Vermicomposting uses specific types of worms, primarily the Red Wiggler (Eisenia fetida), to recycle food scraps and organic waste into a rich soil amendment called castings. These worms are surface-dwellers, unlike common earthworms, and thrive in a specialized bin environment. Their health and the delicate balance of the habitat depend entirely on a carefully managed diet and proper feeding.
The Essential Diet: Acceptable Food Scraps
The bulk of a worm’s diet should consist of fruit and vegetable scraps, which are easily broken down by consuming microorganisms. Acceptable items include apple cores, banana peels, melon rinds, and most non-starchy vegetable trimmings. These items provide nitrogen and should be added in smaller, manageable pieces, not large chunks, to speed up decomposition.
Grains and starches, such as plain bread, cooked rice, oatmeal, or pasta, can be added in moderation, provided they are not heavily seasoned or oily. These secondary food sources help balance nitrogen-rich “green” materials with carbonaceous “brown” matter. Proper balance is achieved when the bin contents remain moist but not saturated.
Carbon-rich material serves as both food and bedding for the worms. Shredded newspaper, unprinted and unwaxed corrugated cardboard, and paper egg cartons are excellent choices. These materials help maintain air flow, manage moisture, and contribute to the finished compost structure.
Used coffee grounds are a favorite food source rich in nitrogen, despite their initial acidity. They should be added alongside plenty of bedding material to help neutralize their pH as they decompose. Similarly, staple-free used tea bags and crushed eggshells are beneficial additions. Eggshells provide necessary grit to the worms, aiding in their digestion, and supply calcium to the bin environment.
Materials to Strictly Avoid
Introducing the wrong materials can quickly lead to an unhealthy bin, attracting pests and creating anaerobic conditions that harm the worm colony. The primary foods to strictly avoid are meat, bones, and dairy products. These items break down slowly, produce foul odors as they putrefy, and attract unwanted pests such as rodents and flies.
Avoid adding any oils, fats, or greasy foods, as these materials do not decompose efficiently in the worm bin environment. Fats can go rancid, creating a strong, unpleasant smell, and may coat the worms’ skin, inhibiting their ability to breathe. Worms breathe through their skin, making a clean, permeable environment necessary for their survival.
Highly acidic foods, especially citrus fruits like lemons, oranges, and limes, should be excluded because they can drastically lower the bin’s pH balance. Worms thrive in a near-neutral environment, and too much acid can irritate their skin and create an inhospitable habitat. While small amounts of some acidic foods like tomatoes are acceptable, large quantities should be composted elsewhere.
Finally, materials that are salty, heavily spiced, or highly processed should not be added to the worm farm. Excessive salt can dehydrate the worms and damage their delicate skin. Inorganic materials like plastics, metals, and glossy or heavily bleached paper must also be avoided, as these will not break down and will only contaminate the final product.
Techniques for Successful Feeding
The method of feeding is as important as the food itself to ensure the worm farm operates efficiently. Worms do not possess teeth; instead, they consume the beneficial microorganisms that colonize and break down the organic waste. This means that food preparation is necessary to increase the surface area for microbial action.
Chopping, blending, or even freezing and thawing food scraps are effective preparation techniques. Chopping or blending creates smaller particles, offering microbes more surface area to colonize, which speeds up the decomposition process. Freezing and thawing scraps causes the water inside the food’s cells to expand, rupturing the cell walls and effectively pre-softening the material for the microbes.
A good rule of thumb is to only feed the worms again when their previous meal is nearly gone, which prevents overfeeding. Overfeeding is the most common mistake, leading to a build-up of uneaten food that can turn sour and create the anaerobic, low-oxygen conditions worms cannot tolerate. A small colony should be started with minimal food until the population grows.
Always bury the food scraps beneath the bedding, a method known as “pocket feeding.” This practice reduces the presence of fruit flies and other pests while encouraging the worms to venture into the new food source. Rotating the feeding location within the bin each time also ensures the worms move throughout the container, processing the entire volume of bedding and waste evenly.