The Cannabis industry has two main cultivation methods. The first one is the indoor method – growing cannabis plants in a completely closed structure, fully isolated from the environment. This way the sunlight does not reach the plant so there is massive use of energy for lightning. The second method is the outdoor method. This way the cultivation is done outside, under sunlight, and without any protection to the plants.

 

There is a middle way for cannabis which is cultivation in greenhouses,  an isolated structure that allows the sunlight to reach the plants.
As the legalization of marijuana spreads throughout the United States, more growers invest in indoor cannabis cultivation. In this industrialized method growers use a large amount of energy to produce greater yields through the intense management of pests, diseases and process control. The idea is to isolate the plant from the natural environment and create an optimal climate for cannabis growing in a closed structure in order to try to increase the yield per sq. ft.

 

Examples for high-intensity energy uses are heating and cooling –maintaining the ideal temperature in the system and generating carbon dioxide by burning fossil fuel to boost plant growth, traditional ventilation, and dehumidification system – removing water vapor to avoid mold formation and lighting.

 

As a consequent of high energy usage, indoor cannabis production is a high carbon footprint related. In average US climate conditions, the carbon footprint of one kg indoor cannabis produced is 4600 kg CO2. One single cannabis cigarette represents 1.5 kg CO2 emissions, equivalent to 25 hours of 100 watt light bulb average emissions.

 

As said, the majority of CO2 emissions come from 3 main categories: humidity treatment air conditioning and lightning. Focusing on the first two categories, wasteful traditional dehumidification methods and air conditioning constitute 27% and 25% accordingly of total emissions. Air conditioning, including space heaters, and CO2 injection to increase foliage require  1681 kWh per kg yield which emits 1120 kg CO2 per kg yield based on average U.S carbon burdens of 0.666 kg per kWh. Dehumidification using traditional methods (including air ventilation) requires 1848 kWh per kg yield, emits 1230 kg CO2 per kg yield.

 

Although indoor cultivation is a common method to grow cannabis, it is not sustainable. On the one hand, it allows growing larger amounts of cannabis per sq. ft., but on the other hand it does not utilize the advantage of the sun and outside climate. The greenhouse method combines the advantages of the indoor and outdoor – the energy from the sun with better air circulation.

 

Either way, both methods create isolated air system from the external air and as a consequence, require high efficient dehumidifiers to remove extra water from the air. The humidity forces the grower to open the greenhouse. In some cases, not only the water goes out but also the carbon dioxide injected into the growing facility. The high density of the cannabis flowers prevents water vapor escape to air and thus causing diseases like grey mold (botrytis) and mildew. A suitable dehumidifier should generate airflow on the leafs and flowers to avoid this problem.

Many of the common methods today in the cannabis industry were originally developed for small-scale growing facilities. When increasing the growing scale to commercial (like many growers do), the technology and growing methods must be adapted accordingly. The commonly used dehumidifiers in small-scale growing facilities are not designed according to the plants’ evapotranspiration loads. DryGair solution treats the humid air separately from the temperature and is used as a complementary tool for humidity problems.

DryGair Energies offers several solutions for air dehumidification in greenhouses and indoor commercial production. DryGair solution allows control of the humidity while improving the energy efficiency and creating uniformity and homogeneous conditions in greenhouses and warehouses. DryGair units were designed to answer the plants’ needs. One DryGair unit can cover 300-1400m2 (3,000-14,000 ft2) of cannabis growing facility, and removes 45L/h (12G/h) @ the design conditions (18oC and 80% relative humidity). DryGair saves 50%-80% of the energy consumption compared to other solutions thus prevents at least 920 kg CO2 emission per kg yield in warehouse indoor production. The energy saving in greenhouses is achieved through  low electricity consumption, saving energy for heating and for CO2 production because the greenhouse can stay completely closed. Additionally, DryGair raises the temperature of 1-8oC.

For more greenhouse energy saving methods check out 6 Tips to Increase Energy Efficiency

Finally, cannabis growers face many challenges, the increasing competition requires more advanced technics and technology that reduce the initial investment, the operation cost and maintain a sustainable environment – reduces the carbon footprint.

This file is based on Evan Mills “The carbon footprint of indoor Cannabis production” April 2012. Link