Heavy carbon footprint - A growing problem in the cannabis farms

In a protected, controlled environment, they can grow a profitable mix of high-potency, medicinal marijuana and any number of milder strains appealing to a new market.

But the venture comes with both a business and social overhead: high energy bills and a heavy, carbon footprint

A recent study estimated a single, indoor marijuana plant takes the equivalent of 70 gallons of oil to grow. Energy demand at Colorado's largest utility grew about 2 percent after marijuana was legalized.

Even the promise of new technology - including energy saving LED lighting, sensor-filled growing pods and a network of artificial intelligence and high-efficiency electronics - may not be enough.