By Jim Hole
In September 2000, Edmonton hosted the 10th annual National Composting Conference. The focal point of the conference was the Jekyll and Hyde nature of compost. So, how do we turn liabilities like dead plant matter, lumber mill waste, and manure into a manageable resource?
Climbing the C:N Tower
Delegates at the conference noted that any material to be broken down must be organic; in other words, it must contain the element carbon. Fortunately, all terrestrial life is made with carbon building blocks, so this is never a limiting factor. What can limit your compostable materials, though, is nitrogen, the same nutrient found in many fertilizers. The carbon:nitrogen, or C:N, ratio was frequently discussed at the conference. Unless the C:N ratio is within the correct range, the breakdown of organic matter comes to a virtual standstill. Ideally, the waste that you are breaking down should have a C:N ratio of 30:1.
Sawdust—a waste product many have tried to compost with frustrating results—has a C:N ratio of 400:1. Sawdust's very low nitrogen count explains why it takes so painfully long to decompose. Grass clippings, on the other hand, have tons of nitrogen, and if added to a pile of sawdust they can help to strike the right balance between carbon and nitrogen.
Finding the correct moisture balance is the second big issue in composting. In one presentation, researchers from the Agriculture and Agri-Food Canada Research Centre in Lethbridge explained the difficulty they faced with composting feed lot manure. Initially, the moisture level in manure is excessive, but after a few short weeks of hot, dry winds, the composting manure becomes too dry for proper decomposition. Whether the compost is too wet or too dry, the breakdown process slows down to a crawl. In back yards, the scale is smaller but the problem can often be the same. Ideally, compost should feel like a moist sponge that's just been wrung out. If your compost is too dry, simply water it. If too wet, turn it with a pitchfork to expose as much of the material as possible to the air.
Finally, remember that compost should never be allowed to get too heavy or dense; this, too, will hinder decomposition. Regular aeration of the compost pile is critical, and easily achieved by turning the pile with a pitchfork once a week.