production of 2.3-butanediol as well as compatible technology for its recovery. The new process also reduces feedstock cost by using new, cost effective, renewable substrates and co-substrates such as formate and crude glycerol.
“Most 2.3-butadienol producing microorganisms produce EPS, which are associated with two major problems. First, a significant amount of substrates, which should have been used for the synthesis of the butadienol, is used for the production of unwanted EPS; and second, EPS produced during 2.3-butadienol fermentation would make butadienol recovery from the fermentation broth and purification difficult or costly,” said the team. Further experiments are being conducted to galvanise the novel technology.
Food wastes to green tyres
Food wastes like eggshells and tomato peels are being given new lease of life and value. They can replace part of the petroleum-based fillers used in manufacturing tyres, according to researchers at the Ohio State University. In tests, rubber made with the new fillers exceeds industrial standards for performance, which may ultimately open up new applications for rubber.
According to lead researcher, Katrina Cornish, the technology has the potential to address three issues, namely, making the manufacture of rubber products more sustainable; minimising dependence on oil, and keeping wastes out of landfills.
Cornish’s patent-pending method for turning eggshells and tomato peels into viable, and locally sourced substitute is for petroleum-based filler carbon black.
Based on tests the researchers conducted, they found that eggshells have porous microstructures that provide a larger surface area for contact with the rubber, and give rubber-based materials unusual properties.
Tomato peels, on the other hand, are highly stable at high temperatures and can also be used to generate material with good performance. By replacing different portions of carbon black with ground eggshells and tomato peels caused synergistic effect, for instance, enabling strong rubber to retain flexibility, said the researchers.
The developed biorubber takes on a reddish brown colour, depending on the amount of eggshell or tomato in it. The university has licensed the patent-pending technology to Cornish’s company, EnergyEne, for further development.
The Ohio-headquartered company is also pushing for guayule as a biobased platform to produce natural rubber latex.