Medusa Fast Crash Extraction Butane Propane Gases Bars Formation Research



LPG Solvent Contaminants and the Medusa Stone Problem

I’m a Ph.D. chemist with extensive analytical, foods and beverages, petroleum and petrochemical experience. In the past couple of years, I’ve had funding to research hemp processing and extraction aimed at improving and ensuring consumer product safety.

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Unfortunately, the industry has only been able to come out of the shadows in the past  few years, and basic research that should have been done hasn’t been done. So development of standards and practices is behind where it should be.

Solvent Direct connected with me recently to discuss the Medusa Stone issue. They arranged for me to visit a couple of labs that were dealing with this problem and directed me to Future4200 website to learn what solvent users are experiencing.

The following is my opinion. The bootstrap mentality of leaders in the cannabis extraction industry has served it well. In a relatively short time, the scientific method was employed, tests were conducted, results were discussed and solutions were proposed.


This was not an easy problem. LPG (liquefied petroleum gas) solvents are challenging to analyze because they consist of at least two phases (gas and liquid, throw in water and biomass and you have four phases). Furthermore, the solvents are nonpolar, whereas many of the contaminants of interest, e.g. methanol and monoethanolamine (MEA) are polar molecules that are “sticky,” meaning they like to adsorb onto surfaces.

Others in the industry have also risen to the challenge and devised work arounds and cleaning procedures to get address the problems.  That is how the industry has dealt with  these issues in the past and certainly will need to continue to do so   while solvent suppliers work to get control of the situation.

Solvent Direct is of the same mind that I am about getting to root causes and implementing  preventative process controls, otherwise issues  will continue to arise, like mystery oil, benzene and now the Medusa Stone problem.


All industries have their own vocabularies. Please let me share some relevant terms from the petroleum industry which relate to LPG operational problems. These are “burp,” “puke,” “upset” and “carryover.”

These refer to events that result in materials getting into LPG that shouldn’t be there, and these types of process upsets have been occurring for as long as the industry has been around without impacting most LPG uses. Further, today, fracking and regulations and rules aimed at eliminating hydrogen sulfide have likely contributed to situations giving rise to the Medusa problem.

Many fracked wells are remotely located, away from facilities and utilities. So, shortcuts are taken out of necessity. I won’t go into detail, but there are numerous treating chemical, scavengers, inhibitors, anti-foaming agents, etc., that have the potential to contaminate LPG. Routine monitoring is not done for all of these chemicals and that’s a problem, which somewhat arises because there is a knowledge gap between LPG producers and extractors.

To prevent future problems, the industry must establish standards and specifications in order to close the gaps. I’m thankful for Solvent Direct's vision and the opportunity to possibly help.

Dr. R


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