Schatz Lab Finds Indoor Grows Use Huge Amounts of Power

Marijuana should be grown either outdoors or in greenhouses to prevent the use of vast amounts of electrical power and the resulting addition of carbon dioxide to the atmosphere, according to the Schatz Energy Research Center (SERC) at Humboldt State University.

SERC Director Peter Lehman says energy use is dramatically lower for plants grown in natural light. There are other important benefits to outdoor and greenhouse cultivation. Use of pesticides and fungicides is reduced, along with their embedded energy. Greenhouses provide security and a hedge against power theft.

Nationally, indoor cultivation consumes what Lehman calls “an astounding two percent of all domestic electricity.” In Humboldt County, the situation is far worse. Based on 2007 data, he estimates that indoor grows consume 10% of all the county’s electricity, enough to power an additional 13,000 homes.

That’s bad enough, for all kinds of reasons, Lehman contends, “but the worst of it locally are the diesel-powered grows in rural Humboldt County.”

Growers use diesel generators to power lights indoors, so that marijuana can be cultivated clandestinely and securely and yield several crops a year. “Diesel generators are less efficient by a long shot than the state-of-the-art electric generators PG&E uses,” according to Lehman. “Not to mention the spills of diesel fuel and the pollution that goes along with the generators. It’s ugly.”

Diesel or no, much indoor-grow equipment is electricity intensive: oversize lamps, carbon dioxide generators, dehumidifiers, fans and ventilation equipment. “The electricity use is gigantic and it’s outrageous,” says Lehman. “Consumption is typically 10 times what it is for a normal home, sometimes 20 times more.”

For instance, the local district attorney’s office prosecuted a case in which a single Humboldt grow house consumed almost 10,000 kilowatt hours in one month, nearly 20 times higher than the average household.

“Humboldt County’s residential electricity consumption has skyrocketed since Proposition 215 was passed in 1996,” Lehman points out. He adds: “There is also the egregious fact that a lot of pot growers use PG&E’s CARE program and get subsidized utility rates because they don’t have any reportable income. That means all of us pay higher electricity bills. You and I and everybody in the county are underwriting lower rates for illegal growers.”

Because the number of indoor grows has multiplied so extensively since 215’s adoption, Lehman recommends such operations be carefully designed and built. Code officials should supervise them, he advises. “My colleague Evan Mills at Lawrence Berkeley National Laboratory estimates that indoor growing could be three times more efficient.”

At present, indoor cannabis production results in energy costs of $5 billion a year, nationwide, according to Mills, who spoke recently at Humboldt State in connection with the Sustainable Futures lecture series. That level of expenditure represents electricity use equivalent to that of two million typical U.S. homes.

Analyzing the impact at the consumer level, Mills found that a single marijuana cigarette represents two pounds of CO2 emissions, an amount equal to operating a 100-watt bulb for 17 hours, or 30 hours on California’s cleaner grid.

At the strategic level, Mills notes, “Large-scale industrialized and highly energy-intensive indoor cultivation of cannabis is driven by criminalization, pursuit of security and the desire for greater process control and yields.”

Asked if marijuana consumption should be taxed proportionate to the energy consumption involved, Lehman said the best approach is to charge producers directly. “People who use a huge amount of energy should pay a lot for it; they certainly should not pay a subsidized rate, for heaven’s sake.”