How to Brew Compost Tea

June 28, 2015 by  
Filed under Blog, Compost/mulch, Permaculture, Soils

I am a founding member of the Lebanon Organic Gardening and Permaculture Club, here in Central Pennsylvania. The best part of the club is being able to collaborate and learn from other members. We currently have 61 members and growing. One of our members, Joe, is a permaculture designer, and he had the club over to his permaculture site to learn how to brew compost tea. He had a nice setup that I would like to copy.

Finished Compost Tea


I am not a big fan of traditional composting. I much prefer the Ruth Stoudt method of composting in place and feeding scraps to livestock. My main problem with composting is the time and effort required to make it. Compost tea is a different story. I love compost tea, because you can make a lot of compost tea from very little compost. Basically, you are taking a small amount of compost and growing the beneficial microorganisms by feeding them in an aerated slurry of water, molasses, and other nutrients. Once the beneficial microorganisms have multiplied, which usually takes 1-1.5 days, you can harvest the slurry and spread directly on your plants and soil giving them a huge boost. Compost tea will help with the overall health of your plants as well as their disease and insect resistance. In addition to the molasses to feed the microorganisms, other nutrients can be added as well, such as kelp. There are tons of compost tea recipes, so I won’t detail them here. Just know that at a minimum you’ll need some finished compost and something to feed the microorganisms, unsulphured molasses.  


1. At the very least, you’ll need a container, an aerator, some compost, and unsulphured molasses. It is important that you have good quality finished compost. Your brew will only be as good as your ingredients. If you have a worm farm, worm compost is best in my opinion. Do not use anaerobic compost. You’ll know if the compost in anaerobic because it will smell bad.


2. Place well water or rain water into your bucket or barrel and begin aerating the water for at least twenty minutes. City water is not great for the microorganisms. If that is the only water you have, aerate for 24 hours for the chlorine to off gas.

Aerating a 5 gallon bucket


3. Add about 1 pound of compost in a mesh sack or nylon panty hose per 8 gallons of water. This ratio can vary too. Nothing is set in stone with compost tea. Place your sack in the water. Tie it up to the lid or the side of your container so it does not fall in.

Putting in the compost in a nylon sock


4. Add your food sources. An ounce of liquid kelp, humic acid, and unsulphured molasses per 5 gallons of water is a simple recipe, that I like, but there are tons to choose from and don’t be afraid to experiment. Other common food sources are fish hydrolysate, soybean meal, oat bran, oatmeal, fish oils, cellulose, lignin, cutins, rock phosphate dust, and many others.

Unsulphured Molasses


5. Let the tea aerate for at least 24 hours, but not more than 36. If you brew beyond thirty-six hours, you risk anaerobic bacteria taking over. The brew will stink if it does. If that happens, do not put the brew on your plants. I just throw a bad brew in the grass, because I hate grass.

Compost Tea Brewing


6. If it smells good, spray the tea on your plants!

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