CBD extraction is the process of separating cannabinoids from hemp plant material so they can be made into a finished product. Four methods are in commercial or home use: supercritical CO2, ethanol, steam distillation and olive oil infusion. They differ in purity, cost, and how much of the plant survives.<\/p>\n
This guide explains how each method works, what happens to the crude hemp extract afterwards, and how to read the difference on a certificate of analysis. It is written for anyone comparing CBD products and wondering why two oils sold at the same strength can be so unlike each other.<\/p>\n
CBD, otherwise known as cannabidiol, is a compound found in the cannabis plant, and the richest source of it is the flower of the hemp plant. Plenty of products contain it, including oils, capsules, topicals such as balms and creams, and chewing gum.<\/p>\n
Before any of those can exist, the cannabinoids have to come out of the plant. That is what extraction is: separating the compounds you want, meaning cannabinoids and terpenes, from the ones you do not, meaning waxes, chlorophyll, cellulose and plant fibre. The material that comes out of that first step is called crude hemp extract, and it is the starting point for everything else.<\/p>\n
There are several ways to do it, and some are cleaner or more efficient than others. The difference matters, because the method affects the purity of the finished product and determines whether solvent residue can end up in the bottle.<\/p>\n
Three things separate a good extraction from a poor one:<\/p>\n
Supercritical CO2 extraction allows for a clean extraction with no additional additives and no solvent to remove afterwards. It produces a high-quality extract, gives efficient yields so more is recovered from each batch of hemp, and is comparatively sustainable, because the carbon dioxide can be captured and reused rather than vented.<\/p>\n
The underlying principle was first identified in 1822 by the French engineer Charles Cagniard de La Tour, who described the supercritical state of matter. That state is what allows a great deal of control over the separation of plant components during a single run.<\/p>\n
Temperature and pressure are used to create a series of changes in carbon dioxide. Pushed past its critical point, CO2 stops behaving purely as a gas or purely as a liquid and takes on properties of both. It has something close to the density of a liquid, so it can dissolve compounds, and the diffusivity of a gas, so it can move through packed plant material.<\/p>\n
That combination is what makes it useful. By adjusting temperature and pressure through the run, an operator can create conditions in which compounds of different molecular weights come out at different stages and can be separated during a single extraction. Lighter terpenes come off under one set of conditions and heavier cannabinoids under another.<\/p>\n
When the pressure is released at the end, the CO2 returns to gas and simply leaves. Nothing is left behind to remove, which is the central advantage of the method and the reason a CO2 extract does not need a residual solvent panel to be trusted.<\/p>\n
Trade-offs.<\/strong> It requires expertise to perform and it is expensive. Equipment runs to hundreds of thousands of pounds, the vessels are pressure-rated and need maintaining, and it is slower per batch than ethanol. This is why most of the industry does not do it.<\/p>\n Ethanol extraction is the most widely used method in commercial CBD production, largely because it scales. Where CO2 needs expensive pressure vessels, ethanol needs tanks, and the volume a facility can process is limited mainly by how much solvent it can handle and recover.<\/p>\n Ground hemp is soaked in food-grade ethanol, which dissolves cannabinoids and terpenes out of the plant material. The plant solids are filtered off, leaving a solution of ethanol and hemp compounds. That solution goes into an evaporator, usually a rotary evaporator or a falling film unit, where gentle heat and reduced pressure boil the ethanol away and recover it for the next run. What remains is crude hemp extract.<\/p>\n Producers usually run this cold, at temperatures well below freezing, in a variation called cryo-ethanol extraction. Ethanol is a polar solvent, so at room temperature it also pulls out chlorophyll and water-soluble plant material that make the extract dark, bitter and harder to refine. Chilling the ethanol first leaves most of that in the plant.<\/p>\n Steam distillation is a centuries-old process, used to distil alcohol and to take essential oils out of botanicals. It is considerably less complicated than CO2 extraction.<\/p>\n The plant matter is loaded into a distillation tank. Water is heated below it, and the steam that rises carries oils up to the top of the tank. The vapour then passes through a condenser, which returns it to liquid, producing a mix of water and oil. Further distillation separates the water from the oil, leaving a full spectrum oil behind.<\/p>\n This is much simpler than supercritical CO2 extraction but it is more prone to error, it is less efficient, and it can damage part of the essential oil profile of the plant, because sustained heat degrades terpenes and converts acidic cannabinoids. For those reasons steam distillation is rarely used for cannabinoids now. It is largely a legacy method in this industry and belongs to essential oil work.<\/p>\n Olive oil extraction can be performed at home, but the plant material has to be decarboxylated first. That means the acidic cannabinoids are converted by heat. It happens when hemp is smoked or vaped, and it can also be done deliberately in an oven.<\/p>\n Once the plant matter is decarboxylated, you mix it with olive oil and heat it on the hob for several hours. The cannabinoids, along with the terpenes, bind to the fat in the oil, producing an infused product. Once the mixture has cooled, you filter the oil and remove the leftover plant material.<\/p>\n This is a reasonable method for making a hemp-infused oil at home, and it is relatively safe because no volatile solvent is involved. There is very little control over the result, however. The CBD content is weak and unreliable compared with professional methods, and because the oil is not concentrated it cannot be stored for long or standardised to a known strength.<\/p>\nEthanol extraction<\/h2>\n
How ethanol extraction works<\/h3>\n
Strengths and limitations<\/h3>\n
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Steam distillation<\/h2>\n
Olive oil extraction<\/h2>\n
CBD extraction methods compared<\/h2>\n