Organic Gardener's Composting
By Steve Solomon
CHAPTER SIX
Vermicomposting
It was 1952 and Mr. Campbell had a worm bin. This shallow box--about
two feet wide by four feet long--resided under a worktable in the
tiny storeroom/greenhouse adjacent to our grade school science
class. It was full of what looked like black, crumbly soil and
zillions of small, red wiggly worms, not at all like the huge
nightcrawlers I used to snatch from the lawn after dark to take
fishing the next morning. Mr. Campbell's worms were fed used coffee
grounds; the worms in turn were fed to salamanders, to Mr.
Campbell's favorite fish, a fourteen-inch long smallmouth bass named
Carl, to various snakes, and to turtles living in aquariums around
the classroom. From time to time the "soil" in the box was fed to
his lush potted plants.
Mr. Campbell was vermicomposting. This being before the age of
ecology and recycling, he probably just thought of it as raising
live food to sustain his educational menagerie. Though I never had
reason to raise worms before, preparing to write this book perked my
interest in every possible method of composting. Not comfortable
writing about something I had not done, I built a small worm box,
obtained a pound or so of brandling worms, made bedding, added
worms, and began feeding the contents of my kitchen compost bucket
to the box.
To my secret surprise, vermicomposting works just as Mary Appelhof's
book _Worms Eat My Garbage_ said it would. Worm composting is
amazingly easy, although I admit there was a short learning curve
and a few brief spells of sour odors that went away as soon as I
stopped overfeeding the worms. I also discovered that my slapdash
homemade box had to have a drip catching pan beneath it. A friend of
mine, who has run her own in-the-house worm box for years, tells me
that diluting these occasional, insignificant and almost odorless
dark-colored liquid emissions with several parts water makes them
into excellent fertilizer for house plants or garden.
It quickly became clear to me that composting with worms
conveniently solves several recycling glitches. How does a northern
homeowner process kitchen garbage in the winter when the ground and
compost pile are frozen and there is no other vegetation to mix in?
And can an apartment dweller without any other kind of organic waste
except garbage and perhaps newspaper recycle these at home? The
solution to both situations is vermicomposting.
Worm castings, the end product of vermicomposting, are truly the
finest compost you could make or buy. Compared to the volume of
kitchen waste that will go into a worm box, the amount of castings
you end up with will be small, though potent. Apartment dwellers
could use worm castings to raise magnificent house plants or scatter
surplus casts under the ornamentals or atop the lawn around their
buildings or in the local park.
In this chapter, I encourage you to at least try worm composting. I
also answer the questions that people ask the most about using worms
to recycle kitchen garbage. As the ever-enthusiastic Mary Applehof
said:
"I hope it convinces you that you, too, can vermicompost, and that
this simple process with the funny name is a lot easier to do than
you thought. After all, if worms eat my garbage, they will eat
yours, too."
Locating the Worms
The species of worm used for vermicomposting has a number of common
names: red worms, red wigglers, manure worms, or brandling worms.
Redworms are healthy and active as long as they are kept above
freezing and below 85 degree. Even if the air temperature gets above
85 degree, their moist bedding will be cooled by evaporation as long
as air circulation is adequate. They are most active and will
consume the most waste between 55-77 degree--room temperatures.
Redworms need to live in a moist environment but must breath air
through their skin. Keeping their bedding damp is rarely the
problem; preventing it from becoming waterlogged and airless can be
a difficulty.
In the South or along the Pacific coast where things never freeze
solid, worms may be kept outside in a shallow shaded pit (as long as
the spot does not become flooded) or in a box in the garage or
patio. In the North, worms are kept in a container that may be
located anywhere with good ventilation and temperatures that stay
above freezing but do not get too hot. Good spots for a worm box are
under the kitchen sink, in the utility room, or in the basement. The
kitchen, being the source of the worm's food, is the most
convenient, except for the danger of temporary odors.
If you have one, a basement may be the best location because it is
out of the way. While you are learning to manage your worms there
may be occasional short-term odor problems or fruit flies; these
won't be nearly as objectionable if the box is below the house. Then
too, a vermicomposter can only exist in a complex ecology of soil
animals. A few of these may exit the box and be harmlessly found
about the kitchen. Ultra-fastidious housekeepers may find this
objectionable. Basements also tend to maintain a cooler temperature
in summer. However, it is less convenient to take the compost bucket
down to the basement every few days.
Containers
Redworms need to breathe oxygen, but in deep containers bedding can
pack down and become airless, temporarily preventing the worms from
eating the bottom material. This might not be so serious because you
will stir up the box from time to time when adding new food. But
anaerobic decomposition smells bad. If aerobic conditions are
maintained, the odor from a worm box is very slight and not
particularly objectionable. I notice the box's odor only when I am
adding new garbage and get my nose up close while stirring the
material. A shallow box will be better aerated because it exposes
much more surface area. Worm bins should be from eight to twelve
inches deep.
I constructed my own box out of some old plywood. A top is not
needed because the worms will not crawl out. In fact, when worm
composting is done outdoors in shallow pits, few redworms exit the
bottom by entering the soil because there is little there for them
to eat. Because air flow is vital, numerous holes between 1/4 and
1/2 inch in diameter should be made in the bottom and the box must
then have small legs or cleats about 1/2 to 3/4 of an inch thick to
hold it up enough to let air flow beneath. Having a drip-catcher--a
large cookie tray works well--is essential. Worms can also be kept
in plastic containers (like dish pans) with holes punched in the
bottom. As this book is being written, one mail-order garden supply
company even sells a tidy-looking 19" by 24" by about 12" deep green
plastic vermicomposting bin with drip pan, lid, and an initial
supply of worms and bedding. If worm composting becomes more
popular, others will follow suit.
Unless you are very strong do not construct a box larger than 2 x 4
feet because they will need to be lifted from time to time. Wooden
boxes should last three or four years. If built of plywood, use an
exterior grade to prevent delamination. It is not advisable to make
containers from rot-resistant redwood or cedar because the natural
oils that prevent rotting also may be toxic to worms. Sealed with
polyurethane, epoxy, or other non-toxic waterproofing material, worm
boxes should last quite a bit longer.
How big a box or how many boxes do you need? Each cubic foot of worm
box can process about one pound of kitchen garbage each week.
Naturally, some weeks more garbage will go into the box than others.
The worms will adjust to such changes. You can estimate box size by
a weekly average amount of garbage over a three month time span. My
own home-garden-supplied kitchen feeds two "vegetableatarian"
adults. Being year-round gardeners, our kitchen discards a lot of
trimmings that would never leave a supermarket and we throw out as
"old," salad greens that are still fresher than most people buy in
the store. I'd say our 2-1/2 gallon compost bucket is dumped twice a
week in winter and three times in summer. From May through September
while the garden is "on," a single, 2 foot x 4 foot by 12 inch tall
(8 cubic foot) box is not enough for us.
Bedding
Bedding is a high C/N material that holds moisture, provides an
aerobic medium worms can exist in, and allows you to bury the
garbage in the box. The best beddings are also light and airy,
helping to maintain aerobic conditions. Bedding must not be toxic to
worms because they'll eventually eat it. Bedding starts out dry and
must be first soaked in water and then squeezed out until it is
merely very damp. Several ordinary materials make fine bedding. You
may use a single material bedding or may come to prefer mixtures.
If you have a power shredder, you can grind corrugated cardboard
boxes. Handling ground up cardboard indoors may be a little dusty
until you moisten it. Shredded cardboard is sold in bulk as
insulation but this material has been treated with a fire retardant
that is toxic. Gasoline-powered shredders can also grind up cereal
straw or spoiled grass hay (if it is dry and brittle). Alfalfa hay
will decompose too rapidly.
Similarly, shredded newsprint makes fine bedding. The ink is not
toxic, being made from carbon black and oil. By tearing with the
grain, entire newspaper sections can rapidly be ripped into
inch-wide shreds by hand. Other shredded paper may be available from
banks, offices, or universities that may dispose of documents.
Ground-up leaves make terrific bedding. Here a power shredder is not
necessary. An ordinary lawnmower is capable of chopping and bagging
large volumes of dry leaves in short order. These may be prepared
once a year and stored dry in plastic garbage bags until needed. A
few 30-gallon bags will handle your vermicomposting for an entire
year. However, dry leaves may be a little slower than other
materials to rehydrate.
Peat moss is widely used as bedding by commercial worm growers. It
is very acid and contains other substances harmful to worms that are
first removed by soaking the moss for a few hours and then
hand-squeezing the soggy moss until it is damp. Then a little lime
is added to adjust the pH.
Soil
Redworms are heat-tolerant litter dwellers that find little to eat
in soil. Mixing large quantities of soil into worm bedding makes a
very heavy box. However, the digestive system of worms grinds food
using soil particles as the abrasive grit in the same way birds
"chew" in their crop. A big handful of added soil will improve a
worm box. A couple of tablespoonfuls of powdered agricultural lime
does the same thing while adding additional calcium to nourish the
worms.
Redworms
The scientific name of the species used in vermicomposting is
_Eisenia foetida._ They may be purchased by mail from breeders, from
bait stores, and these days, even from mail-order garden supply
companies. Redworms may also be collected from compost and manure
piles after they have heated and are cooling.
Nightcrawlers and common garden worms play a very important part in
the creation and maintenance of soil fertility. But these species
are soil dwellers that require cool conditions. They cannot survive
in a shallow worm box at room temperatures.
Redworms are capable of very rapid reproduction at room temperatures
in a worm box. They lay eggs encased in a lemon-shaped cocoon about
the size of a grain of rice from which baby worms will hatch. The
cocoons start out pearly white but as the baby worms develop over a
three week period, the eggs change color to yellow, then light
brown, and finally are reddish when the babies are ready to hatch.
Normally, two or three young worms emerge from a cocoon.
Hatchlings are whitish and semi-transparent and about one-half inch
long. It would take about 150,000 hatchlings to weigh one pound. A
redworm hatchling will grow at an explosive rate and reach sexual
maturity in four to six weeks. Once it begins breeding a redworm
makes two to three cocoons a week for six months to a year; or, one
breeding worm can make about 100 babies in six months. And the
babies are breeding about three months after the first eggs are
laid.
Though this reproductive rate is not the equal of yeast (capable of
doubling every twenty minutes), still a several-hundred-fold
increase every six months is amazingly fast. When vermicomposting,
the worm population increase is limited by available food and space
and by the worms' own waste products or casts. Worm casts are
slightly toxic to worms. When a new box starts out with fresh
bedding it contains no casts. As time goes on, the bedding is
gradually broken down by cellulose-eating microorganisms whose decay
products are consumed by the worms and the box gradually fills with
casts.
As the proportion of casts increases, reproduction slows, and mature
worms begin to die. However, you will almost never see a dead worm
in a worm box because their high-protein bodies are rapidly
decomposed. You will quickly recognize worm casts. Once the bedding
has been consumed and the box contains only worms, worm casts, and
fresh garbage it is necessary to empty the casts, replace the
bedding, and start the cycle over. How to do this will be explained
in a moment. But first, how many worms will you need to begin
vermicomposting?
You could start with a few dozen redworms, patiently begin by
feeding them tiny quantities of garbage and in six months to a year
have a box full. However, you'll almost certainly want to begin with
a system that can consume all or most of your kitchen garbage right
away. So for starters you'll need to obtain two pounds of worms for
each pound of garbage you'll put into the box each day. Suppose in
an average week your kitchen compost bucket takes in seven pounds of
waste or about one gallon. That averages one pound per day. You'll
need about two pounds of worms.
You'll also need a box that holds six or seven cubic feet, or about
2 x 3 feet by 12 inches deep. Each pound of worms needs three or
four cubic feet of bedding. A better way to estimate box size is to
figure that one cubic foot of worm bin can digest about one pound of
kitchen waste a week without going anaerobic and smelling bad.
Redworms are small and consequently worm growers sell them by the
pound. There are about 1,000 mature breeders to the pound of young
redworms. Bait dealers prefer to sell only the largest sizes or
their customers complain. "Red wigglers" from a bait store may only
count 600 to the pound. Worm raisers will sell "pit run" that costs
much less. This is a mix of worms of all sizes and ages. Often the
largest sizes will have already been separated out for sale as fish
bait. That's perfectly okay. Since hatchlings run 150,000 to the
pound and mature worms count about 600-700, the population of a
pound of pit run can vary greatly. A reasonable pit run estimate is
2,000 to the pound.
Actually it doesn't matter what the number is, it is their weight
that determines how much they'll eat. Redworms eat slightly more
than their weight in food every day. If that is so, why did I
recommend first starting vermicomposting with two pounds of worms
for every pound of garbage? Because the worms you'll buy will not be
used to living in the kind of bedding you'll give them nor adjusted
to the mix of garbage you'll feed them. Initially there may be some
losses. After a few weeks the surviving worms will have adjusted.
Most people have little tolerance for outright failure. But if they
have a record of successes behind them, minor glitches won't stop
them. So it is vital to start with enough worms. The _only time
vermicomposting becomes odoriferous is when the worms are fed too
much._ If they quickly eat all the food that they are given the
system runs remarkably smoothly and makes no offense. Please keep
that in mind since there may well be some short-lived problems until
you learn to gauge their intake.
Setting Up a Worm Box
Redworms need a damp but not soggy environment with a moisture
content more or less 75 percent by weight. But bedding material
starts out very dry. So weigh the bedding and then add three times
that weight of water. The rule to remember here is "a pint's a pound
the world 'round," or one gallon of water weighs about eight pounds.
As a gauge, it takes 1 to 1-1/2 pounds of dry bedding for each cubic
foot of box.
Preparing bedding material can be a messy job The best container is
probably an empty garbage can, though in a pinch it can be done in a
kitchen sink or a couple of five gallon plastic buckets. Cautiously
put half the (probably dusty) bedding in the mixing container. Add
about one-half the needed water and mix thoroughly. Then add two
handfuls of soil, the rest of the bedding, and the balance of the
water. Continue mixing until all the water has been absorbed. Then
spread the material evenly through your empty worm box. If you've
measured correctly no water should leak out the bottom vent holes
and the bedding should not drip when a handful is squeezed
moderately hard.
Then add the worms. Spread your redworms over the surface of the
bedding. They'll burrow under the surface to avoid the light and in
a few minutes will be gone. Then add garbage. When you do this the
first time, I suggest that you spread the garbage over the entire
surface and mix it in using a three-tined hand cultivator. This is
the best tool to work the box with because the rounded points won't
cut worms.
Then cover the box. Mary Applehof suggests using a black plastic
sheet slightly smaller than the inside dimensions of the container.
Black material keeps out light and allows the worms to be active
right on the surface. You may find that a plastic covering retains
too much moisture and overly restricts air flow. When I covered my
worm box with plastic it dripped too much. But then, most of what I
feed the worms is fresh vegetable material that runs 80-90 percent
water. Other households may feed dryer material like stale bread and
leftovers. I've found that on our diet it is better to keep the box
in a dimly lit place and to use a single sheet of newspaper folded
to the inside dimensions of the box as a loose cover that encourages
aeration, somewhat reduces light on the surface, and lessens
moisture loss yet does not completely stop it.
Feeding the Worms
Redworms will thrive on any kind of vegetable waste you create while
preparing food. Here's a partial list to consider: potato peelings,
citrus rinds, the outer leaves of lettuce and cabbage, spinach
stems, cabbage and cauliflower cores, celery butts, plate scrapings,
spoiled food like old baked beans, moldy cheese and other leftovers,
tea bags, egg shells, juicer pulp. The worms' absolute favorite
seems to be used coffee grounds though these can ferment and make a
sour smell.
Drip coffee lovers can put the filters in too. This extra paper
merely supplements the bedding. Large pieces of vegetable matter can
take a long time to be digested. Before tossing cabbage or
cauliflower cores or celery butts into the compost bucket, cut them
up into finer chunks or thin slices. It is not necessary to grind
the garbage. Everything will break down eventually.
Putting meat products into a worm box may be a mistake. The odors
from decaying meat can be foul and it has been known to attract mice
and rats. Small quantities cut up finely and well dispersed will
digest neatly. Bones are slow to decompose in a worm box. If you
spread the worm casts as compost it may not look attractive
containing whitened, picked-clean bones. Chicken bones are soft and
may disappear during vermicomposting. If you could grind bones
before sending them to the worm bin, they would make valuable
additions to your compost. Avoid putting non-biodegradable items
like plastic, bottle caps, rubber bands, aluminum foil, and glass
into the worm box.
Do not let your cat use the worm bin as a litter box.. The odor of
cat urine would soon become intolerable while the urine is so high
in nitrogen that it might kill some worms. Most seriously, cat
manure can transmit the cysts of a protozoan disease organism called
_Toxoplasma gondii,_ although most cats do not carry the disease.
These parasites may also be harbored in adult humans without them
feeling any ill effects. However, transmitted from mother to
developing fetus, _Toxoplasma gondii _can cause brain damage. You
are going to handle the contents of your worm bin and won't want to
take a chance on being infected with these parasites.
Most people use some sort of plastic jar, recycled half-gallon
yogurt tub, empty waxed paper milk carton, or similar thing to hold
kitchen garbage. Odors develop when anaerobic decomposition begins.
If the holding tub is getting high, don't cover it, feed it to the
worms.
It is neater to add garbage in spots rather than mixing it
throughout the bin. When feeding garbage into the worm bin, lift the
cover, pull back the bedding with a three-tine hand cultivator, and
make a hole about the size of your garbage container. Dump the waste
into that hole and cover it with an inch or so of bedding. The whole
operation only takes a few minutes. A few days later the kitchen
compost bucket will again be ready. Make and fill another hole
adjacent to the first. Methodically go around the box this way. By
the time you get back to the first spot the garbage will have become
unrecognizable, the spot will seem to contain mostly worm casts and
bedding, and will not give off strongly unpleasant odors when
disturbed.
Seasonal Overloads
On festive occasions, holidays, and during canning season it is easy
to overload the digestive capacity of a worm bin. The problem will
correct itself without doing anything but you may not be willing to
live with anaerobic odors for a week or two. One simple way to
accelerate the "healing" of an anaerobic box is to fluff it up with
your hand cultivator.
Vegetableatarian households greatly increase the amount of organic
waste they generate during summer. So do people who can or freeze
when the garden is "on." One vermicomposting solution to this
seasonal overload is to start up a second, summertime-only outdoor
worm bin in the garage or other shaded location. Appelhof uses an
old, leaky galvanized washtub for this purpose. The tub gets a few
inches of fresh bedding and then is inoculated with a gallon of
working vermicompost from the original bin. Extra garbage goes in
all summer. Mary says:
"I have used for a "worm bin annex" an old leaky galvanized washtub,
kept outside near the garage. During canning season the grape pulp,
corn cobs, corn husks, bean cuttings and other fall harvest residues
went into the container. It got soggy when it rained and the worms
got huge from all the food and moisture. We brought it inside at
about the time of the first frost. The worms kept working the
material until there was no food left. After six to eight months,
the only identifiable remains were a few corn cobs, squash seeds,
tomato skins and some undecomposed corn husks. The rest was an
excellent batch of worm castings and a very few hardy,
undernourished worms."
Vacations
Going away from home for a few weeks is not a problem. The worms
will simply continue eating the garbage left in the bin. Eventually
their food supply will decline enough that the population will drop.
This will remedy itself as soon as you begin feeding the bin again.
If a month or more is going to pass without adding food or if the
house will be unheated during a winter "sabbatical," you should give
your worms to a friend to care for.
Fruit Flies
Fruit flies can, on occasion, be a very annoying problem if you keep
the worm bins in your house. They will not be present all the time
nor in every house at any time but when they are present they are a
nuisance. Fruit flies aren't unsanitary, they don't bite or seek out
people to bother. They seek out over-ripe fruit and fruit pulp.
Usually, fruit flies will hover around the food source that
interests them. In high summer we have accepted having a few share
our kitchen along with the enormous spread of ripe and ripening
tomatoes atop the kitchen counter. When we're making fresh "V-7"
juice on demand throughout the day, they tend to congregate over the
juicer's discharge pail that holds a mixture of vegetable pulps. If
your worm bin contains these types of materials, fruit flies may
find it attractive.
Appelhof suggests sucking them up with a vacuum cleaner hose if
their numbers become annoying. Fruit flies are a good reason for
those of Teutonic tidiness to vermicompost in the basement or
outside the house if possible.
Maintenance
After a new bin has been running for a few weeks, you'll see the
bedding becoming darker and will spot individual worm casts. Even
though food is steadily added, the bedding will gradually vanish.
Extensive decomposition of the bedding by other small soil animals
and microorganisms begins to be significant.
As worm casts become a larger proportion of the bin, conditions
deteriorate for the worms. Eventually the worms suffer and their
number and activity begins to drop off. Differences in bedding,
temperature, moisture, and the composition of your kitchen's garbage
will control how long it takes but eventually you must separate the
worms from their castings and put them into fresh bedding. If you're
using vermicomposting year-round, it probably will be necessary to
regenerate the box about once every four months.
There are a number of methods for separating redworms from their
castings.
_Hand sorting_ works well after a worm box has first been allowed to
run down a bit. The worms are not fed until almost all their food
has been consumed and they are living in nearly pure castings. Then
lay out a thick sheet of plastic at least four feet square on the
ground, floor, or on a table and dump the contents of the worm box
on it.
Make six to nine cone-shaped piles. You'll see worms all over. If
you're working inside, make sure there is bright light in the room.
The worms will move into the center of each pile. Wait five minutes
or so and then delicately scrape off the surface of each conical
heap, one after another. By the time you finish with the last pile
the worms will have retreated further and you can begin with the
first heap again.
You repeat this procedure, gradually scraping away casts until there
is not much left of the conical heaps. In a surprisingly short time,
the worms will all be squirming in the center of a small pile of
castings. There is no need to completely separate the worms from all
the castings. You can now gather up the worms and place them in
fresh bedding to start anew without further inconvenience for
another four months. Use the vermicompost on house plants, in the
garden, or save it for later.
Hand sorting is particularly useful if you want to give a few pounds
of redworms to a friend.
_Dividing the box_ is another, simpler method. You simply remove
about two-thirds of the box's contents and spread it on the garden.
Then refill the box with fresh bedding and distribute the remaining
worms, castings, and food still in the box. Plenty of worms and egg
cocoons will remain to populate the box. The worms that you dumped
on the garden will probably not survive there.
A better method of dividing a box prevents wasting so many worms.
All of the box's contents are pushed to one side, leaving one-third
to one-half of the box empty. New bedding and fresh food are put on
the "new" side. No food is given to the "old" side for a month or
so. By that time virtually all the worms will have migrated to the
"new" side. Then the "old" side may be emptied and refilled with
fresh bedding.
People in the North may want to use a worm box primarily in winter
when other composting methods are inconvenient or impossible. In
this case, start feeding the bin heavily from fall through spring
and then let it run without much new food until mid-summer. By that
time there will be only a few worms left alive in a box of castings.
The worms may then be separated from their castings, the box
recharged with bedding and the remaining worms can be fed just
enough to increase rapidly so that by autumn there will again be
enough to eat all your winter garbage.
Garbage Can Composting
Here's a large-capacity vermicomposting system for vegetableatarians
and big families. It might even have sufficient digestive capacity
for serious juice makers. You'll need two or three, 20 to 30 gallon
garbage cans, metal or plastic. In two of them drill numerous
half-inch diameter holes from bottom to top and in the lid as well.
The third can is used as a tidy way to hold extra dry bedding.
Begin the process with about 10 inches of moist bedding material and
worms on the bottom of the first can. Add garbage on top without
mixing it in and occasionally sprinkle a thin layer of fresh
bedding.
Eventually the first can will be full though it will digest hundreds
of gallons of garbage before that happens. When finally full, the
bulk of its contents will be finished worm casts and will contain
few if any worms. Most of the remaining activity will be on the
surface where there is fresh food and more air. Filling the first
can may take six months to a year. Then, start the second can by
transferring the top few inches of the first, which contains most of
the worms, into a few inches of fresh bedding on the bottom of the
second can. I'd wait another month for the worms left in the initial
can to finish digesting all the remaining garbage. Then, you have 25
to 30 gallons of worm casts ready to be used as compost.
Painting the inside of metal cans with ordinary enamel when they
have been emptied will greatly extend their life. Really high-volume
kitchens might run two vermicomposting garbage cans at once.
For those of you who read this entire chaper and think I might be violating copyright laws - let me put your mind at ease.
This book is in the public domain - so no royalties are due for sharing the content in this format.