Lazy bastards, rejoice — letting your highly manicured patch of lawn grow could help reduce levels of global warming.
That's what North Carolina researchers say. At least, that's what you can tell your potentially pissed-off neighbors.
OK, it's a bit more complicated than that. But a new study led by Appalachian State University geochemist Chuanhui Gu found that even though grass sequesters carbon dioxide, the leading human-generated greenhouse gas, tending to your lawn through mowing, irrigating, and fertilizing creates a lot more greenhouse gases.
"In terms of overall percentages, I would say it's emitting about five or six times more CO2 than what is absorbed," Gu told VICE News. "It's not even close. It's a big deficit."
That deficit doesn't just come from running lawn mowers and leaf blowers, though the noisy, smoky two-cycle gasoline engines that power most of those devices don't help matters.
Most of the carbon footprint of an urban lawn comes from the manufactured fertilizers used to boost their color and density, Gu said. When those nitrogen-based fertilizers are broken down in the soil by microbes, the end product is nitrous oxide.
"Nitrous oxide is a very potent greenhouse gas, almost 300 times stronger in global warming potential than CO2," Gu said. So in the end, a neatly manicured swatch of green could end up producing the equivalent amount of greenhouse gas emissions as one transcontinental flight every year. That adds up to an estimated US total equivalent of about 25 million tons of carbon dioxide, he said.
'If you don't fertilize your lawn, it's going to become crappy, and you're going to get a complaint from your neighbor.'
That's a tiny piece of the total US carbon emissions of 6 billion-plus tons in 2012, according to US Environmental Protection Agency figures, six percent of which was nitrous oxide. But its share has been growing in recent years.
The findings appear in the latest issue of the Journal of Environmental Management, a peer-reviewed scientific publication.
Gu and his colleagues studied a patch of grassland in Nashville, Tennessee and fed the data they collected into a computer model to calculate the emissions from three different levels of lawn maintenance. After all, nobody can be expected to just let their yard be reclaimed by the weeds: Appearances and peer pressure eventually kick in.
"If you don't fertilize your lawn, it's going to become crappy, and you're going to get a complaint from your neighbor," Gu said. But he said that by using the minimum amount of fertilizer, irrigation, and mowing, a homeowner could cut emissions 60 - 80 percent.
Using an electric lawn mower instead of a gasoline-powered one can reduce your carbon footprint — but since electricity is still produced largely by coal-fueled power plants, it may be less effective than you think.
Gu told VICE News the best way to cut lawn emissions is to reduce the amount of fertilizer by leaving grass clippings on the lawn, rather than dumping them in the trash.
"Later on, when they're buried in the landfill, the decomposition is going to release a lot of CO2 and methane back into the atmosphere," he said. But letting those freshly cut blades of grass sit where they fall "can serve as a very good nutrient source."
It also saves money, "so it's kind of a win-win situation," he said.
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