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The leaf of a marijuana plant is seen under a grow light at Oaksterdam University July 22, 2009 in Oakland, California.
Pot smokers aren't known for being particularly energetic, and yet they use a surprising amount of energy. A new study finds that indoor pot growing operations in California account for eight percent of all household electricity usage in the state.
Evan Mills from the Lawrence Berkely Lab is the author of the study.
Mills explains that indoor pot growing operations use a lot energy, because the growers compensate for everything from temperature control to humidity control, air changes (60 time more often than a typical house), electric heating, and electric drying.
He says that on average, "it's about as much lighting as a hospital operating room... about 50 times the normal light you need to read a book."
The indoor pot growers are also contributing to global warming, says Mills. Indoor growers of all kinds will often burn propane or natural gas to pump the environment full of carbon dioxide. The technique is called carbon fertilization and it leads to higher yields. It also contributes a significant amount of CO2 to the atmosphere.
"If you add up all of the energy, and you look at the emissions behind that energy... it's the CO2 emissions nationally of about 3 million typical American cars," Mills said.
Some may argue that it's because the growing process is illegal, in many places that people are forced to grow inside.
But that's not true says Mills. He explains that people want higher security; they want to control pests and atmospheric conditions, all of which will contribute to a greater yield.
Some states, including California, have legalized the growing of medical marijuana plants. Mills believes people won't be motivated to grow outside, or to monitor their carbon footprints, until they're offered carbon neutral incentives.
He suggests that dispensaries could even take steps towards promoting an Energy Star style sticker on their products, which would indicate a carbon neutral product.
"[Over] the last few decades... we've had policies, programs, incentives, information and education to improve efficiency, but ironically, this sector has really been passed over."