Cultivation
Originating from Central Asia, the Cannabis sativa plant is an annual herbaceous specie meaning it grows anew and dwindles each year. On average these plants can reach a few metres tall, and most frequently grow as a segregated male (staminate) and female (pistillate) plants. Customarily in the wild, cannabis seeds germinate in the spring and come to flower some six months after. Female plants develop trichomes, which store many different chemical compounds, many of which are secondary metabolites that unambiguously contribute to plant growth, nutrient recycling or reproduction however despite that, it can participate in roles such as defence. One of these metabolites, CBDA (cannabidiolic acid) the precursor to CBD is distinctive to the cannabis plant. CBD and its counterpart THC descend from compounds found in their most potent concentrations in cannabis leaves and flowers at the end of the growing season. At this stage the compounds are ready for harvesting. Modern techniques and procedures have become more sophisticated since the nineteenth century, which were carried out by Indian farmers where the cannabis plants were dried followed by rubbing or beating the flowers to gather the detached trichomes.
As soon as the plant material containing the most potent levels of cannabinoids has been isolated from other plant tissue such as the stalks and roots, the lengthy process of extracting CBD can commence. The next phase is to remove the unwanted matrix entirely (cellulose and other cellular matter that makes up the structure of the living plant). Instead of detaching the trichomes physically, a modern day chemistry-driven approach is to chop the plant into parts to then further undergo an extraction method. Extraction involves physically or chemically removing the cannabinoids (and the likelihood of other beneficial compounds such as terpenes) out of the parent plant. Cannabinoids do not dissolve naturally in water therefore a simple method utilizing a cannabinoid-friendly solvent such as ethanol is employed. Ethanol generally draws out cannabinoids and terpenes along with other elements such as chlorophyll therefore ethanol extraction generally results green in colour. A less popular alternative is to use hydrocarbon such as butane, which is a more selective method however is highly flammable and requires caution during treatment and storage. Contrary to ethanol, the use of butane will not accumulate chlorophyll however will still extract terpenes.
Extraction
The most popular method for garnering high yields is via supercritical carbon dioxide (CO2) extraction. With this expression, ‘supercritical’ implies that the CO2 is retained at a high enough pressure and temperature that it acts in a way that is intermediate between a liquid and a gas. This switch allows it to passage through the dried plant matter where it draws out cannabinoids and terpenes along with a variety of plant waxes and fats. The CO2 is then eliminated by decreasing the temperature and pressure, making it a clean process to extract desired chemical compounds and recycle the solvent for future use. One drawback CO2 extraction comes with is that the extremely waxy and fatty elements require further refining from its raw oil sludge nature. This refining process is called ‘winterisation’, which involves adding the oil in with an ethanol solution and cooling the mixture below freezing temperature. This enables the different elements accompanied by their different solidifying temperatures to isolate and be physically removed. No matter the specific solvent employed, the finished product is an oily liquid or solid that is comprised of essentially the desired compounds. This blend can then be utilised to develop full spectrum (including THC) or broad spectrum (THC absent) cannabis derived product.
Keep in mind that CBD is not found naturally in the cannabis plant, but its parent precursor molecule CBDA. And so the unmentioned stage is decarboxylation, which means removing a ‘carboxyl’ group, reducing CBDA to CBD. The most time effective method to carry out this transformation is by the use of heat. Increasing the temperature speeds up the change, however remaining careful to not increase the temperature too high which may result in combustion. Decarboxylation can be performed at any stage throughout the extraction process, however just prior or after winterisation is ideal and logical due to the cannabinoids being more concentrated. After this process is completed, CBD is the major component of the oil blend.
Purification
From here, the CBD product can further undergo two final processes to produce a pure product known as CBD isolate. This process is called distillation and crystallisation. Distillation is the final isolation stage where precise boiling points are calibrated so that the cannabinoids and terpenes are evaporated at different times leaving behind pure fractions of each compound, which is then collected, obtaining 99% pure CBD. The 1% is extremely difficult eliminate however will likely contain the slightest amount of solvent and plant compounds. Once it has dried, a white crystalline powder is formed. In this form the powder can be added to a broad range of product configurations such as creams, drinks and vapes. Other product configurations include tinctures and edibles and while the specific manufacturing methods will vary for each and every product in the trade, the standard principle for integrating CBD will generally remain constant. And that concludes the journey from cultivation, to extraction and purification. Hopefully this has given you considerable insight into the innovative mix of agriculture and chemistry that journeys into creating CBD derived products.