How to Make Compost Tea

Best Location for Your Brewer:

  • Place your brewer on a flat and level surface located near a power outlet.
  • Choose a location that can tolerate a few spills.
    • Brewing compost and garden teas can be messy at times.
  • Provide a stable environment such as a basement, barn, garage or shaded location outdoors.
    • If possible choose a location that can maintain a temperature between 55°-80°F.


  • Always start with pure filtered water
  • Microbes in compost are highly sensitive to anti-microbial agents found in many municipal water sources.
    • Chlorine, fluoride, chloramine and fluoramine tare some of the potential additives in many municipal water sources.
  • If you have a municipal water source you can at the least evaporate as much chlorine as possible.
    • This can be achieved by allowing your water to sit in an uncovered bucket / brewer overnight or you can aerate your water for 15-30 min prior to use.
  • Chloramine & Fluoramine cannot be evaporated and are best removed thru filtration. Please note that not all filters are capable of removing these harmful chemical agents. Fresh, clean rainwater can be a great alternative to the tap.
    • Humic acids added to water (prior to your sensitive compost) will help to bind these agents and immobilize their harmful affects.
    • Good quality compost contains sufficient humic substances to assist in mitigating the harmful affects of the above-mentioned additives. More on this in the section on compost extracts.


  • The ideal temperature range for brewing compost tea is between 60° - 80°F
    • An aquarium heater can be used to maintain constant temps for more precision brewing and reduced brew times.
  • High temperatures can kill or limit a diversity of microbes.
  • Low temperatures will slow microbial activity and limit a diversity of microbial growth.
    • Do not to exceed a water temperature of 95°F
  • Brewing in a temperate environment is a pretty safe option
  • Match your water temperature to the temperature of the soil or leaf zone where the tea is to be applied.
    • The microbes that are cultivated in your compost or garden teas are more likely to remain active when applied to the soil or a leaf surface that is a similar temperature as your tea.

Ensuring A Quality Extraction:

            In brewing compost teas we are attempting to transfer the multitudes of beneficial organisms and soluble nutrients from the compost into a solution that can be easily applied to soil, potting/ planting mixes and plant surfaces.  The compost serves as a starter agent, much like yeast is to bread. Water is the medium and the food sources serve as a catalyst feeding active and dormant organisms present in the mature compost. Aerating and agitating the compost in good quality water and providing select food resources will help to promote the growth of the target organisms present in the compost.

Extraction & Brewing Methods:

I. Compost Extract:

          Compost extracts can be made in minutes and applied immediately, making them very convenient if there is not enough time to brew aerated tea.  Compost extracts will provide a similar concentration of the microbes found in your starter compost. You can use compost extracts as a soil drench, root dip when transplanting or to inoculate; compost heaps, potting and planting mixtures.

  • Fill your brewer with 4 – 5 gallons of chlorine free water or aerate municipal water as described above.
  • Place 2 – 4 cups of compost into a 400-micron filter bag
    • The filter bag will help to keep your brewer cleaner, but is not necessary if you are only stirring the compost in a bucket or barrel.
  • Place the compost bag into your vessel and aerate, gently massage or stir for 3 – 5 minutes.
  • Remove the filter bag and use as desired
    • Energize by stirring rhythmically, alternately clockwise and counter-clockwise forming a vortex for 1 min before changing directions.  

    Compost extracts can provide the necessary humic acids to help bind-up and immobilize the harmful affects of chemical agents found in some municipal water sources. If you are using a compost extract for the humic acids to help with your municipal water then follow these steps.

  1. Make a compost extract as mentioned above
  2. Remove the tea bag and discard the compost onto a compost heap or mix into soil.
  3. Use this liquid to brew a batch of aerated compost tea.

II. Aerated Compost Tea (ACT)

   This method of brewing is also referred to as actively aerated compost tea (AACT) and will cultivate the greatest concentration of microbial life in your teas. ACT or AACT can be applied as a soil drench or a foliar spray.

  • Place the recommended amount of compost into a 400-micron filter bag
  • Place the compost bag into your bucket or barrel of chlorine free water and aerate
  • The compost bag can be removed after 12 - 24 hours
    • The bulk of beneficial organisms are now suspended in the water.
    • Do not squeeze or press the filter bag as you may force sediment thru the mesh that could clod your air-diffuser and/ or spray nozzles.
  • Add the recommended liquid or soluble foods sources
  • Brew your compost tea for the recommended minimum or maximum time and apply

III. Fertilizer / Garden Tea

  Use this method for herbal, mineral or guano based fertilizer teas

   Much like herbal teas, fertilizer tea can be made by soaking or aerating dried herbs, bat or seabird guano and/ or minerals such as rock powders or salts in chlorine free water to extract the many beneficial nutrients. Your options here are limitless. 

  • Place the recommended amount of raw ingredients into a 100-micron filter bag or filter your tea after the ingredients have been mixed.
  • Place the bag or ingredients into a bucket or barrel of chlorine free water.
  • Stir for 10 min – 1 hour or steep and/ or aerate for up to 12 hours
  • The time your tea is allowed to steep will depend upon the ingredients used.
  • Use a PPM or TDS meter to measure the concentration of nutrients in your fertilizer teas (these can be purchased for under $20 at aquarium and some garden centers)
    • PPM meters measure the parts per million of a solution
    • TDS meters measure the total dissolved solids
  • The concentration of nutrients in your liquid tea will vary based upon ingredients used and your water source. Well water or rainwater may have more minerals than municipal water sources.
  • Remove the bag and apply tea as a soil drench
  • Do not squeeze or press the filter bag as you may force sediment thru the mesh that could stop up your air-diffuser and/ or spray nozzles.

What to do with the spent ingredients after making tea for your plants?

            The spent compost, herbs, guano and/ or minerals can be added to a compost pile or worked into the top few inches of soil. The best parts of these ingredients have been depleted but the remnants will be a nice addition any compost pile.

Customize Your Compost Tea for Plant Types, Disease, or Pest

These are general guidelines; recipes may need to be adjusted according to active biology present in your compost.

  • All-purpose / Balanced Tea (equal Bacteria to Fungi biomass ratios): 
    • This is the most effective tea for all types of plants and soils: Use on most vegetable crops, grasses and pastures, flower and herb gardens, berries, fruit trees or to manage some pest and pathogen outbreaks.
  • Fungi/ Humus Tea: Use on deciduous and conifer trees, orchards, vine crops shrubs, acid-loving plants, or to manage pathogen outbreaks. Fungi dominated teas can also be used to enhance the growth of moss.
  • Bacterial Tea: Use on brassica family crops or to help manage pests.

Brew Times:

  • Temperature of both water and the outside environment will affect your brewing time
    • When ambient air temperature is above 60°F brew for 12-24hrs
    • At temperatures below 60°F extend brew times generally 48-72 hours      
  • All-purpose / Balanced Tea (equal Bacteria to Fungi biomass ratios): Brew for 12 - 36 hours to encourage a more balanced life within the compost tea.
  • Bacterial Teas: Brew for 12 - 24 hours to encourage bacterial biomass.
  • Fungi/ Humus Teas: brew for 36 - 48 to encourage a fungal biomass. After 48 hours compost tea begins to express protozoa dominance, which mainly feed on bacteria.

You may use the minimum brew times if you are starting with a few quarts of a good quality compost tea from a previous batch. Think of this like a bread starter.