What is Compost?

Compost is essentially the stabilized by-product of broken down organic matter. The organic matter can be leaves or other plant material, wood shavings, kitchen scraps, paper, stems and stocks of plants, leftovers from grapes (pomace) or brewing beer, etc. Some compost recipes call for animal manures. These are typically manures from farm animals, such as chickens, rabbits, goats, llamas, horses, cows and sheep although any manure will work.

The most species diverse compost is made from a combination of manure and green waste. Composters should avoid manure from cats, dogs and people as it may contain microorganisms that can cause diseases may not be killed during the composting process. These diseases can be transferred from the tea onto your plants. To a certain extent, compost can be formulated to favor specific microorganisms by manipulating the feedstock (ingredients) to encourage either bacteria to grow or fungus to grow.

When properly formulated and managed, a compost pile will heat-up on it’s own because the microorganisms living on organic matter and in manure consume the nutrients contained in the feedstock and produce heat as one by-product of their activity. As they consume the nutrients and break down the cellulose structure of the organic matter, they produce even finer organic material, carbon dioxide, water, heat, and finally humus, the relatively stable organic end result.

The heat generated from the thermophilic microorganisms in the pile cause other microorganisms to activate that will break the cellulose material or structure of the organic matter down into smaller and smaller pieces.

The temperature of a well-constructed compost pile should never exceed 150 degrees because at those temperatures, another set of microorganisms are activated that can actually heat the organic matter up to combustion temperatures.

Compost will naturally cool off when the organic material is completely broken down and the nitrogen and carbon is consumed by the micoorganism. Composting microorganisms need oxygen to live and can quickly consume all the available oxygen in a pile. Frequent turning of the pile or injecting oxygen into the pile becomes necessary as the organic material breaks down.

Under optimal conditions, composting proceeds through three phases:

  1. Mesophilic (up to 105f), or moderate-temperature phase, which lasts for a couple of days
  2. Thermophilic (up to 150f), or high-temperature phase, which can last from a few days to several months, and finally
  3. Conditioning, a several-month cooling and maturation phase.

What Lives in My Compost Pile?

Compost should have a wide variety of both bacteria and fungi. Compost does not contain mycorrhizae, the filamentous network of underground fibers that connect plants together and also bring nutrients from far and wide to your plant. but most natural soil does. Bacterium causes the pile to heat up while fungi break down the structure of the organic matter, making it easier for the bacteria to do their job.


Bacteria are the smallest living organisms and the most numerous in compost; they make up 80 to 90% of the billions of microorganisms typically found in a gram of compost. Bacteria are responsible for most of the decomposition and heat generation in compost. They are the most nutritionally diverse group of compost organisms, using a broad range of enzymes to chemically break down a variety of organic materials.

Bacteria are single-celled and structured as either rod-shaped bacilli, sphere-shaped cocci or spiral-shaped spirilla. Many are motile, meaning that they have the ability to move under their own power. At the beginning of the composting process (0-40°C), mesophilic bacteria predominate. Most of these are forms that can also be found in undisturbed topsoil.

As the compost heats up above (104f), thermophilic bacteria take over. Members of the genus Bacillus dominate the microbial population during the thermophilic phase of composting. The diversity of bacilli species is fairly high at temperatures from 50-55°C (121-132f) but decreases dramatically at 60°C (140f) or above. When conditions become unfavorable, bacilli survive by forming endospores, thick-walled spores that are highly resistant to heat, cold, dryness, or lack of food. They are found everywhere in nature and become active whenever environmental conditions are favorable.

Bacteria of the genus Thermus are activated at the highest temperatures occurring in a compost pile. Thermus bacteria were first identified in natural hot springs found in Yellowstone National Park and may have actually first evolved there. Other places where thermophilic conditions exist in nature include deep sea thermal vents, volcanoes, manure droppings, and accumulations of decomposing vegetation that have the right conditions to heat up just as they would in a compost pile.

Care must be taken when composting at high temperatures (above 155f) and combustible material is nearby because compost piles can heat up enough to cause combustion of the dry material in the pile, particularly when wood-chips or dried straw or grass has been used as a feedstock. Managing a compost pile that has heated to above 155f requires frequent turning to replace the oxygen that is consumed by the rapidly reproducing bacteria and copious amounts of added water to replace what is lost as steam.

Once the compost cools down, mesophilic bacteria again predominate. The numbers and types of mesophilic microbes that re-populate compost as it matures depends on what spores and organisms are present in the compost as well as what is found in the immediate environment. In general, the longer you can extend the conditioning or maturation phase, the more diverse the microbial community it supports. This is where the ratio of carbon to nitrogen becomes most important because these are the microorganisms that are found in compost tea.


The characteristic earthy smell of soil is caused by actinomycetes, organisms that resemble fungi but actually are filamentous bacteria. Like other bacteria, they lack nuclei, but they grow multicellular filaments like fungi. In composting they play an important role in degrading complex organics such as cellulose, lignin, chitin, and proteins. Their enzymes enable them to chemically break down tough debris such as woody stems, bark, or newspaper.

Some species appear during the thermophilic phase, and others become important during the cooler curing phase, when only the most resistant compounds remain in the last stages of the formation of humus. Actinomycetes form long, thread-like branched filaments that look like gray spider webs stretching through compost. These filaments are most commonly seen toward the end of the composting process, in the outer 10 to 15 centimeters of the pile. Sometimes they appear as circular colonies that gradually expand in diameter.


Fungi include molds and yeasts, and collectively they are responsible for the decomposition of many complex plant polymers in soil and compost. In compost, fungi are important because they break down tough debris, enabling bacteria to continue the decomposition process once most of the cellulose has been exhausted. They spread and grow vigorously by producing many cells and filaments, and they can attack organic residues that are too dry, acidic, or low in nitrogen for bacterial decomposition.

Most fungi are classified as saprophytes because they live on dead or dying material and obtain energy by breaking down organic matter in dead plants and animals. Fungal species are numerous during both mesophilic and thermophilic phases of composting. Most fungi live in the outer layer of compost when temperatures are high. Compost molds are strict aerobes that grow both as unseen filaments and as gray or white fuzzy colonies on the compost surface. .


Protozoa are one-celled microscopic animals. They are found in water droplets in compost but play a relatively minor role in decomposition. Protozoa obtain their food from organic matter in the same way as bacteria do but also act as secondary consumers ingesting bacteria and fungi.


Rotifers are microscopic multicellular organisms also found in films of water in the compost. They feed on organic matter and also ingest bacteria and fungi.

Compost Recipes

  • Bacterial Compost: Bacterial dominant compost is made using 30% dry straw (brown material), 45% alfalfa (green material), and 25% manure.
  • Fungal Compost: Fungal dominant compost is made using 45% dry straw, 30% alfalfa, and 25% manure. If you would like to create more balanced compost, use 35% dry straw, 35% alfalfa, and 30% manure.

Tip: If you have a bacterial compost that has ‘finished’ and you would like to create a good environment for fungal growth, blend into the compost approximately 4-5 lbs per (cubic yard of compost) moistened oatmeal or bran, alfalfa meal, or rice bran. Make sure the pile is moist but not wet, cover it loosely with a tarp to retain moisture and let it stand for 2 weeks. For this step, appropriately hydrated compost sounds like a damp sponge when squeezed firmly but won’t present water. If water streams through your fingers when you squeeze your compost, let it dry out for a few days before adding additional ingredients or simply don’t cover it while it cures.

Worm Castings

Worm castings are essentially worm poop. Worms actually consume the natural bacteria found on organic matter. They first take the organic matter in through their mouth and pass it through their gizzard much like a chicken and then digest it. They have no teeth so the gizzard prepares the food for digestion by grinding it up using sand and small rocks as grit.

The bacteria on the organic matter is further concentrated in the worms gut and then combined with digestive enzymes and finally passed as ‘castings’. These castings are rich in digested organic matter, protein as bacteria, chelated essential minerals and digestive enzymes.

Chemical Analysis of Typical Castings

Nitrogen 14.4 % Calcium 1.58 % Phosphorous 0.89 % Potassium 0.34% Magnesium 0.34 % and traces of sodium, magnesium, iron, zinc, manganese, copper, boron, and aluminum.

Charles Darwin said of worms: “They are the intestines of the Earth”.

Cleopatra supposedly declared the earthworm sacred, and any exporter of earthworms was subjected to the death penalty.

Simple Worm Bins

The bin will consist of two, 10-gallon Rubbermaid (or similar) containers stacked on top of each other, with a third bin being added later on. Holes, one half-inch in diameter, will be drilled into the upper sides and bottom of the top bin (which will contain the bedding) to allow for aeration and drainage.

The bottom bin will be used to catch leachate drainage, materials falling out through the holes, and escaping worms. When the material in the initial bin has been sufficiently processed, a third bin with fresh bedding is added on top. The worms will migrate up through the holes to the fresh material, leaving behind vermicompost in the bottom bin to be harvested.

Preparing the Bin

Bedding is necessary for worms to burrow, bury food scraps, and also for moisture retention. Bedding material must be a non-toxic, fluffy material that holds moisture and allows air to circulate. Popular bedding materials include organic coconut fiber, shredded newspaper, computer paper, decaying leaves, grass clippings, peat moss, or some mixture of the above. Our own favorite is organic coconut fiber (approximately 2.5 lbs dry).

Before adding your worms, the bedding materials must be mixed and wetted with approximately1 gallon of water per pound of dry material. When using just dried coconut fiber alone, no mixing the materials is needed. Simply add water slowly until the dried fiber is completely wet. Warm water will speed up the process of wetting the material, but you must wait until the bedding has completely cooled before adding your worms. Once the worms are added to the bedding, the moisture level should always remain approximately that of a wrung-out sponge.

Composting Worms

The best composting worms are red wigglers (Eisenia foetida), which can be obtained from Dirt Cheap or online. Generally, they cost about $20 a pound, not including any shipping fees. Regular garden and compost worms will not survive in worm bin conditions and therefore should not be used.

Red wigglers can typically consume about a half-pound of food scraps per one pound of worms in a 24-hour period (one pound of worms equals roughly 1,000 worms). You can adjust your bin size and worm population to accommodate your food-scrap load. Keep in mind that in about two weeks the worms will begin reproducing, increasing the population. One pound of worms should be a good starting population for the 10-gallon bin.

Once you have your worms, place them on top of the moistened bedding and they will quickly burrow in. To check your worm’s health, gently pull back the bedding and watch for worm tails quickly burrowing back into the bedding. Worms cannot live in light so they move into the pile as you remove the top of the bedding. Small white worms are an indication of acidic or overly wet conditions. They will not hurt your worms or cause any problems in your garden and often live in healthy worm populations.

Feeding Red Worms

Red Worms eat a wide variety of organic material. The smaller particle size of the material, the faster they will consume it. Worm food includes all kinds of manures, coffee grounds, shredded paper, cardboard, eggshells and kitchen scraps and even human and animal hair. Worms eat protein. Protein is found in the glue that holds the cardboard layers together; the organisms that reside on the surface of the organic matter; and hair is made up of primarily protein in the form of Keratin.

If your worms castings are to be used for making tea or directly applied to food crops you must avoid the manure from dogs, cats and humans! Since worm castings do not go through a heating or pasteurizing process, human diseases can be transmitted to your food crops!

It’s best to avoid bones, dairy products, meats, garlic, onions, and spicy foods. Citrus foods should also be avoided as they can cause the bin environment to become too acidic (an over-acidic bin can be corrected by adding crushed eggshells). To speed the decomposition process, food should be chopped or shredded before being added to the bin.

To feed your, gently pull back the bedding, put in the food scraps, and then re-cover with bedding. This will help minimize mold, flies, and other pests.

Where to put the bin

The main concern when deciding on a location for your worm bin is temperature. The ideal temperature for red wigglers to grow in is 55-75? F. Popular indoor spots include the kitchen, garage, laundry room, or basement. If you want to keep your worm bin outdoors, you must shade it in the summer and insulate it in the winter (with hay bales or other material) to maintain the proper temperature range. Also, if your bin is outdoors remember to protect it from flooding conditions as worms can easily drown inside the bin.

Harvesting Vermicompost

You can harvest vermicompost after about three months. To do this, prepare your second bin of fresh moist bedding exactly as you did the first. Place the second bin on top of the first, making sure that the holes in the bottom of the second bin are flush with the surface of the bedding in the first bin (worms cannot crawl through air).

The worms will then begin to migrate up to the new bin, leaving behind vermicompost. The process may take up to two weeks, and adding fresh food scraps to the new bin will encourage the migration.

Harvested vermicompost can be added to potting mix or garden soil to provide an excellent source of readily available plant nutrients and organic matter or made into ‘tea’ that reproduces the biology and then distributes it evenly throughout the garden soil.

As long as you maintain a healthy worm-bin environment (i.e. proper temperature, moisture, pH, and food), the worm population will stabilize itself and there will be no need to purchase additional worms or remove surplus worms.

Compost Tea

Compost tea is simply thermophilic compost or worm castings soaked in water. The simplest compost tea method is to just fill a burlap or mesh sack full of compost or manure or some combination thereof and soaking it overnight in water, agitating or stirring either periodically throughout the brewing process or right before use.

Using modern methods, the biology that is suspended in the water can be encouraged to reproduce exponentially. These modern methods commonly include aeration with electric pumps and specially engineered diffusers.

In Biodynamic principal, compost tea is usually referred to as either ‘herbal tea’ or ‘liquid manure’ tea. Herbal teas usually consist of one fermented plant extract, while fermenting a mixture of herb plants in combination with fish or seaweed extracts is typically referred to as ‘liquid manure’. The purpose of herbal teas and liquid manures are many-fold. They perform dual roles by supporting biological as well as dynamic processes in plants and crops. They provide a rich source of soluble plant nutrients; they stimulate of plant growth and enhance disease-suppression and in the Steiner model, they are the carrier of cosmic and earthly forces. They are often called immune-building plant extracts, plant tonics, biotic substances, and bio-stimulants.

Why Use Compost Tea?

  • Rhizosphere: The microbial rich area directly surrounding plant roots
  • Phyllosphere: The surface of the leaf

A well prepared compost tea has in it all of the necessary bacteria and fungi needed to maintain healthy growing conditions for most plants. The populations of microbes contained in compost tea cycle nutrients through the soil and into a plant and also create and maintain plant health by overwhelming pathogens with beneficial microbes that take the space and food source that might otherwise establish a population and attack your plants.

Compost and worm castings both contain huge populations of these beneficial bacteria and fungi. Compost tea is essentially all of these organisms suspended in a three dimensional matrix reproduced to maximum populations. The population of these important microbes found in properly prepared compost tea is much more dense than is present in compost or worm castings in their natural state.

The water in the tea serves as a breeding ground and as carrier for these microorganisms allowing them to be more evenly distributed over greater areas of soil. Using water to suspend the microorganisms also allows them to be sprayed directly onto the plant leaves facilitating nutrients and minerals to be taken through plant stomata found on the leaf surface.

About half the energy produced by a plant is exuded back into the soil as sugars and mineral rich liquids. The soil houses microbes, organic matter, aggregates, minerals and primary nutrients or N-P-K. The exudates from the plant feeds the microbes that process the organic matter and other minerals into plant nutrients and encourages those microorganisms to proliferate on and directly around the plant roots. The plants will then take the nutrients in through the roots through a process called ‘osmosis’. This is the result of the magnetic and chemical interplay between ions, anions and cat-ions. Each having an electrical charge that either attracts or repels each other. The membrane of the plant root is coated with bacteria that primarily cycles nutrients and protects the plant from pathogenic bacteria.

About half the energy the microbes produce is returned to the soil as nutrients and minerals. The other half of the energy soil bacteria can change their digestive enzymes to suit the food source it comes into contact with. Some strains of composting bacteria will produce up to 150 different types of enzymes depending on food sources and conditions.

When compost tea applied to the soil, it increases the soils microbial life. Increasing microbial activity in the soil will help suppress diseases while increasing uptake of primary and trace nutrients by adding the necessary microbes for digesting nutrients and chelating minerals.

Some recipes for compost tea involve the addition of carbohydrates, simple sugars, micronutrients, humates and sources of protein (nitrogen). These additional products are added to cause the microbes to multiply more rapidly and to increase the diversity of the populations. Recipes containing sugar, such as molasses must be managed carefully because they create explosive microbial growth that can quickly deplete all the oxygen resulting in anaerobic conditions and spoiled tea.

There are several important basic rules that should always be followed when preparing compost tea.

  1. Always use extremely high quality fresh compost or worm castings.
  2. Maintain appropriate aeration throughout the duration of the brew.
  3. Use brew immediately.

Compost Tea Recipes – 5 gallon

Note: Some recipes for compost tea involve the addition of carbohydrates, simple sugars, micronutrients, humates and sources of protein (nitrogen). These additional products are added to cause the microbes to multiply more rapidly and to increase the diversity of the populations. Recipes containing sugar, such as molasses must be managed carefully and used quickly because the added sugar creates explosive microbial growth that will quickly deplete all the oxygen resulting in anaerobic conditions and spoiled tea.

Basic Compost Tea Recipe

1.5 pounds of balanced compost (equal parts bacterial to fungal biomass) 1.6 ounces of humic acids 1 ounce of liquid kelp 1 ounce of soluble unsulphured blackstrap molasses. Liquid kelp is used in this recipe. You may also add a tablespoon of kelp meal to the compost providing surfaces for the fungi to attach too.

Bacterial-Dominated Compost Tea Recipe

1.5 pounds of bacterial-dominated compost (Worm Castings will work)
2 ounces of soluble unsulphured blackstrap molasses
1 ounce of soluble kelp Bacteria proliferate when fed simple sugars, such as sugar, sucanat and maple syrup. The blackstrap molasses is great because it naturally contains a number of beneficial minerals such as iron and potassium.

Fungal-Dominated Compost Tea Recipe

2 pounds of fungal-dominated compost
2 ounces humic acids
2 teaspoons of yucca extract
1 ounce of liquid kelp
2 tablespoons of ground oatmeal
Add yucca extract near the end of the brewing process because it creates a lot of foam. Make sure your yucca doesn’t have any preservatives, but does have high saponin content. Thermex X-70 is a good brand.

Building a Brewer

Compost tea brewers should be scaled to the needs of your garden because compost tea does not store. Brewers range in size from a 5 gallon bucket to multi-thousand gallon brewers. When engineering your brewer, consider that the aeration must evenly produce bubbles throughout the brewer and the air pump must be appropriately sized to the vessel. The aerator should ideally produce a massive quantity of small and medium sized bubbles. Air diffusers can be home made or store bought.

Air Pumps

Most aquarium air pumps can’t produce enough air to use in a container larger than 1 gallon. A minimum 0.05 CFM (cubic feet per minute), open flow of air and an optimum 0.08 CFM per gallon (US) or higher to make aerated compost tea. Tea should have the dissolved oxygen (DO2) at or above 6 PPM. Small aquarium pumps produce around 0.02 to 0.16 CFM. 25 watts of power usually produces 0.75 to 1.0 CFM in diaphragm air pumps. The wattage is usually marked on the pump. That can help you figure out the approximate output if it is not stated on the pump.
Small bubbles keep the brew oxygenated and agitated by forcing bubbles into the solution. The larger bubbles will physically ‘scrub’ the microbes and fungi off of the surface of the compost by vigorously agitating the water and compost together.

FYI: 1 cubic foot = 0.0353 liters so a 70lpm pump is equivalent to 2.47cfm or enough air for a 55-100 gallon brewer.

Diffusers and Air Stones

If you are not using the Venturi Method, diffusers are absolutely necessary to tea brewers. Diffusers break the stream of air from the pumps into bubbles allowing them to bind with the water and stay in suspension. Without a diffuser, the air would take the shortest route out of the solution and have very little beneficial effect besides stirring the brew.

The best diffusers make both small and medium sized bubbles. Some diffusers are weighted to keep them on the bottom of the tank while others may require some other way of sinking it. Diffusers can be homemade or store bought. It is best to chose one that can be wiped clean or soaked in cleaning solution periodically. Make absolutely sure that you have thoroughly rinsed off all of the cleaning solution or it may kill the microbes and cause excessive foaming. Inexpensive aquarium style diffusers or ‘air stones’ should be periodically discarded as they are not cleanable and can harbor pathogenic microorganisms that will contaminate or spoil your tea.


The container used for a brewer should have no corrugations (wrinkles or ridges) , have straight sides and smooth and easily cleaned inner surfaces. Following these guidelines will help keep pathogenic microbes from finding a place to hide from the air bubbles. The vessel should be plastic, glass, stainless steel or some other non-corroding and easy to clean material. Avoid copper tubing and galvanized buckets and fittings as the copper and special coatings may leach into your tea and suppress microbial growth.

Venturi Method

You can make aerated compost tea with just a water pump by creating a venturi. The venturi creates a vacuum forcefully drawing air into the water. It is an efficient method of oxygenating and stirring water. You can either use a ‘trash pump’ that can handle debris or affixing mesh bag or fine screen surrounding your pump is necessary to keep the pump from clogging up with debris. For a small brewer of 100 gallons or less, a screen size 400 microns is ideal.

The Venturi Method requires a valve to regulate the water flow so all of the water does not just take the easiest route to the pipe that is ideally suspended above the water. The water should splash back into the tank from above. This will break the surface tension of the tea and allow the metabolic gasses from fermentation that are trapped in the solution to exchange with the oxygen that you are adding to the solution.

Note: The Venturi Method does not produce fungal hyphae very well as the pump tends to destroy the filaments but it will produce fine bacterial brews.

Methods for Brewing

Compost tea is made by either suspending compost and/or worm castings along with the other desired ingredients in the solution while aerating, stirring or agitating the liquid over a period of time or by simply dumping the ingredients into a bucket and essentially doing everything else the same. Using a mesh bag or something similar, the compost tea can be easily pumped from the bucket without clogging pumps and lines. Otherwise, you must use a mesh bag or pump screen and still be prepared to deal with some frustrating clogs.

Compost tea is typically brewed for a period of 24 to 48 hours at temperatures between 65 and 80 degrees. Higher temperatures require more oxygen. Longer brews are much more difficult to manage but can be achieved if necessary. If long brew times are anticipated, do not add carbohydrates (sugars) until just before application.

Using Compost Tea

Compost tea can be applied either on the surface of the soil or sprayed directly on plants. For soil applications, a sprinkler, watering can or other methods can be used. It is best to use as large an orifice as possible when using sprinklers as the small orifice can damage the microbes. Also, diaphragm style pumps as opposed to impeller pumps do less harm to the microbes. When viewed through a microscope, the most damage was seen when using a pressure-type sprayer with a fine spray nozzle to distribute the tea. The least damaging to the microbes was to simply sprinkle the compost tea directly onto the surface of the soil and leaves using a watering can. Biodynamic method suggests using a paintbrush dipped in compost tea and then ‘fan’ or splash the tea directly onto the plants completely coating the leaves and stems with enough liquid to cause the solution to run-off to the soil. This technique will give an even application without damaging the microbes.

Compost tea has been purported to suppress diseases on some plants and crops. This is an area of agriculture that is highly theoretical; in practice applications of compost tea to suppress diseases that are present has not been proven to be entirely effective in all situations.

Remember, gardening and perhaps particularly so, compost tea brewing is perhaps the greatest ongoing experiment conducted by humans so always try small-scale applications and trials before attempting anything new on a large-scale, particularly when diseases are present and controlling them is the intended outcome of your application.

In carefully monitored tests, some types of powdery mildews have been successfully controlled by applying compost tea while downy mildew was not controlled from the same application, and in some trials, diseases such as Potato Wilt that was not visibly present have shown up and even proliferated immediately after applications of compost teas. Because of the extraordinarily wide range of brewers, composts, methods and levels of expertise, it is nearly impossible to predict what will happen in your garden based on the experience of others. My best advice to tea brewers from novice to expert level is to always keep meticulous dated notes and accompany them with photos of before and after applications and good luck!