making and using worm compost

Biernbaum, Vermicomposting and Vermicompost, January 2013, pg 1

Making and Using Worm Compost Soil Fertility and Biology for Small Scale Intensive

Organic Farming in Rural or Urban Settings John A. Biernbaum

Michigan State University Horticulture Department and Student Organic Farm Background and Introduction The purpose of this publication is to provide information about worm or vermi composting and the use of worm compost with an emphasis on intensive low acreage organic food production in bed systems or protected cultivation including high tunnels, hoophouses and greenhouse. The project was initiated in May, 2010 with funding support from the MSU Office of Campus

Sustainability and Residential and Hospitality Services as one of several strategies to address campus food sustainability issues.

An important part of this project is to explore the justifications for worm composting compared to hot composting and eventually whether worm compost has unique valuable properties compared to hot compost. For example, can nitrogen recovery and mineral availability be improved?

Another important part of the project is to increase the collection and composting of kitchen preparation residue (KPR) and food waste (FW) for the purpose of returning valuable minerals and organic matter to gardens and farms while reducing the movement of KPR and FW to landfills and sewage treatment systems where the minerals are effectively lost to organic farming systems.

A third part of the project is to investigate and refine medium scale methods of vermicomposting. Small scale worm composting in 10 to 20 gallon plastic totes (a “worm bin”) ( 2 to 4 square feet of surface area each) suitable for processing family kitchen residue and home gardening is one common worm composting method. Large scale worm composting with flow through mechanized systems with thousands of square feet of bed surface area is less common but feasible. The focus here is on medium scale systems (50 to 1000 square feet) suitable for either a) a small scale commercial composting operations, b) an institutional vermicomposting operation or c) a market gardener or farmer with a diverse operation where worm composting to cycle nutrients from food residue or animal manure and make an on farm nutrient source and crop protectant is one of many daily responsibilities.

Outline 1. Worm composting comparisons and uses 2. Basic worm biology 3. Environmental factors to be measured and managed 4. Estimating quantities and the rate of composting 5. How and where to obtain or purchase worms 6. Worm composting systems 7. Using a passive solar greenhouse (hoophouse) for worm composting 8. Harvesting worms from finished vermicompost and screening compost 9. Using the worm compost 10. Additional sources of information 11. Appendix – Background Information

1. Worm Compost Comparison and Uses Why Worm Composting in addition to or rather than Hot Composting?

Can be done in small or large space. No minimal pile size although larger piles can reduce the risk of stressing the worms. Piles are normally shallow, with 1.5 to 2’ maximum.

Can be done with limited equipment; worms can do much of the work of turning. More manageable / practical under winter weather conditions and in closed spaces.


Turning of hot compost in an enclosed environment is not recommended due to negative potential health impact of gasses (ammonia) and molds on human lung function (breathing).

Can retain more of the nitrogen that can be lost to the atmosphere in hot composting. (?) Hot composting is by thermophilic bacteria at temperatures over 110 to 120oF and up to 160oF

which can decrease the diversity of microorganisms. Vermicomposting by mesophilic microorganisms in addition to worms at a temperature of less

than 100oF. Worms eat microorganisms which can increase in the gut of the worm. Finished worm compost or castings reportedly can have a higher concentration of available

minerals, particularly phosphorus. Can be fast (40 to 60 days; 6 to 8 weeks) if worm population is high; with no requirement for a

maturation phase that is needed with hot composting. High moisture materials with potential for unpleasant odors are transformed into easy to

handle and odor free from materials (usually also true for hot composting). Worm composting is generally more exciting / interesting to the non-farming or gardening

public and is a more visual way of teaching the importance of organic matter and nutrient cycling for the long term sustainability of farms. The soil food web is more visible through the worms.

Worm compost can sell for $0.25 to $1 per pound ($250 to $1000 per cubic yard) compared to $15 to $45 per cubic yard for municipal or manure based compost (10 to 20x).

Potential Limitations of Worm Composting Compared to Thermophilic Composting Seasonal temperature range and susceptibility to temperature extremes is more limited than

for thermophilic composting. Anaerobic conditions can lead to rapid and total loss of the worm composting population. Low or excess moisture conditions can lead to rapid and total loss of the worm population. Bacterial and fungal populations responsible for thermophilic composting can be developed or

recovered much faster than worm populations. Seeds will often remain viable after the worm composting process. Limited evidence is available to address human food safety concerns regarding possible

human pathogens that may survive the worm composting process.

Why Worm Compost? Worm compost can be used several ways in rural or urban commercial agriculture. An on-farm produced growing medium component (usually at 5 to 20% by volume) for

container grown transplants or plants. An on-farm produced source of balanced available nutrients/minerals which can be applied as

a dry surface application or extracted with water and applied as a fertigation (nutrients+water). An alternative to fish based fertilizers which are commonly used in organic farming. A source of microorganisms and micronutrients that can contribute to plant and soil health. A “crop protectant” that may help mitigate insect infestations and disease infections.

Is Worm Compost Significantly Different than Thermophilic Compost to Justify the Effort?

A weakness of many claims or proposals relative to all types of compost is that the diverse effect of the feedstock and composting methods on the quality and characteristics (physical, chemical and biological) of the compost have not been carefully considered.

Comparing worm compost made from high nutrient content dairy cow manure with thermophilic compost made from municipal yard and garden residue is not a good comparison.

The maturity of thermophilic compost changes significantly over the first six to eighteen months and is a different process than occurs with worm composting.

My current perception is that worm composting has more relevant comparisons to hot composting than is generally accepted or recognized.


2. Worm Taxonomy (type), Anatomy (appearance) and Biology (life cycle) Not just any worm will do. While there are reportedly over 6000 species of worms, only 6 or 7 are

used for composting. Composting worm, manure worm, red worm, red wigglers or Eisenia fetida are names for the same type of worm.

These are not burrowing worms that make either vertical burrows (anecic) or horizontal burrows (endogeic) into the soil but a non-burrowing or epigeic worm that is typically found in the litter or decaying organic matter near the surface, including animal manure.

The worms are cold blooded meaning the body does not self regulate and is typically the temperature of the surrounding media. Like amphibians, low temperature means limited movement or physiological activity (limited food consumption). Excessive heat is also damaging.

The worms do not have lungs so oxygen is obtained through the body skin so water / moisture is important for active growth. A bedding moisture content of 60 to 90% is recommended. Worms can survive in very wet or flooded systems if there is adequate oxygen.

Bright light can induce a paralyzed state so exposure to bright light must be minimized. This type of worm reproduces quickly when food and water are available and survive by leaving

cocoons when food or water is not available. Red worms have both male and female organs and exchange genetic material/sperm with a

partner to reproduce. The “sperm” is stored and used to fertilize eggs over a period of time. Multiple eggs are encased in a cocoon until the eggs hatch and the young worm emerges. The presence of cocoons and newly emerged and young worms (variety of stages) during

composting is an indication that the culture is healthy and the environment is favorable. The presence of a band or clitella around the worm body indicates the ability to reproduce. The size of the worm will vary (small to large) depending on the food available and moisture

content of the environment. A commonly provided figure is 1000 average size worms per pound with a range of from 500 large or 2000 small worms per pound.

The worms consume organic matter that has already been decomposed by microorganisms such as bacteria, fungi, protozoa, etc. so biological activity and a food web is important. The microorganisms are also influenced by moisture, temperature and oxygen availability.

Life Cycle Reported time for cocoon to go from formation to hatching in favorable conditions: 4 to 6 weeks Reported time that cocoon can protect young worms in unfavorable conditions: months to years Reported time for worm to develop from emergence to maturity (producing young): 6 to 8 weeks Reported time a redworm will live, feed and reproduce in a favorable environment: 3-4 years Reported that a mature worm can release up to 2 to 3 cocoons per week Reported that in a worm bin the population can double about every 2 months.

http://northeastparkscience.wordpress.com/page/2/ http://www.vermica.com/articles/worm_birth.htm

Pile on left is one pound. Red worms have male and female organs but mate at maturity before producing eggs which are encased in a cocoon. Young worms emerge with favorable conditions.


3. Environmental Factors to be Measured and Managed As with any system of crop production or animal/livestock husbandry, a good place to start is learning about the variables that can be measured and managed to improve biological and physical conditions. Bedding – to provide favorable conditions for the worms and microorganisms, the bedding

provides moisture, aeration and available carbon for decomposition and structure to provide aeration and moisture. While not generally stated in worm composting literature, the bedding is similar to the “browns” of hot composting. The bedding provides a source of carbon for the decomposition process, as well as structure for holding water and allowing gas exchange. Minimum 6”-8” deep at start. Examples of bedding materials suitable for on-farm worm composting include:

o aged leaf mold; ground or shredded leaves from a lawn mower o shredded office paper or news paper o straw (wheat, oat, spelt, rice, etc), chopped if possible; rice or spelt husks o stable compost that is not high in soluble salts (less than 1.5 (1:2) or 3.0 (SME) mmhos o coconut coir or peat moss also work well if available and economically justified; which

is the case if the compost is sold for $1 per pound or more. o horse manure works very well, both as a bedding and as a food source

When worms are moved from one type of bedding to another type of bedding, there is usually an adjustment period to the new environment. Take steps to avoid drastic changes. Flow through composting systems are routinely supplied with a mixture of materials that provide both the function of bedding and feed; for example precomposted dairy manure.

Feed – decomposable organic matter that is comparable to the “greens” of hot composting. An important factor is not adding too much food and not adding it in a way that will cause thermophilic composting or heating that can kill the worms. Heating is more of a concern in small containers or small piles where the worms cannot move away from the heat. The size of the pieces of feed will also impact the rated of decomposition with smaller breaking down faster. Pineapple and melon skins as cut off will decompose much slower than if put through a garbage disposal or pulper first. The same for garden or farm organic matter that has been chopped or ground first. Examples of feed materials include:

o farm manure (dairy, beef, pork, horse, sheep, llama, alpaca); poultry in small quantities;

o vegetable and fruit scraps from food processing facilities or homes, institutions, restaurants or grocery stores; uncooked preconsumer kitchen preparation is different that post consumer food waste that may contain cooked food, animal products (meat, fat, bones, etc) and or dairy products, all of which may be more difficult to compost.

o spoiled grain, hay or animal feed including beans, corn, rice, etc o brewery waste – spent grain / seeds, good nitrogen source o coffee grounds – ground up coffee seeds, good nitrogen source

An operator/owner of a successful large scale flow through vermicompost operation offered some very important advice. He recommended that it was very important to not think of the worms as a waste disposal system that could survive on whatever was provided as feed. Instead a key factor for long term success is to think of the worms as livestock that require a balanced diet. Like humans or livestock, worms can survive for an extended time with less than a balanced diet, but not for ever. The more balanced the diet the better expectations for the worms and the worm compost. This is consistent with the view that the overall inputs made with bedding and feed must be balanced from a carbon to nitrogen perspective as with thermophilic composting.

Moisture – on the moist to wet side as long as well aerated. Bedding can be 70 to 80% moisture (60 to 90%). Worms breathe through the skin which must be kept moist. The high moisture also impacts the biological activity of microorganisms such as bacteria. Similar to hot composting, the bedding should be moist enough so that some free water can be squeezed out as if squeezing water from a sponge. Worms can be submerged in water for a short time (maybe even a long time) if there is enough oxygen in the water.


Oxygen – often regulated by depth of the bedding and the amount of moisture and feed. Too deep (>15-18”), too wet (>90% moisture), or too much decomposing food in a closed space can lead to low oxygen. Remember, conditions that favor decomposition of organic matter – warm and moist – also favor biological activity of microorganisms that are generally using oxygen. If the oxygen gets low, some microorganisms can still survive without oxygen, but the worms cannot.

Temperature: Tolerate 40 to 90oF; favorable at 60 to 70oF; low activity at 40 to 50oF: reportedly heat stressed at 80 to 90oF. As a cold blooded organism, worms are generally the temperature of the surrounding environment. In cold conditions worms will move towards a warmer space and will move away from excessive heat as long as there is a place to move to. High temperature can also reduce the solubility of oxygen in water and therefore aeration. To date a graph or curve of biological activity with a change in temperature has not been identified.

Light: As indicated previously, worms can be paralyzed by extended exposure to light. Shade can also help to decrease bedding temperature, for example a cardboard cover. Light can carefully be used to drive worms lower into the bedding or compost as a method of removing them from the compost. Low intensity light (10 to 50 footcandles?) can also be used to help keep worms from moving out of the bedding when not desired. If your hand casts a shadow, the light is intense for the worms. This is more of an issue worming in a greenhouse or outside then working in a building or under a roof.

Bedding and Feed pH: pH is a measure of positive (H+) or negative (OH-) ions in the water (H2O) that influence what minerals and gasses will or will not dissolve in the water. Red worms seem to tolerate pH 5 (acidic- more H+) to pH 8 (basic- more OH-), at least for short periods of time; the target range provided in the literature is 6 to 7.

o Bedding pH can be lowered by adding sphagnum peatmoss (acts immediately) or finely ground elemental sulfur (acts over weeks or months if soil is cold).

o Bedding pH can be raised by adding lime or much smaller amounts of wood ashes which are very reactive and best if first mixed with some bedding material.

o Certain feedstocks are often reported to be acidic or acid forming, such as leaves or coffee grounds or citrus, but evidence to support this claim is not readily available.

The pH is measured either using a colorimetric system such as litmus paper or using a pH meter and electrode. An alternative is to send a sample to a lab for analysis. A pH meter can be purchased from www.specmeters.com .

Ammonia Concentration: Ammonia (NH3) is a gas that is toxic to living organisms at low concentrations. It usually results when ammonium (NH4

+) is present as a form of nitrogen resulting from the breakdown of proteins and amino acids. Ammonium is common in fresh manure or animal urine. If the ammonium is present at high concentrations and the pH of the bedding/ medium/ compost is high (greater than 7.5), ammonia gas can form. As little as 5 ppm (5 milligram per kilogram) can be toxic to worms. ??? Equipment to measure ammonia is not relatively available. If you nose can detect it, the level is probably too high.

Soluble Salts: Salts are made up of cations (positives) and anions (negative). For example sodium chloride is composed of Na+ cations and Cl- anions. When there is an excess of ions present, living organisms are unable to remain hydrated with adequate water. Soluble salts usually accumulate over time if there is no rainfall to wash them away. Soluble salts are usually measured by testing the electrical conductivity (EC) of the bedding or medium and the units of measure are usually mS/cm or millimhos/cm. The higher the salts the more electricity conducted. No salts as in purified water or rain water is zero electrical conductivity. It is not clear just how high and EC worms can tolerate. A starting recommendation is to have the EC below 3 to 5 ms/cm with a saturated medium extract or below 1.5 to 2.5 with a 1 medium to 2 water (1:2) dilution. In parts per million (ppm) the critical concentration may be around 2500-5000 ppm. The critical level will depend on the salts present with Na or Cl being more toxic than K (potassium), Ca (calcium) or H2PO4 (phosphate). Cooked or prepared food waste may be higher in Na and Cl. An electrical conductivity meter can purchased from www.specmeters.com .


4. Estimating Feeding Rates and Process Time Feeding Rates - Background A common estimate is that a pound of worms in a healthy and properly managed (biologically

active) system can process approximately 0.5 to 1.0 pound (lb) of food residue per day. In other words, worms reportedly can eat approximately 50% to 100% of body weight per day.

Current feeding recommendations usually do not differentiate between feed sources that are +80% water such as kitchen preparation food residue (vegetables and fruits) or lower moisture (30 to 50%) feed such as manure compressed to remove moisture or coffee grounds or grains. The amount of food content or value increases rapidly as the percent moisture or water decreases.

Much of the current literature does not clearly explain that worms do not have teeth and likely are not directly “eating” the feed provided. Feed most likely is first digested by the activity of bacteria, fungi and other microorganisms before it is in a form consumed by the worms.

Estimates from large dairy manure flow through worm composting facilities are that the feeding rate is more like 0.25 to 0.35 lb of feed per pound worms (25% to 35% of body weight) per day. These facilities use a flow through composter where the conditions stay more constant for the worms. The feed is also a mixture of “bedding and feed” and the moisture content of the feed is also more likely in the 50 to 70% moisture range.

With batch systems, as in piles or bins, the conditions can change more over time as the worms stay in compost that is maturing and the feeding rate may slow due to increased soluble salts or other changing conditions like pH or moisture. Overall my current perception is that feeding recommendations have been oversimplified for the sake of small scale bin composters and that more details would be helpful.

Feeding Rates - Estimating One pound of worms is a minimum and 3 to 4 pounds worms is a maximum in an average sized

worm bin (18 gallons or 12 inches wide by 24 inches long (2 square feet) by 20 inches deep). This corresponds to 0.5 to 2 pounds of worms per square foot of bed surface area. The bed volume necessary is about one cubic foot (2 feet of surface, 6 inches deep) to 2 cubic

feet (2 feet of surface, 12 inches deep). So approximately 0.5 pound food per square foot of bed surface area per day (3.5 pounds per

week) is possible but only in a biologically active moist environment with the correct mixture of feed and bedding at a favorable temperature. It may be hard to maintain stable conditions.

It appears that a more realistic estimate in many settings that are not intensively managed or not under ideal environmental conditions – ie our current research setting - is 1-2 pounds of high moisture (60 to 80%) feed per square foot of bed surface area per week.

For example, a five gallon bucket of fruit and vegetable waste might weigh from 15 to 20 lbs. If fed to worms weekly, the amount per day would equal 2.5 to 3 lbs per day requiring 5 to 6 lbs of worms and a minimum of 10 to 12 sq ft of surface area (~0.25 lbs food/sq ft surface per day or 1.5 to 2.0 lbs per square foot per week).

MSU Feeding Trial A feeding trial was conducted in a heated greenhouse (65-70oF) using 12, 18 gallon plastic totes. Approximately one pound of worms (400 grams) were established in each of 12 boxes with a mixed bedding. The worms were fed at 10 to 14 day intervals with an amount equal to either 50% or 100% of initial worm body weight per day of either fresh horse manure (~30% moisture) or ground pre/post consumer food waste (~70% moisture). While the worms did well with 4 feedings over the 8 week trial period, without the addition of more bedding and without room for the population to expand, the initially healthy population with the food waste declined, possibly due to ammonia accumulation, higher soluble salts, or lower oxygen due to the high rate of decomposition. The feed rate could not be maintained in the small container and even with feeding stopped some worms died. With some reflection and common sense, it is reasonable that a higher rate of feeding is possible in a system that is under more ideal and constant


conditions where worms are constantly moving into fresh material compared to a bin or batch system where the conditions are fluctuating and or the rate of feeding acceptable in fresh bedding becomes excessive for decomposed bedding. The picture below is an example of the worms isolated from one set of four worm bins after eight weeks of the feedings. With the horse manure, which in some respect has already been “composted” by the horse, there is less available feed and the population grew less. With the pulped food residue there was a great deal of feed available and the population grew very rapidly, most likely both increasing in size per worm and the number of worms.

Other Feeding Considerations: In the high tunnel - unheated greenhouse (PSGH) environment it has been important to bury fresh

materials in the bedding in order to prevent fly populations from developing in warm conditions. This is contrary to recommendations for surface application of feed materials in more controlled

environment conditions. Surface application reduces the potential for overheating if it can be done in a way that does not lead to fruit flies or other nuisance flies. (See precomposting below.)

Under summer / high temperature conditions in the PSGH, regular applications of water are necessary to maintain bed moisture. Evaporation also helps with cooling. Shading methods that reduce evaporation may lead to reduced aeration and increased heating of the beds. Methods to minimize or eliminate leaching are important if collecting nutrients is the goal.


Composting worms can survive in large piles (3 to 4 feet tall or deep) of relative stable or mature organic matter or compost; usually near the surface. But if there is actively decaying food, manure or organic matter present, the pile or bed needs to be shallow (6 to 18 inches deep) to prevent overheating (temperature over 90oF), and to insure adequate aeration and feeding throughout the bed. In the high light greenhouse environment, surface feeding is reduced for at least part of the day.

Food residuals can be very wet and may need to be mixed with bedding or another carbon source such as newspaper, leaves or straw if the bed is not already well prepared with bedding that can absorb the moisture.

Pros and Cons of Precomposting with Hot Composting For some feedstocks / systems, hot composting prior to worm composting may be beneficial

Reduction of food safety concerns related to animal manure or post-consumer food waste. Removal or reduction of weed seeds or seeds from foods such as tomatoes or melons. Removal of reduction of flies or other possible agricultural pest or disease concerns. Stabilization of high moisture or foul smells; balancing of the carbon to nitrogen ratio.

Precomposting reduces the feed supply available for the vermicomposting system and may contribute to a loss of nitrogen. However, with continued experience at MSU and with consideration of the skill level of the workers feeding the worms, and the willingness of workers to handle the raw food waste materials, precomposting is beginning to look like a preferred option for mid scale food waste vermicomposting. The use of an “in-vessel” composter – that continuously mixes the ingredients for a period of 3 to 4 days in a rotating drum - allows high temperatures to remove seeds and possible human pathogen concerns quickly and efficiently. However, in-vessel composters of this type require a significant financial investment. Schools or institutions able to invest in longer term solutions are considering the use of in-vessel composting followed by worm composting. Examples of In vessel comp: From England, 7.5 minutes http://www.youtube.com/watch?v=Ez3zrpuvXGw Music Background, 3 minutes http://www.youtube.com/watch?v=okvUrIw45VI Rotary Composter: http://www.jetcompost.com/index.html How Much Time is Required for Worm Composting? Useable compost can be ready in as little as 5 to 6 weeks with high worm populations and

frequent management; 2 to 3 months (60 to 90 cays) under favorable conditions; but 4 to 6 months is a better estimate with minimal management of the worm beds.

With high volume flow through systems, it has been reported that a marker such as a coin placed on the surface of the bed will typically drop out the bottom of the bed in about 60 days.

An important question for batch systems is how long a time is necessary from the last feeding until finished material can be harvested? With a high worm population, kitchen preparation residue or animal manure will be decomposed in 4 to 6 weeks. If the material is to be used in certified organic production systems, the required worm composting time for a batch system is four months (16 weeks). But from the first feeding or the last?

Worm populations will clearly decline with no added feed for four months. Our current strategy is to begin removing worms with surface trap containers once food residuals are no longer visible (estimated one month from last feeding). Worms are extracted over a one month period. A low population of worms is left for up to one month prior to sieving the finished compost. This also allows time for additional worms to emerge from cocoons. We then hold the compost prior to use or sale so the time from last feeding to use is at least four months. The majority of the material has been worm composted for as much as eight to ten months as fresh feed is added weekly or biweekly.


How Much Worm Compost is Produced by a Given Size Bed or from Input materials? A current estimate is that a well managed 25 ft2 bed can produce 0.5 to 1 cubic yard of worm

compost per year. A well managed 4’ x 25’ bed (100 ft2) can produce 2 to 4 cubic yards of worm compost per year. Results reported from a North Carolina State University experiment were that 5200 lbs of swine

manure applied to a flow through system resulted in 1,500 lbs of worm compost or a 29% recovery or 3.5 pounds in for 1 pound out. It was reported that 42% of the input nitrogen and 85% of the phosphorus was recovered. (Conference presentation)

A large scale vermicomposter of dairy manure with a flow through system reported approximately 10 million pounds in and 2 million out or 4 pounds in and 1 pound out. The dairy manure had been extracted from barn cement floor scrapings using a screw press and then mixed with some bedding and old feed and precomposted for about a week so there was no dripping of excess fluid at the time of application.

5. How and Where to Obtain or Purchase Worms It may be possible to find or isolate worms from farms with animal manure or wooded areas with

leaf litter by placing a pile or crate of fresh bedding and feed and keeping it moist and dark. If purchasing, start by trying to identify vermicomposting or worm production facilities in your

geographic region that can provide five to twenty pounds of worms or more with no or minimal transportation costs.

While there are many suppliers that will sell one to two pounds of composting worms in the price range of $20 to $25 per pound plus the cost of shipping ($15 to $20), there appears to be only a limited number that are able to provide larger quantities (5 or 10 pounds or more) needed for starting commercial operations.

In Michigan, two reliable worm suppliers are o Morgan Composting (www.dairydoo.com) (worms raised in Michigan) o Flowerfield Enterprises (www.wormwoman.com). (worms may come from outside

Michigan) Other on-line options include

o http://www.redwormcomposting.com/buy-composting-worms/ o http://www.thewormfarm.net/ (California) o http://www.wiserwormfarm.com/ (Washington State) o http://unclejimswormfarm.com/ (Florida?) (reliability has been questioned)

Diversified farmers just starting with worm composting can reduce/minimize risk by starting with small amounts of worms (less than 5 pounds) in order to develop a new system and favorable environment.

It is important to have moist bedding prepared prior to arrival of worms. Worms that have been transported / vibrated may need an adjustment period and are reportedly

more prone to trying to leave the new environment for the first few days. If fresh bedding is provided, feeding the worms can be delayed a few days to allow the worms to

acclimate to the new environment.

6. Vermicomposting Systems Choosing a system is in part based on the production area available and the amount of feed available for processing but also on the amount of finished product desired. In the compost use section that follows, example estimates of quantity of compost needed for production of farm transplants are provided. If the goal is compost production for farm income / sales, a sales target can be identified and a weight / volume of compost to be produced estimated. We do not currently have estimates of pounds of vermicompost produced per square foot of bed area for our systems, but we expect to be able to make such calculations in the future.


Other important considerations are the time available for management if worm composting is part of a diversified operation. Much like maintaining animals or honeybees on a farm, the worm beds must be regularly managed for consistent outcomes. Once an appropriate size population of worms is established in the culture bed, the primary maintenance is watering and feeding the bed with occasional turning. While an experienced manager is necessary to insure success, much of the routine work can be accomplished with inexperienced workers. On the small scale farm the required financial resources and equipment investment is also important. Minimal equipment is necessary for managing beds less than 100 square feet (4’ x 25’). As the size of the operation grows so does the potential required equipment investment. Our emphasis to date has been for a system with minimal required equipment investment. Batch: buckets, barrels, boxes, bags As stated previously, the goal here is for systems other than a 10 to 20 gallon plastic tote/bin. We

have used a variety of other plastic or wood containers. In a batch system, how to or whether or not to have drainage holes is an important decision. If the

bedding becomes excessively wet due to lack of drainage, anaerobic conditions can develop. However, high moisture conditions can be tolerated to a point and often benefit worm activity and growth. Leaching of moisture from the bottom of a container can result in loss of valuable nutrients so if not prevented, the leachate should be collected.

Plastic bulb crates, used to ship tulips and daffodils from the Netherlands to greenhouses and wholesalers, or bread delivery trays, can serve as worm composting containers that can be stacked. Worms can move from lower containers to upper containers. Containers of compost can also be used for raising crops if food safety concerns are addressed.

A fruit bulk bin, approximately the size of a pallet has worked well at the MSU Student Organic Farm. The bin can be moved with a fork lift, loader or pallet jack so can be outside for part of the year and inside for the winter.

We have also made use of 4”x4” pine lumber that was previously used to construct lofts or bunk beds in university dormitories. Each May the wood is removed from the rooms and is available for sale at the MSU Recycling Center. The available wood is 84” long so beds are 84” x 42”. By stacking 4 or 5 high we are able to make a bed that is large enough for easy feeding. One method we used was to connect the wood using 4” lag bolts and washers in counter sunk wholes (left picture). We also used a method of notching the ends to allow stacking and drilling a 0.75” vertical hole to accommodate a 0.5” x 2’ piece of rebar driven through the holes and into the ground. Both methods allow easy disassembly. The bottom of the bed is the sand floor of the greenhouse.

Bed above made with lag bolts and stacked 4x4. On right beds covered with 2 layers of frost fabric.


Bed below with notched ends and rebar anchor. Bed on right is 4’x8’ and 2’ tall from 2”x6” lumber.

We also constructed 4’ x 8’ wooden boxes using 2”x6” pine wood.

2 - 4"x4" x 8' - get cut in half to be the supports on the ground - one near each end and two equally spaced across the 8' length of the box.

21 - 2" x 6" x 8' 9 become the bottom boards (1 board has to be ripped to get 48" width). The others are used to make the walls - takes 3 for each layer - so the walls will be 4 2x6 high or (4 x 5.5"= about 22" tall).

2 2" x 2" x 8' cut into pieces for vertical joiners in the corners and inside the box. decking screws - 3" - need at least 150 – approximately a 1lb box.

We started by attaching the 2x6 for the bottom to the 4x4 pieces that held the box off the

ground. 4x4 were near each end and then 2 equally spaced. Don't put right on the end - leave about 4" for a handle for lifting and to have room to attach the 2x6 in the next step at the end. Remember to use a square or measure the diagonals to line up the boards.

We then turned it upside down on top of the first row of 2x6 vertical side and end walls and put deck screws through the bottom and into the 2x6. The reminder of the side walls were simple attached to the vertical corner pieces inside the box and some additional verticals that split the box into thirds. The way it is shown, with an alternating pattern - either the end pieces had to be reduced by 3" or the side pieces had to be reduced by 3" to end up with a consistent size. If the wood is dry, pre-drilling for the deck screws will prevent cracking and splitting.

Bedding and worms were placed directly in the box against the untreated wood. In hindsight we would prefer to have a sheet of plastic on the bottom to prevent leaching so have tried this in the second box. The hoops are used for shade fabric in summer and thermal blanket covering in winter. This box has not been through the winter yet so we need to monitor the temperature since it is not in direct contact with the greenhouse floor / soil.

An above ground pile is a viable option for part of the year, but an in-ground insulated bed/corral is needed for the winter in northern U.S. climates.

Cement block, straw or hay bales can be used to provide boundaries to contain composting material and worms. Plastic liner can be used to minimize leaching and worm migration.

For a small farm or market garden, a worm composting area can be developed using straw or hay bales to provide an insulated wall or border. Over time the decomposing bales can be mixed into the worm bed and fresh bales placed on the perimeter. Bales placed over the top may provide adequate winter insulation. A rain shelter over the bed will prevent leaching of nutrients.

Another system used to contain worm composting is vinyl or woven fabric bags or beds. We are planning a trial of bulk root media bags supported by a metal conduit frame.


On farm batch systems have been made from 50 gallon plastic barrels (food grade or non-toxic contents) cut in half either vertically or horizontally. Large diameter water or drainage pipes have also been cut in half for use as worm bins. Systems in India that can be viewed on the internet include cement or cinder block beds and large woven vinyl bags. Both systems allow collection of leachate. Larger plastic or metal containers often used for providing water to livestock can make effective batch worm bins. Based on a discussion with a student returning from a study abroad in Sri Lanka, we researched “vermiwash” systems. We used a Rubbermaid livestock water reservoir with gravel and sand layers in the bottom separated by landscape fabric and worm bedding as the surface layer to produce a combination worm composting and vermiwash system. Farm-scale Windrows or Angled Wedge Systems. Large windrows of manure or food waste can be managed vermicomposted outside if properly protected. Outdoor composting is either done in low rainfall areas or windrows are covered with a roof or maintained under breathable covers that provide aeration but limit moisture loss and prevent leaching from rainfall. Windrows can also be maintained in temperature-controlled insulated buildings where the greater concern becomes keeping worms in the piles rather than keeping rain out. Windrows can be managed by adding fresh material to the top, the small end, or the long sides. For long windrows managed with the angle wedge system, fresh material is added to one end or side of the sloped/angled piles and worm populations move laterally. Over time the finished material is removed from one side and new material continues to be added to the opposite side. When the edge of the available composting surface/floor area is reached, finished material can be collected from the older/aged side and the direction of the pile reversed so the “composted” side becomes the “fresh” side. Our limited experience is that it has been easier to have the worms move up rather than sideways. When the windrow becomes too deep, the surface layer can be removed and placed in a new location to start a new windrow. We have maintained two 4’ wide by 20’ long beds with a 1.5’ center walkway placed on an initial layer of greenhouse polyethylene covered by woven landscape fabric and bordered/contained by cement blocks on the outer perimeter and wood at the center walkway. Fresh feed is buried in trenches and covered weekly during the warmer months to prevent flies. In the winter months fresh material can be layered on the surface. We initially used side applications similar to a wedge which was also successful but less effective to manage with manual feed additions. The method of trap removal of the bulk of the worms using crates of fresh bedding/feed to the surface of the beds has so far been an efficient method of removing the bulk of the worms to new beds. Pass Through Systems For larger, indoor commercial operations the beds are maintained in metal frames held off the ground. Fresh material is added to the top of the beds and finished material is removed from the bottom of the beds by mechanically moving a scraper bar across the open mesh or screened bottom of the bed so that finished material drops to the floor and is then collected. This system has been used for food residue processing in institutional settings and for very large scale processing systems for food waste and animal manure. See web sites for Worm Power (NY) and Sonoma Valley Worms (CA). The Charlotte, North Carolina Airport has also installed a large flow through system. The investment required may not be possible or practical for a small scale farm. The cost is much more than the cost of a passive solar greenhouse that can serve multiple purposes on the farm. Another important factor is labor availability. These systems require minimal labor and are usually mechanized. Community based farms often benefit from member or volunteer labor that need entry level activities with no requirement for prior experience.


Recommendations for how to build a home or small scale flow through system are available and will be a part of our future research. If as effective as described, worm compost may be easier to harvest with this type system. http://www.redwormcomposting.com/vermbin-series-plans/

FloThr2 (10 min) http://www.youtube.com/watch?v=iKhDe8dWvhM&NR=1&feature=endscreen Preventing or managing migration and predation If conditions are unfavorable, worms will move out of the bedding and seek new lodging, particularly under the cover of darkness. If there are greener pastures nearby, you lose your worms. If there is nothing suitable (wet) nearby, mass migration means mass murder. Either way you lose as a worm farmer. Beds must be provided feed regularly or fresh bedding and feed placed nearby so migrating worms are not lost. Use of low intensity lighting will also reduce the probability of mass migration. Worms are also a good food source for moles, voles and other scavengers such as raccoons. A large population of worms can disappear in a short time so take precautions. Using Passive Solar Greenhouses A key part of our project has been to test the use of a passive solar greenhouse (PSGH) also known as a high tunnel or hoophouse for maintaining worm activity through the winter in a northern climate (Climate Zone 5, winter low of -20oF). Use of PSGHs for extending the production time of warm season vegetables and allowing winter harvesting of cool season vegetables is having a significant impact on the availability of local food. A PSGH with two layers of inflated polyethylene and rollup or drop down sides will cost in the range of $2.50 to $5.00 per square foot floor area. We are currently using 25% of the space for beds. The greenhouse cover and typically a second interior cover of either polyethylene film or frost fabric trap the radiant energy of the soil or worm beds and prevent freezing conditions. In our trials in 2010-2011 and 2011-2012, worm beds were maintained at a temperature of 45 to 50oF with no supplemental heating. Vermicomposting activity continued but at a slower rate. We also are testing the addition of feedstocks to the worm beds that provide small hot spots (<0.5 ft3) through thermophilic composting in order to maintain worm activity when outdoor temperatures drop below 10oF for more than a few days. We were given 50lb bags of pig feed which primarily consisted of soybean and corn meal and oat seed. As little as a quart of moistened material could create a hot spot and we typically used 0.5 to 1 gallon of material. Liquid application of diluted molasses can also increase biological activity and provide warming for short periods of time. Future research will include legume hay and alfalfa meal. MSU Compost Commons or WORMhouse The high tunnel or passive solar greenhouse (PSGH) pictured on the next page cost approximately $10,000 to build in September 2010. The footprint size is 30’ x 72’ with drop down sides and thermostatically controlled end wall vent louvers. The interior tent pictured is 10’ x 25’ and is used for two worm beds 4’ x 20’. Tent is covered with polyethylene in winter for heat retention and shade cloth in summer for cooling. Our first beds were formed with cinderblocks and were 4’ wide. We used old greenhouse polyethylene film and landscape fabric to contain the worms and help hold moisture. While the film can reduce aeration, our primary goal was to contain leachate. We managed aeration by not overwatering. We soon realized that larger beds have more forgiveness and room for worms to move in the case of problems due to heat or excess moisture. We later developed the 42”x84” wood beds for further research. The bed is small but allows replicated units needed for research. These beds are open on the bottom and sit on the sand (2NS) that was purchased for the floor of the WORMhouse. The minimal bed size we are recommending to farmers is the 4’x8’ bed constructed from 2”x6” lumber that is pictured.


Bed position and shape changed over time as we trialed several management methods. Lower right picture is large cover system over six wood beds, each 20 square feet. 30x72 PSGH with side and peak vents. Initial interior tent in Fall 2010.

System in Fall 2010 just starting. Revised system in winter 2011-12.

Summer shade cloth cover, now taller structure. Frost fabric cover over small beds and plants


Examples of temperature data collected starting in late December; a) early January and b) early February 2011 of worm bed temperatures under an interior tent in a passive solar greenhouse (high tunnel). Temperature was recorded hourly by electronic recorders at a depth of 2 to 3 inches and is available as the hourly average. The edge of the bed remained warmer due to thermophilic composting of material added to the bed at two to three week intervals.

Worm Bed Edge recorder malfunctioned during the early February period but temperatures measured with analog thermometers were higher similar to January.


7. Harvesting of worms from finished compost or castings and screening finished compost A key management process is separating the worms from the castings. There are at least four options:

Option1 – Place fresh bedding and food adjacent to or on the surface of vermicompost beds and worms will move into fresh material. In Michigan several large greenhouse businesses import tulips, daffodils, hyacinths and other bulbs from the Netherlands. The bulbs are transported in plastic crates which can be purchased. These crates packed with fresh bedding and feed have worked well for collecting and moving worms. An 11” x 22” by 6” deep crate (about one cubic foot) can collect 2 to 3 pounds of worms and can be moved by one person.

Option 2 – Keep worms moving up through fresh material and collect vermicompost from the bottom through a screen or by using stacking layers with large screen bottoms (variation of option 1).

Option 3 – Use either light or drying to move the worms to the bottom of pile of finished worm compost and remove the surface layers of worm compost. This works well if workers can be doing other tasks in the PSGH and occasionally removing the next layer of material as worms move down. If taken to an endpoint a “worm ball” will form and worms can be collected, weighed and redistributed in new beds.

Option 4 – For commercial production of worms for fishing bait, the bedding can be passed though a rotating, pitched screen that will sieve out the castings and collect the worms at the end of the screen. Based on our limited experience primarily the larger worms are collected and smaller worms pass through the screen with the finished compost. The small worms can be extracted from the finished compost by placing fresh bedding/feed at the surface of the pile as an attractant.

Screening A first step for providing uniformity and a consistent particle size is to screen the material.

Common screen sizes are 0.125 (1/8th), 0.25 and 0.5 inch. We started with a simple wooden frame with hardware cloth that was designed to rest on a large

wheelbarrow. Later the screen was set up as a swing screener that was suitable for compost where the worms were already removed. As pictured below the materials cost was about $100.

We recently purchased a Jet Worm Harvester that cost about $3400 and $900 to ship from Nevada to Michigan. http://www.jetcompost.com/harvesters/index.html

Either 0.125 (1/8) or 0.25 (1/4) inch hardware cloth will work for most applications. The 0.5 (1/2) inch screen is good for removal of large clumps or for course screening of inputs.


We used the 0.125 for finished product to sell. It removes cucurbit seeds from the compost and greatly improves the quality of the product.

For use in teas or bed production, material with larger particles (0.25 and 0.5) will usually be adequate.

As much as 30 to 40% of the material did not pass through the 0.125 screen initially. Aggragrates/clumps were broken up by hand and the material was passed through the screen again with about a 50% recovery rate, bringing total recovery over 75%. We plan to look at roller based methods of crushing the larger aggregates. Or using the aggregates in root media.

Smaller batches of vermicompost with a variety of feedstocks can be mixed together for a more uniform larger batch of final product.

8. Organic Certification Requirements For organic certification, vermicomposting requirements (as opposed to hot composting) are:

Allowed feedstocks – must provide records of feedstocks used and how non-allowed substances were excluded.

Applied in shallow layers – presumably to allow rapid composting without heating. Aerobic conditions (can’t use worms any other way) High moisture (70-90%) – information is not provided regarding the basis for this requirement

but the high moisture favors rapid decomposition. Duration: 12 months for outdoor windrows, 4 months for indoor container systems or angled

wedge systems, or 2 months for Continuous Flow Reactors It is interesting that there does not appear to be any requirement for an average or recommended worm population per square foot of bed surface area or cubic foot of bedding/feed. As previously presented the worm population density will impact the rate of composting. This is also no recommendation for feeding rate. Excessive feeding will not likely allow for complete composting. For the USDA National Organic Program and Organic Certification Handbook see: http://www.ams.usda.gov/AMSv1.0/nop


9. Using Worm Compost Benefits: fertility, biology, water holding The reasons for using vermicompost as stated earlier are multipurpose. One goal is to provide a source of quickly and slowly soluble nutrients for plant growth. Mature

worm compost may have higher soluble nutrients including nitrate nitrogen than hot compost. However, based on initial research, the feedstocks used will likely have a larger impact on the nutrient concentration in the final compost than the method of composting. Commercially available worm compost often comes from dairy manure. Dairy manure hot composted is typically a much higher nutrient content than other garden or farm materials that are hot composted.

A second goal is to increase the quantity and diversity of microorganisms present in the soil. It is assumed that the lower temperature of composting together with the impact of the microorganisms in the worm gut lead to a greater diversity of microorganisms but it is unclear whether good comparisons of mature compost with both methods using the same feedstocks have be compared.

A third is to impact the soil water holding capacity and moisture release characteristics. Worm compost is typically a stable material with high humus content.

A fourth is to add stable organic matter as humus that can increase the cation exchange capacity or the ability to retain nutrients including anions in forms available to plant roots.

How Much is Needed for Various types of Production? Here are some examples of how much vermicompost might be needed for plant production. At the MSU Student Organic Farm we grow approximately 900 flats (11”x22”) for a year-round 5

acre vegetable farm with high tunnels. o Total transplant root medium needed would be approximately 6 cubic yards. Worm

compost at 20% volume would be 1.3 cu yds. o To treat 1000 flats with 1 cup vermicompost top dressing requires: 8.33 cu ft or 0.33 cu yd.

Multiple applications may be needed so a seasonal estimate is 1 cubic yard. For container grown plants such as 3 to 5 gallon patio pots (or buckets) or hanging baskets,

surface application of 1 to 3 cups is a good starting point. For raised bed production, a starting rate is 5 to 20 pounds per 100 square feet spread across the

soil surface and then incorporated prior to seeding or transplanting. For trees or shrubs, as much as 1 to 5 gallons of worm compost spread over the root zone or

under the reach of the branches is a reasonable starting point. Variability – not all worm composts are the same (also true for thermophilic compost) As with many biological products, understanding and accounting for variability is important. While many use recommendations call for “vermicompost”, a compost made from manure based

feedstocks will have quite different nutrient content than one made from plant based materials or kitchen preparation residue (vegetables and fruit).

Manure from grain fed animals such as dairy cows or poultry will tend to contain more nutrients. Poultry manure contains both solids and urine (comes out one hole as someone once said) so has more residual nutrients and nitrogren. Cow manure collected with urine from a cement barn floor will make higher nutrient value worm compost (or thermophilic compost) than pasture or paddock manure, unless liquid is extracted first.

It is helpful to have a nutrient or soil analysis of the material to determine the total nutrient content as is done for plant analysis and the water soluble nutrient content as is done for greenhouse potting media.

Testing and Analysis High organic matter compost can be analyzed like a plant sample (ashing and dissolving in acid)

to determine the total nutrients present. (Table 1 and 2)


Total nitrogen is typically analyzed with a separate test. Vermicompost can also be analyzed with the saturated media extract (SME) method like a

greenhouse peat based media sample to determine the pH and water soluble nutrients including nitrate and ammonium nitrogen and the electrical conductivity. (Table 3)

Compost is not normally analyzed with a standard mineral soil extraction method but it could be. An advantage of that analysis is the cation exchange capacity (CEC) is determined as well as the cation balance.

The percent organic matter analysis can be used to estimate the percent carbon which can then be used with the nitrogen analysis to calculate the carbon to nitrogen ratio (C:N).

It is also helpful to have the bulk density. For any compost sample, the weight in pounds of a five gallon bucket filled with compost multiplied by 40 will give the weight of a cubic yard. Mature compost can range from 800 to 1200 lbs per cubic yard at 35-45% moisture (20 to 30 lbs per five gallon bucket). An average is often assumed to be 1000 lbs per cubic yard (25 lbs/5 gal). Recent mature samples of our food residue worm compost were approximately 25 lbs per five gallons.

Table 1. Vermicompost Organic Matter, Carbon, C:N and N (Abbreviations: HM= horse manure collected from paddock (no urine) at PTF; KPR= kitchen preparation residue, mostly fruit rinds; PULP= pulped pre and post consumer food waste; HT=high tunnel; PTF= Pear Tree Farm)

Worm Compost ID %

OM % C C:N % N Plant Compost+ HM boxes (Sum 2010) W1 30.1 17.4 13.2 1.32 HM+ PULP in Bins (Win 2011) W2 31.1 18.0 10.5 1.71 HM in Bins (Win 2011) W3 28.4 16.5 11.4 1.44 KPR + leaf & straw bedding (Win 2011) W4 38.0 22.0 10.5 2.10 Plant/leaf Compost (Sum 2011) W5 47.6 27.6 17.2 1.60 Dairy Cow Manure & Urine (Sum 2011) W6 41.5 24.1 16.6 1.45 Mix of W1 & W4 (for transplants) W7 37.6 21.8 14.1 1.55 HM piles outside at PTF 2010 W8 18.9 11.0 11.7 0.94

KPR from HT Windrow 2012 W9 33.4 19.4 13.1 1.48

HM+ KPR from HT Batch (Win 2011-12) W10 20.9 12.1 10.4 1.16

PreCompost PULP (Win 2011-12) W11 33.5 19.4 9.5 2.05

Average of all Mean 32.8 19.0 12.6 1.53

Organic matter is as expected in the 30 to 40% range and the C:N is as expected in the 10 to 20% range for mature compost. The kitchen preparation residue is the main production from 2011 and it is good to see the high nitrogen content (2.1%). Future research will need to test whether the coffee grounds contributed to the higher nitrogen concentration.

Table 2. Vermicompost Total Nutrients by Ashing (macros as % and micros as ppm). Worm Compost ID N P K Ca Mg Na S Fe Zn Mn Cu B Al Plant Compost+ HM boxes (Sum 2010) W1 1.32 0.30 0.76 2.12 0.51 0.03 0.19 3849 81 240 29 16 2328HM+ PULP in Bins (Win 2011) W2 1.71 0.49 0.75 2.34 0.73 0.07 0.26 4093 104 289 31 19 2108HM in Bins (Win 2011) W3 1.44 0.44 0.63 2.05 0.55 0.05 0.20 4053 81 225 28 16 2104KPR + leaf & straw bedding (Win 2011) W4 2.10 0.38 1.60 2.45 0.64 0.12 0.24 3920 61 210 18 21 1839Plant/leaf Compost (Sum 2011) W5 1.60 0.36 0.72 2.15 0.47 0.05 0.24 3851 94 234 31 21 2116Dairy Cow Manure & Urine (Sum 2011) W6 1.45 0.60 1.49 3.49 0.88 0.14 0.35 4325 140 342 58 20 1759Mix of W1 & W4 (for transplants) W7 1.55 0.30 0.96 2.04 0.71 0.06 0.19 4467 69 197 26 16 2265HM piles outside at PTF 2010 W8 0.94 0.29 0.57 1.94 0.49 0.01 0.13 3399 58 197 14 10 1864

KPR from HT Windrow 2012 W9 1.48 0.24 0.78 3.23 0.85 0.10 0.18 4449 58 195 21 13 1817

HM+ KPR from HT Batch (Win 2011-12) W10 1.16 0.34 0.55 2.27 0.83 0.05 0.15 3979 62 215 19 12 1871

PreCompost PULP (Win 2011-12) W11 2.05 0.26 0.94 3.39 0.95 0.12 0.23 4336 56 224 24 17 1737

Average or Mean of all Mean 1.53 0.36 0.89 2.50 0.69 0.07 0.21 4066 79 233 27 16 1983


The following evaluation and comparison of the worm composts are based on comparison with a data set of analyses of 23 hot composts in 2003 and 23 hot composts in 2010. The average carbon, C:N, and total nutrient concentration of the 11 worm composts collected over the past two years are similar to the averages of the two prior data set means. Worm composts are typically reported to be of higher nutrient concentration. Looking at the three data sets overall, the feedstocks used to make the compost, for example the addition of animal manure from animals on high protein diets, appears to have a larger effect on nutrient concentration then the method of composting. The higher N and K concentration in the kitchen preparation residue compost from the main composting bed cannot be fully explained at this point. One possibility as mentioned above is the contribution of coffee grounds which were not a feedstock for W1 to W3. Another is that the compost was managed for a longer time than other systems sampled with more total food residue added to those beds. The high concentration of P, K, Ca, and micronutrients in the vermicomposted cow manure is expected based on the dairy cow diet and provides evidence for the high commercial sale value of dairy manure vermicompost. Approximately 4 cu ft of dairy manure was used for this trial. The worm activity and reproduction in the sample was very high. Table 3. Vermicompost Saturated Media Extract or Water Soluble Nutrients

Worm Compost ID pH EC NO3-

N ppm

NH4-N

ppm

P (ppm)

K (ppm)

Ca (ppm)

Mg (ppm)

Na (ppm)

Cl (ppm)

Plant Compost+ HM boxes (S2010) W1 6.5 8.92 850 7.5 93 2106 900 177 105 352

HM+ PULP in Bins (Win 2011) W2 7.2 4.67 272 4.1 147 985 420 126 128 290

HM in Bins (Win 2011) W3 7.1 5.15 371 1.5 182 1080 420 149 97 255

KPR + leaf & straw bedding (2011) W4 7.6 11.8 834 1.7 90 3498 1260 93 312 1175

Plant/leaf Compost (Sum 2011) W5 6.5 5.15 410 1 100 1061 480 120 70 178

Dairy Cow Manure & Urine (S2011) W6 8.7 7.51 294 4.4 138 2052 900 113 220 513

Mix of W1 & W4 (for transplants) W7 7.0 9.39 694 1 122 2388 960 137 188 588

HM piles outside at PTF 2010 W8 8.0 4.67 280 0.8 35 1251 420 67 40 297

KPR from HT Windrow 2012 W9 6.5 12.89 904 6.5 124 2357 1500 247 433 1441

HM+KPR from HT Batch (W 11-12) W10 6.9 6.99 450 5.3 124 1326 750 176 138 467

PreCompost PULP (Win 2011-12) W11 6.4 11.69 748 5.3 124 1971 1200 194 333 1088

Average of all Mean 7.1 8.07 555 3.6 116 1825 837 145 188 604

Compost pH in 6.5 to 7.6 range is desired for general use but lower pH can also be acceptable. The average pH for the worm composts is similar to the average for the previous data sets. The higher pH in cow and horse manure composts is consistent with previous observations. More mature or older composts also tend to have a lower pH in this data set as in the previous data sets. Low ammonium nitrogen concentrations (< 5 ppm) and increased nitrate nitrogen concentrations are also a good indication that composting is complete. The kitchen preparation residue sample has the highest EC and nitrate nitrogen which in this case is considered desirable for nutrient recovery. The total soluble salts are a good indicator of the fertilizer value of the worm composts. There are 3 composts with EC over 10 mmhos and 3 additional between 8 and 10 which are high compared to values in previous data sets of primarily hot composts. Previous data sets have included compost samples with nitrate nitrogen concentrations in the 2000 to 4000 ppm concentration so the values in this data set are not excessive. The owner and manager of the largest worm composting facility in the US who sells worm compost to greenhouse operators has proposed that the higher nitrate nitrogen content of worm compost compared to other


composts is one of the primary values or selling points. This is another area where further research and analysis is recommended. Based on both individual worm compost samples and the data set averages, there is a trend of higher soluble phosphorus in the worm composts which is consistent with previous reports. Storage of Worm Compost There are not clear recommendations for how to store worm compost or how long worm compost

can be stored while maintaining biological activity that impact plant growth. Moisture is important and a good starting point is to maintain 30 to 45% moisture. Aeration is also important to maintain oxygen for living organisms but it is not clear whether

storage in a sealed plastic bag or a sealed five gallon bucket or larger container in order to maintain moisture is detrimental to biological activity. For our compost stored in 5 gallon buckets we drilled a small hole in the lid of each bucket.

Incorporation into root media Formulation of a peat or bark based growing medium for container grown greenhouse or nursery

crops is based on combining “components” (present at greater than 10% by volume) and amendments (present at less than 10% by volume).

Depending on the nutrient analysis, vermicompost would typically be included at 10 to 20% by volume with components like peat moss, perlite or vermiculite.

The cost / value of the vermicompost may limit higher rates. Top dressing / surface application as supplemental fertilizer Surface application of compost or vermicompost to container grown plants is not a very common

cultural practice or recommendation but it is being done with good success. In limited trials at Michigan State University, surface application of 1 to 2 cups of very mature hot

compost (8 to 16 months old) or 0.5 to 1 cup of finished, matured worm compost to the surface of an 11”x22” multi cell plug or transplant tray has resulted if visible greening in 3 to 4 days and sustained growth. More research is needed but this is a rapid and easy method of providing nutrients and maintaining biological activity prior to field transplanting.

Leachate, Vermiwash, Water Extraction and Aerated Compost Tea Alternatives to media incorporation or surface application of compost are liquid obtained by short

term water extraction (5 to 30 minutes) or longer term steeping or brewing of finished compost either in an unmixed, non aerated system or in a system with agitation provided by aeration of the water and compost mixture. A common recommendation is for 1 part by volume compost mixed with 10 parts by volume of water. Smaller or larger dilutions can be made depending on the quality and nutrient content of the vermicompost.

It is important to differentiate between compost leachate, compost extracts and compost tea. Leachate of liquid from worm bins or containers during composting may contain biological contaminants such as E. coli. or salmonella that are not safe for use on food crops. Leachate is not tea although the two are sometimes confused. A system called “vermiwash” is based on adding water to active worm beds and collecting the leachate from the bed for application to plants. There are numerous books, web pages and on-line videos that refer to worm bin leachate as “tea”. Technically speaking it is not tea and should not be used in the way that compost “tea” as defined below is recommended. It can be applied to the root zone of flower or ornamental crops or food crops where harvested crop parts do not come in contact with the soil.

Extracts are made by adding water to finished vermicompost that would meet the time requirement for organic certification. The water and compost (usually 1:10) are mixed/stirred and the water is removed about 15 to 30 minutes. With this method there is usually no addition of amendments and no growing of additional microorganisms.


Non-aerated Teas are made by allowing compost and water to sit for 12 to 72 hours without mixing.

Aerated teas are made by using aeration pumps and air stones in the compost water mixture (usually 1:10) to increase the resident microbial population. Amendments may be added.

10. Additional Sources of Information Web Sites MSU Power point http://www.michiganorganic.msu.edu/uploads/files/31/biernbaum%202.pdf NCAT-ATTRA Publication: https://attra.ncat.org/attra-pub/summaries/summary.php?pub=256 North Carolina State Extension Vermicomposting Site (Rhonda Sherman) publications:

http://www.bae.ncsu.edu/topic/vermicomposting/ Ohio State Research Laboratory: http://www.biosci.ohio-state.edu/~soilecol/ Vermicomposting at Wikipedia - http://en.wikipedia.org/wiki/Vermicomposting Worms for urban farming - http://www.cityfarmer.org/wormcomp61.html#wormcompost Flower Field Enterprise: www.wormwoman.com Largest commercial worm composter in United States http://www.wormpower.net/ Sonoma Valley Worm Farm - www.sonomavalleyworms.com California, flow through system Vermicompost Operation in Wisconsin - Wiggle Worm http://www.vermiculture.com/ Books and Publications: Vermiculture Technology; Earthworms, Organic Wastes, and Environmental Management. 2011.

Edited by Clive Edwards, Norman Arancon and Rhonda Sherman. CRC Press. 600 pgs. The Complete Guide to Working with Worms: Using the Gardener’s Best Friend for Organic

Gardening and Composting. 2012. Wendy Vincent. Atlantic Publishing Group. 288 pgs. Beyond Compost: Converting Organic Waste Beyond Compost Using Worms. 2009. Tom

Wilkinson. Create Space Independent Publishing Platform. 116 pgs The Worm Book; the complete guide to gardening and composting with worms. 1998. Loren

Nancarrow and Janet Hogan Taylor. 10 Speed Press. 150 pgs. Raising Earthworms for Profit. Revised edition 1994 (original 1959). Earl B. Shields. Shields

Publications. 126 pgs. Worms Eat My Garbage. 1997. Mary Appelhof. Flowerfield Enterprises. 162 pgs. YouTube Videos of Possible Interest There are many, many videos. Here are a few to get started.

Overview of many ideas (6 min) Music background – fast moving images http://www.youtube.com/watch?NR=1&v=cRAq2chA7HA&feature=endscreen

Dirty Jobs (9 minutes) http://www.youtube.com/watch?v=44AvH-fPxp0&feature=related Tank Method (8 minutes) http://www.youtube.com/watch?v=2SuBT7SukdI Worm Power (6 minutes) http://www.youtube.com/watch?v=X6TiawLx0J8 Simple Harvester (4 min) http://www.youtube.com/watch?v=KRI69IO5y3c&feature=related Morgan Composting (10 min) http://www.youtube.com/watch?v=U27Aizi64Wg Flow Through in Hoophouse (4 min) http://www.youtube.com/watch?v=vQEQ-gWLHJU Stacking Tray System (8 min) http://www.youtube.com/watch?v=VMdJxfPuMOE Flow through System (17 min) http://www.youtube.com/watch?v=ZWb5knRBRM8 FloThr2 (10 min) http://www.youtube.com/watch?v=iKhDe8dWvhM&NR=1&feature=endscreen Hanging Bag Idea (5 min) http://www.youtube.com/watch?v=VxDrkGRKXt4 Ideas from a tropical setting (8 min) http://www.youtube.com/watch?v=E-PKWnVeuSo Hoophouse Setting (6 min) http://www.youtube.com/watch?v=kNl_4Axd3BE


Contact Information This document is under development/review and while every effort has been made to insure the accuracy of the information, there still may be some mistakes. Comments or concerns about the information presented are appreciated. This document is not for publication or reproduction without permission of the author.

John Biernbaum Department of Horticulture, Michigan State University Email: [email protected] Phone: 517-355-5191 x 1419

11. Appendix: Historical Perspective and Project Background I remember “discovering” the large population of composting worms that developed in horse manure piles at our home farm. I was using a bucket loader to place llama and horse manure compost in a small trailer. I happily gave the compost to an enthusiastic gardener who had asked if I wanted to be paid for the compost. While I did not take any payment for the compost, the next day I realized that I had likely given away easily $100 worth of worms. From that point I started managing the manure piles in a way that the worms could easily move from one pile to the next when composting was completed and the finished material was ready for application to a pasture. I also started using the worm composted horse manure in my hoophouse for vegetable growing. In January of 2010 I was invited by my colleague Laurie Thorp to participate in a discussion about quantifying, minimizing and managing food waste on the Michigan State University campus. Some efforts were already underway including construction of an anaerobic digester. My proposal to use worm composting and to focus on the importance of cycling nutrients from farm to fork and then back to the farm was accepted more with curiosity than confidence. I was aware that worm composting was used more or less successfully at a variety of institutions from schools to prisons. Dr. Thorp had actually introduced worm composting bins to a local elementary school where we both worked in the late 1990’s. I was also aware that a new organic certified greenhouse production facility in Michigan was purchasing significant quantities of worm compost from New York State at a price of $800 per ton. Hot composting and the use of compost for transplant production and passive solar greenhouse management were already essential components of the year round farming program that I helped start in 2003 at the MSU Student Organic Farm (www.msuorganicfarm.org and www.hoophouse.msu.edu). A key component of our worm composting project has been to demonstrate how a PSGH can be used for year round worm composting. While the winter temperatures are low and summer temperatures high for the worms, if properly managed the moderate cost structure ($2.50 to $5.00 per square foot) can be used for additional farm activities such as transplant, leafy green, culinary herb, mushroom, or fish production. Internal covers are used to trap the thermal radiant energy and increase temperature during cold winter nights and roll-up or drop-down side wall ventilation is used to reduce temperature during the summer so energy costs are near zero. I am grateful to the past and ongoing support of Michigan State University Office of Campus Sustainability, the Division of Residential and Hospitality Services, and the campus Recycling Center and Surplus Store who financially and enthusiastically supported the development of worm composting methods for campus and for use by farmers and students. Several staff and students at MSU were instrumental in the development of the important objective to “close the food cycle loop” on campus by keeping food waste from landfills and keeping the nutrients available for future farmers and gardeners. The shared commitment and passion was critical for me and the students involved in the project. I now (2012) have eight plus years experience with the worms in our horse manure piles at home and two full years of experience with food waste vermicomposting in a PSGH at the MSU Student Organic Farm. I have read many publications and websites about vermicomposting and looked at a lot of on-line videos. I am sorting through all that experience and information and thinking about what is most important to share with future worm farmers. And here is the first attempt. Enjoy! John Biernbaum, December 2012

making and using worm compost

Education

worm composting systems

worm composting population

worm composting comparisons

hot composting

small scale worm composting

large scale worm composting

worm population

common worm composting