Locally grown does not always mean a lower footprint?

Food production is taking root in cities, from commercial rooftop greenhouses to indoor “vertical farms” in warehouses that maximize space efficiency by growing plants in layers from floor to ceiling. For Neil Mattson, associate professor in the School of Integrative Plant Science at Cornell University, the viability of these projects comes down to their carbon footprint. Mattson directs the college’s Controlled Environment Agriculture group, which aims to reduce New York state’s dependence on imported food.

Neil Mattson. Photo by Chris Kitchen.

“One of our research topics is looking at the carbon footprint of producing food in different ways,” he says. “Looking specifically at lettuce, strawberries, and spinach, we found that there’s a much smaller carbon footprint if they are field grown in California and shipped to New York than if they are grown locally in greenhouses. We have more cloud cover and need to provide more supplemental light, which increases energy use.”

However, Mattson has been researching advances in lighting and greenhouse technologies that can reduce the carbon footprint of local greenhouse-grown produce. Efficient LEDs use less energy and can turn on and off in milliseconds in response to the temporary shade of a passing cloud—unlike the more commonly used high-pressure sodium lights that take 15 minutes just to warm up. LEDs also allow growers to adjust the light spectrum to make photosynthesis more efficient and improve crop quality.

New York is already second in the nation in controlled-environment agriculture, netting $27 million a year in wholesale income in the 2012 Census of Agriculture, and Mattson’s research has led him to conclude that of the options for growing food in the city, greenhouses are the best choice for environmental sustainability. Growing food in warehouses (or “plant factories”) requires artificial light—and HVAC systems to manage the heat produced by such light—creating a much higher carbon footprint.

While Mattson remains skeptical about the ability of urban agricultural practices to feed entire cities, he has seen firsthand the ripple effect community gardens can have on a neighborhood’s nutrition, particularly in food deserts where schoolchildren have only been exposed to a handful of common fruits and vegetables.

He cites the example of Harlem Grown, a community garden located in the middle of a Harlem food desert, which has shown him that the impact of exposing children to gardening goes far beyond diet. In addition to operating local urban farms, Harlem Grown provides garden-based development programs to Harlem youths. In turn, kids have been bringing home vegetables their parents can’t find in the grocery store, from mustard greens and dwarf kale to koji—and their parents have begun to request local bodegas carry them.

“Even if urban agriculture can only provide a small portion of our daily nutritional needs, the psychological and educational benefits are huge,” Mattson says.

Source: Cornell University