Steven M. Brown and Jessica Anne Blohm
Household kitchen waste can be disposed of in a variety of ways. One option is to throw trash out and eventually it will be put into a local landfill. There are several long-term problems with this approach. First, we are running out of landfill space. Secondly runoff from landfills creates a liquid called "leachate" which carries contaminants that eventually leak back into our groundwater systems.
An alternative to getting rid of household kitchen waste is your kitchen garbage disposal, which grinds the material for ultimate disposal through pipes to your local sewage treatment plant or septic system. But as cities and suburbs continue to grow, additions from wastewater disposal systems put an added demand on water treatment facilities. If we can divert waste from landfills and sewage treatment plants and create a useful end product, we can reduce waste going to diminishing landfill space and keep our groundwater cleaner. Vermicomposting may be a solution to this problem. Vermicomposting is the process of using worms and microorganisms to recycle organic waste into a fertilizer and soil amendment called worm castings or vermicompost. Using this system turns kitchen waste into black, earthy-smelling, nutrient-rich humus, beneficial to the garden.
Vermicomposting breaks down organic wastes, rapidly transforming them into a stable, nontoxic material with good structure, porosity, aeration, drainage and moisture-holding capacity. (1) Vermicompost is a finely divided peat like material, which supplies minerals and improves nutrient availability to plants
In the thermophilic stage that occurs during regular composting, most pathogens and other disease-causing organisms are eliminated. In Vermicomposting pathogens are eliminated during an aerobic process, which leads to an increased nitrogen mineralization rate due to the earthworms activity. The humification processes that take place are greater and faster during Vermicomposting than during regular composting as in a pile or a bin. (3) A decrease in the carbon from fulvic acids and an increase in the percentage of carbon from humic acids are observed in the Vermicomposting process.
There are two main types of earthworms, earth-movers or composters. Many people think of nightcrawlers when thinking of worms Nightcrawlers are an earth-moving type of worm. These worms ingest soil to extract their nutrients. They are good for aerating the soil in a field situation, but do not work well in a Vermiculture system. Composting worms, notably redworms (Eisenia foetida), swarm into decaying organic matter and, working as a group turn the organic waste into Vermicompost and worm castings. In a soil where earthworm populations are large and active, reductions occur in the organic nitrogen content and the nitrification rates are higher.
To set up a Vermicomposting system you need a container with a depth between eight and twelve inches. Bins need to be shallow because the worms feed in the top layers of the bedding. Wooden bins allow for better air movement than plastic. Depending on the size of the container, 8 to 12 holes (1/4 - l/2 inches) are drilled in the bottom for aeration and drainage. (3) Worms are aerobic digesters and require oxygen just as we do. The oxygen diffuses through their skin and they exhale carbon dioxide by the same process. If their environment becomes anaerobic, the worms will eventually die.
The bin should then be raised on bricks or wooden blocks and a tray placed underneath to capture excess liquid, which can be used as liquid plant fertilizer. The bin needs a cover to conserve moisture and provide darkness for the worms, which do not like light. Worms do not have eyes, but they do have sensory receptors in their skin that are sensitive to light.
The bedding for Vermicomposting systems must be able to retain both moisture and air while providing a place for the worms to live. Half-finished compost, shredded leaves, shredded cardboard, newspaper or computer paper may be used as bedding. A small amount of peat moss can be added initially to help retain moisture if using the last three items. Commercial worm bedding is good, but expensive. Any combination of these types of organic matter can also be used. The amount of bedding depends on the size of the box. The bin should be 2/3 filled with "fluffed" prepared bedding. Water is needed to moisten the bedding, which must remain moist at all times.
Redworms prefer temperatures between 55 and 77 degrees Fahrenheit. The temperature of the bedding should not be allowed to get below freezing or above 84 degrees. (2) The amount of kitchen waste generated per day will determine the number of worms needed. One pound of redworms will consume about a half-pound of garbage per day. The kitchen waste fed to worms can come from many sources, including all vegetable and fruit waste, pasta leftovers, coffee grounds (including filters) and tea bags. You shouldn’t feed your worms certain things such as heavily salted foods like peanuts and potato chips, manure from household pets or horses (this may contain antibiotics that kill worms). Excessive quantities of coffee grounds, orange, lemon or other citrus peels, and onionskins are acidic and can contribute to low pH conditions. Adding large amounts of grass clippings or any other kitchen wastes at one time could creates too much heat. Any “food” added to your Vermiculture system should be placed a few inches under the bedding every few days. Your nose will tell you if you’ve been feeding too much. If you detect a foul order, add more moistened bedding and stop feeding for a few days. If conditions get too moist adding a small amount of dry bedding and aerating the bin should alleviate the problem.
. Grit is needed to help the worms digest food. Redworms do not have teeth. Instead, they digest food material in their gizzard. The gizzard needs a small amount of grit to grind food. This gritty material can include sand, garden soil, and/or finely crushed eggshells. Fat, meat scraps and bones should be avoided because they may attract rodents.
Many variables affect how much your worms will eat. For example, they are more active at room temperature than at 40°. F (4) Redworms will consume approximately ½ their body weight in food waste per day.
A pH between 7 & 8 is ideal for Redworms. Extremes in either direction may damage or kill your worms. Using some litmus paper or a pH meter you can monitor pH. To adjust a high pH (alkaline): add a mixture of three parts water to one part white vinegar. To adjust a low pH (acid): add crushed eggshells, oyster shells, powdered limestone (not hydrated lime), or even baking soda. (1)
Vermicomposting will work faster than any other compost method. The material will pass through the worms' bodies and be excreted as "castings." Worm castings have nutrients needed by plants plus compounds to control plant pathogens. Castings are also coated, allowing the nutrients to be time released to your plants. Unlike chemical fertilizers, you cannot burn your plants by using too many castings.
In about 3-4 months, the worms will have digested nearly all the garbage and some of the bedding and the bin will contain a rich, black natural fertilizer and soil amendment. Compared to ordinary soil, the worm castings contain five times more nitrogen, seven times more phosphorus and 11 times more potassium. They are rich in humic acids and improve the structure of the soil.
To keep your bin going, you will need to remove the castings, or finished Vermicompost from time to time. Harvesting is important every 4-8 weeks to remove the worm castings and add more bedding material. Castings alone are actually toxic to the worms. Redworms reproduce quickly and frequently. You will find small, oval shaped cocoons throughout the bedding. Each cocoon contains one to several worm eggs that will hatch in about 21 days. Baby worms look like tiny, white threads. Because the worms need calcium to reproduce, finely crushed eggshells, oystershells or a small amount of ground limestone can be added to the bedding. The worm population is controlled largely by the limitations of their environment, so you needn’t worry about over-reproduction.
There are many different methods of harvesting the finished compost. This involves separating the humus from the worms. One way to do this is to dump out the contents of the bin on a flat surface, and mound it up into a cone shape. Shine a bright light on top of the pile and when the worms are exposed to the light, they will bury themselves in their bedding. The worm free layer can than be removed. By repeating this process a few times there will be left at the bottom a mass of wiggling redworms which can then be added to a new bin. Another method of harvesting is to push the black, decomposed material to one side of the bin, and fill the other side with new, moist bedding and kitchen scraps. Then wait several days. The worms will migrate to the freshly filled side of the bin and you can just scoop out the finished compost. For harvesting small amounts without depleting your stock in any way simply fill a one or two gallon flower pot with fairly well decomposed bedding, food and worms and place this on top of your worm bin. The worms, even those that hatch after being placed in the pot, will travel down through the holes in search of food leaving pure “worm soil” which can be added to your houseplants or garden. To use the vermicompost simply add it to the soil and then work or till it in.
Why choose Vermicomposting as opposed to regular composting. The difference between the two mainly has to do with the optimum temperatures for each process and the types of microbial communities that are present during active processes. In regular composting, thermophilic bacteria are present while mesophilic bacteria and fungi are present in Vermicomposting. (2)
“Regular composting is an accelerated bio-oxidation of organic matter passing through a thermophillic stage (45 to 65C) where microorganisms (mainly bacteria, fungi and actinomycetes) liberate heat, carbon dioxide and water.” (2) The heterogeneous organic material is transformed into a homogeneous and stabilized humus-like product through turning or aeration. “Vermicomposting is also a bio-oxidation and stabilization process of organic material that, in contrast to composting, involves the joint action of earthworms and microorganisms and does not involve a thermophilic stage.”(2) The earthworms are the agents of turning, fragmentation and aeration. The difference is in the temperature during the process and the types of microorganisms and bacteria feeding on the food.
Vermicomposting could help to reduce wastes headed to landfills significantly and is an amazing source of nutrients for large and small scale farming applications. Who thought worms could be so beneficial in an approach to sustainability.
1. LET AN EARTHWORM BE YOUR GARBAGE MAN; Henry Hopp, U.S. Dept of Agriculture.
2. HARNESSING THE EARTHWORM; Dr. Barret
3. Vermicore Operations - The Daily Life of a Worm Farmer; Lonnie Richardson
4. Wormwoman.com- Mary Appleton’s Site for worm composting resources.
5. And more locally, a worm supplier in Enfield, CT.