JARS v45n2 - Compost in Two Weeks!

Compost in Two Weeks!
Bob Freeman
Victoria, British Columbia, Canada
Reprinted from the Victoria Rhododendron Society Newsletter, February 1990.

After I built my rhododendron beds, I began to investigate ideas about composting. From previous experience, I knew that making compost by the usual methods took about a year. Somewhere I read about an idea for instant compost. I checked with Camosun College and got details about a course called "Creative Composting." I eventually attended the course to get the "know-how" and the results are phenomenal.

I now produce sufficient compost every week to keep my rhododendrons happy with enough left over to supply the neighbors and a few bags for the Rhododendron Society. This type of composting is comparatively new, very quick and a proven method.

A suitable blend of ingredients with a proper carbon to nitrogen (C:N) ratio is needed. The C:N ratios of various organic materials are as follows; food wastes 15:1, grass clippings 19:1, shredded leaves 40:1, rotted manure 20:1, plant stalks and foliage 15:1.

The ingredients have to be adjusted so that the starting ratio is 25:1 to 30:1. As an example, one weight of grass clippings (19:1) mixed with an equal weight of shredded oak leaves (40:1) will produce material with a C:N of approximately 30:1.

An ample nitrogen content is the key to rapid composting. Some materials, such as food wastes, manure or grass clippings, act as a starter for the decomposition of the drier, coarser materials, such as oak leaves. The addition of a commercial chemical starter is simply not necessary. The pile must be kept moist but not soggy wet.

Obviously, lawn clippings are in just the right form already. Other materials need to be chopped or shredded. For example, I always crush egg shells and chop up vegetable stalks. Weeds and their seeds can be used because the heat that is generated in the composting process destroys their ability to germinate.

The size of the pile must be more than one cubic yard or the heat will not be retained. Furthermore, the pile must be turned regularly and thoroughly so that the outer parts of the pile are brought to the interior and vice-versa.

The finished pile will heat up to 100° F (43° C) within the first day. After that stage passes, the pile, if properly turned, will undergo another stage during which temperatures of 155° to 165° F (68° to 74° C) will be reached. On subsequent turnings there will be smaller increases in temperature, but eventually the temperature will drop to 110° F and will not rise above this regardless of how often the pile is turned. This process takes about two weeks. During that time, the pile should have been turned at least three times. The C:N ratio will now be about 10:1.

My composter is 8 feet long, 3 feet wide and 5 feet high, divided into three bins, topped with a fiberglass roof. The bins are about 6 inches off the ground to improve air circulation and made of 1" x 6" boards spaced one inch apart to improve air access to the pile. The front boards of the same size are placed in slots for easy removal so that the compost can be turned and transferred to the next bin. Across the bottom of the bins, reinforcing rods are spaced at 7 inch centers and covered with stucco wire to hold the compost off the ground.

Each week I put one cubic yard of raw material in the first bin. At the end of the first week, I transfer it to the second bin and refill the first. The next week, I move the contents of the second bin to the third and so on down the line. When I remove the material from the third bin, it is ready to use in the garden - after just two weeks!