Is it possible to use old tires safely?

A thread about tire-use was created in the recycling forum. There was good discussion, but was also full of toxic gick, which at Permies belongs only here in the Cider Press.

There's all kinds of evidence that tires, under load, in motion, being scraped along asphalt, are serious pollutants:
..... https://www.nrdc.org/stories/tires-emerging-threat-our-waterways-our-seafood-and-ourselves
..... https://e360.yale.edu/features/tire-pollution-toxic-chemicals
..... https://www.theguardian.com/environment/2022/jun/03/car-tyres-produce-more-particle-pollution-than-exhausts-tests-show

But it looks like all I can find about their use in the garden is varyingly informed guesses. Until there are real studies, we have to also guess and factor in our own risk-aversion. For me: there were soil-filled tires present when I bought my place and I removed them to the local solid waste transfer station. But I did nothing more than that to remediate the soil. I clearly wouldn't use them as planters myself because it's a gamble not worth taking in my estimate.

I'd love to hear evidence of either their safety or danger to the soil, but also, and probably more useful, what are some ways that they can be used safely even if we assume that growing food in tire-lined soil is too risky?

The hazard of tires as a source of microplastics and particulate emission, while they are being used on a vehicle, would seem to be eliminated if they are being used in a static way. I considered used tire construction at one point, when the fact that they were available for free was a powerful inducement. Rammed earth in stagger-stacked tires for earth walls sounded pretty clever. But they are never going to be attractive, unless you cover them with ferrocement or something similar, and if there were any residual risk of particulates, that would make it even less of a problem.

I know microplastics are a big concern nowadays, but also tires are mostly rubber and carbon black (until you get down to polyester belts), and neither rubber nor carbon black is toxic (except to the extent any microplastic might be able to disrupt cell function, perhaps). So with all the sources of particulates and plastics around anyway, I have a hard time getting particularly worried about old tires.

Even without being on the road where friction emits contamination from the tire, I have seen tires that have been laid on the ground outside deteriorate by dry rot. This is caused by UV light exposure and extreme temperatures from what I am gathering. This risk could be then be theoretically reduced by burying/encasing the tires?

I found one very small study about tire planters and lead levels.

Chives were compared from a tire planter full of soil and then another site in just dirt. The chives in the tire planter had detectable lead and the soil in the tire planter had high lead levels found. I don't particularly like this study because the variability of the soil from site A. and site B. could be the reason and the tire having no effect after all. It really speaks to needing better testing and tests to be conducted!

Even if they do pose some risk, there might be circumstances where you want to use them. I mentioned above that I had to dig some out, haul them to the county, and pay the recycling fee to get rid of mine. I could do that, but for many people that extra expense might mean not buying something fairly critical. Maybe those people could turn that part of the garden into a flowering perennial garden and enjoy the 'shabby chic' elements, while growing their foods elsewhere.

Today, while driving into town and back, I noticed a spot where there are just some discarded tires and then I saw a mailbox with some tires around the post, used as bumpers I guess.

I cut the tires into 3 pieces,  Two sidewall rings and one strip of tread about 7 feet long and 8 inches wide.  I weave the tread strips into sheets about 12 feet wide and as long as needed and lay them in my trails over soft spots.  I can then drive over that area with no worry of sinking in mud.

I also weave the sidewalls together like chain mail and use that as temporary swamp mats.  They are much rougher than the mats made from the treads so I don't like using them on trails I use every day.

In the past I have used free, second hand, conveyor belting for the same use , but when it gets wet it becomes very slippery.  Used tires still give traction when wet so they work much better.

You can also cut out just the bead from the sidewall.  It contains over 100 feet of wire in a nice spool.  To get at it you can cut it out with a knife.  Or throw the bead into a fire and burn the rubber off.  If you quench the hot wire in water you will get a stiff wire.  If you leave it in the fire until it burns to ash and let it cool slowly you will end up with a dead soft wire.

Another use for tires could be for building walls the same way as an earth ship but for buildings you aren't living in.  Such as a barn or a retaining wall.  

Or filled with gravel in a trench  as a foundation for a straw bale or earth bag home.  It still has the same possible issues as an entire home built of tires but on a much smaller scale.

I think I’m going to give the burning of tires a hard pass, myself.

Christopher Weeks wrote:I think I’m going to give the burning of tires a hard pass, myself.

I am talking about only burning the bead of a tire after cutting it off the rest of the tire, so maybe a couple ounces of rubber being burned.  Which for some people is too much.

Depending on how used tires are stored or used, a concern in my area is that they tend to hold stagnant water and become mosquito breeding grounds.

So if you are going to be storing them, please try to keep rainwater out of them, or drill holes in key spots so that they will drain.

Around here, both privately and in commercial shooting ranges, they're often used to bulk up, shape, & solidify mounds for creating safe firing ranges, for target practice. As long as they're covered with plenty of dirt or are ground up, they are amazing for it. You can put a lot of old tires to use, for this.