Functional health and medicinal products containing cannabidiol (CBD) are growing in popularity, and the U.S. market for CBD is now worth $1.62 million a year, according to research from statistica.com.
Traditional extraction processes do not always capitalize on the latest evaporation technology, and there are a number of techniques for extracting CBD from the hemp plant. Most of these techniques require the use of solvents that are effective at separating the CBD from other chemical compounds found in the plant. Once the CBD has been extracted, the solvent is evaporated off, leaving pure CBD oil.
Some methods use supercritical carbon dioxide in a closed-loop extractor to extract the CBD under pressure, resulting in a liquid mixture of CO2 and CBD, which must then be separated by evaporation, but a step involving alcohol solvents is usually still required. For this reason, liquid solvents based on alcohols (ethanol or isopropyl alcohol) or hydrocarbons (butane or propane) are also sometimes used and are much simpler and more straightforward. Unless the evaporation step is carried out correctly, however, some alcohol residues may remain in the CBD oil mixture.
It is important to remember that even where CO2 extraction is used, a further stage involving alcohol solvents will still be required. Each method has its own benefits and drawbacks, and the best method for one manufacturer may not be right for another.
Once the CBD oil has been separated from the solvent, it is then usually refined and distilled to produce pure CDB oil that is free from other compounds, such as THC, waxes, and lipids. The exact nature of this refining process will impact the chemical profile of the resulting CBD product and depends on the extraction method used.
The Basics of Evaporation
Evaporation is the separation of a liquid from dissolved or suspended solids using energy to make the liquid volatile so that the required solids are left behind. Evaporation differs from dehydration or drying in that the product of evaporation is a concentrated liquid, not a dry solid; however, evaporation can be combined with dehydration or drying processes. It also differs from distillation in that the concentrated solution, rather than the condensed evaporate, is the valuable product.
Evaporation systems have been around for more than 100 years and are used widely in the food, pharmaceutical, and chemical industries for a wide variety of purposes. Each sector has different reasons for choosing evaporation as a process, and there are appropriate differences in implementation. For example, in the food industry, products may be concentrated to increase shelf life, reduce volume or weight, and decrease storage and transport costs. A common example is the concentration of fresh fruit juice to enable the extension of processing periods beyond the harvest window of the crop. In contrast, in the pharmaceutical sector, evaporation is often used to create concentrated solutions that can then be dried to create powdered products, as is the case with many CBD products.
Although the basic principle of evaporation remains the same—the removal of water (or another solvent) from a solution by converting that water or solvent into its vapor phase—there are a number of established and novel techniques to achieve this under different temperature and pressure conditions. The type of evaporation most suitable for a particular purpose depends on several factors, including the nature of the solvent and the solution, the required end product, and the energy available.
In practice, depending on the technology used, evaporation can produce solutions containing anything from 0% to 92% solids. High-efficiency evaporation is more energy and cost efficient than drying or other methods of removing water and produces higher concentrations of solids than other methods of concentration, such as reverse osmosis or ultrafiltration. Evaporation may be carried out as a batch or in a continuous process. It consists of two elements—a heating phase and a vapor/liquid separation phase—although both may be incorporated in a single vessel.