Worm composting, or vermicomposting is often used for composting kitchen scraps. It is an appropriate option for a basement or other semi-heated indoor space.
Red worms (Eisensia foetida), also known as red wigglers, are the best species of worms to use for vermicomposting at home. Red wigglers only burrow 3-8 inches deep and more horizontally; unlike earthworms who burrow deeper. Red wigglers like temperatures between 55-75 degrees F. An adult red wiggler worm is 2-3 inches long and is dark red. Red wigglers reach maturity after 90 days. When they reach breeding maturity, they lay a cocoon that contains several babies. They can lay a cocoon about every 7-10 days, which means that when healthy, the supply of worms will maintain steady and even grow. Worms can be obtained from reliable bait supply stores or from online sources.
Bins for vermicomposting can be made from plastic or wood. Plastic bins are easy to make. The best bin size is 2 foot by 3 foot and one foot deep. Do not use clear plastic bins as the inside must stay dark. Drill 1/16-inch holes every 2-3 inches on the bottom of the bin for drainage and place the bin on two bricks or pieces of wood over a tray to allow for airflow and to collect excess moisture that drains from holes. Monitor bins carefully to ensure it does not get too wet. Extra layers of dry newspapers can be added to the top of the bedding to absorb extra moisture. Good airflow is important. Drill several ¼ holes around the top of the bin and place the lid over the bin to exclude light, but do not close it tight to allow for better airflow. The lid can also be a piece of cardboard or a frame built from scrap wood and several layers of burlap; this will allow more air ventilation and keep the light out.
Wooden bins require more work to construct but allow you to have more control over the size, shape, and appearance of the container. Construct the box with untreated plywood or pine boards. Drill holes in the bottom ½ to 1 inch across and cover the bottom of the bin from the inside with a window screen to allow the moisture to drain out but keep the worms in. With a wooden bin, you may have to add moisture to the bin occasionally as the wood pulls moisture away. Elevate the bin over a water collection tray to promote good airflow and collect excess moisture.
Pre-mixed vermicomposting bedding material can be purchased from a bait shop or the fishing department of a sporting goods store. You can make your own bedding from shredded newspaper, shredded corrugated cardboard, shredded unwaxed pressboard, shredded egg cartons (not Styrofoam), shredded brown paper bags, or shredded fall leaves. Bedding can also be a mix of home and store-bought materials.
Mix the materials together with unsoftened water that is free of chlorine. Add enough water so it feels like a wet sponge. Mix in a handful or two of garden soil. The worms need the grit to help digest their food. Also, there are micro-organisms in the soil that will help to break down the food and bedding.
Worms like temperatures from 55-77 degrees F with 65 to 70 degrees F being the ideal temperature. Keep the bin in a dark, quiet place. Avoid storing it next to the dishwasher or washing machine as they produce vibrations that the worms don’t like. Often worms will attempt to crawl out of the vermicomposting bin when first introduced so keep the lid on tight for the first 3 to 7 days.
Feed the worms almost any organic, plant-based kitchen waste. Vegetable scraps, cores, peelings, rinds, leaves, stems, or roots are great food sources. Coffee grounds, unbleached filters, tea bags, bread, and corn cobs can also be added. Avoid adding onion, garlic, peppers, or citrus fruit or peels (such as oranges, lemons, etc.). Never add meat, fish, cheese, gravies, dressing, oils, vinegar, butter, or heavily salted foods like chips or pretzels. Once a week add a couple of tablespoons of cooked crushed eggshells to their bedding. The worms benefit from the calcium carbonate which helps to maintain the bedding at a safe PH and helps in their reproduction.
Add materials in small pieces. Always bury the food under the bedding by digging a small hole in the bedding, placing the waste in it, and covering the hole with bedding. Rotate burial spots so that wastes are distributed throughout the bin. Alternatively, the waste can be laid on top and covered with shredded wet newspaper. This keeps the compost from attracting fruit flies and keeps the bin from smelling. Worms will eat half of their body weight in food in a day. If you start with a pound of worms, they can eat up to a ½ pound of food a day. The rate of reproduction is determinate by the space and amount of food provided to them. Therefore, the bigger the bin and the more food they have to eat, the more they will reproduce and the more compost you will have for your plants.
Harvesting and Using Finished Compost
The compost is ready to harvest when the texture is light and fluffy and the color is a rich black. This typically takes several months. To harvest the compost, move the finished compost to one side of the bin and add new bedding to the other side. Put food in the new bedding and the worms will move out of the old bedding to the new. Make sure the new and old bedding is touching. After a week or two, remove the finished compost and sift it through a fine screen to remove any stray worms. Mix in approximately two large handfuls of finished compost in the bid to provide the grit and micro-organisms needed to start the process all over again.
Finished compost can be stored in an airtight dark container to use whenever needed. Use the rich compost to add to houseplants, outside plants, or as a top dressing for vegetables in the garden. Worm compost is also called worm “casting.” Casting is the food, soil, and bedding that the worms expel after they have eaten. When they expel their manure there is a small amount of mucus around each granule. When the granule is exposed to air it hardens. When these granules are mixed into the soil they act as a slow-time release packet of nutrients for your plants. Worm castings compared to soil are on average have 5 times the nitrate, 7 times the phosphorus, 11 times the potash and 1.5 times the calcium. Not to mention all the macro and micro-nutrients the castings have from all the fruit and vegetables they eat.
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