Overview
The use of rubber chippings in outdoor mulching, as an alternative to natural bark mulch and wood chippings, is 'reportedly on the rise' - although by how much, we aren't able to say. 'Rubber mulch' can have many applications and go under different names. They are often different product types altogether. Rubber chip and rubber bark, are two of many examples. Yet, there are practical differences to the various types of recycled rubber aggregates manufactured, which is important to know when planning for a project.
Indeed, there are many applications of rubber decorative aggregates, many known generally as rubber mulch. The main ones seem to be in play areas and equestrian surfaces. They can benefit from a soft and bouncy floor, offering a good critical fall height rating which can help to reduce the number of injuries, and minimise their severity. We cover this in rubber mulch for playgrounds.
However, this article will focus specifically on the topic of using rubber chippings as a garden mulch. Our goal is to present the pros and cons to help you make an informed choice about using rubber chippings for mulching in your garden. We will also add a comparison to traditional, organic mulches.
Key Takeaways
- 'Rubber mulch' is a type of shredded recycled tyre rubber. It is often dyed or coated.
- Some marketing product descriptions advertise questionable benefits and lack any balance.
- Rubber mulch seems more suited to where it is most commonly found, in play areas, equestrian and safety surfaces.
- Labeling a decorative aggregate like recycled rubber as 'mulch' may be a misclassification.
What Exactly is Mulch?
According to the Royal Horticultural Society, "Mulches are loose coverings or sheets of material placed on the surface of soil.", of which there are two main groups; biodegradable and non-biodegradable. Both types suppress weeds and conserve moisture.
However, in the section on non-biodegradable mulches, the RHS advises that "it is best not to use any materials made from plastic." Furthermore, as you can see, there is no mention of the new and innovative "alternative" rubber chippings. They do not even make the list.
So What Exactly is Rubber Mulch?
Definitions and names can be very important when trying to buy something new. Identifying which product is most suited to do the job is the way we arrived at the type we will refer to as 'mulch rubber'. For the purpose, we looked at how it is processed. Logically, the product is shredded rubber - thin strands (and nuggets) that range in length from 10- 32 mm.
Now that there is clarity on the specific form of rubber we have chosen to road test as 'rubber mulch', it's nearly time to put the stuff to the test.
Specimen (a) is most commonly used as mulch. (b) is chipped rubber, often confused with type (a)
Looking For The Signal In The Noise
For every topic we cover, we develop our content through a structured process. This helps to imbue a level of impartiality, being built into the outlines by design. Adhering to it helps the final content satisfy a minimum threshold of topical coverage - hopefully, enough for you to be able to form your own empirical assessment of the featured product or project.
Therefore, we feel that it's entirely appropriate to clearly state where Outdoor Aggregates is coming from, especially for this subject. Our ethics page could be a good place to start, but also, here is our mission. Our over-arching philosophy is simple:
"When you market a product or service just by selling the truth, eventually, that market will find you, and from that day, they will always be, and always remain, the greatest marketing, that was forever free!"
An Absence of Balance Or Impartiality To The Truth
With rubber mulch, the process we set out to follow became a bit of an eye-opener. Through our research online, something came to our attention, and what stood out was just how little, if any, reliable information was readily available, especially about any potential negatives. And the same can be said for all types of recycled rubber chippings, generally.
There is an odious imbalance towards a partiality. While it was easy to locate plenty of content touting all of the benefits, and claims about being completely 'harmless'; at the same time, it was almost equally as difficult to find any information about potential downsides.
When marketing content and slick blogs (written by affiliate marketers to seem impartial) almost exclusively occupy the top positions in Google search, it can greatly shape the discourse and therefore public perceptions. To the trusting observer, it could appear the all of these quite gratuitous advertisements are indeed the facts. Perhaps it's partly due to the absence, or lack of visibility, of any other contrary information.
Caveat Emptor - A Word To The Wise
Before we return to our regular format, it might also be worth us mentioning the importance of a product description to marketers, as they are crucial to how you perceive their product online. Unfortunately, it's a cold hard fact these days that many online sellers tend to be very crafty with their product descriptions and marketing techniques. There are entities prepared to employ just about any strategy to outright deceive potential customers about their product's quality or durability - even potential health risks - just to get your money.
That's why it's wise to always try to be a bit skeptical about marketing and do some independent research before buying. If you are feeling skeptical, so are we. Nevertheless, best to keep an open mind!
Advertised Benefits of Rubber Garden Mulch
First, we will use the headings to briefly summarise many of the commonly advertised benefits touted online for using rubber in place of organic mulches. We will then respond to each one with our own assessment based on research. We also use some examples of recurring 'factual' claims online. Once the benefits are covered, we move on to list potential downsides, putting them all on the record in the one place.
Enhanced Durability?
The first is the exceptional durability, particularly when compared to wood mulch, despite being 3-4 times more expensive. The common claim is that because it doesn't rot (like organic mulches), it is a very long-lasting solution for outdoor areas. Here are some of the claims:
"Landscaping Rubber chippings last 10 times longer than wood bark."
"Unlike traditional landscaping materials, they won’t break down or decompose over time, making them a cost-effective investment in the long run."
Unfortunately, rubber mulch is not everlasting; while it does decompose at a slower rate than wood mulch, it deteriorates due to the effects of weather, suffers a fairly common problem of turning white from fungi infestation, and certain bacteria cause it to degrade into leachate. It can also serve as a habitat for various insect species.
We can't find any evidence that rubber mulch lasts ten times longer than wood. The best we could find was 2-3 times longer (but in what condition by the end?)
Given the evidence we found regarding the potential for UV to cause dramatic colour fading within just a year, it's hard to imagine how worn the stuff could look in 4 years, let alone 8 - 10 years time. Our opinion here is that the durability claims are dubious at best. Proceed with caution!
Eco-Friendly Choice?
Benefits such as the notion that gardens love rubber mulch, and that by using recycled rubber tyre mulch as a great way of repurposing materials and reducing waste, you are doing your part for the green revolution, are all too common.
"Made from recycled shredded tires, our product helps the environment. It is nontoxic and safe for children, your pets & your plants." "Perfectly Safe!"
The reality is that rubber mulch can contain potentially harmful minerals and compounds that may come from the tyre manufacturing process or picked up during the tyre's use. The risk of harm increases with the surface area of synthetic rubber waste, potentially leading to the release of harmful constituents. Zinc and organic toxicants have been shown to have an environmental impact when leached from the debris.
Even just applying common sense here should tell you that nature would never benefit from synthetic pollution, especially in place of a non-toxic form of organic mulch.
Lastly, while advertised as generally safe, it's essential to double-check with the retailer, and your veternarian, that the specific type you're considering is non-toxic for your pets.
Low Maintenance?
"Unlike organic mulches, rubber mulch doesn’t need to be replenished or replaced, so once it’s installed, it can last for years without needing to be replaced."
While there is debate about just how long they retain their luster, with services out there for re-spraying, they obviously do deteriorate. By how much and over what period of time is difficult to pin down. The specific conditions will have a large bearing on longevity.
Topping up with new chips is suggested online, but the depth will increase with each new layer. Weeding by hand is also the only alternative when they do get going, and it isn't as easy as with organic mulches. Furthermore, once it's down, rubber mulch is very difficult to get rid of, especially removing all the rubber in the ground. Again, all worth considering.
Natural Drainage?
"Made from shredded recycled tyres, meaning it is environmentally friendly, it is a water permeable safety surface with the look of natural bark."
The benefit of allowing rain water to drain naturally, ensuring surface water doesn't accumulate and the underlying soil remains in good health, indeed seems questionable.
For one, the compulsory landscape fabric may get obstructed by minuscule rubber or soil particles, obstructing the passage of water. This can adversely affect the ecosystem insects such as earthworms by depriving them of oxygen, whilst leaching toxic contaminants simultaneously.
Also, without any organic matter, a sustainable and healthy soil structure composed of mycelium and natural layers of matter, great drainage is not possible. Soils will become anaerobic (favors root pathogens) and water and air cannot enter easily. Hence, conditions may be created that favor disease and since the water can no longer be absorbed, it must run off.
Consider The Downsides
Rubber mulch may offer some advantages, particularly where safety or traction is the primary consideration. However, there are studies that give weight to the genuine concerns which are rarely mentioned or treated with any balance by those who stand to benefit the most.
Non-toxic?: As it degrades, it releases various chemicals, mainly heavy metals like aluminum, cadmium, chromium, molybdenum, selenium, and zinc. Additionally, it emits 2-Mercaptobenzothiazole (MBT) and polyaromatic hydrocarbons (PAHs), which have been proven to have adverse impacts on both human health and the environment.
Aquatic Life: Bucknell University has found that the leachate is capable of killing algae, zooplankton, snails and fish, so beware using it near a pond.
The Zinc Factor: Containing high levels of zinc from its manufacturing process, the effect of excessive levels can be lethal to plants and difficult to remediate.
Emits Gases: Studies have found that crumb rubber can emit gases that can be inhaled. As the material heats, it increases the chance that VOCs leach into the air.
Lack of Decomposition: Being non-organic, rubber doesn't naturally decompose. Thus, it doesn't contribute organic matter to the soil. It is also very difficult to remove.
Heat Retention: It can get very hot under direct sunlight. This heat might make play areas uncomfortable for children and pets.
Highly Flammable: Rubber mulch also burned much hotter and faster than wood and was also harder to put out. If you live in an area of high fire risk, do not use rubber mulch, ever.
As we have demonstrated, there are a raft of downsides which are supported by scientific studies. Aside from the lack of transparency, or rigor, on the part of resellers to advertise the potential dangers, another issue is a lack of long-term studies into its use.
Rubber Vs Organic Mulches?
Longevity and Cost-effectiveness
Rubber bark has a higher initial cost, usually about 3-4 times, although it may not need to be topped up as frequently as bark chippings. This may lead to cost savings, long-term, although the appearance of rubber mulches are known to deteriorate over the years in an unpredictable way. In our opinion, the savings will not be favourable when compared to other alternatives, including wood chippings.
Weed Suppression
While both types will suppress weed growth, one key advantage of rubber may be that it can do the job for a longer duration, with less maintenance.
Aesthetic Appeal
With a wide range of colours, including brown rubber mulch, rubber chippings can add a type of aesthetic that may appeal to some people more than the more natural look, such as bark fines mulch.
The good news is that there are many, natural and non-biodegradable alternatives, like slate chippings. Find out more about that, here.
As A Surface
Wet bark can tend to be more slippery than rubber, which can remain slip-resistant, reducing the risk of accidents. However, walking on mulched areas is not a common activity.
Research Findings
Washington State University's research presents some alarming findings. Their studies showed that rubber mulches, particularly those made from recycled tires, are not the best for gardens or landscapes. Compared to organic mulches like wood chips, they actually seemed less effective in supporting tree growth and controlling weeds. Symptoms like leaf yellowing, stunted tree growth, and even increased tree mortality were observed. For the record, there are also health concerns about using recycled rubber in a children's play area.
Installation of Rubber Mulch
Before you lay rubber mulch, it's essential to prepare the ground by removing any grass with hand trowels and ensuring a smooth, safe surface. Dig to create the required area that will allow you to install at the recommended depth. To prevent weed growth and contain the rubber chips, you must also have laid a weed membrane.
Once you have it in place, spread it evenly across the designated area using a hand trowel or rake. The correct depth of mulch depends on its intended use, with thicker layers needed for playgrounds to ensure safety and less for gardens.
If you are after a bound surface, mixing it with a resin binder creates a solid and more durable layer, which is most suited to high-traffic commercial areas.
Buying Recycled Rubber Chippings
There are countless suppliers who stock rubber chippings sourced from recycled tyres. When it comes to delivery, they typically sell and send in bulk bags, although they can come as loose fill products. Many suppliers offer a range of rubber products, varying in particle size and colour. Be sure to consider this when choosing, and remember - remain skeptical.
Ask the important questions to you, particularly if you have more detailed requirements, and reference our article or suggest the citations if you feel the salesperson is not being honest with you.
Conclusion
With a debate smouldering away about the actual benefits versus the potential downsides, which include health hazards - a somewhat rarity in the word of decorative aggregates - for us, recycled rubber is not suitable as an alternative to any other type of mulch.
The downsides and risks far outweigh the touted benefits as a material to use as a weed suppressant around your beautiful trees and plants. Ultimately, it always comes down to personal choice, but understanding the potential drawbacks and considering the primary purpose should be essential when making your choice.
FAQs
Do you need a barrier for rubber mulch?
A barrier, typically a woven membrane, can be beneficial. It prevents weed growth and ensures the rubber stays in place.
How much is rubber mulch in the UK?
Prices can vary based on quality, colour, and whether it's mixed with resin. It's advisable to contact suppliers for the most up-to-date pricing.
Is rubber mulch safe for dogs?
Generally, yes. However, ensure the type of mulch chosen is non-toxic and safe for pets.
What are the disadvantages of rubber mulch?
While rubber mulch has benefits, it can retain heat in hot conditions, potentially harm certain plants, and might not be as eco-friendly as organic mulches. Find out here.
Is real mulch better than rubber mulch?
It depends. Organic mulch has it's benefits without any risks, while rubber mulch is low maintenance, but best read from the top.
