How to make a worm composting bin
You don't need to have a big back yard to be a composter. An indoor worm bin can process all your food scraps and produce some of the finest compost available. You can keep it in your garage or kitchen or even your bedroom and you'll never know it's there.
Making a worm bin is an easy and satisfying project. It requires only simple tools and a few basic materials available at any home improvement or discount store. (Try your local thrift store first!)
The main item you need to buy is two plastic storage tubs with lids. But any kind or size of container will work, as long as it has a removable lid and is dark, not transparent. Worms like the dark.
Step 1: Determine the Size
The basic rules for determining size are as follows:
1. One square foot of surface area per pound of worms.
2. One pound of worms can process up to half a pound of food scraps per day.
Start by estimating how much food waste you produce per day. For example, save your food waste in a plastic bowl for one week and weigh it. If you have seven pounds you produce one pound a day. Using rule two above, determine that you’ll need two pounds of worms to process a pound of food per day. Therefore, you’ll need two square feet of bin for two pounds of worms. The perfect size in this case is a 10-gallon bin, approximately two feet long by one foot wide by one foot deep. Remember to buy two of these!
Step 2: Build the Bin
Step Two: Build the Bin.
The two tubs will be used together to create the bin, one inside the other. The top bin (the main one) holds the worms. It has air holes and drainage holes and a lid on top to keep it dark. The bottom bin catches any drained liquids or runaway worms. It has no holes in it and the lid is discarded.
1. Use a power drill to drill holes all around the sides of the main bin, approximately two inches beneath the lid. The size of the holes is not very important (a ¼ bit works fine.) Just make sure there are plenty of them. Good airflow is the key to keeping your bin from smelling bad. Without enough air, your scraps will decompose anaerobically (without air) which is a much smellier process than aerobically (with air.) Also, worms breathe air like you and I. If you don’t have a drill you can poke holes with a large nail and a hammer.
2. Drill holes in the bottom of the main bin. You can use a slightly smaller bit here but again, make sure there are lots of holes. Good drainage is the key to keeping you bin from becoming too wet, the other main factor that can cause a bin to become smelly. Also, worms will drown if too much water collects inside the bin.
3. Place two spacers inside the bottom bin, one at each end. Bricks or scraps of 2x4 lumber work well. Place the main bin on top of these, nested inside the bottom bin. Your main bin will now stick up a few inches above the bottom bin. This provides space in the bottom bin to catch runaway worms and the “compost tea” which is a great additive to your houseplants.
4. Cut strips of newspaper to fill the bin to about half its depth. Use scissors to cut strips about one quarter inch to one half an inch wide. This is the bedding. The worms will live in this and eat it. It is also used to cover the food scraps that you’ll place in the bin.
Step 3: Add Worms
Search online to find a local worm supplier. The most commonly used species is Eisenia fetida, commonly known as 'red worms' or 'red wigglers'. They are surface feeders and are well suited to a worm bin environment. There are other species of worm that will work as well. Just remember that not all worms species (like nightcrawlers from your back yard) can live happily in a bin. For the example above we would need two pounds of worms. They will come with some starter compost mixed in. Add all the worms and compost to the bottom of your main bin and place the newspaper strips on top of them. Put the lid on and place your bin somewhere out of the way. Give them a couple days to adjust to their new home. Remember that worms like the same temperature range as you. They will freeze to death in freezing temperatures and will die from extreme heat. Any room in the house, basement or garage is usually fine. Outdoors is fine in comfortable temperatures.
Step 4: Feed the Worms!
Now you can begin feeding your worms. Collect your daily food scraps either in a container on the kitchen counter or in your fridge. You can feed them as often as once a day or as little as once a week. Choose a corner of the bin and lift up some of the paper bedding. Dump the food in and cover it back up with the bedding. This helps prevent insects from finding the food. The next time you feed them choose a different corner.
Step 5: Maintenance and Compost Harvesting
Add some more strips of newspaper every couple weeks as necessary. The worms will consume it and make compost from it. If the bin becomes too wet, try leaving the bin in a dark place with the top off for a day or two and add more newspaper. Check the bottom bin occasionally for escaped worms and place them back in the bin. After a few months you should have enough compost in the bottom to harvest. There are two basic ways to do this. One is to dump out all the contents on a tarp and hand pick out your worms, and then start over from the beginning. The other is to push all your compost to one half of the bin and place fresh newspaper in the other half. Put all new food under the new paper and the worms will migrate over within a week or so.
Then just scoop out the compost!
Learn How to Make a Worm Composting Bin in 5 Minutes!
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