As a natural product, it is easy to dismiss the environmental impact of cannabis. Most people imagine factories or vehicles when they think of pollution, but crops can also leave a large carbon footprint. Cannabis legalization has made the concern of pollution from marijuana crops a serious one. Growers can find ways to boost the efficiency of the crop.
One pound of cannabis grown from seed to harvest can require as much energy as an average American household consumes in about 10 weeks. An estimated one percent of all energy used in the United States is for indoor marijuana crops. The amount of greenhouse gas emissions produced for these ventures equals the pollution caused by three million vehicles. A traditional indoor growing system uses as much energy as 29 household refrigerators but grows only four plants.
The water use for indoor cannabis growing ventures is typically more conservative than outdoor gardens, and growers often use more than they need. Large-scale greenhouses and at-home growers also produce wastewater with fertilizer runoff that can contaminate local waterways.
Indoor growers can reduce their impact in many ways. Updated and maintained equipment works more efficiently. Solar panels and LED lights require less electricity to operate. Reduce equipment use to the minimum needed to reduce expense and waste. Avoid overwatering plants. Improve insulation in greenhouses and growing rooms to prevent energy loss.
More states are working on programs that will offer incentives that help growers transform the efficiency of their greenhouses. Utility companies in Oregon provide their customers in the cannabis industry with technical services to help them learn how to reduce energy waste. Many also offer cash incentives for those that lower their usage. Washington State has similar programs and offers rebates on solar installations.
Outdoor farming is a more efficient option for some growers. Outside gardens, however, still impact the environment. Soil erosion is a concern outdoor growers need to consider. Water usage is one of the biggest concerns. Cannabis needs more water than most food crops. It can use more than twice the water required for crops like wheat and soybeans. In warm and dry climates, it can take twice as much water to grow cannabis outside as it would indoors.
The need for high levels of nitrogen, phosphorus, and potassium in the soil can create dangerous runoff that puts groundwater in the area at risk. Cannabis plants also emit biogenic volatile organic compounds (BVOCs) that could cause air pollution. Too few studies on the impact of cannabis farms on water and soil safety have occurred to give any definitive statistics.
Studies related to soil quality and cannabis crops offer a positive note for cannabis growers. Cannabis has been shown to remove and store heavy metals found in the soil. This could make marijuana a viable bioremediation crop in areas with poor soil quality due to high levels of heavy metals.
Outdoor farmers can reduce their impact by using fertilizer and irrigation only when necessary. Growing small crops to eliminate waste can also reduce energy and water use.
Depending on where it is grown, one ounce of indoor-cultivated cannabis can produce the same carbon emissions as burning up to 16 gallons of gas. As natural, organic, and beneficial as cannabis may be, there are risks for the environment with its production. Growers that reduce their carbon footprint help to ensure that cannabis remains a legal and profitable crop for future farmers.