Guide to Composting With Worms

Learn how to transform kitchen waste into rich garden compost by composting with worms and get step-by-step instructions on how to build a DIY worm bin.

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Hands Holding Clumps of Compost With Worms

Creating Compost With Worms

Composting with worms — also called vermicomposting — creates a crumbly compost that is a fantastic soil amendment and an excellent substitute for fine-textured potting mixtures designed for starting seedlings.

Photo by: Sarah Busby

Sarah Busby

Composting with worms — also called vermicomposting — creates a crumbly compost that is a fantastic soil amendment and an excellent substitute for fine-textured potting mixtures designed for starting seedlings.

Composting with worms is a fun and relatively easy way to create rich, dark, crumbly compost that is a fantastic soil amendment for in-ground and container gardens. Worm compost is also an excellent substitute for fine-textured potting mixtures designed for starting seedlings.

Composting with worms (also called "vermicomposting") is similar to traditional composting but operates on a smaller scale that is more approachable for new gardeners, folks with small gardens and apartment dwellers. Plus, virtually any plant-based kitchen waste can be fed to the worms, which is a useful way to divert compostable waste from the landfill. Whatever your reasons for getting into vermicomposting, cultivating a worm farm can be an entertaining and rewarding activity.

Why Compost With Worms?

"Compost" comes from the word "decompose." When plant-based materials break down and are added to soil, the end product holds on to the moisture like a sponge while improving drainage on soggy sites, feeds soil organisms and releases nutrients that plants need to grow.

While traditional composting systems break down garden waste — including spent plants, lawn clippings and fall leaves — worm compost is usually dedicated to kitchen scraps. In a safe and confined habitat, worms (and other soil organisms) eat banana peels, carrot tops, avocado skins, coffee grounds, tea bags and just about every other kind of plant-based waste.

How to Make Vermicompost

The four key ingredients in any kind of composting system are water, air, "green" materials that have higher levels of nitrogen, and "brown" materials that are rich in carbon. Plant-based kitchen scraps serve as the green materials in a worm composting bin, while shredded newspaper, fall leaves, woodchips or even finished "traditional" compost will all work as brown material. In the context of vermicomposting, it helps to think of the brown material as habitat and the green material as food, although both are technically food and habitat as far as the worms are concerned.

A Bin Filled With Dark Compost and Worms

How to Build a Worm Composting Bin

Traditional composting systems break down garden waste while worm compost is usually dedicated to kitchen scraps such as banana peels, carrot tops, avocado skins, coffee grounds, tea bags and just about every other kind of plant-based waste.

Photo by: Sarah Busby

Sarah Busby

Traditional composting systems break down garden waste while worm compost is usually dedicated to kitchen scraps such as banana peels, carrot tops, avocado skins, coffee grounds, tea bags and just about every other kind of plant-based waste.

It’s best to avoid feeding worms oily food waste or animal products — including meat, dairy or pet waste — which can attract pests, rob the worms of oxygen, or pose human health and safety concerns. You should also keep salty kitchen waste and citrus out of the bin as that can harm the worms’ sensitive skin.

New bins that are just getting started should have mostly brown material with just a little bit of green material. Why? The worms don’t really care about the ratio of brown to green material – they’ll be happy as long as there’s plenty of shade, moisture and food to eat. However, compost systems that have more green material than brown material tend to get slimy and smelly, and they aren’t fun to be around — for us, anyway.

It’s best to limit the amount of kitchen scraps to one 32 oz. container a month (roughly the size of a yogurt container) while the bin is getting established. You’ll know that your composting worm bin can handle more of your kitchen waste when the brown bedding material begins to break down and resemble crumbly soil. Depending on the time of year you built your bin, the number of worms that you started with, and other environmental considerations, it could take three months to a year to reach this point.

Have you ever seen dried-up worms on a sidewalk and wondered what on earth happened? When there’s heavy rain, the soil becomes waterlogged, and worms escape drowning by wriggling onto the pavement. When the clouds part and the sun returns, stragglers left behind on the concrete quickly dry out and die. Worms need just the right amount of water to survive. In addition to providing the best habitat for healthy worms, moist vermicompost bins also generate compost more quickly than drier bins.

It’s crucial to keep an eye on the moisture level of your worm compost bin. If the worm bedding is dry to the touch, gently add a little bit of water with a watering can or spray bottle. Avoid adding so much water that it pools at the bottom of the bin, as this will limit the worms’ habitat to the drier top portion of the bin and cause smelly, anaerobic conditions.

Choosing the Right Worms for Vermicomposting

Not all worms are equal when it comes to composting. If you plan to purchase your worms from a bait shop, the larger worms, like nightcrawlers, aren’t as effective at composting and definitely don’t enjoy living in a confined space. Red wigglers (Eisenia fetida) are the best worms for composting systems. In their natural environment, red wigglers happily eat decaying matter in the top layer of soil, which means they are well-suited for life in a vermicompost bin.

Avoid vermicomposting with species of worms flagged as "invasive" to your region. Some non-native species of worms have escaped from gardens and bait cans and are wreaking destruction in northern hardwood forests by rapidly consuming the thick, leafy duff layer on the forest floor that native forest-dwelling organisms depend on for food and habitat. Check with your state’s department of agriculture to learn if there are any worm species that are invasive in your area.

Red-wiggler composting worms are available from many garden centers, some pet stores, bait shops and even specialty online compost stores. If you have a friend with a successful vermicomposting bin, there’s a good chance they’ll be more than happy to share a healthy scoop of worms to help you get started (the population of an established bin should bounce back very quickly). While you can start a successful worm compost bin with just a few dozen worms, the more worms that you start with, the sooner your vermicompost will be ready to harvest.

DIY Worm Bin: Step-by-Step Instructions

There are some fantastic worm compost bins on the market that are easy to use and even easy on the eyes. When you’re shopping, look for a durable bin that will stand up to the elements, has drainage holes that prevent standing water from collecting in the worm habitat area, a catchment system to hold the runoff (called "leachate"), and ventilation holes.

If you’re comfortable with a DIY approach, however, you don’t need a fancy system to get started with composting. It’s easy to make your own worm farm from two basic 7- to 14-gallon buckets or containers.

1. Choose containers and lids made of durable plastic that won’t deteriorate quickly in the presence of UV light. Set aside one bin for your worm habitat and the other for drainage collection.

Two Black Bins With Yellow Tops

How to Build a Composting Bin for Worm Compost

The first step in creating a DIY worm compost bin is to choose the type of bin you'd like for the project. It’s easy and in expensive to make your own worm farm from two basic 7 to 14-gallon buckets or containers like the black bins with yellow tops seen here.

Photo by: Sarah Busby

Sarah Busby

2. Add drainage holes to the bottom of the worm habitat bin. Make sure the drainage holes are evenly spaced every few inches. If you’re using a drill, a 1/4-inch drill bit is a good size.

Drilling Holes in the Bottom of a Plastic Storage Container

Creating a DIY Worm Compost Bin by Drilling Holes in the Bottom of a Bin

The next step in building a DIY worm composting bin is to drill holes in the bottom of the bin for drainage. Make sure the drainage holes are evenly spaced every few inches. If you’re using a drill, a 1/4-inch drill bit is a good size.

Photo by: Sarah Busby

Sarah Busby

3. Create smaller ventilation holes evenly spaced every inch or so along the top lip of the same worm habitat bin. If you’re using a drill, a 1/16-inch drill bit will work well for the ventilation holes.

Drilling Small Holes in the Side of a Black Storage Container

Use a Drill to Create Small Ventilation Holes in the Side of DIY Worm Compost Bin

The next step in building this DIY worm compost bin is to drill small holes along the side for ventilation. If you’re using a drill, a 1/16-inch drill bit will work well for the ventilation holes.

Photo by: Sarah Busby

Sarah Busby

4. Place a brick or block of scrap wood in the collection container, then nestle the worm habitat bin inside of the collection container.

Piece of Scrap Wood in the Bottom of a DIY Compost Bin

Place a Block of Scrap Wood at the Bottom of a DIY Worm Compost Bin

The next step in creating a DIY compost bin using a standard black storage container is to place a piece of scrap wood at the bottom of the container, then nestle the worm habitat bin inside of the collection container.

Photo by: Sarah Busby

Sarah Busby

5. Add your moistened bedding mixture (Image 1), worms and a handful of "grit" (sand, soil or vermiculite) (Image 2) to help worms digest the contents of the bin.

6. Secure the lid, then pat yourself on the back. You’re the proud owner of your own DIY worm farm!

Woman Holding a DIY Worm Compost Bin With Worms Inside

Harvesting Compost from a DIY Worm Composting Bin

When the contents of your worm compost bin become dark and spongey, like a chocolate cake, that means it’s time to harvest your finished vermicompost. Wait for a dry sunny day to harvest. Set the bin in a warm, bright location and remove the lid. The worms will naturally move lower in the bin as the top layer begins to dry out.

Photo by: Sarah Busby

Sarah Busby

How to Harvest Finished Worm Compost

When the contents of your worm compost bin become dark and spongey, like a chocolate cake, that means it’s time to harvest your finished vermicompost. Wait for a dry sunny day to harvest. Set the bin in a warm, bright location and remove the lid. The worms will naturally move lower in the bin as the top layer begins to dry out.

When the top few inches are dry and crumbly, simply scoop out the finished compost. Sift out any unfinished pieces of compost or food scraps and return those to the bin. Add more moist, shredded newspaper or fall leaves to the bin, and resume feeding your worms as usual. Use the finished compost for the garden or store it for later.

Shop for a Worm Compost Bin

Common Problems With Worm Composting

As exciting as vermicomposting is, there are a few relatively common obstacles that can be very discouraging for new worm composters. Fortunately, the most common problems usually have fairly easy fixes.

  • A smelly vermicompost bin is usually caused by too much kitchen waste or too much water. Check on your bin daily for one week and pour out any leachate that may have collected in the reservoir. Add more shredded newspaper or fall leaves and hold off on adding kitchen waste for a month or two while the worms consume the food that’s already in the bin.

  • Fruit flies and fungus gnats in a worm bin are attracted by kitchen scraps and usually enter through the ventilation holes. Try burying kitchen scraps under an inch or so of the bedding material to discourage annoying flies from moving into the bin.

  • Ants in the vermicompost bin are a sign that the bedding is too dry. Add water and keep an eye on moisture over the next few months. The ants will move out in search of drier habitat.

  • Maggots in the worm bin aren’t always considered a problem. Many gardeners are a fan of black soldier fly (Hermetia illucens) larva, because, like composting worms, they’re super effective at speeding up the composting process. However, finding a wriggling mass of maggots in your vermicompost bin can be a little unnerving. Make sure the lid is firmly secured on the bin and hold off on adding more kitchen waste until the maggots are gone.

  • If there’s no sign of decomposition after three months, there could be a few causes. First, if the bin is too dry, that can slow down the natural rate of decomposition as well as worm activity. Check the moisture level on a weekly basis until you see signs of progress. Environmental conditions could also be slowing down your composting operation. Worms are most active at temperatures between 55 and 75 degrees. Cooler or warmer weather can slow down the rate of composting. To keep worms working later into the fall and earlier in the spring, insulate with straw bales or move the bin into a protected garage or shed. Set in a cool, shady spot, like a north-facing porch, to keep worms cool in the heat of summer.

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