The Ultimate Guide to Sustainable Carbon Scrubbing
Emily Long
Sr. Project Manager
Byers Scientific
Carbon filters are the recommended best management practice (BMP) for cannabis emissions and odor control according to the Denver Cannabis Sustainability Working Group’s 2020 BMP Guide. Carbon filtration is currently the best control technology for reducing VOC emissions from cannabis cultivation facilities. The guide states that cultivation and MIP processing facilities can reduce their VOC and odor emissions by installing carbon filters as control technologies. However, carbon scrubbing is not a one-size-fits-all solution and resource-conscious cannabis operators should take the time to fully understand their facility’s emission rate before installing control technologies. Byers Scientific takes an engineered approach to right-sizing the emissions and odor mitigation technology for a given facility, encouraging an even more sustainable solution.
Advancements have been made to the known effectiveness of molecular filtration (carbon scrubbing) for adsorbing cannabis emissions and odor by developing the industry-leading control technology for commercial cannabis applications, for example the MT-6™ Molecular Filtration System. This environmentally sustainable unit saves cultivators and manufacturers energy and reduces waste.
A Sustainable Approach to Mitigation Equipment Application
To properly determine the required specifications for odor control technologies for an operation, it is critical to start by analyzing air samples collected using leaf enclosure procedures performed at your facility. Gas chromatography with mass spectrometry (GC-MS) should then be used to analyze the samples consisting of over 200 compounds from the plants. With all emissions data, scientists such as those at Byers Scientific, can quantify the site-specific gas-phase emission rate based on the number of strains, plant count, life stage, and estimated plant weight.
Standard ambient air sampling reveals only a fraction of the canopy’s actual emissions. Only through leaf enclosure studies and subsequent GC-MS analysis can you measure your canopy’s true emissions profile. A facility-specific emission profile then provides the foundation for odor mitigation planning.
The team at Byers utilizes the collected and calculated facility-specific data in its Cannabis Emissions Profiler protocol (CEP) to mathematically determine the exact number of commercial-scale Molecular Filtration Units required to sequester the odor molecules as a function of the area’s total volume. Installing the proper number of mitigation units running the optimal number of air exchanges saves energy and reduces carbon waste from unnecessary spent carbon replacement.
For example, it can be determined that a 225,000 ft³ cultivation space requires two (2) 6,000 cfm molecular filtration systems (i.e., 12,000 cfm), which equals approximately three (3) air exchanges/hour. This precision doesn’t just improve efficiency, it also helps prevent “overscrubbing,” which can negatively impact plant health and unnecessary energy use. Understanding the optimal number of air exchanges required to fully capture your site’s cannabis emissions before they have a chance to escape is the first step in comprehensive and sustainable odor mitigation planning.
Environmentally Sustainable Cannabis Emissions Removal Using Efficient and Effective Carbon
One of California’s largest cannabis concentrate manufacturers used this unique approach to help identify and control their facility VOC and odor emissions. After measurements were taken of their facility’s emissions using air sampling methods taken from identified source-point emission loads, several filters packed with Camfil’s Carbon LGX-048 were identified as the optimal solution and installed. Initial removal efficiency data (snapshot below) shows significant reduction of airborne terpenes and odor-causing molecules before they have the chance to reach ambient air and impact air quality and community relations. A research team comprised of Byers Scientific, Iowa State University and Texas-based odor experts recently reported the isolation and identification of the volatile chemical, 3-Methyl, 2-Butane, 1-thiol (3MBT) which appears to be primarily responsible for the downwind skunky-like environmental odor from commercial cannabis.
The combination of data from the sampling events and resulting calculations provided the client with a preventative maintenance carbon replacement schedule to manage the nonlinear carbon consumption curve, thus avoiding any chance of breakthrough. This mathematically derived approach is the best way to meet compliance requirements to reduce total emissions.
Odor Mitigation and Waste Reduction
It is important to consider the waste production and reduction capabilities by installing certain odor mitigation solutions. For example, prefilters, such as Camfil’s proprietary pleated panel filter works to remove airborne contaminants and moisture from the air stream, improving indoor air quality and maintaining the integrity of the activated carbon media before scrubbing odor. By removing moisture, the pre-filters keep it from taking up critical surface area or ‘seats’ within the porous carbon media. By preserving the carbon for intended odor control, the technology itself can reduce the frequency of replacing the carbon canisters thus reducing the amount of carbon waste.
Consistent with the goal of providing environmentally responsible solutions, filters should be designed to have the longest possible service life to reduce the need for changing the filter frequently thus generating less material waste. Finally, some pre-filters require less annual energy consumption (up to 25% per filter), waste disposal and landfill impact in line with corporate cost savings compared to low-cost and/or poor-quality pleated filters found in many competing systems.
With respect to the carbon media utilized in odor control technologies it should be carefully selected with efficiency and efficacy in mind as well as follow a Butane Life Testing Protocol, in accordance with ASTM D5742-95, on this carbon media in order to identify the optimal lifespan of the carbon before replacement is needed to preserve resources, reduce waste and prevent odor break-through based on the specific application.
Odor Mitigation While Saving Energy
Compared to the potential use of hundreds of the common can-fan units for odor and air flow control, an engineered by-design molecular filtration system will have significantly less energy draw. Further, leveraging the above-discussed baseline emissions calculations, the proper approach to indoor odor mitigation is one that is engineered to provide the exact number of required air exchanges to effectively sequester cannabis emissions at the rate they are emitted off the plants, whereas can-fans are moving air at an arbitrary rate. A company’s commitment to sustainability goes beyond the design of its equipment. It is important to consider using control equipment that is approved by a local utility energy rebate program, such as with Colorado-based energy company, Xcel Energy. These programs allow for cannabis businesses to save money by purchasing approved energy-saving emission mitigation equipment.
Example of Energy Savings:
When comparing to the common use-case of a standard can fan array installed for air flow and odor control (# of units required to equal 6,000 cfm) against one MT-6™ Molecular Filtration unit the estimated annual energy savings is significant.
This can fan model is listed at 785 cfm and 1.58 amps. At 6,000 cfm it would take 7.6 of these can fans (12 amps) to equal a single molecular filtration unit listed at 2.8 amps; a difference of 9.2 amps.
Using a more conservative number of $0.10 kwh from the national average of electrical costs with an assumed run time of 24 hours per day, the savings is likely significantly more than this example shows. Using this calculator, a single molecular filtration unit (without optional PCO) running on 2.8amps X 120 volts equals 336 watts. Compared to 7.6 Can fans to equal the cfm of a single molecular filtration unit (6,000) running at 12 amps X 120 volts equals 1440 watts. That is an annual savings of $967.21/yr.
Smart Technology and Equipment Automation
Smart control technologies, such as systems equipped with Cloud-based SCADA (IoT) and automation capabilities can improve equipment efficiencies and allow operators to collect critical data 24/7. Such technology allows operators to manage their odor mitigation equipment in real-time and power up or down depending on weather patterns and facility operation schedules, conserving both carbon media and energy.
Beginning with the data-derived approach to mitigation equipment specifications for a facility and ending with installation of industry-leading sustainable emissions control technology, cannabis cultivators and processors can save energy, waste and money. As a steward for the community and the environment, businesses such as Byers are at the forefront of conscientious cannabis emissions and odor mitigation strategies. It is important to source your emissions and odor mitigation partner carefully. A business that works side-by-side with operators, regulators and community members to educate them on the potential for and perceived impacts from cannabis emissions to ultimately protect the public image of the expanding cannabis market is the business you want as your partner.
