Wednesday, June 19, 2019

A Short History of the Tire Dump

Assorted new automotive road tiresOne of the mantras for waste reduction and energy efficiency is the “Reduce, Reuse, Recycle” slogan, which indicates the order of preference for resource conservation: It’s best to use fewer things in the first place, but once you got ‘em you may as well reuse them. In the end, though, it’s better they get recycled than chucked in a landfill.

Not all products fall neatly into this hierarchy, though. Being round, an automobile tire should be a poster-child for the idea that what comes around should go around as many times as possible. One problem is that the customers most eager to reuse the estimated nearly 300 million car and truck tires that Americans discard each year are mosquitoes. And that fact that tough, durable construction is what defines a good tire makes recycling them a special challenge.

Early on, it was recognized that a discarded tire was a mosquito farm. So in the old days it was common to provide a dead tire with a shallow grave and call it good enough. But on average, a buried tire is 75% air space, so if it is not very deep it becomes perfect for the young rat couple or yellow-jacket queen looking for a nice starter home.

When tires were sent to landfills, one issue was that they could not be compacted, and therefore wasted a lot of space. And it turned out that they rose from the dead, becoming methane-filled and wriggling their way to the surface.

In 2004, the New York State Department of Environmental Conservation (NYSDEC) rounded up a statewide list of tire dumps, revealing 95 sites for a grand total of 29 million tires. Since then, more sites have been located, but the overall numbers of tires are slowly dropping due in part to a 2003 amendment to the Environmental Conservation Law called the Waste Tire Management and Recycling Act. This is the Act which requires garages to charge you a fee for proper tire disposal.

Prior to 1990, only about 25% of discarded tires were recycled, but these days the number is up around 80%, which is below the 95% rate found in Europe, but still a vast improvement. More than half of our recycled tires are used as fuel, mostly by industries such as cement kilns and steel mills. Tires are also shredded or ground, and the resulting crumb-rubber is added to asphalt or concrete for road construction, which imparts resiliency and shock-absorption qualities. For similar reasons, shredded rubber is mixed with soil under athletic fields, and is employed in playgrounds under swings and play structures to help cushion falls.

In recent years, ground rubber has been marketed as a mulch option for landscapers and homeowners. This seemed like a perfect end-use for recycled tires, but some researchers are questioning the wisdom of rubber mulch. According to Dr. Linda Chalker-Scott, an Associate Professor at the Puyallup Research and Extension Center at Washington State University, the toxicity of the rubber is a real concern, especially if it is used near vegetable crops.

In one of her published papers, Dr. Chalker-Scott has stated that “Part of the toxic nature of rubber leachate is due to its mineral content: aluminum, cadmium, chromium, copper, iron, magnesium, manganese, molybdenum, selenium, sulfur, and zinc…rubber contains very high levels of zinc – as much as 2% of the tire mass. A number of plant species…have been shown to accumulate abnormally high levels of zinc sometimes to the point of death.”

The paper notes that in addition to metals, organic chemicals which are “highly persistent in the environment and very toxic to aquatic organisms” leach out of shredded rubber. Chalker-Scott concludes that:

“It is abundantly clear from the scientific literature that rubber should not be used as a landscape amendment or mulch. There is no question that toxic substances leach from rubber as it degrades, contaminating the soil, landscape plants, and associated aquatic systems. While recycling waste tires is an important issue to address, it is not a solution to simply move the problem to our landscapes and surface waters.”

When asked what the best type of mulch is, I generally recommend “free.” Plastic mulch can be handy to smother tough weeds, and old bunker-silo cover is often free for the taking if you know a dairy farmer in your area. But where the rubber meets the road, so to speak, natural, plant-based materials are mulch better. They help conserve water and suppress weeds, as well as improve soil structure and enhance the mycorrhizal (beneficial fungi) community. They also act as a slow-release fertilizer. Rotted wood chips, mature compost, or spoiled hay can often be had for little or no cost. As long as you do not use weed-control on your lawn, grass clippings can be used in moderation (they are very high in nitrogen).

Recycling is great, but keep the tires out of the garden. You can help reduce the number of dead tires in the world by regularly rotating your vehicle tires and keeping them inflated properly, and by having your vehicle aligned as recommended in the owner’s manual. The NYSDEC has more information on waste tires, here.

Photo of assorted new automotive road tires courtesy Wikimedia user HopsonRoad (Stephen Flanders.

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Paul Hetzler has been an ISA Certified Arborist since 1996. His work has appeared in the medical journal The Lancet, as well as Highlights for Children Magazine.You can read more of his work at or by picking up a copy of his book Shady Characters: Plant Vampires, Caterpillar Soup, Leprechaun Trees and Other Hilarities of the Natural World

10 Responses

  1. Mary Anne says:

    I am impressed by this article. I did not know about rubber tire leachates. I always had the fantasy of building and living in an off grid “earth ship” type home built with old tires as the inner structure. Growing food around the home sounds like a definite health problem. I wonder how the earth ships of the Southwest handle this issue. Might be due to lack of much rainfall in desert regions, that the tires do not cause problems to growing food.

    • There does not seem to be any problem with living in homes like you describe, Mary Anne.

      When rubber is shredded, the surface area is increased exponentially, and so the leaching potential is too.

      • Mary Anne says:

        So, if the tires are encapsulated in rammed packed earth they are safe. However, I have seen homes where the stacked tires are left exposed to sun and air.

        I am glad I did not buy that rubber mulch I saw at Home Depot, as I was going to use it in my garden beds to cut down on weeds!
        Yes, it’s used in playgrounds around here too.

  2. Phillip Bobrowski says:

    Pulverized, powdered, and crumb rubber have no place in our “recreation” areas, be they playgrounds or sports fields. Our school district went “balls-to-the-walls” in replacing MULTIPLE school and district surfaces with “artificial” turf with crumb rubber coverage, simply because they had the money to do so.
    I urged them to wait until the final study was published.
    But, they said the state-fed capital funding was a “use it or lose it” offering. So, they rationalized it was OK to spend nearly $10 Million dollars, district-wide, to install these fields that, as with the football fields, only say action for 8-10 weeks a year.
    Then, to add insult to injury, the district had to purchase brand new equipment to properly “clean” these same surfaces, all this within 5 years after spending other MILLIONS of dollars to, in one instance, install a new drainage and watering system.
    The speed and volume of chemicals released during the degradation of re-used rubber in the recreational and landscape processes has not been quantified. And the insistence that it’s OK until proven otherwise is a fools tale.

  3. Susan Gaffney says:

    If shredded tire material isn’t safe for mulching, why would it be safe for playgrounds?

    • I was wondering that as well. Since leachate into the soil over time is the main concern in gardens, it may be that brief encounters with mainly dry rubber in playgrounds is deemed OK. On the other hand, we let kids play on wood structures treated with copper-chromated arsenic for decades…

    • Phillip Bobrowski says:

      One of the BEST ground-covers for playgrounds and recreation use areas is “pea gravel”. It allows for drainage, moves easily upon impact, reduces the possibility of vegetation growth, and can be scooped out for periodic rinsing.
      But, it’s also more expensive than crumb rubber, mulch, or sand

  4. Chester Rosinski says:

    I must compliment your prose style.

  5. adkresident says:

    Just to clarify, you are charged a disposal tax on a tire making them worth $5.
    That is why places like Walmart take them for free. Anyone who charges a disposal fee is collecting at both ends.

    The statements about the leaching of rubber are overly broad and have no actual numbers, this makes it sound like rubber is toxic to everything.

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