Storing EM and diagnosing a failed EM-A: shelf life, storage, smell, colour and pH

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EM are living products. Like a sourdough starter or a yoghurt, they keep well if you follow a few rules, and they eventually run out of steam if neglected. They also have their reassuring quirks: a swollen container, a white film on the surface… which often cause needless worry.

This guide covers the shelf life of each product, the right way to store them, and how to tell a successful EM-A from a failed one, with what to do in each case.

How long do EM keep?

Shelf lives vary from product to product, and sometimes from one set of instructions to another. Here are the guidelines we go by:

• EM-1 (concentrate): its micro-organisms remain dormant until it is activated. The date printed on our bottles is the use-by date, around 2 years after production, with the cap tightly closed; other licensed producers state around 6 months. In every case, the date printed on the label is the one that counts. An opened bottle takes in a little air each time it is opened: close it tightly and don't leave it lying around.
• Microferm EM-A in Bag-in-Box: until the use-by date printed on the packaging, around 1 year after production. The pouch shrinks as it empties, which limits contact with air down to the last drop. Bottles, on the other hand, take in air every time they are opened.
• Homemade EM-A: this is the most fragile. The manufacturer of our EM-1 recommends using it within a month. Other technical data sheets give 35 days ideally and 65 days at the very most, and some producers, who activate at higher temperatures, go no further than two weeks. Laboratory counts carried out on an activated solution showed a significant drop in lactic acid bacteria within a few weeks.

Our advice: use your homemade EM-A within 1 to 2 months, and the sooner the better. After that, it isn't dangerous, but it contains fewer and fewer active micro-organisms.

Key points

Concentrate: according to the date on the label (up to 2 years for ours). Microferm in Bag-in-Box: according to the use-by date on the packaging (around 1 year). Homemade EM-A: 1 to 2 months. The more “awake” a product is and the more it is exposed to air, the sooner it needs to be used.

Storing your EM properly

• Somewhere cool, but never freezing: a room at moderate temperature, a cellar, a pantry. Technical data sheets put the storage range for EM-1 at roughly 3 to 38 °C; the ideal is still a stable room temperature, around 15 to 25 °C. Frost kills the micro-organisms. A fridge isn't necessary.
• Away from light and direct sunlight: a garage in high summer or a windowsill won't do.
• Tightly closed: air lets in unwanted micro-organisms. Always screw the cap back on straight after use.
• In a full container: when the level of your homemade EM-A drops in a large container, decant it into smaller bottles filled to the brim.
• In plastic rather than glass: EM keep producing a little gas, and glass doesn't cope well with pressure.
• Away from household products: bleach, disinfectants and chlorinated products destroy the micro-organisms. Never reuse a container that has held them.

Emy's tip

Keep your EM in a closed cardboard box at the back of a cupboard in a room at moderate temperature. The box protects them from both light and temperature swings.

Good or failed: recognising an EM-A by its smell, colour and pH

Three criteria are enough, to be checked as soon as activation is complete, then from time to time during storage.

A successful EM-A

• Smell: sweet and sour, pleasant, fruity, slightly vinegary.
• Colour: orangey brown, lighter than the original molasses.
• pH: 3.8 or below, ideally between 3.2 and 3.6.

A failed EM-A

• Smell: rotten, like sewage, rotten eggs, rancid butter or ammonia.
• Colour: still very dark, or cloudy with coloured patches.
• pH: above 4, and not dropping when left somewhere warm for a few more days.

pH is the final arbiter. pH paper, such as our pH test strips, costs little and saves a lot of guesswork. If the smell is good but the pH is still slightly high after 7 days, it is often just a question of warmth: leave it somewhere warm for longer and measure again. But if the pH stays above 4 and the smell is bad, the balance of micro-organisms isn't right.

White film, putrid smell, swollen container: what should you do?

A white film or flakes on the surface

This is normal. These are yeasts, which are part of the culture. A small deposit at the bottom of the container is also normal. If the smell and pH are good, you can use your EM-A without worry.

Fluffy green, blue or black mould

This indicates that air has got in or that the container wasn't cleaned properly. In a liquid, don't try to remove it: if it comes with a bad smell, the EM-A needs replacing.

A putrid smell

This is the clearest sign of failure. There's no point persevering or adding more EM-1: start again with a clean container.

A swollen container or pouch

This isn't a problem in itself: EM produce gas. For a container, gently open the cap a quarter turn to release the pressure, then close it again. A slightly bulging Bag-in-Box pouch is normal. What matters is the smell.

Did you know?

According to the manufacturer, almost all failed EM-A come down to two causes: a poorly cleaned container or a temperature that fluctuates too much during activation. Cold and chlorinated water complete the list of usual suspects.

Why an activation fails

To succeed next time, go through these points:

• The container: poorly rinsed, or with traces of household product.
• The water: chlorinated, because it wasn't left to stand for 24 hours.
• The temperature: too low, or rising and falling between day and night.
• Air: a half-empty container, or one opened too often.
• The concentrate: too old, poorly stored, or frozen.
• Re-culturing: an EM-A made from another EM-A, which manufacturers advise against.

The full method, with proportions and temperatures, can be found in our guide Activating EM-1: making your own EM-A step by step.

What to do with a failed or old EM-A?

A failed EM-A should not go on plants, either watered in or sprayed: you would be introducing micro-organisms you know nothing about. The simplest option is to pour it onto the compost heap, away from plants, where it will be diluted and broken down with everything else. We explain how to use EM in compost in the guide Speeding up your compost with EM.

An EM-A that is simply old, still smells good and keeps a low pH isn't “failed”: it is just less rich. Use it first for compost, and keep fresh EM-A for seedlings and the vegetable garden.

To avoid waste, make small batches suited to one or two months' use. And if you only use EM now and then, Microferm EM-A Active Solution, ready to dilute, keeps much longer than homemade EM-A. For regular use and large volumes, EM-1 Concentrate remains more economical. The same storage principles apply to fermented bran for bokashi: see our guide on bokashi bran.

In summary

EM should be kept cool, away from light and frost, tightly closed and in a container that is as full as possible. The concentrate keeps until the date on its label (up to 2 years for ours), Microferm in Bag-in-Box until the use-by date on its packaging (around 1 year), and homemade EM-A should be used within 1 to 2 months. A good EM-A smells sweet and sour, is orangey brown in colour and has a pH of 3.8 or below; a white film or a swollen container are normal. A putrid smell and a pH that stays above 4 mean failure: pour it onto the compost, never on plants, and start again with a clean container and a stable temperature.

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