CompostFungiSoil BiologySoil Rehabilitation

How to Make a Compost Tea Brewer for Under $30

This video makes two things clear:

  1. We don’t need to spend thousands of dollars to make a compost tea brewer
  2. Things in the USA are too cheap! (I couldn’t get the items mentioned in this video for anything near as low a price as $30). It just goes to show how accustomed we are to buying mass-produced products based on cheap energy, cheap labour, impossible-to-sustain globalised trade and externalised costs!

Some of you do-it-yourselfers may well be able to come back to us with an even more environmentally-friendly version of this compost tea brewer. You may even want to out-do this guy by making a video of your own?


  1. Thanks for that link Duane, do you know what sort of diffuser is on the end of the submerged stainless steel pipe in the 250gal IBC container version?

    I was looking at the same membrane diffusers used in the commercial US brewer from Growing Solutions, they’re from the waste water industry, very good for oxygenation and rattling the compost about without damaging fungal hyphae. I’ve also got some soaker hose to use as a diffuser which worked well in past hydroponic shenanigans.

    I’ve put a bunch of links in this thread, more on the science than on making a brewer but useful for anyone thinking of making their own brews who might be at the bottom of this learning curve.

    Tim Wilsons site is great for anyone starting their own microscopy quality control, I found the microscope guide invaluable.

  2. My Soil Food Web instructor Ian Davidson said not to use the air stones because they can’t be properly cleaned, so they turn into a harbor for anaerobic microbes.
    Has anyone heard anything like that?
    I mostly make compost dormant extract that does not need aeration, and only takes about 5 minutes to make. It can only be applied to the soil. If I have a leaf problem (like peach leaf curl last very rainy spring), I made the aerated compost tea, since it is a little slimy, and sticks when sprayed to the leaves. The peach leaf curl was gone 4 days after application!

  3. Please do not make the 5 gallon brewer mentioned in the above video. Spend $40 more and build a brewer that will work. I’ll share the basics of how to build that brewer, but first lets talk about why the above brewer doesn’t make the cut.

    The Pump- When we talk about compost we’re talking about an aerobic process. The same goes for compost tea. Any aquarium pump will not have the power to supply the oxygen to the blooming bunch of microbes in the tea. How do we know? Testing. There have been plenty of companies that have tested biomass, aerobic vs. anaerobic and come to the same conclusion. Aquarium pumps don’t cut it. Here is a quote from Tim Wilsons website on “So you want to build a compost tea brewer.”

    Tim-“First of all I’d like to make it clear that most aquarium air pumps don’t produce enough air to use in a container larger than 1 gallon when considering making an aerated brewer. So don’t even try the 5 gallon pail with the aquarium pump idea everybody is passing around. You need a minimum 0.05 CFM (cubic feet per minute), open flow of air and an optimum 0.08 CFM per gallon (US) or higher to make aerated compost tea (ACT). ACT should have the DO2 sustained at or above 6 PPM. Generally, aquarium pumps produce around 0.02 to 0.16 CFM.”

    The next reason why the above brewer doesn’t work is the air-stones. One of Dr. Elaine Inghams pet peeves is a little something called bio-film. This is the scum left over after the brew. If you don’t clean it off it starts to attract bad bacteria. They start feeding on it and the next time you brew, you add those bad bacteria to your mix. You will get away with it the first time you brew with air-stones, but each time after that, you will have bio-film because you can’t clean the inside of an air-stone.

    Now on to the Solution:

    The Pump: We need to find a diaphragm pump in the range of 18 to 25 watts. That’s around 45 liters per minute. This will be the major price difference from the above model. In the US you can find them for around $45. This will give us the minimum 6ppm DO2 that is required to make compost tea.

    The air conductor replacing the air-stones will be a short section of pvc pipe attached to the pump. One end of the pipe will be submerged into the water while the other end will attach to the pump. The key piece you will need for this, is this;
    You can drill a hole in the 5 gallon bucket lid to hold the pvc pipe in place.

    While it’s true you don’t need to spend thousands of dollars on a tricked out brewer, I think the same logic can be applied to the cheaper model. You get what you pay for and for $30 you’ll get one cheapo brewer. If you are industrious enough spend the extra money and do it right.

    There is a long list of academics who swear compost tea is a fraud. They are bought and paid for by you know who and they use bad brewers to produce bad teas that give compost tea a bad name.

    Know the science behind compost and compost tea and remember, the tea is only as good as the compost.

  4. The design in the OP is based on Bruce Deuleys design, I suggest people view Bruce Deuley & Bob websters video series (9 videos) and listen to what he has to say for themselves, he is at least being very open source regarding this subject, something very lacking from the “experts” so quick to put this simple design down. He claims it was tested by Elaine Ingham in a “brew off” I certainly would not call the man a liar.

    I don;t want to cause an argument, maybe Tim had no success with aquarium pumps, who knows, I do appreciate his open source attitude all the same, and his video DVDs are definitely worth buying if you are doing your own quality control via microscopy, I found them invaluable to aid my microbe recognition learning curve. There are so many different considerations from water quality to size of the aquarium pump, and recipe used, that it is almost impossible to say for sure without putting a sample of the brew under a microscope.

    Having immersed myself in the science since I saw the interview on PRI with Doug Weatherbee, I would say the 5 gal design featured in the OP could work, I would caution to get the largest pond air pump possible for your budget, or buy something bigger second hand, I would caution to add very little microbe food though or the microbes will soon use up available O2 to the point where the pump cannot re-oxygenate fast enough to keep up with the microbes, it will be harder to get a fantastic brew from it IMO, unless you are using a microscope to quantify and quality control it, but if all you want is a bacteria dominated soil drench it could work.

    It is worth mentioning commercial brewers of the 5 gal design do use much bigger air pumps, and the membrane diffusion discs I mentioned earlier. As I think this is only really worth doing properly I am concentrating on a larger design, still doing it very cheaply, I found a Side Channel Blower similar to the pump used on the commercial IBC version on ebay from a dentistry lab for £40, they go for around £200 new from Siemens in Germany and can be found new on ebay :) I am still trying to get hold of the membrane diffusers in the UK, but I have options, they are off the shelf in the US.

    I do have a phase contrast microscope, cheap off ebay which was £350 second hand, mine is an Olympus EHT phase contrast scope from about 1960, todays new versions of this are about £3000, but good optics remain good optics, so second hand works just as well, and todays modern cameras can still be used with them. I am making a stand/clamp for my camera for it now so I can share my findings openly on the web, I can not stand the lag in information leaking out by these save the world one paid download at a time types.

    Air stones will become contaminated after only one brew for sure, use H2O2 to clean the system and stones to get round that, they are consumable items though, and will soon fall to bits after a few uses.

    A note on the importance of dissolved O2. I attended a seminar at a soil food web lab where we came away with a sample. When I got home I put the sample straight under the microscope, it was teaming with microbes, the next morning the sample had less than half the activity, many dead or hibernating microbes. I heard from a farm contractor who had found brewing on site too much hassle (for lots of different reasons) so got a batch made at the soil food web lab/farm and transported it for two hours to the site, the same sample worked to control tomato blight at the SFW farm, but failed at the contractors site after travelling for two hours in an un-aerated tank.

    Become part of the solution, open source please people, all the way, or you are part of the problem IMO.

  5. hi Pete and Dan and all

    thinking outside the brewer for a second. the dissolved oxygen becomes a problem… only because the bugs are stuck in the water!
    they don’t normally live there, they live where they can get atmospheric oxygen.
    perhaps a rotating system, like a biowheel holding the little darlings would work. there are designs where air is bubbled under the wheel to turn it.
    or some type of flood and drain system allowing them to breathe air might do it.
    either if these eliminate airstones and fancy pumps

  6. Hi Duane, my first thoughts when I came across ACT was to replicate a gravel bed bacterial filter type thing from the sewage industry, similar to an aerated septic tank bio-filter where the surface area is massively increased with plastic shapes and the flow run over it.

    But… The best designs (as in tested under a scope for microbial mass & fungal hyphae) are the ones which remove the microbes from the compost with vigorous air flow (membrane diffusers at the bottom of the brewer and large ceramic air diffusers from Koi Carp ponds in the compost teabag) the idea is to get the microbes into the water and keep them there, rather than allow a bio-slime to grow inside/on the equipment, so I soon disregarded this idea.

    Bio film/bio slime is a big issue which can ruin the brew in no time (an hour), microbes are so efficient at glueing themselves together that they can soon form an anaerobic layer in a low flow zone, anaerobes put out toxic compounds as they grow and feed and these compounds can kill an aerobic biomass in no time and turn the brew anaerobic.

    The best designs make sure there are no “low flow” areas in the brewer where bio-slime can accumulate, round brewers perform better than cubes shapes in this regard (that’s not to say cubes shapes don’t work, just not as well as round shapes unless there is massive flow IMO). Hence I soon disregarded my thoughts on gravel bed type stuff as they are designed to accumulate bio-slime, they’re designed to clean the sewage water by running it over a bio-slime rather than extract the microbes.

    The biggest (efficient) design I have seen uses a large fermenting vessel shape, a large round cylinder with a conical bottom (think biodiesel tank), the air is pushed in via a low pressure high volume pump via a Side Channel Blower air pump like these high volume low pressure air is the way to go.

    these are the diffusers in some of the very efficient commercial

    If you can split the airflow so some can be directed straight into the compost teabag/mesh bag to loosen the microbes off the compost it will be more efficient. The little buggers make very efficient slimy glue to hold themselves onto organic matter which has to be overcome with vigorous airflow without damaging the microbes, seems a water jet type thing is too rough on them and damages fungal hyphae which we want to remain intact.

    When moving the liquid via pumps it seems it is best to use diaphragm pumps rather than centrifugal pumps as the latter can also damage the biota, foliar application spray equipment must also be tested by sampling under a scope to make sure the spray head is not damaging the biota (or copy commercial spray equipment already in use in commercial ACT, this company are a UK supplier they use “blue” spray heads.

    This is a good lecture on the science from Professor Alan Gange, from the School of Biological Sciences at Royal Holloway, University of London, facinating stuff

    Where are all the brewer designers with experience? Is this stuff a secret or something? open source people ;)

  7. I’m still a novice at permaculture and the soil food web, yet it seems to me that many ideas still are preoccupied with the bigger and efficient brewers that still are required to have an external energy imput to work. Given that cheap energy will be a thing of the past in the next century, it only makes sense to take a natural approach to the brewing of CT. I have had great success with teas in a 5 gallon pail without air stones or pumps. Sometimes convienence costs energy too. I manually aerate the tea with sticks I’ve purposely composted in the bin. I use the tea the same day it’s made. The only particulars are in the compost itself, and this is key. Knowing what food web the plant prefers is a start to knowing what kind of tea to brew. Longer lived plants prefer fungially dominant soil and softer shorter lived plants prefer bacterially dominant soils. Either way they’re both present. It’s about what you put into the compost and how it’s maintained during the compost process. A good book for beginner soil food web is “Teaming with Microbes”. Cheers and happy gardening.

  8. For us in Oz I found a solution around expensive prices and manufacturer lock out to ship to Australia. A lady in Ballarat started a company called Price USA, no affiliation, that orders on your behalf to their USA location, collates your items into a single shipment to you in Australia.

    i used them to get a good chainsaw for my property at 1/3rd the price here.

    i am interested in large scale compost tea preparation so I’ll search US prices and local and build accordingly.

  9. why don’t you want to break up fungal hyphae?

    I’ve done that all the time when making mass mycelial slurries for innoculation.

  10. Hi Peter, quoting from the compost tea brewing manual 5th ed

    “There are two things to understand about mixing…

    1. Enough energy has to be imparted to the compost to physically remove the bacteria and fungi from the surface of the compost. Bacteria can glue themselves onto the surface of any particle in compost, and it takes significant energy to remove bacteria from these surfaces. Fungi wrap around particles and the hyphae have to be broken enough to let the strands be pulled out of the compost, but not broken so much that they are shredded into tiny pieces. Thus, most extraction methods that involve blades, whirring mixing bars, or blender action can break up the hyphae, or bacterial cells, too much and result in poor fungal and/or bacterial biomass in the tea.
    2. Uniformity of the end product, the tea, is necessary. Good mixing – enough but not too much – produces both effects. Most of the commercially available machines were developed around the principles of enough aeration and enough mixing to get organisms into the tea, but not shred them to death”


  11. Interestingly, the design in the OP is detailed in the compost tea brewing manual, so it seems it does work, with some minor adjustments to brewing times and feeding recipes. some notes from the CBM 5th ed…

    “DO NOT compact the compost or extraction will be poor and the tea may become anaerobic.
    Keep bacterial/fungal food to a minimum, or growth will use up dissolved O2 faster than the pump can replace it. The aerator provides a continuous flow of air and creates enough turbulence to provide mixing. Still in most cases an occasional brisk stir helps the quality of the tea, by removing organisms from the surface of the organic matter.

    Brew for 2 to 3 days, minimum. Longer is OK. Then turn the aerator off and let the brew settle for half an hour until most of the solids are at the bottom of the bucket. The soluble portion can be drawn off the top leaving the solids in the bottom to be returned to the compost pile (presumably for no net bag buckets) for spraying strain the tea through a cheesecloth or fine mesh tea sieve to prevent plugging the sprayer nozzles.”

    seems the addition of a net bag to hold the compost, and the extra air stones in the bag are an improvement on the design detailed in the manual.

    I’d say go for it ;^)

    some useful links and stuff here…

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