Stuart Hoenig, Professor Emeritus, department of agriculture and biosystems engineering.

djunct Professor Emeritus Stuart Hoenig, of the University of Arizona’s department of agriculture and biosystems engineering, thinks he’s on to the next wave in construction materials: scrap tires, especially for building houses.

Actually, Professor Hoenig is known for carrying on a number of projects at once. One current project is a system for electrostatically taking water vapor out the air not really an Arizona problem, but one farmers in other parts of the country deal with daily. “For example the Midwest where they try to get two crops of hay,” notes Hoenig. “The second crop gets rained on and you can’t do anything with wet hay. This is a system that essentially dries out that hay.”

Hoenig notes that the same system is being used commercially by the U.S. Department of Agriculture. USDA developed a similar system for cleaning the air of dust and killing bacteria in chicken coops. The successful system is now sold by a private company.

Hoenig has been at the University for 29 years. While he retired 6 years ago, he stays on as an adjunct to pursue research, though he no longer teaches. He received his doctorate from University of California-Berkeley in 1961, after receiving his bachelors degree at the University of Michigan. He received a number of offers but he and his wife did not want to stay in California. Though there were some better salary offers, they choose Arizona for the climate and the University’s reputation.

Of the projects he is pursuing, he is most passionate about the varied uses of scrap tires, even for landscaping. The UA currently is monitoring one of his demonstration projects on campus.

“You split the tire like a bagel, then you roll the grass back; put the tires down; fill them with dirt and roll the grass back,” explains Hoenig, a national expert in the use of scrap tires. “It uses about 50 percent of the water and the grass looks great”

In fact, the University of Arizona is acting as an agent for a California colleague who has patented this use of split tires to save water.

As another alternative to scrap tire disposal, the UA and other universities have been studying engineering applications for these scrap tires that would offer both cheap construction options and an environmental solution to a growing problem

There are some 500-million, used tires stockpiled in the United States, with a growth rate of the material equal to about 250 million per year posing both a fire and environmental hazard. When they are placed in landfills, they tend to rise, prompting 33 states to ban their landfill placement all together. Because the expected life of used tires is some 20 years, they have become an economical substitute for traditional construction materials.

In 2000, the nation used 32 million scrap tires (the amount generated annually in California alone) in civil engineering projects, up by 28 percent from 1999 and making it the largest end-use for scrap tires in the nation, second only to fuel.

In Pima County, some 700,000 scrap tires find their way to landfills each year.

Currently nine states including Arizona allow the use of whole tires for the construction of dams, erosion control, houses (New Mexico is currently the leader in that), fencing, rifle range bullet stops, bridge supports, terracing, playgrounds, and grain storage structures.

Another use is as bedding for livestock corrals. The University of Southern California at San Luis Obispo has built a huge system of livestock bedding. The bedding, made-up of tire bales, allows the liquid from water and urine to drain, keeping the animals drier and preventing foot diseases. Though the UA’s Agriculture farm at Roger Road isn’t “officially” using the technique, Hoenig is trying to get the funds to pursue such a project.

Another use being pursued by the Center for Integrated Waste Management at the State University of New York (SUNY) at Buffalo is using scrap tires as a replacement for stone in septic tanks, a use that is on the rise.

What the scrap tire advocates like Hoenig are hoping for is that home builders and subcontractors become more aware of the variety of applications scrap tires can be used for in home building.

“The big thing is house construction, the installation is fantastic,” says Hoenig. He feels that building inexpensive homes with tires would be great for poorer areas, particularly since the tires are free and construction doesn’t take any special skills.

“For example, Cochise County has an enormous pile of tires and they can’t afford to haul them to Phoenix to get chopped up, so they’re just sitting there,” says Hoenig.

While chipped tires used in road construction and tire-derived fuel (TDF) are currently the best-known uses of scrap tires, it’s the use of whole tires that has drawn Hoenig’s interest. Whole tires can be “baled.” There are a number of companies all over the USA that bale tires, with five in New Mexico alone. The highly portable baling equipment typically costs $100,000. Hoenig notes that there’s one company that bales in New Mexico that actually produces a square final product, ideal for building.

The baled tires are used for tire wall construction for dams, fences and houses ­ where they are stacked, rammed with earth, and covered with stucco. Like rammed earth and straw bale, baled tire houses are well insulated and resistant to fire and insects.

Though the center for scrap tire home construction is New Mexico, Hoenig hopes it will catch on in Arizona, despite restraints put on it by the state.

“The state has some very archaic provisions,” says Hoenig. “For example, you can’t build a tire house in Tucson the way you can in New Mexico. You have to get special permission.”

That permission comes from the Arizona Department of Environmental Quality, the same agency Hoenig had to approach to build a scrap tire dam. He said they were very accommodating.

In the southwest, typical wash and feeder arroyos frequently drop 10 feet per year due to erosion, and tires are being used to alleviate the problem and slow the flow of rushing water in the form retaining walls. In fact, dams constructed with baled tires cost 60 percent less than a concrete dam.

Hoenig, and his University colleagues, are responsible for a tire bale erosion control structure at the King’s Anvil Ranch 10 miles west of Tucson. Construction was supported by the Goodyear Tire Company and Phelps Dodge. They stacked and tied together the tires with half-inch plastic straps, filled them with gravel and covered them with chain-link mesh.

Interestingly, the 1,200 tires were free and Pima County probationers supplied the free labor. The project was monitored by the Arizona Department of Environmental Quality. The 30-foot-long, 6-foot-high tire dam cost $6,500 to design, estimated to be about $63,000 less then a comparable concrete dam. The dam has stopped has stopped sand some 5 feet deep and 30 feet wide from being lost into the arroyo.

“The ranchers were very dubious of it at the time,” notes Hoenig. “But now it’s four years later and it has withstood two floods. Now they’re convinced.”

Arizona and eight other states allow construction of gomes, fencing, bridges and eroison control dams such as this one near Tucson.

So convinced area ranchers are screaming for more dams.

“They’d all like to have tire dams because they’re cheap and they work well,” says Hoenig. “Right now, we’re trying to get some money to build more tire dams.”

As if he doesn’t have enough projects going, he’s recently received an request for a proposal from Pima County for a 100,000-gallon Anaerobic Digester to break down organics in the county’s growing garbage dumps. He’s planning on using scrap tires to line the site.

Around the country other scrap tire construction projects abound: The U.S. Department of Interior has used whole tires for 20 years at the Salton Sea for erosion and dams. In New Mexico, a 4,400-foot section of Lake Carlsbad was stabilized against erosion with tire bales. In this case the bales were covered with a thin layer of concrete for visual purposes.

Twenty-five foot-high damn in Arkansas using more than 50,000 tires.

California used 860,000 tires to fill in a freeway embankment of a $30-million interchange reconstruction, due to be completed in 2004.

In Maryland, scrap tires have been used for playground structures and ground cover in seven state parks.