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The Flower Show

How to Compost Indoors (Video)

September 22, 2022

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harvesting compost

By Melissa O'Brien

Composting is a great way to reduce waste and improve soil quality, but in an urban setting like a row home or apartment, it often seems inaccessible (and potentially smelly)! However, composting can be done without a large outdoor compost pile – indoor composting just requires a little creativity and patience! 

In the latest episode of PHS’s Garden Mythbusting, we break down everything you need to know about composting to get started today. 

Composting in Small Spaces | PHS Garden Mythbusting​

Composting in Small Spaces | PHS Garden Mythbusting​

What is Vermicomposting? 

Vermicomposting uses worms to break down food scraps. Worms eat the food scraps, which produce compost as they pass through the worm's body. 

While you could do composting indoors without worms, you would have to think about how much space you can dedicate – it usually takes a lot more space for composting without worms! 

How to Start Composting Indoors 

Supplies for Vermicomposting 

Worms: The type of worms you use for vermicomposting are very important. You can’t just go out after a rainstorm and gather the earthworms at your local park! Worms commonly known as red wrigglers are best for composting, as they have hearty appetites and will produce more castings. They can be purchased online for anywhere from about $20 - $50 to start. 

Container: For your container/bin, you can purchase a 5 - 15-gallon plastic storage bin. You can also use a sturdy Styrofoam bin (about 1 - 2 inches thick). Bins should be well ventilated, containing numerous holes on the bottom and at least two rows of holes along the bottom half and middle of the bin. Larger holes can be cut in the lid of the bin but should have a piece of cloth taped over top to discourage fruit flies. 

Starter compost: If you don’t have starter compost, you can use topsoil – you can also incorporate sand! Worms use the sand to create friction to help digest and break down the food scraps. 

Food scraps: Worms love lots of fruits and veggies, like apples, bananas, grapes, pears, and leafy greens. Coffee grinds and tea bags work great too – just be wary of adding too much because of the acidity. When you feed, add a few scraps of newspaper to help with moisture and carbon levels. 

Avoid anything too acidic or spicy: garlic, onions, tomatoes, peppers, ginger, and citrus aren’t great for worms. Other foods to avoid are meat, bones, cheese and dairy, oil, salt, or cooked and processed foods.  

If you’re keeping your worms indoors, avoid wet and smelly foods like squash or melons. You can feed these if you keep them outdoors or in a place in your house where you don’t mind the smell (red wrigglers LOVE melons and squash, but the odor is not-so-pleasant indoors). 

Newspaper or cardboard for bedding: Bedding should be made with a mix of starter compost or peat moss and shredded newspaper or cardboard. A good ratio is mostly shredded newspaper or cardboard and a sprinkle of starter compost or peat moss. 

How to Assemble Your Compost Bin 

You'll need enough bedding to fill the bottom of your bin to a height of ~4 inches. If your bin is going outside, then the bedding depth should be closer to 12 or more inches, so the worms have somewhere to go if temperatures get too hot or too cold for them. And if you’re putting your bin outside, make sure to keep it in a cool, shady spot that won’t get too much sun exposure. 

Assemble your supplies like a parfait – start with your starter compost or peat moss, then sprinkle sand (if using it), and then top with the newspaper. The newspaper will help prevent things from getting stinky. 

The bedding should be moist but not wet, much like a wrung-out sponge. Fill to the required height and then gently place the worms inside. Then, cover with your lid and put them in a dark place between 65 - 85 degrees F. 

How to Feed Your Compost Worms 

For the first feeding, feed 1/5 to 1/4 of the weight of your worm population. Never feed your compost worms until all food from the prior feeding is consumed. The amount of time it will take to be broken down and eaten will depend on how fibrous and big the waste food pieces are. After the first feeding, feed the worms 1/3 to 1/2 of their weight. 

Be careful not to bury the food. Compost worms are surface dwellers and will generally not eat food that is more than 1 inch or 2 below the surface. 

How to Maintain Your Compost Bin 

Water your bin around once per week. Never pour water into a bin because it will lead to over-watering or inconsistent moisture throughout the bin. To wet without overwatering, a spray bottle or light mister works best. 

Make sure the top inch or so of your bin is the moistest part of the bin. The bedding should get drier as it goes to the bottom of the bin. Lastly, don't let water accumulate in the bottom of your bin. If water accumulates, this is a sign you are watering too much. 

Harvesting and Using Your Compost 

You’ll know your bucket is ready when you can’t put anything else in it because it’s full to the brim! Your castings (the output of the worms) should be ready in about 1 - 2 months, depending on the size of your bin.  

The harvesting process itself usually takes a few hours and you can continue to come check on your progress without having to stand over your bin. Just make sure to keep your other worms covered if you’re not harvesting your entire compost. 

Step 1: To harvest your castings, you can dump out either half or your entire bucket. Dump it out onto a flat surface – your lid or a flat piece of cardboard will do. This will make cleaning up a lot easier! 

Step 2: Spread the compost into a thin single layer and place it into the sun or another light source. The goal is to dry out the compost, which will force the worms to look for more moist and cool conditions, which leads them to the center of your compost pile and easier to gather all at once. (Don’t worry if you don’t get all of them – if they end up going into your plants, it will be good for them! And your worms will repopulate in the bin.) 

Step 3: Once your worms have made it to the center of the pile, make sure your bin has been prepared as described in set-up, and put them back into the bin.  

Step 4: Then, collect the castings. At this point, they should be dry since they’ve been sitting out in the sun – but if you notice it’s still a little chunky, you can sift it to make a finer soil. You can also steep your compost in the bottom of a watering can and use it as a liquid fertilizer – also known as worm tea. 

Step 5: Compost can be used pretty much anywhere you’ve got plants – house plants, crops, flowers, window boxes and anything in container gardens will be all the better for having compost! 

Work With a Local Company 

If these options don’t work for you, many local composting companies offer options to compost for you! Most of the time, you can keep your scraps in a container in your freezer until they pick them up. 

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