Botanical Extraction

Rotary & Falling Film Evaporation: Which is Best for Your Budget?

Written by Anthony DiMeo

Evaporating solvents usually comes down to a decision of whether to utilize one of the two more-energy-and cost-efficient solutions to do so: rotary evaporation and falling film evaporation. Both methods have their fair share of industry-wide application, but which one may be best for your operation?


Rotary evaporation

By maintaining a lower boiling point than the concentrates themselves, residual solvents can be essentially boiled away via rotary evaporation. Botanical extractors opt for the use of a rotary evaporator apparatus or “rotovap” to perform this function.

Rotovaps are a crucial piece of post-extraction equipment in order to purge solvents like ethanol, propane, and butane from the concentrates that they helped to create. In today’s cannabis extraction labs, rotary evaporation has the ability for a highly-efficient rate-of-production. The  main difference among rotovaps is the volume that they can accommodate and final throughput. Some entry-level rotovaps like the Rotavapor R-100 by Buchi are smaller and more affordable for a smaller operation than say something like the Echochyll X7 by Ecodyst that features alternative cooling capabilities that can accommodate significantly higher volumes of solvent purging. Many companies also offer full-scale, specialized rotary evaporation solutions that can dramatically increase throughput, but at a much higher cost.


Falling film evaporation

Virtually full-proof, high-purity solvent removal can be achieved (if done correctly) in a number of other ways. Another method to potentially do so is called falling film evaporation. This process also utilizes the lower boiling point of a solvent than the extracted botanical, as well as gravitational force in order remove residual solvents. Also utilizing low vacuum pressure, falling film evaporators feature a shell and heat tube exchanger construction that makes for even evaporation across the entire solution during the process. Maximum production and cost-efficiency is achieved by utilizing as many of the heat tube components in the evaporator surface area that it can functionally incorporate, while post-process condensed vapor can actually be recycled for reuse in the extraction phase. Automated falling film evaporators are great because they ensure steady and precise low heat exposure and a large volume of throughput versus their less-costly, manually-operated versions.


Weighing your decision

The size of your budget is always of course going to be a major factor in deciding one on one process and set of equipment compared to the other. Automation is obviously crucial as well – with more affordable options for rotovaps in that department. However, other parameters like the much higher throughput with automated falling

About the author

Anthony DiMeo