Are tyre planters (tire planters) safe?

I came across this interesting article on the question of using tyres as planters by an NGO working in the developing world.

https://c.ymcdn.com/sites/echocommunity.site-ym.com/resource/collection/62026577-227A-4FB0-8B25-B0838484CED7/EDN130.pdf
The author, Ben Fisher, recommends:
Do not use tires that are heavily degraded
Avoid soil contact with cut surfaces
Consider your crop selection
Use non-acidic media with plenty of organic matter.

We use them as flower planters, but we remain hesitant to use them with things we would actually eat. For us the tire catches us between a rock and a hard place. On one hand we want to upcycle materials that seem to be a pain to recycle, but on the other hand we are concerned about heavy metals leeching into the soil and then into our food. If it weren't for the concern over chemicals we would love to use them for potatoes.

"According to the EPA, benzene, mercury, styrene-butadiene, polycyclic aromatic hydrocarbons, andarsenic, among several other chemicals, heavy metals andcarcinogens, have been found in tires." 

http://www.nbcnews.com/news/investigations/rubber-mulch-safe-surface-your-childs-playground-n258586

It's not so much what's in them as what manages the journey out of them and into the edible portions of your plants.

The relative durability of tires in the environment is a clue there; they do not break down rapidly or easily, but horde their constituents tightly within themselves.

Virtually all of the research I've been able to find about the safety of recycled tire material has focused on machines that chop the tires into small pellets (for use as mulch or an ingredient in concrete or pavement). Chopping up the tires exposes many fresh surfaces to air and water, and has been found to liberate undesirable stuff (mostly metals) in undesirable quantities.

Whole tires? There's no research. So we don't know. Paul Wheaton, in the definitive thread about this here on Permies.com, says the question triggers the inner conflict in him between his organic tendencies and his recycler tendencies but in the end he rejects the tires.

For me, in my environment, planters made from triple-stacked tires offer the virtues of tall raised beds (protection from small nibblers, easier access to the gardener's attention without undue stooping, depth of soil) at essentially zero cost. And when I parse the risks, I find them small enough. But I honor and respect a different conclusion from a person who puts different weights on the irreducible uncertainties.

Dan Boone wrote:It's not so much what's in them as what manages the journey out of them and into the edible portions of your plants.

The relative durability of tires in the environment is a clue there; they do not break down rapidly or easily, but horde their constituents tightly within themselves.

Virtually all of the research I've been able to find about the safety of recycled tire material has focused on machines that chop the tires into small pellets (for use as mulch or an ingredient in concrete or pavement). Chopping up the tires exposes many fresh surfaces to air and water, and has been found to liberate undesirable stuff (mostly metals) in undesirable quantities.

Whole tires? There's no research. So we don't know. Paul Wheaton, in the definitive thread about this here on Permies.com, says the question triggers the inner conflict in him between his organic tendencies and his recycler tendencies but in the end he rejects the tires.

For me, in my environment, planters made from triple-stacked tires offer the virtues of tall raised beds (protection from small nibblers, easier access to the gardener's attention without undue stooping, depth of soil) at essentially zero cost. And when I parse the risks, I find them small enough. But I honor and respect a different conclusion from a person who puts different weights on the irreducible uncertainties.

I don't think there is a right or wrong answer as far as tires go since sadly so very little research has been done on whole tires.

I think what it comes down to is less about whether they are safe or not and more about whether it is worth the risk. For some who live in areas with few trees re-purposing tires is a lot easier of a decision than someone who has to clear trees anyway, the logs of which make great free raised bed walls.

I don't know about how safe they are but I certainly wouldn't use them for food crops.

Also, for the love of god, do not use them for trees! Whoever owned my house previously must have thought tires were the best thing ever and planted about thirty trees using tires as planters. We are still finding trees planted with tires 2 years after moving in. They are the most difficult thing to remove and once the tree gets to a certain size, the tire will start to suffocate it and it will grow all wonky. We have only successfully gotten them off of maybe 4 of the trees. There are several tires that are just shredded right now from us trying to get them off but they won't budge. ARGH I hate those tires.

Sorry, I know not really the point of this post but it just makes me so mad and I don't want anyone to ever have to deal with that aggravation. Carry on

Actually, does anyone here know how much research was done before they started the labor intensive process of recovering the tires they had tried to use to establish new coral reefs? Were they pulled because in addition to not working they were contaminating their surroundings? Or was it just that they didn't work and were considered bad enough eyesores for the tourist trade to be worth the expense of cleaning?

Casie Becker wrote:Actually, does anyone here know how much research was done before they started the labor intensive process of recovering the tires they had tried to use to establish new coral reefs?

I hadn't heard about that. Have you got any informative links that would be better than whatever I could find by random Googling?

Sorry, no. I've been random googling myself. Everything I can find says they're being removed because of the physical harm the tires cause when the bash into natural reefs during storms. Doesn't seem to be any research into if they're leaching chemical contamination.

Gotcha, thanks. I hadn't heard that tires had been used at all for reef construction, although I can sure see why it might be tried. Due to its dynamism and dilution factor, the ocean would be a difficult environment in which to track and measure contamination effects, I don't envy the scientist who has to try and do that!

The Use of Used Tires in Water Systems
Stuart A. Hoenig

Hoenig is an Adjunct Professor, Department of
Agricultural and Biosystems Engineering, and
Professor Emeritus, Department of Electrical and
Computer Engineering, University of Arizona,

Abstract:

"Old tires have many uses in the control of erosion, both
in and out of water. They are pollution-insect free,
good insulators, fire resistant when filled with soil and
last an estimate of 250 years.
Keywords: tire, erosion control, pollution free, long
lasting.

Introduction:

The United States has a vast number of used tires and
they increase at roughly 300 million per year. Some are
burned in smelters or ground up for surface covering.
This process is handicapped by the high strength steel
that is part of the tires. Burning introduces toxic
materials into the air that are difficult to capture.
It seems more effective to use them in their original
condition. They can be used for animal fences on
farms, as subgrades or barriers for road construction,
bullet stops on rifle ranges, off-shore for wave control
and fishing. Wave barriers around lakes and fish
habitat have proved to be successful. Other applications
are construction of houses and water-erosion control.
Many studies have shown that whole tires do not
present smell or pollution problems, are very long
lasting in dry soil or fresh and salt water. When filled
with soil or baled (to be discussed below) they are very
resistant to fire, insect or noise penetration. "

There is more of this report but it all focuses on water dam building.

With so many millions of used tires in this country there are several scientist working with government agencies to come up with viable solutions to the old tire issue.
The current studies are focused on large scale use of these tires so that many can be put to use since they last approximately 250 years when just sitting around.
The real problems with tires come on strong when they are ground up and left to free air circulation, set on fire in a tire dump (can burn for months and put all sorts of nasty things into the air).
Dams seem to be one way to make good use of a lot of tires, coffer dams have been built in Colorado, Texas and California with good results and very little pollution.
The process of vulcanization fairly well locks up the noxious compounds (burning is about the best way to unlock these chemical bonds and thus release them to the atmosphere).

Currently Earth Ships tend to use a fair quantity of earth filled old tires for part of the structure.
Most of the new Running Track surfacing is being done with a rubberized (chewed up old tires) asphalt, which is springy and reduces injuries common to runners.
In our area they seem to be moving to alternative materials and removing the previous preference of chewed up old tire material.

Now on to our particular concerns;
I have access to as many used motorcycle tires as I can haul away and have been toying with the idea of using these "gifts" for some research oriented building projects.
There are a few areas where I could use these for erosion control and if earth filled, I could use them for building the out of ground portion of our root cellar/ storm shelter,
I could utilize tires as terracing wall material, I could use them for planting beds for herbs and bug repelling flowers.
So far I have only brought five onto our land, these are being used as "holders" for water pans for the hogs (select tire for proper size of water pan, fill with expanding foam and trim this so pan fits snuggly but doesn't touch ground).
This application is working out well since the hogs don't tip over and spill their water nearly as often as they did before. It also helps to keep the water from freezing as quickly as it does in a pan set directly on the soil.

I do have some plant seeds that may allow me to do some quantitative analysis of leaching effect in garden use rubber tires.
I am planning to start this study this spring with corn and a couple of other heavy feeding plants.
I'll post results at the end and hopefully that will give folks some up to date data to refer to when thinking about using tires as food plant planters.