Use the Search box at the top of the forum main page to search for Rubber Mulch. You'll see all kinds of discussions on its merits and demerits. All depends on what you are trying to do.

Where are you going to put this mulch? Playground, garden weed control, around the foundation...?

Do you want a durable mulch you don't have to replace or do you want to feed the soil beneath?

There is a huge difference between rubber mulch and other types!! Rubber mulch is not appropriate for anything that is growing but perfectly acceptable as a playground surfacing material. Also a huge difference between any organic mulch versus an inorganic mulch. What are you needing to mulch and what are you trying to accomplish by mulching?

Hi.. I was thinking I would try to use it in front of my house along with the foundation plants, but after hearing this in no appropriate for growing then I should use regular mulch. Thanks.

Also be aware that rubber mulch can really, really smell.

The only thing rubber mulches do is move a hazardous waste into your yard. Rubber mulches will not contribute anything worthwhile to the soil, can smell really bad on a hot summer day, and will not stop weed growth any better than the less expensive vegetative mulch materials.

Many playgrounds that once had shredded tires on the ground have removed it because of the hazardous nature of the material and because those shredded tires tend to catch fire fairly easily.

kimmq is kimmsr

WhO yOU callINg SMelly?

While I don't like rubber mulch for most applications, 'hazardous waste' has a particular legal definition which tire rubber does not fall into. Of course a number of other things that are not particularly good for you are also in that category. But just in case anyone actually thought tires are RCRA Hazardous Waste, they're not.

Back when I was a firefighter we would sometimes find a stash of tires in the woods during a fire and that tire dump would be labeled a Hazardous Waste area and the EPA would come in and monitor the removal of not only the tires but the soil under those tires. Some substances found in the soil under those tires was Cadmium, Chromium, Manganese, Molybdenum, and high levels of Zinc, all plant micro nutrients yes but in toxic, to plants amounts. Suddenly, when someone found they could shred these tires and sell them as a mulch, these problems went away.

I know that one a hot summer day if I encounter rubber mulch someplace
I immediately have difficulty breathing, but then freshly mown grass does the same thing.

kimmq is kimmsr

Wow... I came to the right place to ask about this. I had no idea about the effects of rubber mulch. Thanks so much for all the important information about this. I appreciate it.

Well, the tires are a Solid Waste but of course those are regulated too, hence the oversight. And yeah, there are all kinds of materials that have toxins IN them but the material itself is allowed to be used. Look at asphalt or driveway sealer: it's full of polycyclic aromatic hydrocarbons (PAHs, the carcinogens in soot). Millions are spent remediating sites like former manufactured gas plants where this stuff is in the soil and groundwater. Yet we spread it all over the roads by the millions of tons per year. It's a strange world.

I can't add anything to the toxicity discussion, but I will say that rubber mulch burns way hotter than wood mulch. For that reason alone I would not use it adjacent to any structure, especially if you are in an area prone to wildfire.

Good point, something we don't often think about in the Midwest, but anyone who's watched the news from out West lately knows exactly what you're talking about.

But rubber mulch never really contributes anything to the soil. It's just inert, and displaces things that might contribute to the soil. I guess if you don't want to build soil quality, rubber mulch could work.

It has its uses as long as one understands the limitations, IMO. I have not had occasion to use it since I like to feed the soil with degradable mulches.

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.

The Bottom Line
• Rubber mulch is not as effective as other organic mulch choices in controlling weeds
• Rubber mulch is highly flammable and difficult to extinguish once it is burning
• Rubber mulch is not permanent; like other organic substances, it decomposes
• Rubber mulch is not non-toxic; it contains a number of metal and organic contaminants with
known environmental and/or human health effects

https://puyallup.wsu.edu/wp-content/uploads/sites/403/2015/03/rubber-mulch.pdf

Rubber mulch decomposes, but quite slowly. It is advertised as being good for a decade. One advantage of rubber mulch versus wood mulch is that it's a more effective insulator. So in very cold climates, the soil can be kept a bit warmer with rubber mulch.

As to the toxicity of rubber mulch, which is made up of ground up tires, our environment is loaded with ground up tires. When you wear out a tire, guess where all that rubber has gone? So although there can be bad things in the tires, there really isn't much of them. The EPA seems not too concerned about rubber mulch.

Joe, you are a representative of the rubber mulch company that you are determined to shill. That you are trying to hide it is a clear indication that you're well aware that SPAMMING is not allowed in the Gardenweb.

Go away.

https://puyallup.wsu.edu/wp-content/uploads/sites/403/2015/03/rubber-mulch.pdf

There are a lot of good arguments in this fact sheet but I do wish its claims were accompanied by references. I would like to see the published literature on aquatic toxicity of tire leachates.

One thing that bugs me when people talk about toxins is the following general progression:

"This [product, in this case rubber mulch] contains a certain chemical."

"This chemical has toxic effects."

"In high enough concentrations, it can be harmful to health, with effects ranging from skin and eye irritation to major organ damage and even death."

There is an implication that rubber mulch can kill you, but there is NO information on the expected DOSAGE from exposure. ARE the concentrations high enough to have those effects? Thus the risk is overblown by insinuation. Will rubber mulch in your flower bed kill you? I seriously doubt it - it would require massive amounts of these chemicals to enter your body, which they won't from this type of exposure. It may contribute incrementally to the risk of cancer or other diseases. No argument there, and this is not unimportant, but it's 2017, and we should get over this sophomoric approach of scaring people about toxicity. It's simply not fair to list deadly acute effects requiring high doses and apply this to a chronic low-dose situation. If you do, you have to do the same for other things like table salt, which is just silly.

There are plenty of reasons to do something else with our used tires, and we don't need to stretch the truth to make the point.

I believe Bucknell University did the initial research on the rubber mulch leachate being toxic to marine organisms.

Otherwise, the primary issue with rubber mulches (recycled tires) and the environment is the leachate of heavy metals (including cadmium, chromium, aluminum, copper, iron, manganese, molybdenum,
selenium, sulfur, and zinc) into the soil with degradation over time. Zinc in particular makes up as much as 2% of tire mass and accumulations of it in excess can and does kill plants. There are also issues with plasticizers, rubber softeners, fillers and accelerators used in the vulcanization process that can also be harmful to aquatics, soil life and plant growth. And ground rubber also contains a
class of chemicals called Polyaromatic hydrocarbons (PAHs) that many studies have found
extremely toxic to humans and the environment.

The research is out there. You just need to hunt it down :-)

I'll say it again. There is VASTLY more rubber tire in your environment than you could ever put into it with rubber mulch. Think about it. How fast do tires wear down? When they do, that's rubber dust in the air, on the ground, raining down on our rivers and lakes, and all over the place. You live anywhere near a roadway, you're breathing rubber dust every day. Now, for gardens, I don't think rubber mulch is particularly useful, but if rubber dust was very toxic, we'd all be dead by now. Rubber does contain some toxins, but rubber mulch is pretty irrelevant to the abundance of those toxins in our environment.

No one is arguing that there is rubber dust from tires in the air. And there is a ton of rubber particles that get washed into groundwater and streams, etc. with run-off from roads and highways with heavy rainfall, however this is pretty well documented as a source of water pollution. But neither of these issues are the same as piling inches of rubber mulch onto planting beds and the leaching of the toxins/heavy metals directly into the root system of plants. Probably won't kill 'em but it's not doing them any good and is definitely something to be avoided if these are plants producing anything you might want to eat!!

Gardengal, I have no problem with anything you said. I oversee cleanup of contaminated sites with all these contaminants - especially PAHs which are ubiquitous in the urban environment and many of which are carcinogenic (particularly benzo(a)pyrene which has no beneficial use to anyone on the planet). I only have a beef with the way people equate low level exposure with deadly acute toxic effects. It makes my job harder when I have to explain to someone that the parts per billion plume of solvents under their neighborhood, while not drinkable, is not going to give them convulsions and death just from living on top of it, even though that is a known toxic effect of the chemical in question. People generally have a very poor understanding of dose/response and relative risk.

It would not be that hard for the author to make a bibliography at the end if they're going to cite all that research. I shouldn't have to find it all myself. It's not that I can't, but I would be more likely to be an ally and to repeat the claims if I could easily verify them. I had to, when I wrote technical papers that made claims. But I digress.

None of this is about the facts, and actually the metal leaching concerns me in particular, not so much about runoff and aquatic life but about buildup of metals in the soil that the rubber is placed on. I think the stuff is better used as a fuel. That destroys all the PAHs and plasticizers, and the metals end up managed in the ash. Our local power plant actually burns some of it that comes from a state-run tire pile cleanup program - now that's a win-win!

A good paper about health risks from tire dust that comes from people driving around, and the massive amount of that dust in our environment.

http://file.scirp.org/pdf/JEP_2013061711221865.pdf

On this scale, garden usage of rubber mulch is completely insignificant as an environmental pollutant. Besides particulate hazards (which include that from PAHs), another issue is latex allergies.

There are actually folks who use tires as containers for raised beds. No worse for the environment than if those tires were sitting in a dump somewhere, but yes, I'd think twice before eating stuff that came out of those beds. I am skeptical about whether plants actually take up any of those toxins, though. There has probably been research on that, but I am unfamiliar with it.

Worried about toxic tire dust? Don't worry about rubber mulch. Stop driving.

I use big tractor tires and not big tires with pretty pattern as a raised beds or pots. The mix at the walls is always dry, thus roots never go there. If there is no water in that area how any toxins could arrive to the plant? I painted all my tires several coats with latex paint to close any gases from heating tires under sun. Next time when I change potting mix in them, I 'll paint their inside wall if i won't be too lazy at that point. :)))

Loads of stuff on the web about this. You can find arguments for and against it. This is the only thing I found that comes from what can be considered a credibly scientifically informed source.

https://ask.extension.org/questions/305496

In the short term, I can't imagine that leaching from unshredded tires would be that serious. If tires degraded significantly, they'd fall apart. They don't. As I pointed out above, our environment is absolutely filled with tire dust. You breathe it in every day. It's leaching away in our lungs. It probably coats a lot of our food as well. If it was toxic in those quantities, we'd all be dead. As noted, it's a matter of respecting dose/response and relative risk. So you can worry about what tires leach into your plants, but if you're worried about tire leachates, I wouldn't worry about your plants.

That being said, as to the mix at your tire walls always being dry, I have to wonder if it ever rains where you are. Also, water gradually permeates all through soil in a container. If you water your bed, moisture will make it to the sides. Doesn't take much to move chemicals around.

In theory, it should be wet, but in reality the soil near tire's wall stays dry. We have rain, and very heavy sometimes, and I water those beds/pots ; but,

A tire is a great raised bed because no any sawing/assembly involved, no any termites or other insects will destroy it, it has great heat insulation thanks to material property and constant air gap between inside walls and growing mixture ( that is important for roots in very hot summer days). Easy to relocate if needed. And it is free and saving a tree. :)

I agree that at least structurally, tires look like they make great raised beds. Not sure what you mean by an air gap between the walls and growing mixture, though. Your soil is going to naturally fill the whole space inside. As to water on the sides, I would think that tires have an inside lip where water would tend to collect. The walls probably look dry because the top edge dries out first.

At least where I am, painting the tires white on the outside would be essential just to keep the heat down. Black tires in full sun will get pretty toasty. I don't think rubber tires have insulation that's much better than a similar thickness of wood, though.

I guess if you want to move it, you just roll it, right? And certainly they will last a long time.

I don't know why, but after I fill the tire very tight with growing mixture, some time later it squeezes toward to the center and leaving an air gap between a wall and mixture. It happens again and again after I spread dirt to the walls or add more mixture on top.

That's really interesting. Not sure why it would do that. Maybe as the water applied to the center leaches stuff out of the middle, the sides pull in to fill the space? It is true that in raised beds with wooden sides, the soil tends to pull away from the walls. But I agree that if you end up with an air gap there, the insulation will be good. In principle, if insulation is important, you could stuff the inner rim of the tire with some foam.

I suspect the soil is shrinking when it's dry. If you soak it, it will probably expand back to its original size. There could also be some shrinking and swelling of the tire itself with temperature, but I think that would be relatively minor.

I've researched plant uptake of toxins as part of my work, in search of safe levels of toxins in soil for gardening or row crops. I can tell you that the progress that has been made on that front is minimal. Other than lead, it's not really being studied. All the advice that's out there about reusing abandoned urban/industrial land for gardening, for example, basically says "test it and if the lead numbers are high, replace the soil or build raised beds." "High" is usually defined as 'above a safe level for direct exposure in a residential setting', a number which is not derived directly from plant uptake anyway. Your chances of finding a safe number in parts per million for some plasticizer in garden soil, or even for zinc, are slim to none. That's just where the science is at.

Very interesting. You'd think that toxin uptake by plants would be something that would be analytically straightforward to do. I suppose the reluctance to do it might be because the uptake is highly dependent on other environmental factors. For tires, it's mainly about zinc. I've heard that tires are a few percent zinc! That's pretty toxic to plants, but it isn't clear that it's all that toxic to humans.

Zinc could have various forms in this situation - metallic, or as a salt for example. Or corroded zinc metal (zinc oxide). (There are even organo-zinc compounds but I don't know if these occur in tires). These will all behave differently in the same type of soil. Superimpose differences in soils and it gets even more complicated.

Assessing the risk from soil alone (direct exposure by passive ingestion, inhalation of dust, and dermal contact) is usually based on total concentrations (regardless of form), perhaps an oversimplification but at least it gives some results to work from. Gardening (i.e. eating plants) is more complicated.

Different plants will uptake the various forms of metals at different rates. Any chemical, once taken up into the plant, may or may not degrade (obviously with zinc this isn't a question) and will also be deposited in different parts of the plant at different concentrations. To do a human health risk assessment, you'd have to take all this into account to estimate a dose from eating even a single type of plant out of a garden. Multiply all that by the hundreds of chemicals typically addressed at polluted sites, times all the vegetables you might grow, and it becomes an enormous task.

About the only one we know very much about is Pb since it's been studied to death. You can actually correlate blood lead levels to soil concentrations as well as toxic effects, and as a result it's the only contaminant to have safe levels in soil directly based on known health effects. For everything else, there's a crap ton of modeling in between.