Monday, May 23, 2011

Making a compost screen

This spring is the beginning of my fourth summer in the Green Tenancy, and a couple weeks ago I determined that it is finally time to empty the first of my composters. After removing the sturdy black plastic outer structure and a bit of non-composted straw from the top, I quickly realized the compost would need screening.

You see, different materials take different amounts of time to compost. Almost everything had turned to a nice, rich soil (and it is true that there's no odour save a pleasant earthy smell). But a few bits hadn't broken down sufficiently to go in the garden. Also, because of occasional thin layers of dirt added (it adds micro-organisms and speeds composting), there were a few bits of gravel.

I needed a screen.

Thankfully, I'd put the composter on a sturdy metal mesh. This I placed on top of the wheelbarrow, then shovelled some compost onto it. With my son holding the mesh in place, the system worked. But, being eight, he soon lost interest and I found the mesh wouldn't stay in place on its own.

Making my own screen
Because the mesh nicely fit the length and width of the wheelbarrow, I took it down to my basement workshop. On a shelf I keep some lengths of wood for whatever projects come along. In this case, I selected some old railings from a retired bed.

Normally I am an advocate of careful measuring, but this is no fine woodworking. Here's what I did.

  1. Set the mesh on the floor
  2. Cut two pieces for the longer sides. These I made so they'd stick out 7 or 8 inches on either end. This was partly to make sure they'd be long enough to straddle any wheelbarrow, but also to serve as handles for shaking the compost through.
  3. Position those two pieces on the mesh, with 2-3 inches left over on either side (to later fold up and staple into place.
  4. Cut two pieces for the ends, just long enough to fit inside the sides. Again, leave some extra mesh to fold up and staple in place.
  5. Pre-drill and nail sides into place. I used two nails on the end of each sidepiece and selected 1 1/2" (4d) spiral finishing nails
  6. Place the mesh on top, then push it down into place so that there's an inch or more of mesh going up the inside of the box on every side.
  7. Tack the mesh into place. Heavy-duty staples or U-nails make the most sense, but finding none handy, I just tapped finishing nails in part way and bent them over.
The result? Well, art it ain't. But it worked well. It stayed on the wheelbarrow, was easy to shake, and gave me nice, evenly screened compost.

What didn't compost?
Not much. Almost everything broke down nicely. There were some exceptions, though.
  • Rocks. Obviously.
  • Black olives. They were partway there and had turned red and cork-like on the inside. I put them back for another year or two.
  • Wood. Even the sturdy stems I'd lined the bottom of the composter with had broken down, but a couple larger chunks of wood had to go back.
  • Egg shells. Don't compost these. Instead, bake or boil them to kill micro-organisms, then grind them with your mortar & pestle and apply the coarse powder to the garden. It adds calcium (handy if your soil is too acidic) and may also deter some annoying pests (slugs, I'm lookin' at you!). We did find one whole, uncracked egg, which was unfortunate.
  • Rabbit poo. Some was still in pellet form, but with two years of composting, I'm betting it'll be okay for the garden, so I let it go through. The critters in the garden seem to have broken it down already.
That's about it. Two very full wheelbarrow loads provided a thin layer for all four beds, and only about three shovelfulls of material went back for another cycle. And I continue to send less than a pound a week to the city's green bin (occasional chicken bones, for example) and greedily hog all the lovely banana peels, apple cores and tea leaves for myself!

Oh, and I also keep my coffee grounds separate. I've heard they repel slugs, so am scattering them directly on the garden. We'll see if it turns the lavender brown.

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