Minimizing fire hazards in cannabis extraction

To date, much of the focus has been put on extraction equipment, but more can be done to ensure processes are safe

Extracting chemical components from plants is nothing new. Many pharmaceutical companies have long discovered, developed and marketed therapeutic compounds extracted from plants found throughout the world.

The emerging cannabis industry is extracting various chemical components, including THC and CBD, from the biomass of the cannabis plant. With little to no current federal oversight, this industry is regulated state by state and relies on the due diligence of companies operating extraction facilities to provide crucial fire safety in the workplace.

Although the industry is evolving, the focus has largely been on the equipment used to extract the cannabinoids, with little consideration to the overall process and facilities required to operate safely. The extraction process uses hazardous gases, including liquified compressed gases such as carbon dioxide or butane, so safety cannot be overlooked.

In addition to the compressed gases, flammable and combustible (ignitable) liquids are used in the extraction process. Ethanol, for example, is commonly used in a purification step of the extracted product.

Every ignitable liquid has a flash point, which is the lowest temperature where sufficient flammable vapors can ignite (flash) in the presence of a competent ignition source. Flash point is one of the characteristics referenced when determining the fire safety hazard of a liquid.

As the cannabis industry develops, one problem that could arise is extraction operations being scaled up from a laboratory process (small scale) to an industrial batch process (large scale) without heeding the need to step up safety protections to accommodate increased production quantities.

By focusing on the safety of operations, companies can manage risk, achieve operational resiliency, protect employees, facilities and market share and allow for the ability to strengthen and grow.

Fire Risk

While cannabis is a new industry, there are a multitude of industries that use flammable gases, flammable liquids and other hazardous materials successfully, safely and in accordance with established fire safety standards, such as those set forth by the National Fire Protection Association.

The requirements when using these materials are well understood and implemented in these other industries. Existing NFPA standards apply to the extraction of chemicals from cannabis biomass. Local, state and federal regulations may also apply.

In addition, in January 2021, the NFPA released NFPA 420, a standard on fire protection of cannabis growing and processing facilities, which is in the early developmental stages prior to beginning full public review and an initial revision cycle.

Chemical, pharmaceutical and related industries that handle flammable gases and flammable liquids adopt the management philosophy of “from cradle to grave” to track the handling of these hazardous materials from receipt, through use, to proper disposal. The cannabis industry would benefit from adopting this concept, including handling residual quantities as hazardous waste, especially considering that the regulations will catch up with the industry.

Process

To better understand the inherent hazards and risks, the extraction process must be viewed in its entirety. The extraction process for butane hash oil can be separated into four distinct steps or tasks. They are:

– Propane and butane cylinder delivery and storage.

– Transfilling of butane and propane from storage cylinders to the “operating tank.”

– Solvent extraction of botanical resins.

– Dehydrating and residual solvent gas removal of oils (product) under vacuum.

The BHO extraction process begins with receiving the bulk cylinders of butane and/or propane. Both are extremely flammable. Handling and storing compressed gas cylinders require careful planning. Both gases are heavier than air, and the configuration and design of facilities, as well as their location, must take this into account. Proper storage should be determined on a case-by-case basis. The area should be well-ventilated and separate from the populated spaces. It is important to be cognizant of low-lying areas where gas can accumulate.

Extraction equipment requires the use of a pressurized storage cylinder (process cylinder) to receive and store the process gas mixture. Butane and propane are individually transferred to the process cylinder. In most state versions of the International Building Code and International Fire Code, the transfilling of flammable gases in the open of the interior of a building is prohibited because it is not a closed system.

Batch processing in extraction utilizes small-scale process equipment that is typically housed in pre-manufactured enclosures commonly known as C1, D1 booths. C1, D1 refers to Class 1, Division 1 electrical equipment and systems summarized in Article 500 of the National Electrical Code. Class 1 specifically applies to flammable or combustible gases or vapors. Division 1 locations are defined as those that contain flammable gases or vapors or combustible vapors resulting from normal operating conditions; repair, maintenance or leakage; or faulty operations or equipment.

When a Class 1, Division 1 area is identified, there must always be a Class 1, Division 2 “buffer” or “step-down area” between the C1, D1 area and locations that contain ordinary electrical equipment and service.

Further steps

The extraction process is not complete with the removal of the product from the process equipment. Biomass saturated in liquified butane and/or propane must be properly processed, handled and disposed. Additionally, the extraction process equipment must be safely cleaned and prepared for the next batch. Typically, an ignitable liquid is used in the cleaning process.

The next step in the extraction process is the transfer of the extracted product to vacuum ovens to “dry.” Although often identified as a step to drive off water, it also removes residual butane and propane that could be harmful to the end user. The residual butane and propane removed during the drying process remain flammable and should be captured, not released into the environment.

Similarly, the CO2 extraction process has its own occupational safety concerns, because CO2 is an asphyxiant gas. Storage and use of CO2 in cylinders in the workplace should include monitoring for concentrations that could be harmful as well as other safety requirements.

The cannabis extraction process contains many hazards that must be addressed to provide a safe workplace. Safeguards must be installed, and operations should be performed in a properly designed protected environment that, depending on the process, may include fire sprinkler systems, fire-rated separation walls, specialized electrical equipment and fire/explosion isolation (such as a separate structure).

As the industry evolves and develops, the implementation of stricter regulations will follow. While the mandated regulations may not yet be in place, properly managing the hazards and risks now is prudent and will result in a safer workplace and the ability to be compliant when enacted.

Bruce Rottner is a consultant and expert witness in fire protection, fire prevention and construction safety. He works with the Forensics Department at H2M to investigate the needs of the insurance community, public agencies and private owners. Leveraging a degree in botany and previous pharmaceutical industry experience, he brings unique knowledge and perspective to his fire and process safety consulting services for cultivation and extraction facilities in the cannabis industry.