Solvent recovery is an essential part of any hemp or cannabis lab. Whether you extract with a liquid solvent or winterize, you will need a method of bulk recovery.
Not to be confused with solvent recycling, solvent recovery is the process of removing the vast majority or all of the solvent in your crude cannabis extract. Solvent recovery can be a huge bottleneck in your lab’s operations if not managed properly. Consider the example of winterization. The unrefined oil is dissolved in ethanol at a ratio of 10:1 (10 liters of ethanol for every 1 liter of crude). For a lab that seeks to produce 10 liters of finished distillate in a day, they must remove more than 100 liters of ethanol! Fortunately, there tools made specifically for the job.
Rotovaps are a tool seen in many labs across all industries. They use low heat, light vacuum, and rotation of the flask to efficiently evaporate the solvent. Rotovaps are both cheap and basic. They are readily available from international sources. Rotovaps are virtually all made of glass which can be a plus or a minus. The plus being available spare parts, the con being the possibility of breakage. Glass is also an insulator, meaning it takes more energy to heat or cool.
There are a wide variety of manufacturers from all over the world and subsequently many variations of the rotovap. Rotos can be modified to run semi-continuously by introducing a feed tube.
Ecodyst uses a systems that allows for solvent recovery and decarboxylation in a quick and efficienct way. Their metal condesensing coils also save massively on energy and the amount of space needed. They also can’t break! Similar to a rotovap, the Ecodyst systems can be fed externally allowing you to run in a semi-continuous fashion.
Falling film evaporators or FFEs are an alternate style of solvent recovery systems. FFEs are generally made of stainless steel. They use heat exchangers and steam to evaporate the solvent. Falling Film is best used when hundreds of liters of solvent are needed to be recovered in a shorter period of time. FFEs can be designed to run continuously at large scales.
Similar to falling-film is rising film. These two methods use gravity differently to quickly strip solvent away from winterized crude. Both options are for high volumes and have the option for full to partial decarb.
What’s it all mean?
In summary, for small to medium scale recovery, rotovaps are a great option due to their simplicity and affordability. The can be uses for many different solvents easily and are a great tool to just have in your lab. A crappy rotovap will cause you many headaches. You don’t need Ferrari-vap, but it is nice to have reliable and safe equipment.
For the people looking to processes hundreds and hundreds of pounds of biomass a day, you would need an army of rotovaps. The only solution is to get a larger capacity and throughput system.