How to Build an Indoor Worm Composter
Building an indoor worm composter is an easy and fun project. An indoor worm composter is a great way to keep your composting efforts going in the wintertime when temperatures are too cold outside. It is also a fantastic teaching tool to show children how soil forms and feeds plants. Does this Spark an idea?
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Things You'll Need
- Two 5-gallon food-grade plastic buckets
- One package plastic embroidery canvas
- Shredded newspaper
- Food scraps
- Drill
- Wood glue
- Permanent marker
- Scissors
Instructions
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Obtain two clean 5-gallon food-grade plastic buckets that nest inside of each other. These 5-gallon buckets can frequently be gathered for free from restaurants or grocery stores. It is important they they are food-grade and have never contained any chemicals or other toxic substances that could be impregnated in the plastic. Wash the pails out thoroughly with soap and water and allow to air-dry.
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Turn one of the pails upside down and drill several 1/8-inch holes through the bottom of the pail, spaced evenly over the surface. Flip the pail back over and remove any attached plastic bits from the holes. Set the pail inside the second pail.
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3
Invert one of the plastic buckets on top of a sheet of plastic embroidery canvas. Trace the outline of the bucket onto the canvas with a fine-tipped permanent black marker. Cut out the circle with sharp scissors just inside the outline. The canvas should fit snugly into the bottom of the bucket without curling upward. If the canvas circle is too big, trim until it fits properly. This way the worms cannot escape through the holes in the bottom of the bucket.
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Cut a 3-inch-diameter hole in the lid of one of the buckets. You can use a box cutter or a lock (or mole) cutter, or you can drill holes around the perimeter of the circle and punch out. Cut a 5-inch-diameter circle of plastic embroidery canvas and glue to the underside of the lid hole, ensuring that there are no gaps where worms could escape.
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Nest the first bucket once again into the second. Fill the composter loosely with shredded newspaper approximately two-thirds of the way full. Do not press down on the newspaper. The worms need lots of loose, fluffy bedding in which to move through and get enough air.
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Spray the shredded bedding with water from a mister, turning it around and mixing it up in the composter until all newspaper is thoroughly damp but not soaking wet. There should not be enough moisture to drip through the top bucket into the second yet.
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Add the worms. Worms can be purchased online from a reputable source or from your local bait shop. Red wigglers are a common variety of composter worm. For a 5-gallon composter, 1 lb. of worms is plenty to start with. Soon you will have enough worms to start another bucket or to share with friends. Place the worms in a hole you have made in the center of the bedding so that they land about halfway down into the bedding.
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Feed your worms. Indoor worm composters operate best when they receive small amounts of compostable scraps daily, rather than larger doses more infrequently. Cut larger pieces of compost like watermelon rinds into smaller pieces to make composting easier. Every day, place the food scraps into the middle layer of the composter near the wall of the bin. The next day, move to an adjacent spot. Continue to do this in a circular pattern until you reach the first spot again. This allows the worms time to compost the scraps by the time you reach the first spot again. Continue rotating the placement of the food scraps. Keep the ventilated bucket lid on tightly between feedings.
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Keep the bedding damp but not soaking wet regularly. Excess moisture will drip through the bottom of the bucket into the second bucket. This liquid makes a wonderful organic fertilizer for your plants. As more composting happens, the volume of the bedding will decrease. Add more fresh shredded newspapers to the top of your composter to keep it at the two-thirds level.
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Harvest your compost. After 2 months, your worms will have completed a large portion of their job in your compost bin. When you add bedding, pull the existing compost and bedding to one side of the composter and add new bedding on the now empty side. Also, add your food scraps only on the new half. This will encourage the worms to migrate to the "fresh" side and will make it easier to scoop out your finished compost on the old side. There are still likely to be worms present in the harvested compost, so gently pick them out and return them to their home.
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Tips & Warnings
Use the liquid that accumulates in the bottom of the second bin as a nutrient-rich plant food.
Do not feed your worms citrus, onion or garlic since these are toxic to worms. Do not add eggshells to your worm composter since they could injure the worms.
