SAN FRANCISCO (KCBS) – A new study found indoor medical marijuana growers now account for 3 percent of California’s electricity usage, enough to power 1 million homes.

The plant itself may be green, but indoor pot farms produce greenhouse gas emissions equivalent to 1 million automobiles, according to an independent analysis by Evan Mills, a researcher at Lawrence Berkeley National Laboratory.

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KCBS’ Susan Leigh Taylor Reports:

Mills’ findings (.pdf) are not surprising considering how much machinery is needed to ensure ideal growing conditions, said collaborator Scott Zeramby.

Zeramby, who owns Dirt Cheap, an agriculture equipment supply store in Ft. Bragg,  said his medical marijuana customers find grow lights are just the beginning.

“There’s a bunch of ancillary equipment—water pumps, fans, some people use air conditioning. There’s carbon dioxide generation equipment. It’s a pretty energy intensive process,” he said.

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Zeramby questioned the cost effectiveness of growing almost any crop indoors, although he and Mills did not compare medical marijuana to other indoor growing operations.

“There’s an economy that seems to support the ineffeciencies,” he said, adding that privacy and security are what drive most marijuana growers inside.

And in an effort to control the climate precisely, Zeramby said many growers wind up with heating and cooling systems that work against each other and drive up energy use.

Less energy intensive techniques such as LED lighting are becoming more common, he said, but the fractured nature of the medical marijuana industry has made information sharing difficult.

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