Alcohol extraction is the process of using extracting terpenes and cannabinoids from cannabis using alcohol as the solvent. The most commonly used alcohol is ethanol because of its low toxicity, which makes the solvent recovery step easier because 0.5% residue in the product is acceptable. Ethanol extraction can be done in warm, room temperature and supercooled conditions. Warm conditions are limited to predominantly small-scale batch production and thus are not suitable to large scale production.

Ethanol Extraction

The process for the extraction using room temperature and supercooled ethanol is the same initially. Both require the input biomass to be suspended in the solvent and then are mechanically agitated, eventually followed by cycling compression. The reason for the suspension is that full saturation of the biomass is required for the extraction to take place. The cycling compression is used to maximize recovery of the extract rich solvent from the biomass. Once extraction begins there will be a difference in the products between the processes running at room temperature and supercooled conditions. Processing at room temperature will have greater efficiency at the cost of selectivity; extracting more triglycerides and waxes than the supercooled process. The supercooled process will result in lower yields, but much greater selectivity, meaning that an inline dewaxer can be utilized to remove the waxes and triglycerides. In contrast, a separate step for the removal of the waxes and triglycerides may be required for room temperature processes. It should be noted that both of these methods have better selectivity than scCO2, but lower efficiency.

The difficulty associated with this method of extraction revolves around three main factors: selectivity, power consumption and yield. The first issue is that the set up for alcohol extraction varies much more drastically than with scCO2, for instance the same alcohol may not be used, or the method of compression is different or is not even preset in lower end systems. These variance means that very different operating conditions will be necessary for each and that the yield despite the compensation of other factors, such as input particle size, will not be uniform, with some systems being superior. Provided a superior system is being used finding the balance between the, previously mentioned, three factors is extremely difficult.

The main issue that dictates the balance is the operating temperature. The goal is finding the optimal temperature that gives sufficient yield, while maintaining high enough selectivity to simplify the removal of high melting point lipids, with the added dimension of minimizing the energy consumption. The energy consumption has the complicated relationship with the other two factors. The higher the selectivity, the lower the operating temperature and the higher the energy demand; however, the higher the yield the more significant the energy consumption for the separation step. This is not even factoring in the effect of operating temperature on the amperage required for compression, which is affected by viscosity of the batch. It also does not account for higher operating volumes associated with lower selectivity.

Through proper consideration it is possible, and necessary, for the identification of a point between room and supercooled operating temperatures that will maximize production, while maintaining premium quality and at the best price point.