Can tires ever be re-cycled into harmless products?

Hello,

So I am starting this thread as a companion to another thread HERE:

https://permies.com/t/74736/tires-dangerous-health-nature

Regarding the suitability of using old tires as planters.

It had me wondering if it is possible to ever safely reduce something like a tire into completely benign or possibly even beneficial breakdown products.  I am not suggesting we just toss them on the ground and let them degrade.  Rather I was wondering if there are any microbes—perhaps some bacteria or fungi—that could break down the rubber into its components.  Please correct me if I am wrong but I am thinking that most of a tire is ultimately made of hydrogen and carbon with probably some oxygen and sulfur thrown in.  Theses are substances found in soil.  Is It possible for some microbe to turn this toxic substance into a benign substance?  I personally don’t know but I thought it worth a thought.

Let me know what you think.

Eric

Are tires actually still made of rubber? They don't feel or act like the old ones...
I'll be watching this, I have a thing in my head that would work REALLY well with the old tractor tire I have, but I'm cautious of the toxins.

Pearl Sutton wrote:Are tires actually still made of rubber? They don't feel or act like the old ones...
I'll be watching this, I have a thing in my head that would work REALLY well with the old tractor tire I have, but I'm cautious of the toxins.

Yes, they are. But there have probably been changes to the vulcanization process and the construction of the tires.
https://www.goodyear.com.ph/learn/how-tires-are-made

My money is on high-temperature pyrolysis in an oxygen-free retort, or straight-up high-temperature incineration in an exhaust-controlled setup. If everything is broken down, leaving carbon dioxide and water, and then that carbon dioxide and water enter a greenhouse-based water treatment instead of exiting a stack, you could reclaim all the materials that don't incinerate, and there's very little, if any, waste in such a scenario.

At very least, if you're exceptionally careful about temperatures, waste tires, which some consider toxic in the environment, could be converted to useful energy. There are projects underway to reduce tires into useful constituent parts, but to my knowledge, apart from those using controlled pyrolysis and distillation, most leave some undesirable residues, and utilise chemicals and processes not really suitable for the homestead.

-CK

Hmmmm... looking up what they are made of

https://www.michelinman.com/howTireMade.html
Over 200 ingredients go into a tire. They play vital roles in safety, fuel efficiency, performance and eco-friendliness.

These components fall into five groups:

   Natural rubber: the main component of the tread layers
   Synthetic rubber: part of the treads of car, van and 4x4 tires
   Carbon black and silica: used as a reinforcing agent to improve durability
   Metallic and textile reinforcement cables: the "skeleton" of the tire, forming the geometric shape and providing rigidity.
   Numerous chemical agents: for unique properties like low rolling resistance or ultra-high grip

Copying from https://www.ustires.org/whats-tire-0



Natural Rubber
Natural rubber provides specific performance characteristics to tires. It is especially good for tear and fatigue crack resistance.

Synthetic Polymers
The two main synthetic rubber polymers used in tire manufacturing are butadiene rubber and styrene butadiene rubber. These rubber polymers are used in combination with natural rubber. Physical and chemical properties of these rubber polymers determine the performance of each component in the tire as well as the overall tire performance (rolling resistance, wear and traction).

Another important synthetic rubber is halogenated polyisobutylene rubber (XIIR) commonly known as halobutyl rubber. This material causes the innerliner to be impermeable, which helps to keep the tire inflated.

Steel
Steel wire is used in the tire belts and beads, and the plies for truck tires. The belts under the tread serve to stiffen the tire casing and improve wear performance and tire handling. The bead wire anchors the tire and locks it onto the wheel.

Textile
Textiles in tires are various types of fabric cords that reinforce the tire. Tire fabric cords provide dimensional stability and help support the vehicle weight.

These textiles are polyester cord fabrics, rayon cord fabric, nylon cord fabric, and aramid cord fabric. They are used to make the tire plies in passenger tires. While they serve as the primary reinforcing material in the tire casing and they also help the tire keep its shape in different road conditions which provide added endurance and performance characteristics to the tire.

Fillers (Carbon Black, Amorphous Precipitated Silica)
Both carbon black and silica are fillers that reinforce the rubber, that is, improve properties such as tear, tensile strength and abrasion. This results in improved wear performance and traction. Silica use improves rolling resistance.

Antioxidants
Antioxidants help to keep rubber from the breaking down due to the effect of temperature and oxygen exposure.

Antiozonants
Antiozonants are used to impede the effects of exposure to ozone on the surface of the tire.

Curing systems (Sulfur, Zinc Oxide)
Sulfur and zinc oxide, are crucial ingredients to transform rubber into a solid article during vulcanization or tire curing. Curing systems shorten the vulcanization time and impact the length and number of crosslinks in the rubber matrix that form during tire curing or vulcanization.

<end quote>

That looks complex to break down.... I don't know enough about breaking things down to say any more.
hmmmmm

I suspect the real game would be to make tires less harmful.  

John,

In practical measures you may be correct, but....

Pearl,

Nice bit of research.  I suppose the part that concerns me the most are the natural and artificial rubber/latex used in tire construction.  In my mind, this is the part that partially degrades, spreads but does not "compost" to use an imperfect phrase.

So my thinking was that all that natural (and I think artificial) rubber/latex is made from crude oil.  Crude oil is made from ancient trees.  I think it would be interesting if we could discover some bacteria, fungus, whatever that actually could feed on the rubber/latex.  It turns out that there are microbes that eat crude oil and some types of algae can grow inside diesel tanks, so this may not seem as far-fetched as it seems at first.  I am just hypothesizing, but it seems to me that "composting" tires would be a great way to get rid of them.

Again, I don't actually know if this is possible and this is why I am posting the question in the first place.

Eric

Eric Hanson wrote:

I am just hypothesizing, but it seems to me that "composting" tires would be a great way to get rid of them.  

Yeah - the devil's in the details!
What parts compost and what doesn't?
Can it be done in such a way that what doesn't compost can be re-captured in some way? For examples: 1) at a medium scale "tire composting factory" the compost could go on a belt with a big electro-magnet that would "re-capture" the steel (assuming it's not stainless) 2) the compost could go into grow beds where specific plants are grown that are known to capture nasty chemicals like heavy metals. Those plants then get composted to concentrate the toxins until they're dense enough to be worth value recycled into new tires or something else. (This has been done on Brownfield sites in England if the article I read is accurate, but I think it was done with lead.)

I wish there was more trusted research on this subject. I *do* know that one of the worst air-quality days a year or two back was when a tire stockpile in a nearby city went up in flames. That is *not* a good way to go! We need a better way than that, but may have to accept a "less than perfect way" just to avoid it. Rubber's just too darn useful for things modern humans like.

Has anyone looked into alternatives to modern tires? I don't think we're keen on going back to wooden wheels! That's not the topic here, but I still love to hear ideas!