Does Compost Tea Stink? The Truth About Its Unique Smell

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What Is Compost Tea?

Compost tea is compost steeped in water. The liquid contains various particles from decomposing organic matter, including cellulose fiber, bacteria, fungal spores, insects, and “humates,” a group of additional compounds found in plants.

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Even though a healthy human gut and healthy living soil contain 70% of the same microorganisms, compost tea is not made for humans to drink. Instead, think of it as a health elixir for your plants! (Though it can sometimes look a bit like tea because of the dark brown liquid it creates).

What Is The Ideal Smell Of Compost Tea?

Compost tea’s ideal smell is slightly earthy and sweet. As the material composts in the liquid, it should have a fermented tinge to it, similar to the smell you might get in a brewery or when you open a fresh pack of active yeast.

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Generally, the smell is not pleasant or unpleasant. Most people describe it as neutral, like the smell of a forest on a wet spring morning. If the scent departs from this, it can indicate a problem with the bacterial composition of the compost or the presence of a contaminant.

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What Does It Mean If Compost Tea Stinks?

If compost tea stinks, it is usually a sign something’s wrong. Unpleasant odors can arise if the constituents of the brew are off somehow. Regular plant matter shouldn’t produce foul smells as it decomposes.

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Human waste or food substances are the most likely suspects in any search for the causes behind bad-smelling tea. However, even if your compost is just grass and clippings, it can still create bad smells if you pack it too densely. Too much organic matter can create an unpleasant funk that escapes beyond the water, stopping the natural balance of microbes from developing.

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The most common bad smells you will detect include:

• Sewage-like smell from decomposing human or animal waste
• Rotten-egg smell from the release of hydrogen sulfide, usually because of a bacteria imbalance
• An ammonia-like smell from composting high-nitrogen materials, like fresh grass clippings and manure

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What is Making Those Smells?

There are many mechanisms behind the various smells of decomposition, but the easiest way to think about them are imbalanced populations within the microbial communities. For instance, if you have a population of actinobacteria that’s getting out of control, the acids they excrete as waste products are going to become apparent. To get technical, here’s some of the chemicals that are creating those nose-turning odors:

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If you’re smelling something on the left, the chemical on the right is what’s causing it!
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Many of these arise from a lack of oxygen in the water. Friendly bacteria can’t access the gas and get out-competed by other microbes.

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How To Avoid Bad-Smelling Compost Tea

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Fortunately, there are several strategies you can use to avoid bad-smelling compost tea. The more you adopt, the less likely your brew will stink.

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Start by finding a way to pump air through the tea. Beneficial organisms (the ones you want to cultivate) almost always thrive in aerobic conditions, as opposed to anaerobic ones. The word “Aerobic” refers to the presence of oxygen. Providing the microbes inside with a ready supply of oxygen will prevent the smelliest non-aerobic bacteria from dominating the mixture.

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Pumps that are specifically designed for compost tea are rare, but aquarium oxygenation systems can function exactly as needed, with a few minor modifications. They provide a steady stream of bubbles into the mixture, giving bacteria oxygen they can use to perform their metabolic processes and divide.

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Next, ensure you only place high-quality organic material in your compost tea. Select combinations for optimal microbial ecosystems.

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Don’t use animal manure in your compost. It contains the wrong type of microbial colonies, preventing the tea from developing in a smell-free manner. Luckily, plant material available from your own garden can be a prime selection.

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Fill the compost bucket half full with compost material (such as hedge clippings) and use water for the rest. Don’t overfill the container because it can lead to problems later on.

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Temperature and brewing time also matter. If the weather is hot, keep the mixture in the shade and stir it twice daily. Moving the tea around can prevent dangerous clusters of bacteria from building up that might cause it to smell. Remember, controlling those populations of anaerobic bacteria will be crucial.

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Also, be careful of direct exposure to sunlight. UV rays can damage friendly bacteria and help the smelly ones outcompete them.

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Lastly, measure the brewing time. Most compost teas are ready in 36 to 48 hours. Don’t leave the concoction for longer than this because bacteria won’t have enough food to survive. They need to be introduced to your plants so they can continue their life cycles. Leaving them suspended in your brewer for too long can allow different species may take over, leading to bad smells all over again.

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How Do You Deal With Smelly Compost Tea?

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If your compost tea is already smelly, you may be able to salvage it. One simple step you can take is to pump air through the mixture and stir it to see if the smell improves. Sometime all you need to foster the growth of the bacteria you want is proper aeration.

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Another option is to add more organic material to the mix. This can help support new beneficial populations, but it may not eliminate the smell.

Sometimes, you may just have to discard the compost tea and try again. Luckily, you’ll find it’s not terribly difficult to start a new batch with the steps we’ve laid out here! And if you’d prefer to leave this kind of work to the professionals, hopefully you live within the service area of a local compost tea landscaper.Compost tea only smells awful if prepared incorrectly. Like conventional compost, it should have an earthy, natural aroma. If the odor is unpleasant, it usually indicates poor microorganism balance or the use of the wrong recipe.