Worm composting: setting up and feeding a worm bin
A worm bin turns small, regular amounts of food scraps into worm compost in a closed box that fits indoors. This chapter helps you decide whether one suits your week, then sizes, beds and feeds it.
- Start here: the essentials
- Is a worm bin for you?
- Size the bin and choose the worms
- Bedding, moisture and where the bin sits
- Feeding, and what to do when it goes wrong
- Harvesting the worm compost
- The sources side by side
- See it: Noor weighs a bin and waits
- Practice: decide, then size and start
- Your system
- Check your work
- Knowledge check and scenario
Start here Essentials
For a first pass, this chapter asks for one decision and, if the answer is yes, one small bin started and checked after a week. A written no finishes the chapter.
- Decide whether a worm bin fits your space and your week, and write yes or no on the system plan. The questions are in the first section (is a worm bin for you, system plan).
- If yes, weigh one week of food scraps and size the bin with the calculator. Order red wiggler worms, not garden worms (size the bin, worm calculator).
- Bed the bin, add the worms, and feed a small amount buried under the bedding. Start well below what the worms could eat (bedding, feeding).
- Check the bin a week later and log moisture, smell and how much food is left. (feeding, worm log).
Minimum time: the decision is one sitting. A yes adds one setup day and a check a week later. Done when: the plan says yes or no, and for a yes, the worm log shows a set-up date and the first week's check.
Is a worm bin for you? Understand
Vermicomposting is composting with worms. A small number of worms live in a bin of damp bedding (shredded paper or similar material), eat food scraps along with the bedding, and leave castings (their droppings). The mixture of castings and partly decomposed bedding is vermicompost, or worm compost. No heat is involved: Oregon State describes vermicomposting as a cold process that relies on microorganisms and worms, and says it does not destroy weed seeds (Oregon State's EM 9034).
EPA says a worm bin can sit indoors, for example under a sink, in a closet or in a basement, or outdoors in the shade (EPA's Composting at Home page). New York City's worm bin brochure is written for households without outdoor space (NYC Compost Project's indoor worm bin brochure). Four questions help you decide.
| Question | If yes | If no |
|---|---|---|
| Do you make food scraps in small, regular amounts (fruit and vegetable scraps, coffee grounds, tea bags)? | A bin sized to your weekly scraps can keep up. Weigh a week of them first | Yard waste does not suit a worm bin. A bin or a leaf cage does (The slow pile) |
| Is there a place indoors or in shade that stays in the range worms like, roughly 55 to 77°F? | Go on to size the bin | An outdoor bin in a hot or cold climate needs more care (Go deeper); a drop-off may suit better (Kitchen and collection) |
| Will you feed it in small amounts and check it, every few days to weekly? | Feeding is the main task: a small amount, buried, then a look | A bin that is not checked can overfeed or dry out. A slow pile asks for less |
| Can you give the meat, dairy and oily food a different route? | Those stay out of a worm bin; use the trash, a drop-off or bokashi (Bokashi and burying) | A worm bin does not take them; a method that does, or a program, may suit better |
Attention here is tasks and how often: feed in small amounts, bury the food, look at moisture and smell. We give no minutes, because no source does. Oregon State contrasts vermicomposting with conventional composting, which it says needs frequent turning and complex ratios; a worm bin's tasks are small and regular instead.
Write the answer on the plan. A no that names what you will do instead is a complete result, and a yes is a plan to start small and let the bin set the pace.
Size the bin and choose the worms
The worm
The worm used in bins is Eisenia fetida, the red wiggler (also called red worm, tiger worm or manure worm). It is a surface dweller that lives in decaying litter, not in the soil. NC State says that of more than 9,000 earthworm species, only 7 suit vermicomposting, and one is used by most people (NC State's Worms Can Recycle Your Garbage). Oregon State says the common garden earthworm and the European nightcrawler are burrowing worms and are not the worm you want, and NYC's brochure says garden worms and nightcrawlers will not survive in a worm bin. NC State advises against taking worms from a bait shop or your yard. Oregon State lists other sources: a commercial worm grower, an outdoor compost or manure pile, a friend's or neighbor's bin, a Master Gardener program or a local solid waste district. Ask for Eisenia fetida by name and check the species before you pay.
The bin
Any opaque container with a tight lid, air holes and a way to drain can be a bin; plastic totes are the common choice. Worms are sensitive to light, and Oregon State says to use an opaque bin. Oregon State's two-tote design (a top tote with air and drainage holes, nested in a second tote that collects the liquid) and NC State's drilling instructions are two ways to make one. Do not use pressure-treated wood or wood with a natural pest deterrent such as cedar, by Oregon State.
How big
The default is NC State's rule of thumb: about one square foot of bin surface for each pound of food scraps you add per week. Convention The surface matters more than the depth, because red wigglers live near the top. NC State gives 8 to 20 inches for the depth in its example; Oregon State says no more than a foot, and WSU's Thurston County master composters say about 12 inches is best (WSU Thurston County's worm composting tip sheet). We use about 8 to 12 inches and the calculator's default of 10. To find your weight, weigh your food-scrap container once at the end of a week and use that figure. What goes in's scrap log gives the gallons; a gallon of scraps has no standard weight, so the weighing is the step that matters.
| Food scraps per week | Surface by NC State's rule | Example |
|---|---|---|
| 1 pound | 1 square foot | A bin about 12 by 12 inches |
| 2 pounds | 2 square feet | NC State's example: 2 feet by 1 foot |
| 3 pounds | 3 square feet | By the rule, not a source's example |
| 6 pounds | 6 square feet | Oregon State's example for a family of four to six: 1 foot deep, 2 feet by 3 feet |
The worm calculator does this arithmetic and shows the range of worm numbers. Oregon State's own example is a common 14-gallon tote, 1 by 1 by 2 feet, which it says suits about 2 pounds of kitchen waste a week.
How many worms to start
Our default is about a pound of worms for each pound of food scraps a week. Oregon State puts it as about 1 cubic foot of bin space and 1 pound of food waste for each pound of worms, and NC State says to start with at least a pound of red wigglers (about 1,000) per square foot of surface. The calculator also shows a lower figure, half a pound, because NC State also says a pound of worms eats up to two pounds of food a week. These numbers differ between sources; the comparison is under Go deeper. Starting with fewer worms than the bin could carry means the first weeks need a lighter hand with the food.
Bedding, moisture and where the bin sits
Bedding
Bedding gives the worms a damp, airy home and part of their diet. Suitable materials by NC State are shredded black-and-white newspaper, paper bags, office paper or cardboard, decaying leaves and coir (coconut fiber). Oregon State suggests mixing at least two or three of its materials, lists straw (not hay with seed) and shredded partly decomposed leaves, and says not to use cross-cut shredded paper because it can compact. Both say not to use glossy paper. Convention Oregon State says to put in 4 to 6 inches of bedding and to keep a 2-inch layer of fresh bedding over the worms and food.
The moisture target is a wrung-out sponge. Oregon State's version is that only a few drops come out when you squeeze a handful; NC State's is two to three drops, a little wetter than a moist sponge. Soak the bedding for 5 to 10 minutes and wring it out (NC State). Fluff it as you add it. Use a spray bottle to moisten later, and do not pour water into the bin. Grit helps the worms break down food in their gizzards: NC State adds a handful of garden soil; Oregon State suggests crushed eggshell, oyster shell or a little sand about every couple of months.
Temperature and place
Oregon State and WSU Thurston County give about 55 to 77°F as the range where red wigglers do best. Your apartment, a closet or a shaded porch is often in range for part of the year. Keep the bin out of direct sun; NC State says sun can overheat the bin and kill the worms. Outdoors, put it in shade, and secure it against rodents, raccoons and other animals (Oregon State). Keep it away from washers and dryers and heavy foot traffic, because vibration can make the worms leave the bin. No source we read gives a temperature at which worms die, so we give none; the Go deeper table lists the ranges the sources do give.
Setting up
- Prepare the bin before the worms arrive. Drill the air and drainage holes, set the drip tray, and add moist bedding (NC State: about halfway up the bin; Oregon State: 4 to 6 inches).
- Add the worms on top of the bedding. Oregon State describes three ways to introduce them: with a few days of food already in, with a few days to settle before the first food, or both together. Watch them every day for the first weeks.
- Wait a couple of days, then add the first small amount of food. NC State says the food should not exceed 1 inch in height.
- Close the lid and write the date in the worm log.
Feeding, and what to do when it goes wrong
How much
The default is to start low. Oregon State says to add about a quarter to a half pound of food scraps per pound of worms per week at first, and to increase gradually as the worms multiply if the bin stays between 55 and 77°F. Convention Other sources give much higher figures for an established bin, and the difference is why we start low (Go deeper). Under these figures, a bin with a pound of worms starts at about a quarter to a half pound of scraps a week. NC State advises waiting to add more until the worms have eaten the previous food.
How to feed
Chop scraps small; Oregon State suggests pieces of half an inch to an inch or smaller, and NYC suggests one to two inches. Bury them, by pulling the bedding aside, putting the food in and covering it with 1 to 2 inches of bedding (NC State), and use a different spot each time. NYC says to store scraps in the freezer or refrigerator between feedings. Freezing fruit before it goes in also helps with fruit flies, below. NYC suggests freezing fruit or microwaving it for 60 seconds to kill eggs.
What goes in and what stays out
- In: fruit and vegetable scraps, coffee grounds, filters and tea bags with staples removed, crushed eggshells, and small wet amounts of plain bread, cereal or pasta (Oregon State, NC State).
- Out: meat, fish and poultry; dairy; oils and greasy food; pet waste; and, by NC State and Oregon State, citrus and onions (NYC says to avoid large amounts of citrus). Oregon State's guideline: when in doubt, leave it out.
Check it each week
Open the bin about once a week and write what you see in the worm log: food added, bedding added, moisture, bin temperature, fruit flies and a note. Look for untouched food. Oregon State says untouched food two to three weeks after you added it means you have overfed; stop feeding and wait up to two weeks.
| What you see | Likely cause (Oregon State) | First change |
|---|---|---|
| Bad smell, flies, wet bedding | Too wet, or food exposed | Add a 4-inch layer of dry bedding and stop feeding for two to three weeks |
| Fruit flies | Food exposed, or too much fruit | Bury and cover food; freeze fruit first; cover the bedding with damp cardboard; stop feeding for two to three weeks |
| Ants | Bedding too dry | Moisten the bedding |
| Worms dying or leaving | Too much food, too wet or dry, or extreme temperatures | Reduce the food; check moisture and where the bin sits |
| Sowbugs and beetles | Common | Oregon State says they coexist with worms; leave them |
Fruit flies at the kitchen container are Kitchen and collection's question: see fruit flies. The troubleshooting table has the rest. If you will be away two to three weeks, Oregon State says to feed well before you leave and check the bedding and the temperature.
The sources' feeding figures differ by about three and a half times, from about 1 pound of food per pound of worms a week to half the worms' weight a day. This manual starts low and lets the bin's condition set the pace; a bin that is eating, smelling earthy and not drawing flies is giving you the answer for that bin. No source we read gives a lethal temperature, so this manual gives none, only the ranges the sources call best or tolerated. A worm bin takes small amounts of food scraps. It is not sized for yard waste, and it does not destroy weed seeds. What to do with the worm compost, and in what amount, is Finished compost's question.
Wash your hands thoroughly with soap after handling worms or the bin, as Oregon State advises. It notes that bins also hold fungi and molds, and to be aware of allergies to spores. If you have a weakened immune system or a lung condition, ask your doctor about handling a bin. Ask a doctor
Harvesting the worm compost
Oregon State and NYC both give about three to six months from set-up to finished worm compost; NC State says about four months, and WSU Thurston County says 6 to 12 months. Oregon State's signs are a look like crumbly chocolate cake and an earthy, fresh smell. It also says to harvest at least twice a year, because castings at high concentration are unhealthy for the worms. Convention The worms are still in the compost, and there are three common ways to separate them.
- Migration to one side (our default). NC State says to feed on one side of the bin only for several weeks, and most of the worms move there. Then remove the compost from the other side. NYC calls this the easy way and puts it at about a month. Oregon State's bait-and-switch version works for bins over 2 cubic feet.
- Light and scrape. Spread the contents on a sheet in strong light. The worms move away from the light, and you scrape off the top layer every few minutes (NC State). Oregon State's dump-and-sort version waits about 20 minutes and calls it the most recommended method.
- Stacked bins. Two bins in a stack, with food only in the top one (NC State).
Return worms and their lemon-shaped egg capsules to the bin; NC State says each holds two to seven baby worms. Oregon State says worms do not digest seeds and the bin does not get hot enough to kill them, so volunteer seedlings may appear where you use it. Worms in a potted plant do not do well, so remove them first (Oregon State, NC State). Finished compost covers the signs, the germination test and where to use it: using finished compost.
The sources side by side Go deeper
The chapter gave one default per decision: NC State's surface rule, Oregon State's starting feed, a depth of about 8 to 12 inches, and a range near 55 to 77°F. This section shows what the other sources say. The Limits box above applies to everything here. The Penn State figures come from a Master Gardener article on an extension site and describe one gardener's setup.
Feeding rate, per pound of worms
| Source | What it says | As food per pound of worms per week |
|---|---|---|
| Oregon State EM 9034 | Start with 1/4 to 1/2 pound of food per pound of worms per week; the bin rule is 1 pound of food per pound of worms; it also says a worm can eat as much as its own weight a day | 0.25 to 0.5 at the start; 1 at the bin rule |
| WSU Thurston County (Rule of One) | 1 pound of food per 1 pound of worms per 1 square foot per week, for 1 to 2 people | 1 |
| Penn State article | A pound of red wigglers in an established bin eats about a half pound to a pound of scraps each week | 0.5 to 1 |
| NC State AG-473-18 | A pound of red wigglers will eat up to two pounds of food scraps a week | Up to 2 |
| NYC Compost Project | One pound of worms can process about three and a half pounds a week; red wigglers can eat half their body weight a day | 3.5 |
| UC Master Gardeners of Orange County | A pound of worms will eat about half a pound of food per day | 3.5 |
The rates run from about 1 to 3.5 pounds a week where a source gives a bin rule, about three and a half times, and Penn State's half-pound low end and our starting 0.25 to 0.5 sit below that. The sources do not say what the bin was like when the figure was measured, so we cannot pick one. The sources do not say what bin each figure was measured in, so we cannot pick one, and a new bin has not yet shown what it can eat. Hence the low start.
Bin density, worms per pound and depth
| Item | What the sources say |
|---|---|
| Surface or volume per pound of food a week | NC State: 1 square foot. Oregon State: 1 cubic foot. WSU Thurston: 1 square foot (Rule of One) |
| Worms per bin | NC State: at least 1 pound per square foot of surface. Oregon State: 1 pound per cubic foot. UC Orange County: about 1/4 pound of worms per cubic foot, and about 4 cubic feet for a starting pound |
| Worms per pound | NC State and Oregon State: about 1,000. WSU Thurston: 600 to 1,200, about a pint. Oregon State adds that a purchased pound may include bedding |
| Depth | NC State: 8 to 20 inches in its example. Oregon State: no more than 1 foot. WSU Thurston: about 12 inches is best. UC Orange County: 8 to 12 inches |
| Bedding depth | Oregon State: 4 to 6 inches. Penn State: about 6 inches. NC State: fill the bin about halfway. NYC: about two-thirds |
Temperature
| Source | Range it gives |
|---|---|
| Oregon State | Do best 55 to 77°F; tolerate 40 to 90°F; peak activity 71 to 89°F; less active below 50°F |
| NC State | Keep the bin at 59 to 77°F; lists limits of 32 to 95°F |
| NYC | Prefer 55 to 80°F |
| WSU Thurston | Ideal bin 50 to 80°F; thrive 55 to 77°F |
| Penn State article | Indoors, 60 to 75°F |
These are the ranges each source calls best, ideal or limits. None gives the temperature at which worms die, though NC State says direct sun can overheat the bin and kill them, and Oregon State says worms in a bin buried outdoors may die in an unusually cold or wet winter.
Time to harvest
Oregon State and NYC: three to six months. NC State: about four months. WSU Thurston County: 6 to 12 months. Your time depends on the number of worms, the feeding and the temperature.
Outdoor bins in cold and hot climates
Oregon State prefers the north side of a structure, where temperatures vary less, with protection from rain and wind. For heat it suggests painting a wooden bin white on the outside. For cold it suggests a frost-free space, or burying the bottom half of the bin and insulating with straw or leaves, with a risk that the worms die in an unusually cold or wet winter; it says worms eat at about half the summer rate in cold. WSU Thurston County says to move a portable bin to an insulated place or to add insulation in winter. If your climate freezes or has hot, dry summers, your worm log with the bin temperature column is the record to keep.
The liquid that drains out
Leachate is the liquid that drains from the bin. Sources differ. Oregon State says diluted leachate (10 parts water to 1 part leachate) can be used in the garden; WSU Thurston County describes a 10 to 1 dilution used within 24 hours and says to discard leachate (we do not teach worm tea); NC State's gardener handbook says not to use leachate on food crops (NC State's Extension Gardener Handbook). No source gives a dilution that settles the question for food crops. We give no use for it in this manual.
See it: Noor weighs a bin and waits See it
Noor Haddad is a fictional person, and every fact about her here is invented for this manual. She is 28 and lives alone in a fourth-floor apartment with no balcony, kept between 64 and 72°F. Her scrap log shows 1 gallon in her first week, including some cooked rice and cheese rinds. She takes scraps to a weekly Saturday drop-off at a farmers market 0.8 miles away, May through November, and to a library branch on Wednesdays in winter. Her kitchen container is a lidded 1-gallon container in the freezer, emptied each Saturday. Cooked food with oil or dairy goes in the trash.
Known: her apartment range, 64 to 72°F, sits inside every temperature range in the table above, from 55 to 77°F at Oregon State to 60 to 75°F at Penn State. Under the assumption that her week of scraps weighs about 1 pound, the calculator gives about 1 square foot of bin. Her assumptions: the weight of a gallon of her scraps, which she has not weighed; a pound of worms for that pound of weekly food. Open: the real weekly weight (a scale settles it); whether she will keep up regular small feedings (running a bin for a season settles it); what the drop-off does with worm compost, if she ever wants to give it away (the program's list settles it).
What she would do if she starts. The cheese rinds stay out, as dairy. She would bury fruit and vegetable scraps in a 1 by 1 foot bin or a common 14-gallon tote, which Oregon State's example sizes for about 2 pounds a week. She would start with a quarter to a half pound of scraps a week. The bin would stay in the apartment's range, out of the sun.
What she decides. She decides to wait one season and review the question in Your compost system. The plan line reads: "Worm bin: not yet. Wait one season, keep the freezer container and the drop-off. Review in Your compost system." The decision is complete, and the calculator's number is saved for the review.
Jun and Lena Ito are fictional, and every fact about them here is invented for this manual. They rent a sixth-floor apartment with a balcony about 6 by 10 feet and nine containers of herbs and tomatoes. They run two bokashi buckets under the kitchen sink and a 30-gallon lidded storage bin of used potting soil on the balcony as a soil factory.
The stated alternative. Their plan's worm bin line reads: "No worm bin. We use bokashi and a soil bin instead (Bokashi and burying)." That is a written no that names the alternative. Open: whether they add a worm bin later (their review settles it).
Free demonstrations of setting up a worm bin, from sources we fetched on 2026-10-26:
- NYC Compost Project's indoor worm bin brochure: a one-cubic-foot bin for households without outdoor space.
- Oregon State's Composting with Worms: a two-tote bin, with troubleshooting and harvest methods.
Practice: decide, then size and start Practice
Minimum: answer the four questions and write yes or no on the system plan with the reason. If yes, size the bin, start it and log the first week. Time: the decision is one sitting, once; the setup is one day, and the check is a week later. Materials: the system plan, a kitchen scale, the worm calculator, a bin with a lid and holes, bedding material, red wiggler worms, a spray bottle.
- Answer the four questions on the plan. Write yes or no with the reason in terms of your scraps, your space and your week.
- Weigh a week of food scraps. Enter the pounds in the worm calculator and write the bin surface it gives.
- Prepare the bin. Drill the holes, add moist bedding, and set it in a spot in range and out of direct sun.
- Add the worms and, after a couple of days, a small amount of food buried under 1 to 2 inches of bedding.
- A week later, open the bin and log it. Write moisture, smell, how much food is left and any flies in the worm log.
Weigh your worms at harvest. Oregon State suggests weighing the worms you collect when you separate them, because you need to know the space your next bin needs. Write the weight in the worm log's notes.
Your system Your system
Check your work Check your work
Criteria
- Does the plan say yes or no to a worm bin, with the reason?
- For a yes: is the bin sized from a weighed week of scraps, and does the worm log show a set-up date and the first week's check?
- Is the first feeding well below what the worms could eat, and buried?
- Does the log record moisture, smell and food left, not a conclusion about the bin?
Worked example
Noor's plan has a no for now, a reason, the calculator's number saved for later, and a review in Your compost system. Jun and Lena's plan has a no with the alternative named. A reader who says yes has a set-up date, a weighed week, the bin size and a first-week row. All three pass.
Common mistakes
- Feeding to the highest figure. The sources' rates differ by about three and a half times. Start low.
- Using garden worms or bait-shop worms. Red wigglers are the species the sources name.
- Leaving food on top of the bedding. Bury it under 1 to 2 inches. Exposed food draws flies.
- Adding meat, dairy or oily food. They stay out of a worm bin.
- Putting the bin in direct sun. NC State says sun can overheat it.
- Treating the bin as a yard-waste bin. It takes small amounts of food scraps.
What is still unresolved
The right feeding rate for your bin is settled by the bin: what it eats, how it smells and whether flies appear. Whether your scraps weigh what you assumed is settled by a scale. When the compost is ready is settled by the signs in Finished compost. Whether a worm bin stays in your plan is settled by the review in Your compost system.