Crumb-rubber infill is derived from scrap car and truck tires that are ground up and recycled. It’s the most widely used infill in the synthetic sports field and landscape market — according to the Synthetic Turf Council, there are an estimated 11,000 multi-use synthetic turf sports fields and playgrounds in North American schools, colleges, parks and professional sports stadiums. Crumb-rubber infill has been a source of debate across the country since late 2014, when parents and health and environment advocates began demanding studies about whether repeated contact with the material, suspected by some to be carcinogenic, could cause cancer (the ground-up rubber pieces can end up in the mouths, ears and clothing of athletes). SportsField Management recently reported on the debate of whether or not synthetic turf athletic fields with crumb-rubber infill cause cancer.
The fact is, crumb rubber is just one of several available synthetic turf infills. Here are some infills that can be used as alternatives to crumb rubber:
Several organic infills are available in the North American market, and all utilize different organic components, such as natural cork and/or ground fibers from the outside shell of the coconut. At the end of its life cycle, it can be recycled directly into the environment. There are concerns regarding heat and mold with organic infills, however.
2. Sand (Silica)
Pure silica sand is one of the original infilling materials utilized in synthetic turf. This product is a natural infill that is nontoxic, chemically stable and fracture-resistant. Silica sand infills are typically tan, off-tan or white and — depending on plant location — may be round or sub-round in particle shape. As a natural product, there is no possibility of heavy metals. It can be used in conjunction with many other infills on the market to provide a safe and more realistic playing surface. The round shape plays an integral part in the synthetic turf system. Silica sand can be coated with different materials as a standalone product or can be used to firm up traditional crumb-rubber infill systems.
3. Nike Grind
This is a multi-colored rubber made from 100 percent recycled athletic shoes. Made of contaminant-free recycled materials, a “slice-and-grind” technique is used, as each shoe is cut into three slices — rubber out-sole, foam mid-sole and fiber upper. These slices are then fed through grinders and refined for use.
4. Coated Rubber
Both ambient and cryogenic rubber can be coated with colorants, sealers or antimicrobial substances if desired. Coated rubber provides additional aesthetic appeal, reduction of dust by-products during the manufacturing process and complete encapsulation of the rubber particle.
EPDM (Ethylene Propylene Diene Monomer) is a polymer elastomer with high resistance to abrasion and wear and will not change its solid form under high temperatures. Typical EPDM colors are green and tan. EPDM has proved its durability as an infill product in all types of climates. Its better-thanaverage elasticity and resistance to atmospheric and chemical agents provide a stable, high-performance infill product.
Thermo plastic elastomer (TPE) infill is non-toxic, heavy-metal-free, available in a variety of colors that resist fading, long-lasting, and 100 percent recyclable and reusable as infill when the field is replaced. TPE infill, when utilizing virgin-based resins, will offer consistent performance and excellent GMAX numbers over a wide temperature range.
7. Coated Silica Sand
Consisting of coated, high-purity silica sand with either a soft or rigid coating engineered for synthetic turf, these coatings are either elastomeric or acrylic (nontoxic) and form a bond with the sand grain sealing it from bacteria. Coated sand is available in various sizes to meet the application’s needs. Depending on the amount and type of infill, coated sands can be used with or without a pad and are available in various colors. All of the coatings are nontoxic and are bonded to the quartz grain for durability.
EDITOR’S NOTE: Many of these alternative synthetic infills are more expensive than crumb rubber, and many lack long-range performance data.