Due to the shortfall in natural rubber, major car makers are working with researchers to develop sustainable plant-based rubber, says Angelica Buan in this article.
What would industrial progress be without natural rubber? It’s hardly imaginable. Hevea brasiliensis, the Pará rubber tree, sharinga tree, or most commonly, the rubber tree, is an important commercial source of natural rubber . It has been so since the Hevea trees, native to Brazil (parts of the Amazon Basin and Matto Grosso) and the Guianas became an impor tant source of rubber latex.
Only about a century ago was this tree variety transplanted to Africa, Indonesia, Thailand and Malaysia. Over time, the latter three countries have become chief rubber producers in Asia and the wor ld. Soon, countries like China, India, Vietnam, Laos and Myanmar also emerged as pivotal rubber producers, taking over from South America. Although rubber is still tapped from wild trees in the Amazon basin, production in South American plantations is hampered by a fungal disease known as South American leaf blight .
With demand for rubber increasing, glut and shortage or tight supply; rising and falling prices, as well as land conversions to cash crops like oil palm are issues rubber producers have to contend with. Since in many rubber producing countries, cultivation is carried out by small farm holders, thus, farming and harvesting methods or inadequate technologies are found to significantly affect the output.
A research published in the Global Environmental Change earlier this year advised that poor farming methods are fatal for the global rubber supply, and action should be taken.
Scottish researchers from the Royal Botanic Garden Edinburgh and the World Agroforestry Centre, led by Antje Ahrends, estimated that more than half of the plantations in Southeast Asia (which supplies about 70% of global rubber ) may not be sustainable. Down the line, this could cripple global industries dependent on rubber, said Ahrends, suggesting for more efficient rubber management methods and policies in the region.
Development of synthetic rubbers has been an overture for the shortage of the polymer. However, important applications like tyres and car parts demand the tenacity of natural rubber .
For this reason, development of plant-based alternatives to Hevea rubber has begun making inroads that will diversify sources for natural rubber.
Cornucopia of solutions: Guayule and Russian dandelion
A study in 2006, which started the discovery of guayule shrub as a viable natural rubber source, also raised an issue regarding Hevea’s proneness to crop diseases due to its lack of genetic diversity. Researchers John Vederas and Andrew Scholte from the University of Alberta in Canada, hence, suggested on developing viable alternative sources of rubber
Apart from Hevea, there are more than 2,000 plants that can yield rubber latex. However, experts say that guayule and the Russian dandelion are the most promising.
For major car makers like Michigan-based Ford Motors, the stakes are high with the depleting supplies of rubber. Pre-empting such a scenario, Ford has initiated the development of a more sustainable source of rubber, domestically via the Program of Excellence in Natural Rubber Alternatives (PENRA) Consortium, based at the Ohio State University’s (OSU) Ohio Agricultural Research and Development Centre (OARDC).
The team has picked the Russian dandelion and guayule shrub, which is native to the south western US and northern Mexico, to extract rubber latex from.
Arizona-based guayule producers Yulex and PanAridus supply the guayule while OSUOARDC is working with Ford in producing a rubber prototype from both guayule and dandelion roots, expected to be unveiled by next year.
Latex from guayule is extracted the same way as with Hevea, according to Ford. The resulting rubber materials can be used in many car parts such as the chassis, suspension bushing, vibrat ion damper , isolator pad, engine mount and floor mats.
Developing further for tyres
For tyre applications, the materials are still undergoing further developments initiated by large US tyre manufacturers and PENRA members, such as Cooper Tire & Rubber Co, Bridgestone, Goodyear Tire & Rubber Co, and Ford. Cooper, as a result of its research undertakings with Cornell University and Clemson University, is expected to roll out a complete tyre from guayule-derived parts by 2017.
Japanese tyre maker Bridgestone has also established a research facility in Arizona, the Bridgestone Biorubber Process Research Centre, following its opening of the Agro Operation Guayule Research Farm in Eloy. It expects to undertake further research on guayule, to make it suitable for tyre and automotive applications, as well as increase its production and make it cost competitive with Hevea.
Bridgestone’s research delves into plant genetics, process quality and rubber yields. The company projects the period of 2020s as the earliest possible time that guayule rubber can be used in tyres for commercial distribution.
Developing prototype tyres from guayule and Russian dandelions started percolating in 2012. Dutch tyre maker, Apollo Vredestein Banden, a subsidiary of India’s Apollo Tyres, piloted tyre prototypes made from the biorubber via the EUR5.9 million-funded EU-PEARLS project . The latter is a European-based initiative for the production and exploitation of alternative rubber and latex sources supported by the Food, Agriculture and Fisheries, and Biotechnology (KBBE) theme of the European Union’s Seventh Framework Programme (FP7).
Search is far from over: prickly lettuce the subject
Guayule is already being produced on a largescale biomass in Spain. It is found to be not only an excellent rubber alternative as the plant also produces resins that can be used for adhesives aromatics and biofuels, to cite a few other uses.
However, the hunt for natural rubber alternatives continues. A study by a team of scientists from Washington State University (WSU), published online in April this year, highlighted the potentials of prickly lettuce (Lactuca serriola) for providing raw material for rubber production.
Prickly lettuce is a common winter weed that is a member of the sunflower family with flowers resembling dandelions. A native of the Mediterranean region, after which it was introduced to Ontario, Canada, in the late 1890s, its leaves, roots and stems give off a milky sap when damaged.
Study author and ESU weed scientist, Ian Burke, started exploring the rubber potentials of prickly lettuce and its cultivated cousins after reviewing many studies related to it. One study that was published in 2006 found that the latex in prickly lettuce was akin to the polymers found in natural rubber. The WSU study was funded in part by a special US Department of Agriculture/NIFA grant.
An earlier published study carried out by the Faculty of Science, University of Calgary team, likewise focused on various plants as sources of rubber. It initially looked into the lettuce’s promise as a sustainable source of natural rubber. The team, led by associate professor Dae-Kyun Ro and PhD student Yang Qu in the Department of Biological Sciences, used lettuce stems “to identify one of the key enzymes required to synthesise natural rubber in lettuce and other plants”.
According to Ro, the stem of a lettuce, once it is bolted, can produce latex, which contains biopolymers. The lettuce, being a common plant that cross-pollinates itself, makes it ideal for continuous analysis.
The study findings were published in the Journal of Biological Chemistry in January this year. “It represents the first natural biosynthetic model for rubber production supported by concrete experimental data in over 50 years of research,” the researchers said.
The sunflower approach
A breakthrough development effort using sunflowers is being carried out by North Carolina-headquartered Edison Agrosciences. The US-based agricultural biotechnology firm is developing a sunflower rubber crop that it says will diversify global rubber production, as well as provide the US with an alternative source of rubber.
Edison said that it will use its integrated suite of technologies, including proprietary rubber pathway engineering technology, to increase the levels of rubber production in sunflowers.
Rubber accumulates in commercial sunf lower leaves to levels of 1-2% of dry weight. Increasing this level four to five times of rubber production would be sufficient to make sunf lowers a commercially viable source of natural rubber , the firm said.
The US had 1.56 million acres of sunflower crops in 2014 according to Edison’s data. Adding to the sustainability of sunflowers is its short growing season, relatively low water requirements and tolerance to stresses induced by both high and low temperatures.
Moreover , sunflower product ion is “highly mechanised”, thus enabling large-acreage cultivation with minimal labour costs.
Thus, it can be concluded that the research being undertaken by US firms on alternative sources of rubber latex point to a non-reliance or lessened reliance on Asian supplies of rubber .