Activating and expanding EM

Why activate EM?

EM mother culture

Our EM (Effective Micro-organisms) mother culture does not have to be activated and it is perfectly ok to use it straight out of the bottle. The main reason to activate (or expand) EM is to save money. By activating EM you can increase your EM supply by over 20 times. Activated EM typically costs less than $2 a liter; including the cost of the EM mother culture.

By following these instructions, the activated EM will have the same strength as the mother culture EM. The activated EM can be used in exactly the same way as the EM mother culture.

The only downside to activating your activated EM is that activated EM only stores for up to 30 days (compared to the mother culture which will store for a year or more).

How to activate EM?


To activate EM you will need (per liter):

  • 1 part EM mother culture (40ml)
  • 1 part molasses (40ml)
  • 20 parts water (800ml) *
  • A clean plastic container with lid (approximately the same volume as the recipe being made) **

* We recommend using dechlorinated water as chlorine can kill microbes. Rain water and spring water work well for activating EM. If water is chlorinated then allow the water to stand in an open container for at least 24 hours.

** There may be some off gassing and expansion during the activation process so don’t use glass or metal containers.


  1. First, boil approximately 30% of your water.
  2. Mix the hot water with the molasses and stir thoroughly.
  3. Top up with the remainder of (room temperature) water.
  4. Mix in the EM mother culture and place in the sealed plastic container.
  5. Then place the mixture in a warm place 77-95 F (25-35 C) for 5-7 days. The container may need to be ‘burped’ every day or two as gases may build up within the container.
  6. Your activated EM should have a sweet smell and is now ready to use. A good fermentation may lead to white yeast flakes on the surface of the activated EM. These white flakes are completely harmless and do not affect the product.
  7. Store unused activated EM in the sealed container at room temperature and use within 30 days. The activated EM has gone bad if it develops a putrid smell and/or the pH rises above 3.8.

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2 thoughts on “Activating and expanding EM

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