Spring is on the way and that means a long list of gardening chores. Before the children prep the beds for planting, we need a good supply of humus. Because each class has been contributing their snack and lunch waste since September, we have a ready supply at hand. We just need to separate the finished humus from the material which is still decomposing.
Compost is simply organic material that has decomposed. It is essential to organic gardening because it returns nutrients to soil. Humus is the finished product used as a soil amendment.
We use a system of screens made from nursery plant trays and trays from a worm bin. The first screen set has large openings and the second screen set has smaller holes.
The children scoop material from the compost bin into the first screen set. With a little shaking, the smaller pieces fall to the tray. The larger pieces remaining on the screen get returned to the bin to continue decomposing.
The first tray is poured onto the second screen. A little more shaking and the humus falls down through the small holes to the tray.
The children felt the finished humus and compared it to the original compost material. The humus was described as "small" and "crumbly".
When they looked at the humus, they could not tell what it had been, but the compost material still showed pieces of banana and orange peels. They are able to see that the unused food was not wasted, but is now providing nutrients to the garden. This practice is one method of teaching the concept of bal tashchit.
Here's a little video of a member of the FBI; fungus, bacteria, and invertebrates. They are the allstars of decomposition.