I still remember the look on my parents’ faces when I told them I was going to have worms in my flat in Bristol. It’s true what they say; you never fully grow up and leave your parents until you start keeping worms. Halfway through my second winter with a worm bin there’s been enough trial and error to turn the nagging guilt over wasting food into something productive.
If you’re reading this from your rented London or Bristol flat, you’ll probably understand why I started worm composting in the first place. How does composting happen when you live in a flat with kitchen scraps but no garden, outdoor space, or balcony? Not everyone has understanding neighbours who won’t mind a traditional compost heap either. Enter worm composting…
“The average UK household throws away almost 70kg of easily avoidable food waste every year. The majority of this waste is vegetable peelings, fruit waste and leftovers.”
Most of that 70kg can go in your worm bin. Worms love your leftovers almost as much as you do. In return they transform food scraps you’d normally bin into usable compost you can grow houseplants with and “worm juice” for seriously impressive results on even struggling plants. Vermicomposting is possible indoors in apartments using enclosed bins (source), making wormeries one of the few forms of composting open to those who rent and don’t have outdoor space.
Here’s how I did it in a series flatlets and one cold-but-roomy garage. It takes less time than most houseplants and is way more satisfying.
How worm composting works
When it comes to worms everything is efficient. They eat much faster than you’d expect and reproduce just as quickly.
Unlike hot composting that speeds decomposition with bacteria-generated heat, worm composting is an aerobic process that takes place at ambient temperature in the worms’ gut. Worms ingest organic matter as well as bacteria and microorganisms present in the bedding material. Worm castings contain more nutrients than compost, have a near neutral pH balance, and are ready for your houseplants to use straight away.
Temperature: Worm composting doesn’t do well if it gets too hot or cold, so finding the right temperature balance indoors is important. Fortunately red wigglers are active and feed over a fairly wide temperature range of around 15°C to 25°C (source). The sweet spot for wormeries is between 15°C and 25°C. Worm composting slows down below 10°C and can kill worms if the temperature climbs above 30°C (source). Temperatures in UK flats and garages are rarely hot enough to worry about, although you may need to move bins out of direct sunlight or near a radiator during summer months.
Processing Power: Worm composting has deceptively impressive processing power for such slimy creatures. One pound of worms can process up to 65 pounds of scraps in just 100 days (source). To translate that to something meaningful: 500g of worms can process approximately 15kg of food scraps every three months. That’s enough kitchen waste for one person or a couple to feed worms without overwhelming them.
Moisture levels: Worm farmers aim to keep worm bins at a moisture content of 70% to 80% (source). A handy analogy for ideal moisture levels is a wrung-out sponge. Too little and worms become sluggish and may die. Too much moisture creates anaerobic conditions that smell bad and attract harmful bacteria. Good news is that your kitchen waste will often contain enough moisture that you won’t have to add much. You’ll have to remove excess moisture via drainage holes and your liquid fertiliser outlet once or twice a week.
Timeline to Finished Compost: Full cycle vermicomposting time for indoors bin is 2 to 3 months (source). Other sources from government-backed research report that within “2 to 3 months time” feedstock material will be converted into vermicompost (PDF from UK government). Average vermicomposting time frame ranges from 3 to 6 months depending on environmental conditions, worm numbers, and the mix of food scraps to bedding material (source). Smaller bins will have longer turnaround times than commercial systems but in my experience 2-3 months is about right.
Step by step guide to your indoor worm farm
Here’s where worm composting gets interesting. Building your own worm farm is easier than it sounds. I started with nothing more than a plastic storage box, drilled some holes, and let months of troubleshooting teach me what works and what didn’t.
The Container: Plastic storage bins are my container of choice for most homes with single people or couples. Really any wide shallow container works well for worm bins. Worms would rather feed near the surface than burrow down deep into your scraps so the wide shape encourages good processing. Drill 8-10 holes around the side between 5cm and 10cm from the bottom for drainage. Add another 10-15 small holes in the lid for airflow. Holes should be large enough for air to pass through but small enough that worms can’t escape. About 6mm dia works well.
Drainage: The easiest way to add drainage is to place your plastic container inside another one of a slightly smaller size. Elevate the inner container with small blocks or bottle caps so it doesn’t rest directly on the bottom of the outer container. You now have a gap between containers that will act as liquid runoff collection. Fit your container with a tap or firmly hold lid over drainage holes to drain off weekly. This is your liquid fertiliser. With no drainage excess moisture collects and creates anaerobic conditions that smell horrible and kill worms.
Bedding Materials: Add bedding material to fill half of your container. Shredded newspaper or cardboard are fine as long as it isn’t glossy paper or cardboard packs with heavy inks. You could also use coconut coir or buy ready-made bedding online. Ideally dampen bedding so it feels like a wrung-out sponge then fluff up with your hands. Fluffing introduces air gaps that are important to the worms. Bedding material should take up about half the container. Worms will live in bedding and eat it along with your food scraps.
Worms: Purchase red wigglers from an online supplier or at a garden centre. They’re available at most garden centres in the UK. Look for composting worms or wigglers rather than fishing bait worms. Red wigglers are sold by weight so ask for about a quarter to half kilo in your first bin. A smaller bin with fewer worms allows you to learn the system without becoming overwhelmed. If conditions are ideal they’ll breed like rabbits.
Location: Choose a spot that has consistent temperatures and that’s convenient for adding scraps once-a-week. Under the kitchen sink is great if it’s not too warm and you have decent ventilation. Garages make excellent worm bin homes if they don’t get frosty in winter. Avoid overheated locations like near radiator pipes, on top of cookers, or where sunlight directly hits the wormery through windows.
Once you’re ready to introduce your worms bury an initial food waste feeding (about a cup) in one corner of the bin. Add worms on top then cover them with more bedding. Wait one week before adding more food to allow worms to acclimatise. Food additions should be buried each week in a different section of your bin. This prevents pocket of anaerobic decomposition from building up in one spot.
Feeding and maintenance
Your once-a-week routine will become easier over time. Checking moisture levels and feeding your worms will take you less than 5 minutes.
What to feed your worms: Vegetable peelings, fruit scraps, coffee grounds and tea bags (remove staples first), eggshells, and untreated cardboard. Cardboard egg trays are excellent too. Get your kids involved and see who can make the biggest pile of scraps for the worms each week. Meat, dairy products, oil based foods like cheese or pizza dough, oily foods, and salty or spicy foods must be avoided. Lots of people feed citrus peels in moderation but avoid dumping orange peelings and lemons in the bin whenever you have a juicing session. Same goes for onion and garlic. They won’t kill worms but they take ages to decompose and will kill the smell in your kitchen.
Small additions of bread or cooked plain pasta are okay. Chop large food items into smaller bits to help them decompose faster. Coffee grounds are great for worms too. They add grit which helps worm digestion and most kitchens don’t have enough stored in the bins. Used coffee grounds are usually the perfect moisture level too.
How much to feed your worms: Worms don’t need feeding daily. A handful of food waste every couple of weeks is plenty for a small bin. Too much food builds up androts before worms have time to process it. Add small amounts once or twice weekly and bury each new feeding in a different area of the bin. If you can see food scraps from the previous week’s feeding add no new scraps until they’ve been processed.
Checking moisture levels: Moisture levels should be checked once a week when you add food to the bin. Grab a handful of bedding material. It should feel damp and sticky but not dripping wet. Dry out bedding with a spray bottle or add excess food scraps to bedding. Too much moisture? Add dry bedding material like shredded newspaper. Are you still getting standing water? Check your drainage hole are clear and aren’t blocked by bedding material.
Common Problems: See fruit flies?Excess moisture or too much food exposed to air. Cover food scraps with bedding material. Smells like rotten eggs? Anaerobic conditions from overfeeding or excess moisture. Locate bad spots and bury them under fresh bedding. Worms trying to escape? Too acidic, too wet, or too hot. Check temperature and moisture levels.
Common mistakes to avoid when worm composting indoors
Here are some of the most common mistakes new worm composters make and how to avoid them.
Excited about worm composting? Want heaps of finished compost quickly? Jumping in with both feet seems logical but bin/bucket is too big for your household or you overfeed in desperation. A small worm population in a small bin is more likely to establish successfully than a barrel full of worms trying to process food scraps for an entire street. Start small and expand when you’re confident you can maintain feeding and bin conditions.
Golden rule of feeding your worm bin: Only add enough food waste that your worms can eat in one week. Adding small amounts daily may seem easier but you’re increasing the workload every time you open the bin. Think about what happens to your food waste if the bin takes more than a week to process it. Unless you like sharing your dinner with maggots once-weekly feedings allow you to bury food waste out of sight and out of smell.
I’ve seen it done, so have lots of other new worm composters. Learning on the cheap skips the crucial second container that acts as a drainage layer. Steam emerges wafts from the worm bin whenever you open it. Drainage holes get blocked with bedding material. Worms drown, bedding decays anaerobically and you’re back to square one. Do yourself a favour and fit drainage from day one.
You may be tempted to hide your worm bin where visitors won’t see it. If it’s too far away you’ll forget about it, hate checking weekly progress and seek out other household waste disposal methods. Keeping your worms near where you prepare food is ideal. Don’t place it directly above or below rubbish bins either since fruit flies will find concealed corners to nest in. Also think about seasonal temperature variations. July is not the time to find out your worm bin lives too close to your heating vents.
Vegetable plot warriors are no stranger to seasonal composting challenges. Worm bins aren’t immune to seasonal changes even if they’re kept indoors. Winter dry air requires more ventilation. Summers brings hotter temperatures and more indoor flies. You may also struggle to find enough food waste to keep worms fed in winter. Feed them extra bedding instead to help them through the cold season.
Supporting Research
Information on worm composting’s benefits and effective management comes from academic research as well as home composting reviews.
Large-scale agricultural studies have repeatedly demonstrated worm castings produce superior results to traditional compost and untreated soil (source). Castings have lower carbon: nitrogen ratios than compost, leading to higher concentrations of nitrogen phosphorus and potassium. Nutrients are also more readily available for plant consumption compared to compost or soil alone.
Indoor worm bins have been tested for odour (source) by comparing housefly and outdoor dump fly presence to traditional compost piles. Results concluded worms processed waste and reduced smells compared to unmaintained compost piles. Indoor bins are less likely to attract pests that reproduce in outdoor garbage like cockroaches (source), or fruit flies.
Processing power figures were compiled from vermiculture business case studies then scaled down to home-use quantities.
Does worm composting work in your house? Unless you have unusual pets, heating problems or severe allergies worm bins make great indoor pets. Research the breed of worms you’re purchasing beforehand and ensure they’ve been safely kept indoors before by other composters.
Special Considerations for different living situations
Congratulations, you’re a worm nerd. You know more about worm composting than most people ever will. Consider your options for reaching others who might benefit from keeping worms.
Flat shares: Coordinate worm bin responsibilities with housemates. What goes in the worm bin versus general waste? Who will care for worms and divide up finished compost? Consider a large barrel composter if everyone is feeding scraps.
Households with gardens: Speed up compost production by running multiple bins. One each for food waste, grass clippings, garden weeds and prunings. Even indoors worms can’t eat humid summer grass cuttings year-round.
Bay window flats with outside access: Similar to flat shares except you can run a larger outdoor worm bin. Worm bins still work outdoors in cold weather but should be tucked under an overhang out of direct sunlight. Outdoor bins will process scraps quicker during warm months.
Garages: Run multiple worm bins in series, increasing total capacity without increasing bin width. Temperatures are more stable than outdoors without heating worms kill themselves in winter. Larger bins are possible if garbage trucks won’t crush them. Garages have better ventilation so slightly larger worm populations are okay.
Strict landlords: Keep a file of information on worm composting benefits and maintenance techniques handy. Showing you’ve done your research makes most landlords happy. Mention worm bins don’t smell like traditional outdoor compost bins do, especially when indoor climates fluctuate.
Benefits of indoor worm composting
Once you’re worm farming there’s no going back. Composting indoors is more convenient than you realise. Benefits quickly outweigh problems until you start wondering how you lived without worms previously.
Reduce Waste: The average worm bin handles 60-80% of kitchen waste. There’s less general waste for landfill so you’ll get away with a smaller outside bin. Bonus points for never having to drag yours outside in the rain again.
Produces high-quality compost: Smaller flats still produce 10-15kg of finished compost a year. Enough for pots, houseplants or sharing with gardening friends. Quality is far superior than bags of compost sold at garden centres.
Liquid fertiliser: Additions to your worm bin each week become liquid fertiliser once-removed weekly. Use on houseplants or any fruiting veg you’re growing on a balcony. Many people notice plant growth improvements within weeks of consistent liquid fertiliser applications.
Teaches responsibility: Long-term commitment teaches responsibility and respect for nature. Classroom composting doesn’t come close to caring for your own worm family. Science, maths, and language arts all have real world applications once you start worm composting.
No reliance on external facilities: Cancelled council food waste collections, unreliable community compost schemes, or stalking neighbours with allotments won’t affect your worms. Processing speeds are dictated by the size of your worm population. Red wigglers double in population every 90 days.
Inexpensive to maintain: Bedding is the only supply you have to buy after initial setup. A 50 quid worm composting setup lasts several years. Way cheaper than buying compost and liquid fertiliser indefinitely.
What’s stopping you?
Want to build your own worm farm? Here’s how much time and money you need to get started.
Step 1: Learn and order worms one month before you want to start worm composting
Contact local worm suppliers and order your worms online or ask at garden centres where you can buy composting worms near you. Gather information on what you need to buy and prepare for worm composting indoors. Containers, drill bits, bedding materials and waterproof composters are available for under £75. Set aside £40-£60 for your first worm bin.
Step 2: Build your container 1 week before vermicomposting
Includes time for procuring materials and actually building your container. Two hours spent over the course of a week isn’t too bad.
Step 3: Add bedding, let worms acclimatise – 1 week
Add enough bedding to half fill container. Moisten bedding until damp and toss/pat down with hands to fluff up. Make sure bedding takes up about half of your container.
Step 4: Add worms, wait one week before feeding. –
Add worms to bedding. Bury first food scraps feeding then add worms. Cover worms with excess bedding material. Wait one week before you start adding food scraps to allow worms to acclimatise to their new home.
Step 5: Begin feeding once-a-week routine
With experience you’ll begin to notice bin conditions and learn your worms. Take notes on what you observe.
Estimated Timelines:
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Estimated costs breakdown:
Item
Cost (£)
Notes
Storage containers (x2)
£15-£25
Main bin (60L) and second smaller container for drainage layer
Red wiggler worms (250g)
£15-£20
Online supply or from local garden centres
Bedding materials
£5-£10
Alternatively use free newspaper
Basic tools
£8-£15
Use existing drill bits or buy ones suitable for plastic. Add small blocks/spacers for separating containers.
Spray bottle
£3-£5
Required for adding moisture to bin.
Total
£46-£75
Total Cost
Start worm composting today
Learning patience will be your most valuable skill. If you stick with it vermicomposting becomes easier over time.
Total setup time is four weeks with worms arriving ready to setup in your container. Perfect if you want something productive to do over summer and won’t instantly bite back.
Waiting two months before your first harvest will feel excessive. Extracting liquid fertiliser starts after 2-3 weeks and shows you’re successfully composting months before that first bucket of compost is ready.
There’s no exact science to feeding because everyones habits and purchases are different. Feed worms enough waste to keep them occupied until the following weeks feeding. Add small amounts at a time so worms have a chance to process food before adding more.
Time spent caring for your worms will drop as you get used to once-a-week care and feeding.
Your worm bin’s processing power increases as worm populations double roughly every three months. Planning excess winter food waste storage is helpful but not required. Worms can eat what you can feed them.
