Odor control is one of my favorite topics to discuss in the cannabis industry. Not because we have it figured out or because it’s easy to implement. Quite the contrary; it is one of the most challenging aspects of designing a cannabis facility, precisely because it hasn’t been figured out.
Up until a few years ago, there were about 30 compounds that had been identified as generating the distinctive aromas of the cannabis flower, including limonene, α-pinene, and β-myrcene. Recently, research out of Iowa State1 identified over 200 new volatile compounds emitted from cannabis, whose odors were rated from practically imperceptible to incredibly intense. Not surprisingly to most growers and connoisseurs, the concentration of these compounds changed over the course of drying, such that different smells were more perceivable when fresh, while others became more prominent after desiccation (curing and storage).
One of the more interesting findings of this study demonstrated that some of the most “offensive” odors to the human nose are found in such small concentrations that they were barely detectable by mass spectrometry. In fact, the five most “characteristic” aromas detected by the human nose, “were not the most chemically abundant.” That’s right: The human nose is so sensitive and attuned to the cannabis plant’s aromatic compounds, we are better at detecting them than the advanced technology created to measure them.
What’s more, of the compounds detected, nearly 70% of them have very little information documented in the chemical databases, including their odor detection threshold. This lack of data is most likely because they are found in such small quantities that they did not warrant much thought or research. It turns out these molecules pack a punch, claiming responsibility for much of what we consider “odor.”
How do we control something we cannot measure or detect with modern instrumentation?
The current industry standard is to throw the kitchen sink at the problem, in hopes that available technology will adsorb, unravel, or otherwise eliminate the aromatic compounds emanating from the plant. The problem is that many of these devices are either ineffective (air filters), deficient in humid environments (carbon filters), energy intensive (UV irradiation and constantly running fans), or downright dangerous to humans (ozone). Additionally, these devices do not specifically target the odor-producing compounds we want to remove. They remove everything, good or bad, large or small, pungent or pretty.
So what can we do?
The first step is to continue the research and create new pages in the catalog of chemical compounds that includes Cannabis. Second, measuring tools need to be developed that have greater resolution and sensitivity to these compounds and the concentrations in which they can be found. Only then – after we know what and how much – will we be able to develop technologies that can effectively control odors through targeted elimination.
1. Rice S, Koziel JA (2015) Characterizing the smell of marijuana by odor impact of volatile compounds: An application of simultaneous chemical and sensory analysis. PLoS ONE 10(12):e0144160 https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1994&context=abe_eng_pubs