Seattle Times, May 10, 2015 by Erik Lacitis: Years from now, you might read about a startup that’ll manufacture rubber tires from a common weed found in Washington. It’s called prickly lettuce, and gardeners are very familiar with it. It also seems to particularly like vacant lots and anywhere along freeways.
The wild lettuce kind of looks like cultivated lettuce when it bolts. It doesn’t take long to reach 5 feet and tower over your petunias. Try pulling it out, and you’ll feel its sharp bristles.
If prickly lettuce does go commercial, then you might remember this story about how some basic science research in a Washington State University lab, and farm, in Pullman helped make this happen.
“I think some Americans look at us as being in an ivory tower and think, what a waste of time,” says Ian Burke, an associate professor at WSU’s Department of Crop and Soil Sciences.
His is one of the names, along with former student Jared Bell, on a recently published paper on prickly lettuce and the making of rubber.
The way it works with basic science is that you ask a question, and then ask more questions.
“There’s an old definition of a ‘weed’ that goes something like, ‘a plant whose virtues have not yet been identified,’ ” says Burke.
Prickly lettuce is an invasive species, not native to this country. The U.S. Bureau of Land Management says invasive and noxious weeds (the latter being heavy-duty damagers) are spreading at the rate of 4,800 a day on federal lands in Western states alone.
The weed version of lettuce originated in Mediterranean regions and is the ancestor of today’s cultivated lettuce.
It reached the U.S. the way lots of weeds made their way here — on ships, mixed in with cargo, maybe stuck in a wagon wheel. The winds helped spread the weed so that now it’s found in every state in the Lower 48 and much of Canada.
You have to give weeds due respect. They’re survivors, managing to grow even in gravel.
In Eastern Washington, prickly lettuce bedevils wheat farmers.
One plant can produce anywhere from 35 to an astounding 2,300 flowers, with its buds mixing with the wheat grain and reducing its value. Plus, the white, gooey stuff found in it stems clogs harvesting equipment.
But it is precisely because of that gooey sap that you might read about rubber tires made out of prickly lettuce.
Its goo is latex very similar to that found in rubber trees, which are mainly grown in plantations in Thailand and other countries along the South China Sea.
“It’s my job to work with weeds,” says Burke. “It’s my view that each weed species has something to offer. However, none of the weeds I am working with now have anything close to this potential.”
Although there is synthetic rubber, natural rubber has retained its value: Nearly two-thirds of natural rubber goes for making tires.
“Nature still makes a better quality product than man,” says the website for Bridgestone Truck Tires.
Natural rubber has very high tensile strength, meaning it can withstand repeated flexing, lasts a long time and “tends to run cool,” says Bridgestone.
But the rubber plantations face a major problem, just as do banana plantations.
Their trees are all clones.
“It’s the same plant, which means they’re all susceptible to leaf-blight disease,” says Burke.
The blight hasn’t hit the Asian plantations. But if it does, as decades ago it decimated plantations in Central America, a Fortune magazine article headlined the consequences, “The rubber industry’s biological nightmare.”
It would be “the end of the natural-rubber industry as we know it,” says Fortune.
In 2008, Jared Bell arrived at WSU as a new graduate student. He was to work on a Ph.D. on molecular plant science.
Ever since World War II, there has been a search for an alternative to the rubber tree.
Back then, the Japanese had taken over the Asian rubber plantations, “plunging the U.S. into crisis,” says the Fortune article.
Every Sherman tank had half a ton of rubber in its structure, and every battleship had 20,000 rubber parts. Hence, four days after Pearl Harbor, use of rubber products not essential to the war effort was outlawed in this country.
Back then, the Russians, also needing rubber in their war effort, took to extracting latex from dandelions.
Burke says the Russian dandelion is a different kind than found here. Plus, its latex is found in the root, meaning a lot of soil disturbance.
With renewed interest now in finding an alternative to the rubber tree, Burke saw potential in the prickly lettuce sprouting all over Eastern Washington.
He told Bell about this potential research, and the result was the just-published paper, after more than four years of work.
Plants had to be grown by Bell, tested in the lab, the results analyzed.
Bell’s thesis had 66 references with such tantalizing titles as, “An integrated interspecific AFLP map of lettuce (Lactuca) based on two L. sativa X L. Saligna F2 populations.”
The work he did was at times pretty rudimentary. In crossing two parent lines, “I’d take a flower from the donor, open it, and dab it on the other flower,” says Bell.
Collecting the latex wasn’t high science, either.
It involved making slashes in the stem on the lettuce plant, and letting the latex flow into a tube.
It was then that high-tech equipment such as a DNA analyzer was used.
The results made the professor and student hopeful.
Says Burke, “I’m a scientist. I’m optimistic.”
The prickly lettuce has 5 percent rubber in its latex, compared with 30 percent in a rubber tree.
But, says Bell about increasing the rubber content in the lettuce, “with breeding, it’s doable.”
These days, Bell works in research and development at Dow AgroSciences in Indianapolis.
Burke guesses that in eight years, if he gets funding, “we might plant a small field of this stuff for production purposes.”
That’s actually pretty short term in the basic science world. DNA was first isolated in 1869; the first X-ray showing it had a regular structure in 1937; the DNA double-helix done in 1953.
So, let’s see, maybe in 2023 you’ll see prickly lettuce going for rubber tires. If it happens, out there in Pullman, some researchers will remember how it all started, when they wondered what if.