Activating EM-1: how to make your own EM-A step by step (ratios, temperature, pH)

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EM-1 is a stock solution: a concentrate of dormant microorganisms, designed to be “woken up” before use. By fermenting it with molasses and water, you get about twenty times its volume in EM-A, the active solution you then dilute for the garden, the compost, or around the house. It's simple and economical, and above all it takes cleanliness, warmth, and a little patience.

Here is the step-by-step method, along with the signs that tell you whether your activation has worked. Instructions sometimes differ, so each time we tell you which figure we go by.

What you'll need

• EM-1 Stock Solution, before its expiration date.
• Molasses: this is what feeds the microorganisms during activation. Cane or beet molasses, it makes no difference: our beet molasses from Béarn and our sugarcane molasses, both pure and additive-free, play exactly the same role as a source of sugars.
• Non-chlorinated water: clean rainwater, spring water, or tap water left uncovered in an open container for 24 hours so the chlorine can evaporate.
• A food-grade plastic container, very clean, with a tight-sealing cap. Ideally, use a lid fitted with a valve (or airlock) that lets gas out without letting air in. Avoid glass: fermentation produces gas and builds up pressure. For 2.6 gallons (10 liters) or more, or to activate even in winter, an activation tank such as our EM Activator has everything built in: airlock, heater, and spigot (see below).
• A thermometer and pH paper, to check the temperature and the result. Our pH test strips (scale of 1 to 14) show whether your EM-A is around 3 or already at 4 or above; to read 3.8 to one decimal place, you need narrow-range paper (roughly 2 to 5) or a pH meter.

Rinse the container with very hot water, without bleach or disinfectant: the slightest residue can ruin the fermentation.

The ratios

The standard recipe is the same from the manufacturer of our EM-1 and from other licensed producers: 5% EM-1, 5% molasses, and 90% water, or 1 part EM-1, 1 part molasses, and 18 parts water.

• For 1.1 quarts (1 liter): 1.7 fl oz (50 ml) EM-1, 1.7 fl oz (50 ml) molasses, 30.4 fl oz (900 ml) water.
• For 2.1 quarts (2 liters): 3.4 fl oz (100 ml) EM-1, 3.4 fl oz (100 ml) molasses, 1.9 quarts (1.8 liters) water.
• For 1.3 gallons (5 liters): 8.5 fl oz (250 ml) EM-1, 8.5 fl oz (250 ml) molasses, 1.2 gallons (4.5 liters) water.
• For 2.6 gallons (10 liters): 16.9 fl oz (500 ml) EM-1, 16.9 fl oz (500 ml) molasses, 2.4 gallons (9 liters) water.
• For 5.3 gallons (20 liters): 1.1 quarts (1 liter) EM-1, 1.1 quarts (1 liter) molasses, 4.8 gallons (18 liters) water.

Some European producers offer a variation with 3% EM-1 and 3% molasses, fermented at a higher temperature (90–99 °F, or 32–37 °C) in a heated fermenter. It works too, but we recommend sticking with the 5% recipe, which is more forgiving, with or without a heated tank.

Only make as much as you'll use within 1 to 2 months: EM-A doesn't keep indefinitely.

Step-by-step preparation

1. Warm part of the water and dissolve the molasses in it: since it's very thick, it doesn't mix well when cold.
2. Pour this mixture into the container, top it off with the rest of the water, then check the temperature: aim for lukewarm water, around 86 °F (30 °C), never hot to the touch.
3. Add the EM-1 last, once the water is no longer hot, and stir gently.
4. Fill the container almost to the brim, leaving just a little space for gas: the less air inside, the better.
5. Close it and write the date on the container.

Emy's tip

Use a marker to write the preparation date on the container, along with the use-by date two months later. That way, you'll always know at a glance where your EM-A stands.

Fermentation temperature and time

Warmth is the factor that matters most. The manufacturer of our EM-1 recommends a constant temperature of 77–86 °F (25–30 °C) for one week. Other technical data sheets state that below about 63 °F (17 °C), activation takes well over 7 days. Freezing, on the other hand, kills the microorganisms, both during activation and in storage.

Temperature swings are just as much of a problem as cold. So find a warm, stable spot: near a heater (not on it), in a furnace room, on a seedling heat mat, or in a heated room in winter. Wrapping a blanket around the container helps hold in the warmth. A heated activation tank solves the problem: it keeps the mixture at around 86 °F (30 °C), even in winter. Avoid direct sunlight, and don't go above 104 °F (40 °C), which can damage the microorganisms.

Allow 7 days in good conditions, and up to 10 days, or even a little longer, in a cooler room.

Venting gas without letting air in

By the second or third day, fermentation produces carbon dioxide: the container swells slightly. That's a sign everything is getting off to a good start.

• With a valve, there's nothing to do: the gas escapes on its own.
• Without a valve, unscrew the cap a quarter turn, just long enough to let the gas out, then close it again right away. Once a day is enough at first, then every two or three days.

Don't shake it, don't open it wide, and don't taste it: every bit of air that gets in encourages unwanted microorganisms.

Activating large volumes with an activation tank

Beyond a few gallons, or if your home is cool in winter, an activation tank makes everything easier. Our EM Activator, made by Agriton just like our EM-1, combines three features:

• An airlock (water seal): fermentation gas escapes on its own and no air gets in. No more venting by hand.
• A built-in heater, which keeps the mixture at around 86 °F (30 °C), whatever the season.
• A spigot at the bottom of the tank, so you can draw off the EM-A without opening it.

The recipe stays the same: 5% EM-1, 5% molasses, and 90% non-chlorinated water.

• 2.6-gallon (10-liter) tank: 16.9 fl oz (0.5 liter) EM-1, 16.9 fl oz (0.5 liter) molasses, 2.4 gallons (9 liters) water. Enough for a vegetable garden and a household compost pile.
• 7.9- and 15.9-gallon (30- and 60-liter) tanks: 1.6 quarts (1.5 liters) EM-1, 1.6 quarts (1.5 liters) molasses, and 7.1 gallons (27 liters) water, or 3.2 quarts, 3.2 quarts, and 14.3 gallons (3, 3, and 54 liters). For large gardens, market growers, and small livestock operations.
• 31.7- and 58.1-gallon (120- and 220-liter) tanks: 1.6, 1.6, and 28.5 gallons (6, 6, and 108 liters), or 2.9, 2.9, and 52.3 gallons (11, 11, and 198 liters). For farms.

Choose the size based on what you'll use in one to two months: EM-A from a tank keeps no longer than EM-A made in a container.

Fill the tank halfway with hot non-chlorinated water and dissolve the molasses in it. Top it off with cold water to get a lukewarm mixture, then add the EM-1 and stir. Close the tank, fill the airlock halfway with water, and plug in the heater, which must always stay fully submerged. After about 7 days, check the pH as described below. Unplug it, let it cool, then draw off the EM-A into clean containers, filled to the brim and tightly closed. Never run the heater under cold water while it's still hot.

Emy's tip

Keep the tank out of the sun, in a room between 59–77 °F (15–25 °C), set on a piece of cardboard and wrapped in a blanket in winter: the heater will use less energy. In summer, a room that's too warm can push the mixture above 104 °F (40 °C). Between batches, rinse the tank with hot water and a little white vinegar or citric acid.

How to tell when it's ready

Starting on day 7, check three things:

• The pH: this is the most reliable indicator. A drop on the pH paper should read 3.8 or lower, ideally between 3.2 and 3.6. Above 4, fermentation either isn't finished or has gone wrong.
• The smell: sweet and sour, pleasant, a bit like a fruity vinegar or a mild sauerkraut.
• The color: the initial dark brown turns a lighter, orangey brown.

A light film or whitish flakes on the surface are normal: they're yeasts. A pH slightly below 3.2, with a good smell, isn't a problem. If the pH stays above 4 after 7 days but the smell is good, leave it somewhere warm for a few more days and test again. On the other hand, a rotten or sewage-like smell means the batch has failed: all the signs and fixes are covered in detail in our guide Storing EM and diagnosing a failed EM-A.

Key takeaways

A successful activation means three green lights: a pH of 3.8 or lower, a sweet-and-sour smell, and a color that lightens. When in doubt, the pH has the final say.

Diluting and using your EM-A

EM-A is very acidic: never use it undiluted on living plants. The basic dilution is 1 to 100, which works out to about 2 teaspoons (10 ml) per quart (liter) of non-chlorinated water, or 3.4 fl oz (100 ml) for a 2.6-gallon (10-liter) watering can. Doses for each use (soil, seedlings, compost) are covered in our guides Using EM in the vegetable garden and Speeding up your compost with EM. For other uses, always follow the product label.

Use it within 1 to 2 months of activation. Counts done on an activated solution have shown that lactic acid bacteria drop off sharply within a few weeks: the sooner you use it, the better. Store it somewhere cool, away from light, and tightly closed.

If you'd rather skip activation, EM-A Microferm Active Solution is ready to dilute. Its flexible pouch packaging (Bag-in-Box) protects it from air, giving it a much longer shelf life than homemade EM-A.

Frequently asked questions

Can I use sugar instead of molasses?

One manufacturer's data sheet allows it, but we advise against it: in addition to sugars, molasses provides minerals that benefit the microorganisms. If you run out, buy more molasses rather than improvising: it's the standard ingredient in every set of instructions.

Can I make more EM-A from EM-A?

No. The manufacturers are clear: you activate only once, from the stock solution. If you propagate from EM-A, the balance between the microorganisms drifts from one generation to the next, and you no longer know what you're multiplying. Always start over from EM-1.

Can I use EM-1 without activating it?

Yes, some instructions suggest diluting it directly. But activation multiplies the volume by about 20: for regular use, it's far more economical.

What about making fermented bran?

Bokashi bran is made directly with EM-1 and molasses, without going through EM-A. Our full recipe is in the guide Making your own homemade bokashi activator.

Did you know?

The gas that makes the container swell is mostly carbon dioxide, produced by yeasts, just like in rising bread dough. That's why a container that “bulges” in the first few days is actually a good sign.

In summary

To activate EM-1, mix 5% EM-1, 5% molasses, and 90% non-chlorinated water in a clean container filled almost to the brim, then let it ferment for about a week at 77–86 °F (25–30 °C), at a stable temperature, venting the gas without letting air in. The EM-A is ready when its pH is 3.8 or lower, with a sweet-and-sour smell and a color that lightens. Always dilute it, at 1 to 100 for plants, use it within 1 to 2 months, and start over from the stock solution for each new batch. For large volumes or a cool winter, a heated activation tank holds the right temperature and vents itself. To get off to a good start with EM, take another look at our golden rules.

Related products

Beet molasses | 250 ml bottle

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Other topics in the guide

Vermicomposting30 fact sheets →Composting25 fact sheets →Bokashi24 fact sheets →