I fear that my well-tended lawn is wreaking havoc on the environment. I've considered replacing it with synthetic grass, which requires far less maintenance. But manufacturing that plastic vegetation must give off a lot of carbon emissions, right? So which type of lawn is (figuratively) greener—real or fake?
It's tough to declare a winner here without knowing the specifics of your lawn-care regimen, as well as your geographic location. If you're reckless with the fertilizer, oblivious to the consequences of heedless mowing, and live in a drought-stricken region, then ersatz grass has the clear environmental edge. But if you're diligent about your gardening routine, the real stuff may be better.
The environmental drawbacks of genuine lawns are easy enough to tally. They're thirsty, of course—the average American lawn gulps down 21,600 gallons of water per year. Lawns planted atop sandy soil can be particularly wasteful since they drain more quickly. And the water usage problem is particularly acute when a homeowner insists on laying sod that's ill-suited to the local climate.
Gas-powered mowers, meanwhile, are hazardous to more than just eardrums. A 2001 study by Sweden's Stockholm University found that an hour's worth of mowing resulted in the same amount of smog-forming emissions as driving a car 93 miles. Mower manufacturers contend that their newer models have become cleaner, yet they still resist calls to add catalytic converters to their products; according to the Swedes, doing so would reduce mower emissions by 80 percent.
Another knock against real grass is that it's frequently drizzled with fertilizer, most of which is synthetic. American homeowners use about 3 million metric tons of synthetic lawn fertilizer per year. The fossil fuel equivalent of a barrel of oil goes into manufacturing 560 pounds of such fertilizer, so our collective lawn habit is costing us more than 11.8 million barrels of oil annually. We also use 70 million pounds of pesticides and herbicides on our lawns every year. Clippings that are improperly disposed of can end up polluting major waterways.
On the plus side, lawns do act as carbon sinks. According to a 2005 NASA study, the United States is covered with roughly 40 million acres of tended lawns. Assuming all clippings are bagged and tossed in the trash, those lawns can soak up about 13.2 million pounds of carbon dioxide per year. But the study's authors stressed that the lawns' carbon absorption is likely negated by the amount of energy that goes into making synthetic fertilizer and powering mowers.
While it's not entirely maintenance-free, synthetic grass requires neither water nor fertilizer nor mowing. Its greatest environmental sin occurs during manufacturing, since the production of polyethylene and other essential fake-grass materials (such as polymers and elastomeric coatings) is energy intensive. One must also consider the inevitable disposal issues—like most plastics, aside from those found in beverage and detergent bottles, artificial turf is typically landfilled rather than recycled.
So how bad is fake grass? The best life-cycle study the Lantern could find is this one (PDF), in which Canada's Athena Institute tried to calculate the carbon toll of converting a school's playing field from real grass to artificial. The new field could be made carbon neutral, the study's authors concluded, by planting and maintaining 1,861 trees for a decade. But keep in mind that this was an athletic pitch measuring 96,840 square feet, not a piddling single-family lawn. And Athena's calculations had to take into account the installation of PVC pipes for drainage, something that may not affect the average homeowner.
There are also many environmental activists who revile fake grass that uses rubber infill—that is, crumbs of recycled tires sprinkled between the blades, in order to provide cushioning. They claim that these rubber bits can cause health problems if inhaled; the artificial-turf industry counters that such fears are scientifically unwarranted. The Lantern will note only that the infill issue seems to affect athletic fields more than ornamental lawns and that there are artificial options that don't include rubber crumbs.
The bottom line is that, whichever lawn type you choose, you should commit to managing it responsibly. If you want to minimize your water and fertilizer use by going the fake route, make sure you purchase a quality product that won't have to be replaced for a decade or more.