Fermenting cannabis

What is cannabis fermentation?

Fermentation is a biological process in which microorganisms (bacteria, fungi) break down organic material. With cannabis, fermentation is used, similar to Curing (maturing), to change the aroma and texture of the dried flowers. It is a traditional process that has been used for centuries in certain growing regions (for example for Lebanese or Nepalese hash).

Note: This guide covers the topic from a factual, botanical perspective. In Germany, cannabis containing THC is subject to the Consumer Cannabis Act (KCanG), and medical cannabis is subject to the Medical Cannabis Act (MedCanG).

Fermentation vs. Curing

• Curing (maturing): Controlled drying in tightly sealed jars at 60 to 65 % humidity. Enzymatic processes break down chlorophyll and sugars. Standard after harvest.
• Fermentation: Deliberately triggering microbial activity under controlled conditions. Leads to deeper changes in the aroma profiles and chemical composition.

Fermentation parameters

• Temperature: 20 to 30 °C (the lower it is, the slower and gentler the process)
• Humidity: 65 to 75 % for active fermentation
• Duration: 2 to 8 weeks, depending on the desired result
• Container: Airtight, aired briefly every day (Burping)

What does fermentation change?

• Breakdown of chlorophyll (less sharp, grassy smell)
• Changes in the terpene profile (new aroma compounds form)
• Possible chemical conversion of THCA into other cannabinoids
• Change in consistency (softer, easier to process)

Common mistakes

• Too much moisture: Risk of mold, visible as a white, fluffy coating (not to be confused with trichomes)
• Too little ventilation: Anaerobic fermentation leads to unpleasant odors
• Temperature too warm: Speeds up the process in an uncontrolled way, loss of quality
• Damp starting material: Cannabis must be sufficiently pre-dried before fermentation

Legal situation

In Germany, cannabis containing THC is subject to the Consumer Cannabis Act (KCanG). The KCanG allows adults to possess certain quantities and to grow cannabis privately at home. Processing it into concentrates or extracts is not covered by this. Retail sale is not permitted. Medical cannabis is governed by the Medical Cannabis Act (MedCanG).