Compost Tea Brewing
Brew aerated compost tea to inoculate soil with beneficial microorganisms. A simple bubbler system extracts and multiplies bacteria, fungi, and protozoa from finished compost. Apply as a soil drench or foliar spray.
Version History
Version 1.0 Current
Effective: 2026-03-27Initial version
Procedure Details
Do not brew for more than 36 hours — anaerobic conditions can develop and produce harmful organisms. Use within 4 hours of turning off the bubbler. Do not apply to edible parts of plants within 2 weeks of harvest if using manure-based compost.
You will need:
- 20L bucket
- Aquarium air pump with airstone (or similar bubbler)
- 1-2 cups of quality finished compost (earthy smell, no ammonia)
- Mesh bag or old stocking to hold compost
- Non-chlorinated water (leave tap water out 24 hours to off-gas, or use rainwater)
- Optional food sources: 1 tablespoon unsulphured molasses, kelp meal, or fish hydrolysate
Procedure Steps (Version 1.0)
Fill the 20L bucket with non-chlorinated water. If using tap water, fill 24 hours ahead and leave uncovered to allow chlorine to off-gas.
Place compost in a mesh bag or stocking. Tie it loosely — you want water to flow through freely.
Suspend the compost bag in the water. Place the airstone at the bottom of the bucket.
If using food sources, add 1 tablespoon of molasses (for bacteria) or kelp meal (for fungi) to the water. Stir gently.
Turn on the air pump. The water should be visibly bubbling and moving. This maintains aerobic conditions.
Brew for 24-36 hours. The water should develop a pleasant earthy smell. If it smells bad (sulphur, ammonia), discard and start over — anaerobic conditions have developed.
Turn off the pump. Remove the compost bag (return spent compost to the garden or compost pile).
Apply within 4 hours while organisms are active. Dilute 1:10 with water for foliar spray, or use undiluted as a soil drench.
Apply in early morning or late afternoon (UV kills microorganisms). Water the soil before applying soil drench.
Record the date, compost source, food sources used, brew duration, smell assessment, and where applied.