Rubber mulch is a type of mulch used in gardens and landscaping that is made from recycled rubber, most often crumb rubber sourced from waste tires. Composition Rubber mulch generally consists of either waste tire bits or nuggets of synthetic rubber from tires that are shredded or ground up whole, after having their steel bands removed. Almost any tire can be used to make rubber mulch, including passenger vehicle tires and large truck and trailer tires. Bits or nuggets are produced from shredding and steel removal from waste tires. Rubber Mulch (Bits and Nuggets) range in size from 10 mm to 32 mm, or 3/8 inch to 1 inch. Advantages Rubber mulch provides some advantages over plant mulches. For landscaping and gardening purposes, both nuggets and buffings insulate soil from heat, allowing a 2 or 3 degrees F higher soil temperature difference over wood mulches. Rubber mulch is beneficial for soil moisture, as rubber is non-porous and does not absorb water on its way through to the soil. It also reduces fungus growth and plant growth, and becomes a weed barrier, as weed seeds dehydrate in the mulch before reaching the soil. Another advantage over plant-material mulches is its elasticity, which gives it a springy quality when used in a fairly thick layer. This makes it a choice for playgrounds, where the springiness provides additional safety for children when they fall off of playground equipment. Tests have shown that rubber mulch is superior in breaking falls to traditional bark mulches. The International Play Equipment Manufacturers Association has certified some rubber mulches for ASTM F1292-09. Disadvantages Unlike organic mulch, rubber mulch does not enrich soil or increase soil biodiversity through decomposition. Neither nuggets nor buffings provide any humus to compacted soil types. At worst, it leads to soil contamination (see Environmental Impact and Safety Testing) Some recycled varieties may leach chemicals (some toxic) which are harmful to plants Rubber mulch is a particular hazard if ignited because of the resulting fumes that resemble those produced in tire fires. Rubber mulch is also more likely to ignite and harder to extinguish than other mulches. Compared to organic mulches, rubber mulch can become extremely hot when in direct sunlight. There is concern about the potential for negative effects of rubber mulch nuggets migrating into waterways. Environmental impact and safety testing In the US, the Environmental Protection Agency (EPA) has launched a multi-agency Federal