With disease and high demand threatening the primary supply of natural rubber in Southeast Asia, scientists are working to increase the rubber market in the US by advancing methods to extract latex from two sustainable sources of North American plants: a species of dandelion and a desert shrub.
Innovative technology to increase rubber production in the US
Researchers have reported their methods to improve efficiency and increase latex yield in two recent publications, building on decades of research led by Katrina Cornish, professor of horticulture and crop science and food, agricultural and biological engineering at State University. of Ohio.
Cornish and his colleagues have added specialized agents during processing of the dandelion Taraxacum kok-saghyz (TK) and the guayule shrub to extract a greater amount of latex from both plants. Neither source can simply be “bled” as is done with the tropical trees that produce the only commercially available natural rubber in the world.
Importance of efficient and economical methods
We need to have efficient extraction methods for any alternative natural rubber producing species, especially on a large scale. And they have to be low cost if they are to compete in the tire market in the long term.
Katrina Cornish
Rubber publications and applications
The TK dandelion work was recently published in Industrial Crops and Products, and the guayule research in Environmental Technology & Innovation.
Beyond tires, rubber has applications in about 50,000 products. The need for a domestic natural rubber industry is urgent: while the United States produces synthetic rubber, it is entirely dependent on imports for natural rubber. In 2019, 10% of the natural rubber supply was lost due to disease, and the risk of transmission of leaf blight disease from South America to Southeast Asia has increased with the expansion of direct flights between Brazil and China.
Global risks and sustainable solutions
It’s not an exaggeration, Cornish said, to suggest that if leaf blight were to reach Asia from South America, the disease could wipe out most of the world’s supply of natural rubber in a short time.
And then we could see the collapse of global supply chains and, subsequently, entire economies. We have concentrated an entire global industry around one tropical plant. But TK dandelion and guayule are sustainable and can grow in temperate conditions.
Katrina Cornish
Guayule latex extraction process
Guayule latex comes from widespread cells in the bark of the shrub. Removing the latex involves grinding the bark to break down its cells and release latex particles in what Cornish calls a “shake.” A series of washing and spinning cycles follows to separate the latex from the solid material.
Improvement in efficiency through flocculants
The research team found that adding chemicals called flocculants to the “batter” helped bind other solid materials and separate them from the latex, effectively cutting wash cycles in half and improving the overall performance of the latex. The addition of a substance doubled the available latex, and that yield increased 12-fold when a purifying cream agent was added.
“By adding flocculants, latex extraction is more efficient and cleaner,” said the study’s lead author, Beenish Saba, a postdoctoral researcher in food, agricultural and biological engineering at Ohio State. “We found specific flocculants that work best to improve the quality of latex extraction and reduce the time it takes.”
TK dandelion latex extraction process
Although TK dandelion latex is produced in the roots of the plant, the extraction process is similar: the roots are trimmed, mixed into a slurry, and filtered to remove solid pieces of plant material and soil. The latex floating on top of the remaining liquid is sucked out with a pipette and rinsed up to three times for purification, and then dried.
Advances and improved efficiency
A bit of serendipity led to the improvement of this extraction method. Lead author Nathaniel King-Smith, a graduate student in Cornish’s lab, found that processed samples that were in the lab for three months had significantly more latex floating on their surfaces. An analysis showed that heavy divalent cations, such as magnesium, bound to the membranes of the latex particles and made them heavier, until the connection eventually collapsed.
The team discovered that adding EDTA, a chelator that binds divalent cations, to processing dandelion roots allowed the extraction of more than twice as much latex as without the addition of EDTA.
Collaborations and future expansion
The use of EDTA also increased the gel content of the extracted latex once it was dried, useful information for industries seeking rubber with higher gel content, King-Smith said.
EDTA may be applicable to the extraction of latex from guayule, although Cornish said his lab hopes to partner with flocculant chemists who can help refine that process further. She has been planting, harvesting and extracting TK dandelion latex for more than a decade in Ohio and has a greenhouse full of guayule on Ohio State’s Wooster campus, where she hopes to one day build a large-scale latex processing plant. scale.
We are working on a small scale and focusing on premium latex markets where something of great value can be made with minimal materials in order to finance expansion. And in the meantime, we are making the extraction more efficient so that we can make the material clean and pure.
Katrina Cornish
Via osu.edu
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