Compost tea made with an Aerated Compost Tea Brewer is an inexpensive, regenerative tool you can use to help your garden flourish. This step-by-step tutorial will show you how to build a DIY compost tea brewer of your very own using easy-to-find, affordable supplies. Plus, I’ll share some of the current thoughts on home-brewed compost tea along with the recipe I’ve been using to make aerated compost tea at home for the past 10 years.
I wrote up the steps to make this DIY compost tea brewer to go along with the recipes in the Compost chapter of my book, Garden Alchemy: 80 Recipes and Concoctions for Organic Fertilizers, Plant Elixirs, Potting Mixes, Pest Deterrents, and More. I packed so many recipes into those pages, that we had to cut down on some of the DIY projects. The book is really a recipe book, and while there are a few projects, the book is mostly about mixing concoctions and elixirs to grow a greener garden.
If you have a copy of Garden Alchemy, you may have arrived here to find this project (Yay, you’re in the right place!) and if not, go grab a copy! It has a whole chapter of goodness to go along with this project.
Is Compost Tea Helpful?
First, let’s chat about the Compost Tea Debate.
Compost tea arguably gets some of the most heated discussions from gardeners and experts. They debate whether or not compost tea is beneficial for your garden Some even argue that it could be harmful. Do a bit of googling or scroll down through any gardening forum and you’ll see what I mean!
Let me break down my take on the issue here, starting by answering the question, “What is compost tea?”.
What is Compost Tea?
The term “Compost Tea” has been used for many years in different formulations. Three of the formulations include:
- Compost Dilution – mixing compost with water and applying that to the garden
- Compost Leachate – the liquid that drains out of a compost bin
- Aerated Compost Tea – a brew of compost water and air
Brewing compost tea is essentially inoculating rainwater with the microbes that are active in healthy compost. This is done in order to increase those microbes and disperse them throughout the garden.
The Compost Tea Debate
The two sides of the debate both have excellent points that are worth reading.
Those who use compost tea successfully are converted by the results they see in their organic garden or farm. They have likely tested a variety of methods and found the one that meets their needs to increase production, reduce disease, or improve the overall health of the soil and plants. You can some of these stories here and here.
Those who caution against it, say that there is just not enough testing done on compost tea to prove that it works. Even more, they express concern that if compost tea is brewed improperly, harmful bacteria could be propagated and applied to the garden, potentially harming the plants and people. You can read more about that here and here.
My Opinion About Compost Tea
My opinion is that homemade compost tea is worth testing on your garden, as long as the method is simple and accessible (both cost- and labour-wise). Spreading native microbes and nutrients throughout your garden is a way to nudge the processes that nature intended.
Think of it this way: if your garden was a forest, plant material would compost in place on the ground and do this for you. Instead, we cultivate the plants, clean up the waste, and compost it in a different location. It is then our job to move that compost back.
The soil wildlife that grows in that compost is native to your soil and therefore should have a purpose. So, as long as you are using good quality homemade compost, test it out and see how it goes.
That being said, the more complicated and expensive compost tea becomes, it loses the benefit in my opinion. I add compost to the soil each year if I can make enough. I also nurture the soil and plants using many of the other recipes in Garden Alchemy.
Compost tea is a way to stretch the little compost that I am able to make in a year. I can never make enough compost it seems! This is my way of sending that goodness back to the earth. :)
Does Compost Tea Work?
Great question! But alas, there’s no way for me to know the composition of your compost and if that’s what your plants need. My best recommendation is to test out what feels right for you and decide for yourself.
In Garden Alchemy I share three different recipes for adding homegrown native compost to your garden:
- Nature’s Method, where you top-dress the soil with compost to allow rain or watering to bring those microbes down into the soil.
- Grandmother Method, a compost dilution where you’re not brewing microbes. Instead, you are diluting compost so they can be spread over a larger area.
- Alchemy Method, brewing aerated compost tea using a DIY home brewer and compost tea recipe.
In this post, I want to share my DIY aerated compost tea brewer and recipe so you can try it at home.
How I Designed This Compost Tea Brewer
I spent quite a bit of time researching compost tea history, studies, and methods when writing my Garden Alchemy book. Even though I’ve been using compost tea in my home garden for over 10 years, I was hesitant to include my recipe because it is a basic version and there are many more sophisticated brewers out there.
On the other hand, that is exactly why I did include it in the book. Garden Alchemy is all about testing home recipes in your garden and learning from experimentation and observation. My simple, inexpensive home brewer has been working for me for 10 years now and it works for me practically and functionally because I don’t overthink it. I keep it clean, follow the proper protocol, test before widespread application, and have fun with it.
Design Background for the Compost Tea Brewer
I started brewing my own compost tea at home after learning how to make an aerated brewer at UBC (University of British Columbia) Farm, where I volunteered as a Master Gardener for the Intergenerational Landed Learning program.
This program brought together Master Gardeners, university students studying plant sciences, and school-age children to plan and grow organic food gardens. In the greenhouse shed, there was always aerobic compost bubbling away.
The children would take handfuls of finished compost to fill nylon stockings and hang in the brewer. Then, they would scoop out some of the compost tea to add to two watering cans when they watered their garden beds.
After doing this at the farm, I set up my own system at home to test out the results. I would water one part of the garden with diluted compost tea brewed in my compost tea brewer, and water another part with just plain water. Every time I did this the compost tea part of the garden was always the greenest and healthiest.
I made some modifications over the years and came up with the final design that I use now. Most of the bucket-aerated systems you see have an aquarium bubbler that is weighted to the bottom of the bucket with aquarium stones. I didn’t like that the aquarium stones would build up in biofilm and were difficult to clean after every batch. So, I simplified it.
Compost Tea Safety and Brewer Cleaning
One of the key points to properly using a home compost tea brewer is to make sure that it’s cleaned thoroughly in between each use. For this reason, I switched to open bubble lines and ditched the stones. The lines are guided to the bottom of the bucket and held in place with suction cups.
The line and suction cups are all very easy to wash afterward and all the biofilm comes right out. You can even just throw the whole thing in the dishwasher.
How to Build a DIY Compost Tea Brewer
Ready to build a compost tea brewer of your own? I can’t wait for you to try this out in your garden and see how it does!
Compost Tea Brewer Materials
As you can see, these supplies are not difficult to find. You can grab these at local stores, but I also have linked them below to make it easier for you.
- 5-gallon food-safe bucket and lid
- Aquarium air pump kit
- Aquarium air pump suction cups
- Large 12 x 12 inch nut milk bag
- Small screw end metal hook
Make the Compost Tea Brewer
Assemble the pump together as per the instructions on the box.
Screw the sharp end of the hook through the top rim of the bucket in order to have a place to hang the pump outside of the Brewer.
Use suction cups to guide the hoses from the pump down the side of the bucket and attach them to the bottom of the bucket with the suction cups spaced so that they will each be adding air to roughly half of the bucket.
Fill the bucket with rainwater or dechlorinated tap water. Tap water with chlorination added needs to sit in an open bucket for 24 hours to allow the chlorine to evaporate. Remember, chlorine is meant to purify water and keep out microbes out. This is the opposite of what we want in compost tea! That’s why we want to make sure that there is no chlorine in the water.
Aerated Compost Tea Recipe
Adapted from Garden Alchemy
Of course, I couldn’t give you the instructions for how to make a DIY aerated compost tea brewer without sharing a good compost tea recipe! This is my go-to recipe for my own garden that I really like for it’s simplicity and effectiveness.
Compost Tea Materials
- 5-gallon (19 L) bucket compost tea brewer (from above)
- Large 12 x 12 inch (30 x 30 cm) nut milk bag
- 1 cup (235 ml) excellent quality finished compost
- 1 cup (235 ml) worm castings
- 1 tablespoon (15 ml) soluble seaweed
- Rainwater or dechlorinated water
- Add the water to the brewer and run the aeration for 1 hour.
- Add the remaining ingredients to the filter bag and add it to the water. Follow the instructions that accompany the brewer you are using.
- Continue aerating for 24 hours at 72°F (22°C). If it is warmer, then decrease the brewing time, and if it is colder, increase the brewing time.
- Strain the compost tea and apply to the garden immediately.
When cleaning up, thoroughly wash anything that was in contact with the organisms well. This will help to remove the biofilm and ensure you’re ready for the next use.
Which is the Best Compost Tea Brewer?
Part of the fact that compost tea is controversial is that there are many different methods of making it. Dr. Elaine Ingham from Soil Food Web teaches courses on the best way to brew compost tea. She recommends a cone funnel system that costs quite a bit of money.
Dr. Ingham also recommends a best practice of using a high-powered microscope to evaluate the microbes. In addition, many compost tea recipes suggest adding a food source for microbes like molasses, kelp, and humic acid. Some of these are easy to find, while others require some hunting.
I certainly think that there’s value in getting deeper into the study of compost tea if that’s something that you’re interested in. In that case, I would highly recommend taking a local class on how to properly brew compost tea and use it in your garden.
That being said, compost tea is not the holy grail of gardening or a miracle cure to every disease in your garden. It’s just one component of the many natural and healthy things that you can do in your garden to help build the soil and grow healthy plants.
One of the concepts that I present in Garden Alchemy is this: you should take some time to get to know your garden through experimentation and observation, as each one is unique. Then, test out some of the recipes to see what works best for you.
So, if you want to try compost tea, great! And if not, you will be fine too. Experiment and play to see what works for you—after all, that’s the fun part of gardening!
If you are interested in learning more about the experiments you can do to help your garden thrive, take a peek at Garden Alchemy here.
I’ve heard that comfrey is good to put into the compost. Is that true, and if so, then what does it to for the compost?
Yep! Comfrey is great for compost. It grows fast and has deep roots to suck up nutrients deep down. Read more https://permaculturenews.org/2010/10/01/the-wonderful-multi-purpose-comfrey-plant/
Hi, I noticed you wasn’t using airstones and just the tubing.
Did you get more action out of the little pump by doing so?
Thanks..I just purchased the same model
Hi Johnny, yes, I get more air with just the tubes. But that’s not why I don’t use the stones. The short version is they collect too much biofilm that is hard to clean. The lines are held down with suction cups. it’s described more in the post. Thanks!
Hello! So I just recently bought your book for myself and a copy for my mom…this maybe in the book and I haven’t gotten there yet but I’ve made the brewer and I have a few questions. If I do add molasses would you recommend and if so how much? And then how often do you water your garden w the compost tea and do you spread the remains of the tea bag so to speak after brewing?
Hi Danielle, thank you so much for getting two copies of Garden Alchemy! I don’t use molasses so I can’t answer that. I water my garden with compost tea monthly between April – October, but in the beginning when I was working to repair the soil, I did it weekly. The remains of the bag can go in the compost bin. I hope this helps!
I happen to have just purchased the same air pump to aerate my water. I use Nature’s Living Soil which has a compost tea mix on the website.
Add 2-3 heaping tablespoons of concentrate and one tablespoon of un-sulfured black-strap molasses per gallon of water and let stand for 24 hours.
This concentrated soil is very easy to use and looks like coffee grinds out of the package. Here’s what’s in it.
The base ingredients for our living soils are Organic Earthworm Castings, High Quality Bat Guano, Blood Meal, Bone Meal, Fish Bone Meal, Neem Meal, Humic Acid, Rock Phosphate, Dolomite Lime, Azomite, Alfalfa Meal, Kelp Meal, Coco Coir, Crushed Oyster Shell, Humic Acid, Epsom Salt, Coconut Water Powder and Aloe Vera.
In addition to the microorganisms that are found naturally in our guano, earthworm castings and compost we introduce the following bacteria and fungi Glomus Aggregatum, Glomus Etunicatum, Glomus Intraradices,Glomus Mosseae, Pisolithus Tinctorius, Scleroderma Cepa, Scleroderma Citrinum,Trichoderma Harzianum, Trichoderma Koningii, Saccharomyces Cerevisiae,Azotobacter Chroococcum, Bacillus Amyloliquefaciens, Bacillus Azotoformans,Bacillus Coagulans, Bacillus Licheniformis, Bacillus Megaterium, Bacillus Pumilus, Bacillus Subtilis, Bacillus Thuringiensis, Paenibacillus Durum,Paenibacillus Polymyxa, Pseudomonas Aureofaciens, Pseudomonas Fluorescens.
I may be late to the party, but this is a great post and I’m inspired to (finally) get into brewing my own compost tea.
Question: is the bag essential? Could the compost et al be simply added to the water to allow to bubble freely, then strain the tea afterward? I’m just not sure if it’s more than an issue of tidiness. Seems to me the compost would percolate faster if not confined in a bag.