Municipal Composting

We know about composting at home: using leaves to create a compost pile, to which you add fertilizer, water and turn over regularly. Three weeks to three months later you have organic material that you can add to your soil.

Now, multiply that idea by hundreds of thousands of pounds of material and you get composting municipal style.

There are now compost facilities in many large cities that handle the composting of city waste material. These facilities turn former waste into a usable product derived through recycling. In addition, since December 1993, lawn clippings can no longer be added to landfills in the state of Ohio. Knowing that cities are working on potential solutions to that problem is comforting.

There are actually three ways to compost on such a large scale.Obviously, turning product by hand as we do at home is impossible - instead it's done with specialized equipment. The three techniques are solar reactor, static air and wind row - with windrow being the primary one used.

The solar process simply uses the sun's rays to generate heat for drying the composted product. This seems like a simple process, but is actually made quite complex by the sheer volume of the product. The machinery is considerably different also; digging the product from the bottom rather than actually turning it.
The second method, static air, utilizes the process of heat rising by forcing air through a hose into a bed of wood chips on which the material is placed. No turning is necessary and the pile breaks down as it stands, usually in about three to four weeks.

The process that composts the largest amount of material is windrow. The material is laid out in ling rows about 3-6 feet deep. Machinery turns the piles periodically - usually daily, based on constant temperature checks. When a period of heavy rain is predicted, the machinery is used to consolidate the piles. Unlike home compost piles, the problem with stacks of material in this huge quantity is that it tends to be too wet. If you have material spread out over an acre and 1 inch of rain falls, you have to spread it out even more to dry. If it can be consolidated to only half an acre prior to the rainfall, it does not absorb as much water.

All three processes are weather-driven; meaning the schedule of turning the product is based on the weather predictions. At home, you generally add water when you add fertilizer in order to make the compost pile break down a little faster. With large quantities, the problem is maintaining enough heat to ensure that breakdown will occur.

To encourage breakdown, the material is initially shredded into smaller pieces. Then, careful monitoring is done to ensure that the proper ratio of carbon to nitrogen is maintained for optimum breakdown.

Interestingly, even composting sludge is a good way to handle waste from water treatment plants. When properly composted, 99 percent of injurious bacteria are eliminated. You then have a useable product that can be blended with topsoil to add organic material to gardens.

This material is perfect for top dressing a garden. The amount to use depends on the nitrogen content. The supplier should know the content of the product. A leaf-based material can be added up to a depth of 2 inches. If the product is primarily sludge-based, only about one-half inch should be put on your garden. The reason for this is simple chemistry: the sludge-based product is higher in nitrogen and could cause excessive growth spurt.

Whether this process is a final solution to the problem of waste disposal, I can't say. But, in any case, this procedure provides a good usable organic product and you should consider taking advantage of its availability. Compost by the bag, pick-up load, or in large trucks is now ready for your use. You can also find it as a major ingredient in bagged potting soil.

Take pride in knowing that, as gardeners, you are part of the solution to one of our societal surpluses.

The current good news is that some metropolitan areas are looking at the by-products of other industries that might be composted along with yard waste.