What’s Brewing? Podcast Episode 6: Brewing Compost Tea

What’s Brewing is a podcast all about compost tea hosted by Troy Hinke.

Troy Hinke served as Rodale’s Compost Research Specialist alongside the founder of Soil Foodweb Inc., Dr. Elaine Ingham. Troy now runs Living Roots Compost Tea, where he offers several services including consultations, compost sprays, and compost brewing, among others.

Episode six of a 10-episode series on compost teas, host Troy Hinke goes through the whole process of brewing quality, high-biology compost tea from start to finish.

What We Need to Start Brewing (01:15)

As discussed in the previous episode, we’ll need a few things to get started: a clean container or brewer, clean water, an air pump or air blower, a brew bag, high-quality compost or vermicast, and lastly, foods for microorganisms.

If you’re into doing things all-organic, you can choose to purchase all OMRI-approved (Organic Materials Review Institute) materials and ingredients.

Preparing to Brew (01:42)

At least 24 hours prior to brewing, fill up the clean container with clean water to get the brew to ambient temperature, making sure to keep the lid on to keep out falling leaves or insects out. This step is particularly important if you’re using municipal water, as it will also off-gas any chlorine or chloramines.

No time to off-gas? If we’re tight on time, we can either use an air pump or air blower or use some humic acid to off-gas the chlorine and chloramines in the water. When doing this method, make sure to wait until the water is at ambient temperature before beginning the brewing process.

Adding Microbial Foods (02:21)

We’ll start off the process by first adding microbial foods, which we can stir in manually or by using an air pump or air blower. When stirring in the microbial foods, it’s advisable to stir in one direction to create a vortex, and then stirring in the opposite direction, breaking the vortex to make sure we’re distributing the microbial foods evenly.

When mixing in microbial foods, remember to think positive and send loving thoughts to the microorganisms!

Recipe.            5-gallon brew – 1 tbsp. humic acid
                                                            1 tbsp. fish hydrolysate
                                                            1 tbsp. feather meal or soluble kelp
                                                            1 tsp. unsulfured blackstrap molasses (optional)

                        50-gallon brew –    ½ cup humic acid
                                                            ½ cup fish hydrolysate
                                                            ½ cup feather meal or soluble kelp
                                                            < 3tbsp. unsulfured blackstrap molasses (optional)

                        1000-gallon brew – 7 cups humic acid
                                                            7 cups fish hydrolysate
                                                            7 cups feather meal or soluble kelp
                                                            1 cup unsulfured blackstrap molasses (optional)

After adding in the microbial food, we can get the air pump and air blower going.

Adding Compost (05:37)

When it comes to compost, it’s good to have compost at different ages—from fresh compost to aged compost—to get a good, diverse population of microorganisms. Adding some vermicast will greatly help getting that diversity as well.

The higher the quality of the compost we’re using, the less we’ll need. But generally, for a five-gallon brew, we’ll be using about 2-4 cups of compost. Two to three cups of good quality compost will do the trick, but if the quality of the compost is a little less than ideal, then we can bump that up to 4 cups.

For a 50-gallon brew, we can cut back on the compost and not use the same ratio per gallon of water. Sixteen to eighteen cups or a gallon of compost will work well for this volume of brew. If purchasing a brew bag for a 50-gallon brew, a medium size brew bag will work best.

For a hundred-gallon brew, 28-30 cups or a little less than two gallons of compost will work well along with a large size brew bag. Again, depending on the biology and the quality of the compost, we can either put less or more.

Finally, for a thousand-gallon brew, we can use 6-8 gallons of compost, which would need to be placed in a couple of large size brew bags.

Just a reminder: it’s best to measure compost by volume rather than weight, as moisture content may vary and will affect weight.

Protozoan Infusion (08:04)

Adding a protozoan infusion to the compost tea brew entails adding some straw to the brew bag after massaging the compost, which will be discussed in the next section. Adding protozoan infusion inoculates the tea with microbial predators who will release the excess nutrients in the bacteria’s bodies.

For a 5-gallon brew, we’ll need just a small amount, about 10-20 blades of straw. And for 50-gallons, while this may not sound like the most scientific measurement, we can put in a healthy handful of straw, and that would do the trick.

Brewing Compost Tea (08:51)

Once our compost and protozoan infusion are in the brew bag, we’ll place the bag into the water with the top open. After that, we’ll use our hand to massage the compost for a about 2-3 minutes, which means grabbing handfuls of the compost, breaking up chunks, swirling it around with our hand, and shaking up the brew bag.

Afterwards, we can close the bag and work it from the outside by squeezing, shaking, massaging, and pressing. After working the compost, then we can add the protozoan infusion. The reason for adding in the infusion after massaging the compost is to avoid the straw from clogging up the bag during the process.

Based on research and microscopy, the more we massage the compost, the more we break up those large chunks, the more we increase the available surface area from which we can extract microorganisms.  

After that, we can sit back and let it brew.

Foam in Compost Tea? (10:52)

A pet peeve of Troy’s is the way some people on YouTube or social media talk about foam in compost teas. While microbes will produce a bit of air through microbial activities, it won’t be enough to create an insane amount of foam.

The foam mainly comes from adding fish hydrolysate, which is thick and sticky, and if our brew is having that much foam, then we’ve probably put in a bit too much microbial food in the brew.

“Foam has no indication on the biology or quality of the compost tea.”

Troy Hinke

Brew Length (12:00)  

One of the most common questions about brewing compost tea is brew length, which will depend on the ambient temperature at the time of brewing. Remember that we’re always brewing at ambient temperature.

Microorganisms are dependent on temperature and available oxygen. At hotter temperatures, microorganisms are more active, but there is less oxygen available in the air. On the other hand, oxygen is more abundant at colder temperatures, but the microorganisms won’t be as active.

This means the lower the ambient temperature is, the longer it will take to brew, and the higher the ambient temperature is, the shorter it will take to brew.

The whole idea behind compost tea is to hit a peak population of beneficial microorganisms, so as these microorganisms are eating and reproducing, they’ll eventually hit their peak population, which is when the most food and/or oxygen will be consumed.

Once the oxygen runs out, the temperature will quickly drop, and beneficial aerobic microorganisms will begin to die out, and the anaerobic microorganisms will begin to take over. Because of this, we’ll need to keep a close eye on brew length to prevent our compost teas from becoming anaerobic and going bad.

General rule of thumb. Because Troy has brewed countless compost teas in various plant hardiness zones, he has come up with a general brew length that works for all areas.

Ambient TemperatureBrew Length
40-65°F (4-18°C)72 hours
66-80°F (19-27°C)48 hours
81-90°F (27-32°C)24 hours
> 90°F (>32°C)12 hours or less

When unsure about the length of time to brew, stick to a shorter length of time.

“It’s better to have slightly smaller populations of beneficial biology than to get to a point where you’re getting anaerobic microorganisms and beginning to populate the brew with these anaerobic microorganisms.”

Troy Hinke

An Indicator to When the Compost Tea is Finished (16:33)

Another common question about compost tea is: Is there a way to tell when compost tea is done? And sadly, there aren’t any visual or olfactory cues to be able to tell if a compost tea brew is ready or is at its peak population. The only way to truly know the compost tea’s microbial population density and diversity would be with the use of a microscope.

That said, we would be able to tell if a compost tea has been brewing too long and has gone bad when the brew is giving off a bad smell.

“If you smell something bad and off-putting to you, a human, it’s definitely going to be off-putting to a plant and most likely going to be detrimental to it.”

Troy Hinke

Evaluating the Compost Tea (17:26)

Now that we’re done brewing, it’s time to check how good our compost tea is using a microscope.

What we want to see in the sample of compost tea are not only bacteria and fungi but also some predators such as different protozoa and/or nematodes. We’ll also need to check for signs of anaerobic activity, like the presence of ciliates and other anaerobic bacteria.

In the case of a brew going completely anaerobic, then it would be better to just discard that batch and start a new one rather than applying potentially harmful microorganisms on your plants.

Post-Brew (18:33)

After you’re satisfied with your finished compost tea, then it’s time to either store it or start using it. But before that, it’s important to run the finished compost tea through a second filter. Doing so will make sure that no sediment will clog up our sprayers once we use them or our holding tanks when we store them.

Now that the compost tea has been stored away, we can heft the brew bag out of the container and empty it either as a separate compost pile or back into the compost pile where it came from.

Remember that the contents of the brew bag have been sitting and soaking in microbial foods and have soaked all that up. Putting it back into the compost pile will reinoculate it with microorganisms that are eager to access that microbial food.

After getting rid of the contents, give the brew bag a good rinse and wash off all the debris and residue from it. Occasionally when using fish hydrolysate or molasses, they will leave a sticky residue that can be difficult to wash off. In that case, we can either soak it in water for several hours, or if it’s particularly stubborn, we can soak it instead in water mixed with environmentally friendly dish soap and scrub it when it’s done.

Then we can turn off the air pump. In the case of using a conical brewer, it’s advisable to let it sit for a while after the air blower has been turned off to allow any remaining sediment to flow through to the bottom for easier cleanup.

Clean Your Equipment! (23:41)

As has been emphasized countless times, it is very important to clean the compost tea brewing equipment after every use. The sooner they’re cleaned, the easier they’re cleaned.

After getting the compost tea into the holding tank or spray tank, we should take the time to get a hose and a scrub pad to hose out our brewers, scrubbing the walls to get all the little debris and sticky residue off.

We should also make sure to clean out our air lines, our brew bag, any other hoses we might have used. And even afterwards, we should rinse out any hoses we used to apply the compost tea. Otherwise, we can get some stinky liquid building up on the inside of the hoses—and we don’t want that.

Adding Non-Microbial Foods (24:37)

While Troy adds Azomite to his brews just to add some micronutrients and minerals for the microbes, some people add mycorrhizal spores to their compost teas.

Whatever non-microbial food we’re adding to the compost tea, it’s best to add them after the brewing process and after running the tea through a second filter, especially mycorrhizal spores. Adding them during the brewing process will only get the spores stuck as sediment and would most likely end up getting tossed with the rest of the sediments and residues—which isn’t very economically since they’re quite expensive to buy.

Compost Tea Expiry (25:51)

The finished compost tea should ideally be used within 24-48 hours. It’s important to remember that we’re working with a living entity that requires oxygen. If the compost tea gets bottled and stored for a long time, it’ll eventually run out of oxygen, turn anaerobic, and go bad.  

Seeing Results (26:48)

After applying compost tea, you may see results right away, and you may not. While some people observe changes in their plants within a week, there are some people who don’t see any noticeable changes.

If you’re using it in a vegetable garden, you may not see anything, but you might be getting more nutrients that are available to your plants, which means you’re getting more nutritious foods for you.

“When you do see changes after applying compost tea, it can really show people what an effect biology can have.”

Troy Hinke

Key Points on Compost Tea Brewing (30:05)

  • Brew at ambient temperature
  • Keep microbial foods at a minimum
  • Massage and work the compost in the brew
  • When in doubt, brew for a shorter period of time
  • Run the compost tea through a second filter before storing or spraying
  • Add non-microbial foods after brewing and filtering
  • Thoroughly clean all of the equipment used with the compost tea

Learn More

Learn more about Troy Hinke and his work on compost teas over at Living Roots Compost Tea, Instagram, and Facebook!

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