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How to Screen Compost – Separate Fertilizer from Worms, Sticks, and Debris

screening compostIn this article and video, Uncle Jim’s Worm Farm gives you step-by-step instructions for screening compost. Screening compost is a common way of improving the quality of finished compost. After kitchen scraps and gardening waste has been broken down over several months, it’s almost ready to be applied to the garden. Running it through a screen has many benefits:

  • removes sticks, debris, produce stickers and uncomposted food scraps
  • adds air
  • breaks down clumps into fine pieces
  • removes composting worms, so they can be returned to the composting bin

The finer the compost, the better. Good growing soil is loose and fluffy, with plenty of air in it. Compost will work without screening, but the quality won’t be as good. Also, if you used vermicomposting to make the compost, you will want to save your composting worms!

You will need a composting screen. It can be purchased online, or you can make your own for just a few dollars. Follow these instructions for making your own composting screen. You will need wood to make a frame and 1/4″ or 1/8″ hardware cloth. (P.S. If you don’t want to buy or make a screen, see these other ways of screening compost.

Our short video shows you how to screen compost. And written instructions are below:

Materials to Screen Compost

  • a composting bin or pile that has had enough time to break down into fertilizer
  • a place to shake your compost (could be a tote, a large piece of cardboard, or a clear spot on the ground or pavement)
  • a composting screen
  • a trowel or small shovel

To screen your compost, follow these steps:

  1. Check the moisture level in the bin. It should have the consistency of a wrung-out sponge. (If you have a device to measure moisture, it should measure no more than 80% moisture.) If it is too wet, add some pure peat moss or coconut coir and stir well. Wait a day or two until it dries out a bit. If the compost is too wet, it will stubbornly clump into oval pieces similar to deer droppings on top of the screen.
  2. Place the screen on the target bin.
  3. Scoop some finished compost into the screen.
  4. Shake the screen side to side. Compost will fall through, and larger objects and worms will stay on top of the screen.
  5. Set the larger objects and worms aside. Worms can dry out quickly or try to escape, so keep them out of the sun and contained.
  6. Repeat steps 3, 4 and 5 until you have enough compost.
  7. You will need to leave some bedding behind for the composting worms (at least one inch of depth). If necessary, make more bedding for the worms.
  8. Clean up the debris and worm pile. Remove indigestible items such as sticks, pips, stones and stickers. Place the worms and undigested food back into the worm bin. Let the worms dig down by themselves, so they don’t suffocate. Shining a light on the bin for a few hours will encourage them to dig deep. Feed them.

Now you are ready to use your screened compost. Use it to make starts, dig it into the soil, make a side-dressing, or spray on worm tea. If it’s more than you need, set it aside in a sack for a few months, or give it to a neighbor.

Remember, composting with worms speeds up the decomposition process. The resulting worm castings (worm poop) is called “Black Gold” by gardeners because it is rich in nutrients and soil-friendly bacteria. Uncle Jim’s Worm Farm recommends Red Wiggler Composting Worms for composting bins. The larger Super Reds (European Night Crawlers) are OK for composting, but they are typically released directly into the garden or lawn. Either worm can be used as handy live fishing bait. This website has plenty of composting products and articles about composting. We also carry high-quality, live mealworms for pet food, wild bird food, fishing and science projects. We have been breeding worms for over 40 years, and we are the #1 supplier of composting worms and composting supplies in the USA. Learn more.

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