CABNR Research Studying Rabbitbrush as New Source of Rubber
If you walk anywhere in Nevada, chances are you'll see a bush with greenish-yellow flowers. It's not a particularly attractive plant, but you have to admire anything that can produce a flower in such harsh conditions.
It's called rabbitbrush, and while many people might see it as just another weedy-looking desert plant, CABNR Assistant Professor David Shintani sees it as a potentially lucrative natural resource.
Rabbitbrush is rich in natural rubber, which is essential for the commercial production of tires and other products. It's also rich in oleoresin, which can be used to make biodiesel fuel and in the production of adhesives, dyes and the like. He's even looking at how the cellulosic material left over after the extraction of rubber and resin can be used as biomass to generate electricity.
"We're like the Native Americans hunting buffalo," Shintani says. "We'll use every piece of the plant."
Rubber is a valuable commodity in the world today. The only place to get it is from Southeast Asia, where its production and price is controlled by a commodity group. What's more, scientists have been unable to imitate its chemical properties in the laboratory, and now the limited supply of natural rubber is being tapped by the burgeoning industrial expansions under way in China and India, driving up prices even more and making the search for alternative sources more important.
The last time rubber supplies became dramatically restricted - around the time of World War II when the Japanese controlled the rubber plantations - the United States' frantic search for a domestic source led them to rabbitbrush and a few other desert plants, including the Russian dandelion and the guayule plant. When the British resumed control of the rubber plantations after the war, the government abandoned its research on rubber-producing desert plants, although guayule (pronounced why-YOU-lee) has since become a commercial source of latex for making gloves, medical devices and other natural rubber products.
But now Shintani thinks rabbitbrush's time has come.
"I think it's comparable to guayule," he says. "But rabbitbrush has the added advantage in that it grows in a wider geographic range and is more tolerant to drought and cold stress. It needs less water and it can grow in really lousy soils. In fact, we've found the worse the soil conditions are the higher the rubber content is in rabbitbrush."
Shintani's work involves studying rabbitbrush to determine the best variety for producing commercial rubber. There is a wide variety of rabbitbrush growing wild in Nevada, and some produce a better supply of rubber than others.
Once the best strain is identified, Shintani needs to see how rabbitbrush responds to commercial cultivation. The process for extracting the rubber and latex from rabbitbrush has already been developed, and Shintani says the mechanical process used on guayule can work for rabbitbrush.
Some of Shintani's research is taking place on CABNR's Gund Ranch, where rabbitbrush grows profusely.
Rabbitbrush can grow to be up to 90 inches tall and has a rounded crown and several erect stems coming from its base. Its branches are, as you'd expect, rubbery, and its leaves and stems are covered with a felt-like coating that reduces the loss of water and insulates the plant, allowing it to survive cold temperatures.
One of the nice things is that if rabbitbrush does become a commercial crop, it wouldn't have to displace crops already growing on existing Nevada farmland. The bush grows in a wide range of soils and will happily occupy terrain few other plants want.
Native Americans made chewing gum from the plant by pulverizing its wood and bark, and it was also used as tea, cough syrup, yellow dye and for chest pains.
And now, Shintani, who has been studying rabbitbrush for 10 years and is working with other universities and federal agencies on his research, thinks it might be a cure for some of the country's and Nevada's economic ailments.
"This will take a fair amount of time still - there's still a lot of work to do," he says. "But rubber is an important, strategic material, and we have high hopes that rabbitbrush can be a great source for it."