Fort Collins, Colorado - Students at Colorado State looked into the climate impact of marijuana, and whether legal or illegal, it seems the green is far from being green for the environment if you grow it indoors.

The students dropped a paper in March to give an update on how much CO2 comes from growing cannabis indoors in different parts of the US, and found that the highly sought-after crop doesn't just give you red eyes and a snacky appetite – it is also helping to get our environment baked.

The students looked at detailed information on weather patterns across the US, and matched that info with the CO2 emissions of the whole country.

They fed all that juicy data into a computer model, and then looked at over 1,000 different locations in the US and how the emissions changed place by place.

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They found plenty of reasons for why indoor-grown weed is such a climate polluter.

Electricity is a huge part of it, because any growing operation inside is going to need plenty of heat and light to help the plants grow.

Fertilizer, which isn't very environmentally-friendly yet, is another key ingredient in a healthy crop of plants, and so are all the emissions from getting your bud from A to B.

All things being equal, the study found that growing, harvesting, and transporting one pound of marijuana emits between 5,000 and 10,000 times more CO2 than growing one pound of corn, depending on which part of the US the indoor grow farm is based.

If indoor marijuana farms moved outside, it would drop their emissions by up to 96%, say the Colorado State students.