How to Grind Your Cannabis and Hemp for Extraction

As the old saying goes, size matters. And when you’re grinding cannabis or hemp for an extractor, size matters a lot. Grinding the plant material too small can create low-quality oil; grinding too large can leave valuable cannabinoids in the waste material.

Whether you’re extracting with supercritical CO2, hydrocarbons, or ethanol, finding the right particle size for your solvent and extractor will increase your returns and may even speed up your production.

Read on to learn how you can optimize your grind for your extractor, your strain, and your post-processing equipment.

Why Size Matters When Grinding Cannabis and Hemp

When you grind cannabis or hemp with an industrial mill, you’re increasing the surface area and making the cannabinoids and terpenes easier for the solvent to access. However, the milling also exposes the stuff you don’t want: chlorophylls and plant waxes. Those elements make the oil less desirable and increase the post-processing necessary for most final products.

A finer grind effectively lowers the selectivity of the solvent while increasing its power. The solvent grabs everything it can out of the plant material, and it does so very quickly. Depending on the solvent type, this can be a good thing. A smaller grind size speeds up the action of CO2. But for a powerful solvent like ethanol, grinding too fine can be a mistake.

A coarse grind — or no grind at all — will require more time to achieve the same extraction completion. Depending on the solvent, this can be a good thing. But for most production objectives, ethanol and hydrocarbons are plenty powerful. Running a small particle size may pull out too much wax and chlorophyll.

How Fine Should You Grind Cannabis and Hemp for a CO2 Extractor?

Cannabis and hemp should be milled to a particle size of 1/16” – 3/16” for CO2 extractors.

In general, CO2 could use a little extra kick for dissolving cannabinoids and terpenes. Grinding to a smaller size helps it pull out the good stuff at lower pressures (without the terpene-compromising high temperatures). And it helps in other ways too.

Because CO2 extractors run at super-high pressures (like 2,000 psi), the movement of the solvent through the material column can create “channeling.” When the particle size is too large or the grind is inconsistent, the solvent channels rivers in the material where it can flow through more easily. This leaves other areas of the plant material untouched and under-extracted.

The solution is a smaller particle size and a consistent grind. When all the plant material is evenly packed and homogeneously sized, the supercritical CO2 reaches all areas of the extraction column and retrieves all the oil possible.

So why the range of particle sizes for CO2? After all, there’s a big difference between 1/16” and 3/16”.

Production objectives vary from producer to producer, and so does the plant material. Some strains may require a smaller particle size and longer runs. Other high-potency strains may do better with a larger size and shorter runs because they extract more easily. The desired oil purity may play a role too. Shorter runs with a larger particle size yield a better oil — but less of it.

How Fine Should You Grind Cannabis and Hemp for an Ethanol Extractor?

Cannabis and hemp should be milled to a particle size of 5/64” – 1/4” for ethanol extractors.

Ethanol is a very powerful solvent. Extraction is quick and best performed at lower temperatures so that less chlorophyll and wax co-extracts from the material. A coarse grind is best, and some producers choose not to mill the material whatsoever. For most strains, the optimal grind size for ethanol is on the high end of the 5/64” – 5/16” range.

Another benefit of grinding for ethanol extraction is an increase in production capacity. Grinding also decreases the solvent necessary per pound. When plant material is ground, more material can fit in the extraction vessel per run, thus increasing production speed and reducing the ethanol that needs to be distilled in post-processing.

How Fine Should You Grind Cannabis and Hemp for a Hydrocarbon Extractor?

Cannabis and hemp should be milled to a particle size of 5/64” – 1/8” for hydrocarbon extractors.

Though the perfect grind for a hydrocarbon extractor can be a little larger or smaller depending on the strain, 5/64” – 1/8” is the sweet spot. Hydrocarbons like butane and propane are powerful solvents. Yet, because the solvent flows through the material under pressure, channeling can occur like it does with a CO2 extractor. The channeling problem is less severe, but it’s still best to avoid large particle sizes and unmilled material.

green = recommended | yellow = can be used | red = not recommmended | *** = included with each M210

MILL SCREEN
HOLE SIZE
PRE-ROLLS
CO2 EXTRACTION
ETHANOL EXTRACTION
HYDROCARBON EXTRACTION
FRESH FROZEN
10-02-002806
ULTRA FINE RASP
1.6 mm
green
green
red
yellow
red
10-02-002837
FINE RASP 
2.0 mm
green
yellow
yellow
green
red
10-02-002805
MEDIUM STANDARD MILLING
3.2mm
yellow
yellow
yellow
green
red
10-02-002804
COARSE STANDARD MILLING
4.7mm
yellow
yellow
green
yellow
red
10-02-002803
COARSE BLENDING
6.4mm
red
red
green
yellow
red
10-06-004795C
COARSE CHUNKING
12.7 mm
red
red
green
red
green
10-06-004796U
ULTRA COARSE CHUNKING
19 mm
red
red
green
red
green

How a Cannabis Mill Works on Hemp and Cannabis

An industrial cannabis and hemp grinder can process hundreds of pounds of material an hour while maintaining a precise particle size for consistent results and optimal extraction completion.

A mill, such as the Mobius MBX Mill, typically uses a rotary mechanism and a screen or rasp. A rotor pushes the material across the screen or rasp, and the coarseness of the screen or rasp determines the particle size. Screens are best for coarse material; rasps, which are similar to a file, are ideal for smaller particles.

A good alternative for a coarse grind is a shredder — such as the Triminator ShredMaster, rotating blades tear apart the material. The resulting particle size — 5/16” — works well for ethanol extractors.

The days of FDA-mandated Good Manufacturing Practices (GMP) are quickly approaching, so it’s best if your mill is ready for GMP compliance. It should be stainless steel and easily cleanable. Cannabis and hemp are resinous materials — as you know — and processing equipment must be frequently cleaned.

If you’re ready for a precision cannabis mill that can handle your increasing production volumes, make sure to check out the Mobius MBX Mill.

And if you want to stay current on all the industry’s latest processing tricks, make sure to subscribe to the Mobius blog for frequent updates.

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