A Potentially Important Shrub
Guayule (pronounced why-OO-lee) is a desert shrub that could be on the verge of becoming very important to humans. It produces a latex that can be turned into rubber. Unlike the latex from the Para rubber tree, which provides most of the world’s natural rubber supply at the moment, guayule latex doesn't contain allergenic proteins (as far as researchers know). In some people, rubber tree latex causes allergy symptoms that may be life threatening.
The guayule plant grows naturally in dry areas of the southwestern United States and northern Mexico. In addition to providing a safer latex, the plant may be helpful in alleviating the growing shortage of natural rubber in the world. In addition, it contains resins and waxes that may prove useful to humans. It may also become a very useful biofuel. Farmers, commercial companies, and researchers are growing guayule plants with an eager eye on the future.
A Useful Member of the Aster Family
Guayule is a perennial flowering plant in the aster or daisy family (Asteraceae or Compositae) and has the scientific name Parthenium argentatum. It grows as a low, woody shrub that is generally less than three feet tall. The plant has numerous narrow, grey-green leaves with hair-like structures called trichomes on their surfaces. Small, pale yellow to white flowers are produced at the tips of long stems that emerge from the plant. Each flower is a composite one that contains different types of florets.
Guayule is adapted for survival in a dry habitat. The leaves are densely haired and covered with a white wax to help prevent them from drying out. The plant has an extensive root system that enhances its ability to absorb water. One taproot extends downwards, and fibrous lateral roots extend from the taproot to the side. In some plants the taproot is longer than the lateral roots while in others the opposite is true.
Most of the guayule's latex is located in cells in its bark, unlike latex from the rubber tree (Hevea brasiliensis), which is located in tubes called lactifers. Despite the fact that guayule isn't a tree, the outer layer of the stems is often referred to as bark. At one time it was difficult and expensive to extract the latex from the plant, but improved technology has made the extraction a commercially viable process.
Guayule has the ability to lose most of its leaves and become dormant for as long as several years when the environment is very dry. When a new supply of water is available, the plant quickly produces fresh leaves.
Latex and Natural Rubber Facts
The words "latex" and "rubber" are often used interchangeably, but technically they mean different things. Latex is a milky liquid produced by plants. It contains water, proteins, sugar, rubber particles, and other chemicals. Latex can be concentrated so that the rubber particles coagulate to form a solid material, which is also known as natural rubber. In everyday life, the word latex is often used as a synonym for rubber, however, as in the term "latex gloves". The rubber particles in the Para rubber tree and in guayule consist almost entirely of a molecule called cis-1,4-polyisoprene. (The word "Para" is capitalized because the tree is named after the state of Pará in Brazil.)
Guayule plants were used to produce rubber during the second world war when the Para rubber supply to the United States was cut off. The Russian dandelion, another plant that contains latex, was used for the same purpose. After the war ended, the supply of Para rubber resumed and the production of rubber from guayule, which was a more expensive process, ended. Now interest in the guayule plant and its latex is increasing again.
The Para rubber tree population in South America has been decimated by a fungal infection. Most of the natural rubber supply now comes from plantations containing the tree in Southeast Asia. The production of rubber by these plantations can't keep up with the world's demand, however.
Despite the fact that synthetic rubber can be made, natural rubber is still essential. It has useful properties that the synthetic version lacks. Natural rubber offers better resilience and flexibility than the synthetic version. It's a necessary component of truck and airplane tires.
Rubber Production From Guayule Plants
In the United States, guayule latex extraction has been carried out by the Yulex corporation. This corporation has been licensed by the U.S. Department of Agriculture to use extraction technology developed by the Agricultural Research Service (ARS), part of the Department of Agriculture. The name "Yulex" was created by a contraction of the words "guayule" and "latex". The company has used the plant to produce swimsuits.
The latex of the guayule plant is still important for making rubber, but Yulex seems to have passed the technology to another company. When this article was last updated, the company's website contained the information shown below. The company currently makes natural rubber from Forest Stewardship Council© trees.
Today, the baton has been passed and guayule natural rubber is being scaled up by one of the largest rubber producers in the world for global production and consumption.
Obtaining Latex From the Plants
The Para rubber tree has lactifers—latex-transporting tubes—in its trunk. The tubes can be tapped, allowing the latex to drip out, but this process doesn't work in guayule. Most of the rubber particles are located inside bark cells known as parenchyma cells. These parenchyma cells must be opened up to release the cell liquid and its rubber particles.
The ARS says that their latex extraction process uses water instead of the potentially dangerous solvents used in other extraction methods. The guayule shrubs are ground up in water, which breaks open the cells and releases the liquid containing the rubber particles in the form of a suspension. The suspension is then centrifuged, which causes lighter particles (including the rubber particles) to collect at the top of the liquid and heavier particles to fall to the bottom. The upper part of the liquid is removed and purified to create a thick, white latex.
The latex that is produced has a very low concentration of proteins. Furthermore, these proteins are different from the Para rubber proteins that cause allergies. The coagulation of the guayule latex produces a high-quality rubber.
Researchers have created a new variety of guayule plant. The plant is currently being evaluated for its ability to produce a useful and perhaps improved latex.
Latex That May Be Hypoallergenic
Rubber gloves made from guayule latex were approved for public use by the FDA (Food and Drug Administration) in the United States in 2008. The FDA acknowledges that laboratory tests show that people with allergies to Para rubber latex do not react to guayule latex. It carefully says that guayule gloves "may" be a safer alternative for "some" people with a sensitivity to traditional latex. It won't allow the term hypoallergenic to be used on any types of medical gloves, however. Guayule may be most valuable when used to produce medical devices that are used internally, such as catheters, assuming it is hypoallergenic.
Some scientists feel that more tests need to be done to prove that guayule latex is hypoallergenic. They may never be able to be prove that guayule rubber—or any other material—is hypoallergenic for everybody.
Researchers say that guayule plants are available for harvesting at any time of year and can regrow rapidly if they're cut just above the ground.
Latex Allergy Symptoms
One reason why guayule may be very useful is that a severe allergy to Para rubber latex can be deadly. Latex gloves can cause symptoms in someone with a latex allergy, but so can other objects made of latex, including some balloons, elastic bands, some types of first aid tape, and Halloween masks.
A mild latex allergy can cause itching, skin redness, and hives where the latex product touched the skin. More severe responses include typical allergy symptoms such as sneezing, a runny nose, itchy eyes, a sore throat, wheezing, and coughing.
A very severe reaction to latex can cause someone to experience anaphylactic shock. This is a body-wide response that can be very dangerous. Symptoms include breathing problems, abdominal pain, angioedema (swelling under the skin), a very serious drop in blood pressure, a rapid heartbeat, and loss of consciousness. The condition is a medical emergency. Fortunately, a severe latex allergy is rarer than a mild or moderate one.
Guayule Bagasse as a Source of Biofuel
Stems and branches of guayule are ground up in the latex extraction process. The remaining material after the latex has been removed is called bagasse and isn't a waste product, since it can be used to produce biofuel. Bagasse is a brown, granular substance.
Cellulose is the main component of the cell walls of plant cells. The cellulose in the guayule bagasse is fermented to make ethanol. The hemicellulose and lignin in the cell walls are useful in industry.
Bagasse has been used experimentally to make a bio-oil by heating it without the presence of air. It has also been used to make a gas known as a "syngas", or a synthesis gas. This contains a mixture of carbon dioxide, carbon monoxide, and hydrogen and has about fifty percent of the energy-producing ability of natural gas. Syngas can be used as a fuel to produce electricity.
With all its potential benefits, guayule is a plant that we may hear a lot about in the near future. The process of preparing the plant for widespread commercial use is not moving as fast as some people would like, but people are still interested in the plant and are performing research with guayule crops. The potential to create a hypoallergenic latex and a productive biofuel from the plant is intriguing and could also be extremely useful.
- Guayule latex extraction facts from the Agricultural Research Service, or ARS
- Latex allergy information from the Mayo Clinic
- FDA approval of rubber gloves made from guayale from the Medical Xpress news service
- Guayale rubber facts from Chemistry & Engineering News
- The nature of a syngas from biofuel.org.uk
- An improved variety of guayule plant has been developed from the phys.org news service
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
© 2012 Linda Crampton
Linda Crampton (author) from British Columbia, Canada on July 31, 2019:
Thank you very much, Besarien. I appreciate your visit. I hope the research into guayule uses continues and proves useful.
Besarien from South Florida on July 31, 2019:
Thank you for educating me on guayule rubber. What an important discovery for folks with latex allergies! The biofuel possibilities are pretty exciting too. Great article!
Linda Crampton (author) from British Columbia, Canada on December 24, 2016:
Hi, ayamohammed. Thanks for the visit. Your Internet browser may allow you to save a webpage as a PDF file with all the author information intact.
ayamohammed on December 23, 2016:
can I have pdf of this article ?
Linda Crampton (author) from British Columbia, Canada on September 15, 2014:
Thanks, niveaboy. I will share any information that I find.
M. Subandi from Sumedang, West Java, Indonesia on September 15, 2014:
Thanks for suggestion, share your info if you are the first finder of them (guayule seeds). best regards,
Linda Crampton (author) from British Columbia, Canada on September 14, 2014:
Thank you very much for the visit and the comment, niveaboy. I don't have any seeds or cuttings of guayule, but you could do a search on the Internet to find a supplier. Good luck with your search.
M. Subandi from Sumedang, West Java, Indonesia on September 14, 2014:
Excellent... you give us the guayule fictures, add my inventories of latex producing plants. I know H brasilensis more than guayule. May I have the seeds/cutting as plant material ? thanks.
Linda Crampton (author) from British Columbia, Canada on April 04, 2012:
Thank you very much for the votes, Prasetio! Guayule is an interesting plant, and could be very useful in the future. It was fun to write about it!
prasetio30 from malang-indonesia on April 04, 2012:
My friend, you have wide topic to be written. This one is good example for the neatly hub. I had never heard about "Guayule". So, I learn many things from you. Rated up (useful, awesome, interesting). Take care!
Linda Crampton (author) from British Columbia, Canada on March 27, 2012:
Thanks for the visit and the comment, b. Malin. It is exciting that guayule is accessible, as you say. It's easy to cultivate (in the right climate), and it can serve a dual purpose if desired - the latex can be removed, and the remains of the harvested plants can be used as a biofuel. It's a great advantage that the latex seems to be hypoallergenic, too!
b. Malin on March 27, 2012:
Thanks once again Alicia, for such a Wonderful and Educational read...Really fascinating, and to think "Guayule" is so accessible, and Hypoallergenic to boot. Do our Congressmen know about it...They should!
Linda Crampton (author) from British Columbia, Canada on March 26, 2012:
Thank you very much for the comment, drbj. I agree, guayule is a fascinating plant, and it's a useful biofuel. I don't know which would be a better source of energy - guayule or algae. That would be an interesting topic to investigate!
drbj and sherry from south Florida on March 26, 2012:
Fascinating plant and descriptions, Alicia. It would appear that finding a way to make biofuel from guayule makes much more sense than trying to exrtract it, as our president has suggested, from algae.
Linda Crampton (author) from British Columbia, Canada on March 25, 2012:
Thank you very much for the visit, Peggy. I appreciate your comment and the votes. Yes, it does seem that more guayule research and cultivation would be very worthwhile. It looks like it will be a very useful plant.
Peggy Woods from Houston, Texas on March 25, 2012:
What an amazing hub! It would seem that guayule growth and research should be expanded in our country so that we are not totally dependent upon imports for our latex and rubber needs. The fact of it being hypoallergenic just adds to the value. Voted up, useful and interesting.