How to Construct
a Worm Bin (continued...)
Each bin should have a cover to conserve moisture
and exclude light. Worms prefer darkness. Bins can
be covered with a straw mulch or moist burlap to ensure
darkness while providing good air ventilation. Outside
bins may require a lid to exclude scavengers and other
Outdoor bins should be insulated from the cold to
protect the worms. One option is to dig a rectangular
hole 12 inches deep and line the sides with wooden
planks. The bottomless box can then be filled with
appropriate bedding material, food wastes, and worms.
Food wastes can be continually added as they accumulate.
The pile should be kept damp and dark for optimum
worm activity. During the winter, soil can be piled
against the edges of the bin and straw placed on top
to protect the worms from cold weather. Do not add
food waste to outdoor bins during the winter because
this could expose the worms to freezing weather.
Bedding for bins can be made from shredded newspapers
(non-glossy), computer paper, or cardboard; shredded
leaves, straw, hay, or dead plants; sawdust; peat
moss; or compost or aged (or composted) manure. Peat
moss should be soaked for 24 hours in water, then
lightly wrung out to ensure it is sufficiently moist.
Grass clippings should be allowed to age before use
because they may decompose too quickly, causing the
compost to heat up. Bedding materials high in cellulose
are best because they help aerate the bin so the worms
can breathe. Varying the bedding material provides
a richer source of nutrients. Some soil or sand can
be added to help provide grit for the worms digestive
systems. Allow the bedding material to set for several
days to make sure it doesn't heat up (and allow to
cool before adding worms).
The bedding material should be thoroughly moistened
(about the consistency of a damp sponge) before adding
the worms. Fill the bin three-quarters full of moist
bedding, lifting it gently afterwards to create air
space for the worms to breathe and to control odors.
Adding the Worms
Under optimum conditions, redworms can eat their
own weight in food scraps and bedding in one day.
On the average, however, it takes approximately 2
pounds of earthworms (approximately 2,000 breeders)
to recycle a pound of food waste in 24 hours. The
same quantity of worms requires about 4 cubic feet
of bin to process the food waste and bedding (1 cubic
foot of worm bin/500 worms).
Composting worms can be purchased from dealers listed
in the ad sections of many garden magazines. Some
dealers sell worms as pit-run worms, which consist
of worms of all ages and sizes. Add worms to the top
of the moist bedding when they arrive. The worms will
disappear into the bedding within a few minutes.
Adding Food Waste
Earthworms eat all kinds of food and yard wastes,
including coffee grounds, tea bags, vegetable and
fruit waste, pulverized egg shells, grass clippings,
manure, and sewage sludge. Avoid bones, dairy products,
and meats that may attract pests, and garlic, onions,
and spicy foods. Limited amounts of citrus can be
added, but too much can make the compost too acidic.
The compost should be kept at a pH of 6.5 if possible,
with upper and lower limits at 7.0 and 6.0, respectively.
Overly acidic compost can be corrected by adding crushed
eggshells. Avoid adding chemicals (including insecticides),
metals, plastics, glass, soaps, pet manures, and oleanders
or other poisonous plants, or plants sprayed with
insecticides to the worm bin. Food wastes should be
added to the bin by pulling back the bedding material
and burying it. Be sure to cover it well to avoid
attracting flies and other pests. Successive loads
of waste should be buried at different locations in
the bin to keep the food wastes from accumulating.
Grinding or blending the food waste in a food processor
speeds the composting time considerably.