Cultivated natural grass carries plenty of environmental baggage. According to “Water Management on Turfgrass,” a paper on the Texas A&M University Cooperative Extension website (http://plantanswers.tamu.edu/
), natural grass sports fields can require up to 1.5 million gallons of water per acre per year. The f r e q u e n t m o w i n g required for natural grass lawns and fields also results in emissions of hydrocarbons and carbon monoxide (up to 5% of such emissions in the United States, according to the Environmental Protection Agency).
Natural grass does offer tangible benefits, however. According to Turfgrass Producers International, these include increased pollution control, absorption of carbon dioxide, a cooling effect, water filtration, and prevention of soil erosion. There are also perhaps intangible benefits to a field of grass. Crain presents the idea that replacing grass with synthetic turf can hinder children’s creative play and affect their development. “Today’s children largely grow up in synthetic, indoor environments,” he says. “Now, with the growing popularity of synthetic turf fields, their experience with nature will be less than ever.”
Adds Croft, “Although there is an important need for open spaces, the issue here is not open space but active recreational facilities. I don’t see the connection between open space and installing synthetic turf fields.”
Synthetic turf does offer certain advantages over natural grass. A New Turf War: Synthetic Turf in New York City Parks, a report released in 2006 by the advocacy group New Yorkers for Parks, points out, “Proponents of synthetic turf fields tout the reduction of allergy and asthma triggers. The removal of natural pollens and grasses may be beneficial to children and adults with these afflictions.”
One of the main arguments used in favor of synthetic turf is that it can be installed relatively quickly and, once functional, can be used almost continuously. In contrast, grass fields need time to take root and must be closed periodically for proper maintenance. For example, the Central Park Conservancy, a private philanthropy that maintains New York City’s Central Park, closes grass fields all winter; during the summer and spring, fields are closed on a rotating basis for restoration. Also, tackle football and cleated shoes are prohibited on all of the fields, and the fields are closed whenever it rains or they are wet. According to estimates from the New York City Department of Parks & Recreation, synthetic fields can be open for use 28% more of the time in a year than natural grass fields because they can withstand heavy use, which the department estimates has doubled in the last eight years.
Lower cost for long-term maintenance is another argument that is made for synthetic turf, although the degree of the savings is disputed. It is generally agreed that installation costs of synthetic turf can be almost double those of natural grass. For instance, a synthetic turf soccer field can cost almost $1.4 million compared with a natural grass field at about $690,000. But when the costs are prorated over the expected lifespan of the field, including maintenance, the difference in cost narrows to less than $15,000 more for the natural grass, according to A New Turf War.
Although some, like Benepe, consider this cost savings to be substantial, others consider it insignificant. As Christian DiPalermo, executive director of New Yorkers for Parks, puts it, “The amount of money saved is negligible considering the many unknowns about artificial turf.”
One drawback that both fans and critics of synthetic turf agree on is that these fields can get much hotter than natural grass. Stuart Gaffin, an associate research scientist at the Center for Climate Systems Research at Columbia University, initially became involved with the temperature issues of synthetic turf fields while conducting studies for another project on the cooling benefits of urban trees and parks. Using thermal satellite images and geographic information systems, Gaffin noticed that a number of the hottest spots in the city turned out to be synthetic turf fields.
Direct temperature measurements conducted during site visits showed that synthetic turf fields can get up to 60° hotter than grass, with surface temperatures reaching 160°F on summer days. For example, on 6 July 2007, a day in which the atmospheric temperature was 78°F in the early afternoon, the temperature on a grass field that was receiving direct sunlight was 85°F while an adjacent synthetic turf field had heated to 140°F. “Exposures of ten minutes or longer to surface temperatures above 122°F can cause skin injuries, so this is a real concern,” said Joel Forman, medical director of the Pediatric Environmental Health Specialty Unit at Mount Sinai School of Medicine, speaking at a 6 December 2007 symposium on the issue.
Many physical properties of synthetic turf—including its dark pigments, low-density mass, and lack of ability to vaporize water and cool the surrounding air—make it particularly efficient at increasing its temperature when exposed to the sun. This is not only a hazard for users, but also can contribute to the “heat island effect,” in which cities become hotter than surrounding areas because of heat absorbed by dark man-made surfaces such as roofs and asphalt. From many site visits to both black roofs and synthetic turf fields, Gaffin has concluded that the fields rival black roofs in their elevated surface temperatures.
Although it is often argued that one of the advantages of synthetic turf is that it does not need irrigation, some installations must be watered to control the excessive heat. Benepe stated in public hearings that water misters may have to be installed in some fields to help remedy the heat problem. According to Gaffin, synthetic turf is so efficient at absorbing sunlight, that cooling with water is only temporarily effective. “After a short while of watering, I expect the temperature should rebound and the surface become intolerably hot again,” he says.
In addition to heat control, the International Hockey Federation requires that college teams saturate synthetic turf fields before each practice and game to increase traction, according to an article in the 19 October 2007 Raleigh (North Carolina) News & Observer. The article, which examined why local universities were watering their synthetic turf fields in the midst of severe ongoing drought in the U.S. Southeast, noted that Duke University received a business exemption to water the fields provided overall campus water consumption decreased by 30%.
The EHHI study addressed the question of whether synthetic turf fields can contribute to increased water contamination from rain or from spraying or misting. The study found that 25 different chemical species and 4 metals (zinc, selenium, lead, and cadmium) could be released into water from rubber infill. Moreover, because synthetic turf is unable to absorb or filter rain-water, chemicals filter directly into storm drains and into the municipal sewer system without the beneficial filtration that live vegetation provides. Benepe and others agree this can be an issue that New York City would need to address, as water runoff from synthetic turf fields could overwhelm storm drains, thus contributing to the estimated 27 billion gallons of raw sewage and stormwater that discharge from 460 combined sewer overflows into New York Harbor each year.
Finally, what happens to synthetic turf fields when they are no longer usable? Industry estimates that synthetic turf fields have a lifespan of 10 to 12 years, whereupon the material must be disposed of appropriately. Rick Doyle, president of the Synthetic Turf Council, says the infill could be cleaned and reused; put to another purpose, such as for rubber asphalt; incinerated; used in place of soil to separate landfill layers; or otherwise recycled. Typically, however, it is landfilled.