Introduction: Making Compost Tea

Picture of Making Compost Tea

Compost tea is a liquid solution or suspension made by steeping compost in water. It is used as both a fertilizer and in attempts to prevent plant diseases. Compost tea is made by steeping compost in water for a variable period (24-48 hours), then applying the liquid undiluted as a spray to plant parts, or as a soil-drench , such as to seedlings, or as a surface spray to reduce the amount of harmful bacteria and fungi on plants.

Step 1: Materials

Picture of Materials

There are two parts to the materials. The first group is to brew the tea, and the second set is to filter he tea for actual use.

For Brewing:

1. Compost (I prefer to use organic manure compost, but any kind of compost will do)
2. Five gallon bucket, or any water-tight container
3. Unsulfered Molasses (This acts as food for the bacteria)
4. Air Pump
5. Hose for the air pump
6. Shovel
7. Water

For Filtering and use:
1. Another bucket
2. Wire mesh strainer
3. Cloth for filtering

Step 2: Mixing the Tea

Picture of Mixing the Tea

Fill the bucket about a third of the way with the compost. After you have done this, pour in some molasses, I just eyeballed the amount, but it was roughly 1/4 of a cup. Then simply add the water, you want to fill up the bucket nearly to the top. You can see the ring in the bucket from where I've used it before. The reason for this is because this is a fermentation process, there will be gas bubbles that will form on top of the water, and you don't want this to over flow. I would recommend that if you are on a city water system, that you get bottled water or at least filter the water somehow, because city water will have small amounts of chlorine and fluoride which at least make the process take longer and at worst kill the bacteria that you are trying to grow. Once you have everything in the bucket, give it a stir.

Step 3: Set Up Air Pump

Picture of Set Up Air Pump

This step is very important because we are going to be making an aerobic tea. Take whatever kind of pump you have and set it up with the tubing. You will need enough of the tubing to ensure that it can reach the bottom of the bucket. You will also need to have some kind of weight on the end of the tube to make sure that it stays on the bottom of the bucket. I wouldn't recommend you use an "air stone" like you would in a fish tank, because they will get clogged very quickly and make very small bubbles. With this process you will want to have large bubbles of air. I just used an old socket for the weight, you can use anything at all for this. In the photo below, you can already see bubbles starting to form from the mixing process, these are very good.

Step 4: Brewing

Picture of Brewing

Now that everything is set up, you need to allow the mixture to brew for 24-48 hours. I would recommend for this step that you do this outside and make sure that there is some type of cover on the container. The reason for this is because this will produce odors, just like regular compost this is waste material that is being allowed to rot. The cover is just to make sure that no other water will get into the container. It's not the end of the world if this happens, it just means that you would have to brew for a longer time. I simply used one of my trash can lids. If you are making this on a covered area, you don't need to worry about this.

Step 5: Filtering and Use.

Picture of Filtering and Use.

After waiting for the brewing process to complete, you will need to filter the tea so that it will be able to be spread without clogging whatever it is you are using to get the tea to your plants. For this step, you will need to have another bucket, some type of fine mesh, I have an old pillow case for this, and something to support the mesh over the bucket while you pour the tea through it. This will take some time, and you will have to clean the mesh a few times, as there is a lot of dissolved solids in this mixture. It would actually be best to have several pieces of mesh on hand to get this part done as quickly as possible. What you will end up with two things, the first being the tea that you were trying to make and the compost on the bottom of your brewing bucket. The compost left in the bucket has done its job and can just be poured out into your garden just as you would any type of fertilizer. The tea can be spread by any means that you would spread a traditional liquid fertilizer. The only real precaution that you need to take is that if you decide to spray the tea onto edible plant parts, then make sure that you thoroughly wash these plants before you eat them. Other then that, the tea is a truly universal fertilizer that you should get excellent results from.


SinAmos (author)2009-07-15

The funniest part about this is that I was going to do the compost tea instructable, because I recently did one. Just make sure that people know that the bacteria will smell like vomit and poop rolled into one. You really don't need the oxygenator that much. Just a couple stirs per day and sugar. Mainly a feed source.

realety (author)SinAmos2009-07-15

The air pump is really to make it a self contained process so that you can set it up and leave it alone till you're ready to use it. but just a few good stirs a day would do the trick as well.

duckguy88 (author)realety2016-08-31

See above response. The aerator is necessary to keep the mix aerobic. Otherwise, you may be hurting your soil more than helping it. Hopefully people understand that this is less a plant fertilizer and more a soil fertilizer. It builds up beneficial bacteria and microbes in the soil that will benefit the garden for much longer than traditional fertilizers! Good instructable. You should play with the mix. We make ours with Bat Guano, fresh compost, worm castings, seaweed extract, molasses, alfalfa meal, fish fertilizer, bone meal, blood meal, fish meal and a couple other little ingredients.

duckguy88 (author)SinAmos2016-08-31

Im so late to the game. LOL. we have been making compost tea for several years and I have been looking for suggestions regarding tweaking the mix. This one will work, but our recipe is more complex.

The aerator is needed for just this reason. The good bacteria that you are after are aerobic (require oxygen). If your tea starts smelling terrible do not use it and aerate it! The aerator needs to remain on until you use up all of the tea. It takes very little time in an anaerobic environment for aerobic bacteria to die.

SeanP7 (author)2015-07-08

Do not use tap water as it will have chemicals that will kill your beneficial bacteria. If you have to let it sit out uncovered for at least 24 hours

The Manic Puppeteer (author)2015-04-14

When I saw the thumbnail, I sincerely hoped that this was not supposed to be for human consumption. Nice compost mix, though I would agree with other commentors; this could potentially overfertilize plants if undiluted.

JasonJ8 (author)2015-01-02

So I'm going to throw a warning label out here. If you make 'Compost Tea' from really high end compost like fresh worm castings, or well balanced compost that has broken down VERY well **BEWARE** it will "nutrient nuke" the crap out of your plants! I've found this out the hard way! I made a batch from my worm bin, and had been told several times to cut the tea at least 10:1 (10 H2O > 1 tea concentrate)... The first time I brewed some up cut it correctly and applied... the results were AAAAMMMAAzing! So since my green thumb at that time was more a pastel blue... My thought process was as my over informed and under qualified generation mantra..."If it was that good cut, its gotta be 10x's better straight"... WRONG! It was like going from shooting a cycle of Steroids every other month to drinking a gallon in an afternoon... I was lucky enough that I was keeping close tabs on the matters' and about 24 hours later the undergrowth started curling and yellowing from the tips inward... I immediately flushed them... The crop turned out really well in the end, but If I had not been watching... Death... CUT YOUR CONCENTRATE!

vupton (author)JasonJ82015-01-03

Thank you JasonJ8 for your input!! Wow!! Can't wait to make my worm castings!

Dr.Bill (author)2013-06-26

Chlorine will go away if you leave it in the sun. That's one of the reasons pools have to be re-chlorinated every week.

Pheline (author)2013-05-28

Having the water stand, especially in a warm area, or boiling it drives off chlorine.

2muddyboots (author)2013-04-11

Can't stress enough the importance of dechlorinating the water prior to use. Just aerate for a few hours or better yet use rain water (unless it's acidic). OK, well water is the best. For a detailed description:

cherylncohn (author)2012-08-30

Where would I get an air pump? Would a bike pump do? How often to you aerate the tea?

realety (author)cherylncohn2012-08-31

You can get the pump and the tubing at any pet store in the aquarium section. Another tip is to get an air stone and break the end off to act as a weight to keep the tube submerged.

Dr.Paj (author)2009-07-17

So do I heat it before drinking? Or leave it cold?

teslafan100 (author)Dr.Paj2009-07-22

haha funny :P

DIY-Guy (author)teslafan1002010-04-05

Our family prefers to brew Llama manure tea. The vegetable plants enjoy a drink of good Llama poo tea. Preferably cold but not iced. (Ha-ha) We got the idea from a site with instructions to brew llama fertilizer liquid at http://LlamaPoo.Com

Almost any animal poop will work, Llama poop might be the best organic fertilizer though.

Filtering and/or settling before decanting manure tea is helpful but adds extra labor. We followed the instructions for manure tea on that other website and found that putting holes in the cap of a plastic milk jug worked well for us. The drilled holes keep the large pieces from floating out of the bottle, and little tiny bits flow through.

Pizzapie500 (author)DIY-Guy2011-02-18

I know this is really late, but where do you get llama poo?

Xonk61 (author)Pizzapie5002012-07-08


UQONYX (author)DIY-Guy2011-07-16

do not use any carnivourous animal or domestic animal's poop because they have microbes in the digestive juices that they use are diseas prone and even if they are vegetarian by nature, usually their food formula also includes some type of meat as Quick Protein

realety (author)UQONYX2011-08-08

If you are using just fresh poop from any animal, you are very correct. But After composting most of the microbes that you are talking about have been taken care of because of the heat and chemical "cooking" of the composted manure.

joen (author)2011-04-22

Great instructable. But I had a question about whether it would be a way to make nutriants for hydroponic set ups. Can the compost tea be used in hydroponic set ups and if so, how would you work out the strength? Is there a test so you don't over or under nutrient the plants?

That would make hydroponics a lot more intresting.


Pizzapie500 (author)2011-02-13

I have a question: Do you have to filter it? I figure it's only Compost and Water and Molasses so why can't you just pour it onto the base of the plant w/o filtering?

realety (author)Pizzapie5002011-02-18

The only real reason I filtered it was because of how I was using it. I was putting it in a water can that had lots of little holes in it and if I didn't filter the tea, the little holes kept clogging up. if you are going to be using it in any kind of misting or wide spray nozzle you would want to both filter and water it down. otherwise if you are going to be just using it for a good root soak, by all means you could use it full strength and just pour it on. But it is still a good idea to water it down a bit, just to make sure you have enough for all of your plants.

Pizzapie500 (author)realety2011-02-18

Oh ok THANKS! 5*

hollasch (author)2009-07-15

Why filter the resulting tea? Wouldn't letting the solids settle out for an hour or so do the trick? After that you could decant the entire bucket, or siphon it. By the way, if you hook up a liquid fertilizer intake to your bucket and spray the diluted result on your lawn once a week, it's supposed to really help it along.

realety (author)hollasch2009-07-17

Just letting it settle alone won't get it done properly. The reason is because of all of the dissolved solids in the mixture. If you leave them in there they will clog the container that you are using to disperse the mix. The other way around this would be to use less compost in the beginning, but add more molasses since you will be starting off with less bacteria. If you did that, then you could get away with not filtering it, and letting it settle.

hollasch (author)2009-07-15

Regarding the water source, if your water source is sterilized with simple chlorine, then you could just leave the water out in a bucket for a day to evaporate the chlorine. Even better, just aerate it with your pump for an hour or so to do the job quicker. Try this first to see if it works for you. If your water contains chloramines, then this won't work. In this case, just go to an aquarium store and get some water conditioner. This should be much cheaper than buying bottled water.

realety (author)hollasch2009-07-17

With this I would still be carful with city water. Because Chlorine is not the only chemical that they put into the water supplies, there is also Fluoride and some other nice chemicals to watch out for as well.

pippa5 (author)2009-07-17

Hi great looking brew. But is there any way of telling or testing how strong in N.P.K the mix is. And how "strong" or "weak" the liquid fretilizer is. I dont want to burn my plants. Or is it guess work? I would like to make some suitable for tomatoes should I compost more of a certain materials?

realety (author)pippa52009-07-17

I don't have or know of a way to test it. I pretty much just put it on and that's it. You have to realize that it's not a traditional fertilizer, it's the living bacteria that you are more after. It's like giving yogurt to the plants.

yoshhash (author)2009-07-15

thank you, I'd been looking for an instructible ever since I saw the video with the guy with the gigantic award winning vegetables.

stallionspirit8 (author)2009-07-15

drink it! drink it! drink it! haha jk. nice instructable.

dchall8 (author)2009-07-14

Thank you for adding aeration. I don't go around the Internet looking for bad compost tea setups but they seem to jump out in front of me. Most suggest no air and leaving it for a week to soak. I would suggest not letting it go longer than 24 hours and making it in a cool location. Warm water will not allow any air to dissolve in it, and if you are going to feed molasses to build the microbe population, they will use all the oxygen very quickly - especially in warm water. In San Antonio our tap water is too warm so we would have to make it indoors in an air conditioned space.

realety (author)dchall82009-07-15

I usually don't let it go longer than about 36 hours, usually, I've had to do that once, and when I did that, I added some more molasses to make sure there was enough food for the bacteria. I'm in a pretty warm climate in southwest Florida and I haven't had a problem with the heat, but the water out of the taps are pretty chilled. I would suggest not making this indoors simply because of the odor, unless you have an outdoor shed or something like that. You could try and use ice to counter the heat in the beginning. Or even better to make sure they last long enough, freeze a large block of ice so that they will last longer.

AndyGadget (author)2009-07-14

Great Instructable!
This brew will work wonders for your plants, but to give it a REAL kick, leave some comfrey leaves to rot down in it for a couple of weeks before filtering (but if you do, dilute 20:1 before use as it will be VERY strong). After filtering, don't forget to recycle the solids back onto the compost heap.

realety (author)AndyGadget2009-07-14

That sounds like a great idea to add the comfrey, I'll have to try that. Unfortunately right now I don't have a compost heap as of right now, that's why I just dump it into the garden. Hopefully I can win the grand prize and then I can start to make my own compost for this process. ;-)

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