We bring food scraps from the school kitchen and other local sources to our compost bins in the garden where they decompose. What starts off as a smelly mix of rotten vegetable bits, fruit peels, apple cores, leftover salad, old rice etc., will yield a rich finished product that improves the soil and feeds the plants. The cells in a 3-bin composting unit include the “in” cell to which we add new organic waste, a resting cell that has been filled and is in the final stage of decomposition, and finally the finished or “out” cell from which we screen the finished compost. Kids greatly enjoy digging in all bins. They like finding worms, sow bugs and centipedes, identifying food scraps like pineapple tops, and scooping out the finished compost to spread around seeds or seedlings they have planted.

Circle of life in the garden

To emphasize the need for soil nutrition and the growth/decomposition cycle, we often begin garden activities at the compost bin. First compost is harvested from the “out” bin and screened through wire mesh. The chunks go back into the “in” bin (adding some all-important bacteria) and the finely screened particles are fed to the garden. Another use for the chunks that don’t go through the screen (1/4″ mesh) is compost tea. (More on that below.) After we pick food from the plants to feed ourselves, waste from our snacks is fed back into the compost bin, completing the cycle.

Ingredients of compost

To balance the nitrogen-rich food waste, referred to as “greens”, carbon-rich “browns” must be added in approximately equal quantities by volume. An easy source of “browns” is the shredded paper that comes from the office’s confidential school records. (What a fitting end to that cycle!) Other sources of browns are straw, dry leaves or shredded newspaper. A great source of browns, if it’s handy, is planer waste from a woodworking shop. Make sure the wood is not walnut or cedar, though – these woods inhibit plant growth. And of course, make sure the wood that’s worked is natural, not impregnated with chemicals or glued particle board etc. It’s important that whatever material you use for browns is fairly fine and easy to mix in with the greens, since it’s the increased surface area of both browns and greens that helps speed up decomposition. Some moisture helps (add water if necessary) and air circulation is essential – turning and mixing up the compost is great fun for kids but also should be done by adults to get the materials fully mixed every now and again. This speeds up the decomposition process.

Compost as a soil amendment

Much of the soil in our city suffers from drainage problems: areas that are very sandy drain too quickly; heavy, clay soils don’t drain enough, becoming packed down and impeding root growth. The solution to both drainage problems is adding organic material to the soil – composting is one of the best ways to do this since it adds a balance of nutrients at the same time as it improves the soil’s texture. Compost is also vital for successful container gardens. When apartment dwellers start balcony gardening and see the benefits of using compost, they may have a newfound incentive to participate in composting. Vermicomposting is a mini-cell that works in a slightly different way, using red wiggler worms. A worm bin is a good choice for balcony and apartment gardening.

Landfill diversion

Up to half of the garbage we throw away in the city is organic food waste that could be composted instead. The wet food is what makes garbage heavy and smelly. The more waste we can divert from landfill also means less fuel burned for trucking our garbage out of town. The Green Bin program (a pilot organic waste collection program in Toronto) is a great waste management solution but the finished product has tested high in salt, because of the amount of salt in the inputs, rendering it less than ideal for food production. With school composting programs, we can keep valuable nutrients on hand and use the compost to increase the potential for producing nutritious food for school food programs.