When The Rubber No Longer Hits The RoadPosted: October 27, 2013
What happens to tires when they are no longer suitable for their original use? Vehicle tires are among the largest and most problematic sources of waste simply because of their size, the volume at which they are produced (approx 1 tire/person/year is discarded), their desirable durability and frequently their improper disposal.
Our family signed up in 1989 for Missouri’s Stream Team program in it’s first year of development. Along the creek that runs perennially past our location, tires are not a big problem in our watershed but we have found them dumped down a steep hillside, just off the county dirt road. Twenty years later, we were mentoring the development of a new Missouri Stream Team for the Castor River in Madison County, Missouri; and had our first clean-up effort on Sat, Aug 1, 2009 with only 6 volunteers, half of which were from our own family. Even so, we were able to recycle over 92% of the items taken out of the river; a little over 900 lbs recycled, out of the almost 1,000 lbs of trash we collected in just one day, from just 3 miles of riverway. This included 321 lbs of rubber in the form of 11 car & truck tires.
People often dump tires into streams and rivers as well as alongside roads without a lot of traffic because there is a fee attached (though in Missouri in 2009 that was only $3/each) to their legal disposal; and for some people, it is just too much of a bother to do it properly. In our region, in the past, there were large “dumps”, mountains of old tires, that frequently caught fire. Thankfully, the state has closed these and forced their clean-up.
Due to heavy metals and other pollutants in tires there is a potential risk for the (leaching) of toxins into the groundwater when placed in wet soils. This impact on the environment varies according to the pH level and conditions of local water and soil. Research has shown that very little leaching occurs when shredded tires are used as light fill material; however, limitations have been put on use of this material; and each site should be individually assessed to determine if this product is appropriate for given conditions.
Ecotoxicity may be a bigger problem than at first realized by the tire industry. Studies show that zinc, heavy metals, a host of vulcanization and rubber chemicals leach into water from tires. Shredded tire pieces leach much more, creating a bigger concern, due to the increased surface area on the shredded pieces. Many organisms are sensitive, and without dilution, contaminated tire water has been shown to kill some organisms. Testing for water quality is one of the practices of Missouri Stream Teams.
Happily, tires are also one of the most re-used waste materials owing to the natural resiliency of the rubber itself. Ground up tires are known as crumb rubber in the recycling market. Shredded tires are still being used in some landfills to replace other construction materials, for a lightweight backfill in gas venting systems, leachate collection systems, and operational liners. Shredded tire material may also be used to cap, close, or daily cover landfill sites. Scrap tires as a backfill and cover material are also more cost-effective, since tires can be shredded on-site instead of hauling in other fill materials.
Recent developments in de-vulcanization enable dealing with substantial volumes, taking 40 mesh whole tire crumb and converting it into value-added compounds without degrading the polymer and without generating any pollution. This new generation in de-vulcanization technologies operates with very high productivity while maintaining a low energy footprint. The compounds produced from processed tire scrap can be blended with virgin rubber compounds, maintaining performance while substantially reducing the raw material cost. The substantial economies of scale and value added benefits make burning tires for disposal entirely unnecessary.
Agricultural use of rubber for tires results in very large tires. In Costa Rica, one company is developing processes to de-vulcanize the scrap from producing rubber gaskets (as always, industrial waste is a larger volume problem than post-consumer waste, even though post-consumer behaviors are important because there are so many people now on the planet). They have determined that 10% of that de-vulcanized styrene-butadiene and natural rubber can be used in agricultural tire tread, saving 7% of the traditional cost of manufacturing a conventional ag tire.
Tires can be recycled into road surfaces. At Clemson University, Asphalt Rubber Technology Service (ARTS) promotes the practical utilization of waste tire rubber within asphalt and civil engineering applications. Thirty percent of all the asphalt used in California must contain rubber by law. Arizona, Texas and Florida also use rubberized asphalt extensively, while Washington, Colorado and Georgia are evaluating the material. ARTS also sponsors the Tire Recycling Education and Development Service (TREADS) program, which provides grants for education and technology transfer.
Tires have also been cut up and used in garden beds as bark mulch to hold in the water and to prevent weeds from growing. There are some “green” buildings, both private and public that are made from old tires. Our family has personally visited the Earthship headquarters near Taos, NM (http://earthship.com/) This is a heartening development for the usage of old tires, just as they are. Their website statement declares – “. . . the Earthship is the epitome of sustainable design and construction.” – and having seen this for ourselves, we would tend to agree. Paso Robles, CA known for wineries and hot springs, is also known for specialized industry and a high utilization of sustainable building structures including rubber-insulated concrete and straw bale constructions; as well as hosting several wind farms in the pass, which generate electric power with wind generators.
reRubber (www.rerubber.com/ – “committed towards the best green practices in the crumb rubber industry”) uses an ambient grinding technique to make crumb rubber from 100-percent California scrap truck tires. They say that they are “getting it fine enough where it bonds in different matrices with other chemicals.” Their product diversity includes tire sealants and coatings for automotive, as well as infrastructure and green building applications.
Our business contributes in it’s own small way as a solution to the constant creation of tire waste. Our Tire Veneer material uses 80-100% post-consumer crumb rubber molded into blocks and logs. This material is frequently used for flooring but has applications in furniture and even for weed control (as tested in our own small organic family garden and as a boundary against an ever invasive, jungle like environment around various areas on our farm including as a protective barrier in a rainfall replenished pond for frog and toad breeding activities – yes, the tadpoles and frogs do not seem bothered by it). We also have utilized railroad ties made from 100% rubber for over a decade to contain sand in the children’s large play area.
Just this Oct 2013, at the Omega Institute, they had a conference titled “Where We Go From Here”, a weekend conference (Oct 5, 2013-Oct 7, 2013), that included Paul Hawken and former Pres Bill Clinton. Attendees explored opportunities and solutions for our interdependent world, seeking a unique whole-systems perspective to recognize the reality that all things are interdependent. The global challenges facing us today are complex; and the waste from our vehicle tires is only one small part of that picture but happily one with a high degree of success. A report from 2003, cited by the EPA, said that the market (for “both recycling and beneficial use”) existed for 80.4% of scrap tires, which in 2003 was about 233 million tires per year, at 22.5 lbs per tire. That’s a lot of waste diverted.
Blog author ~ Deborah Hart Yemm is co-founder of
Yemm & Hart, a green materials producer