To solid waste managers in Col-orado, the Rocky Mountains possess much more than beauty. The mountains of trees also bear organic materials which are filling up state landfills.
Realizing the potential for organic materials in the semi-arid West and the need for humus in the tough clay soils on Colorado's plains, the city of Boulder, Colo., in conjunction with Western Disposal Services Inc., sponsored a study to find low-cost ways to make quality compost products. The city of Boul-der wanted to determine:
* The cost-effectiveness of composting with low-tech methods;
* The quality level of the end-product, to ensure that it would be salable as compost;
* If additives such as newspaper or food waste would vary the quality level of compost products; and
* If the compost could be sold at a price that would cover production costs. The city also wanted to de-termine how much the public would pay for the end-product.
Western Disposal's low-cost composting plan required residents to deposit leaves at three drop-off sites. From the 79.5 tons of leaves collected during two-months, the company hauled approximately 155 yards directly to an organic farm to be tilled into the soil; the remaining 681 yards of leaves were composted in three concrete bun-kers at its transfer station.
Western used a front-end loader to turn the leaves and hose them with water. From November 6 to November 20, 1993, the leaves were turned once a week; from De-cember 1, 1993 to January 22, 1994, the loader turned and mixed the leaves twice a week; and from February 1 to April 9, 1994, the leaves were turned once a week.
Western Disposal prepared articles and advertised in local newspapers to inform the public of the available compost. The company's transfer station was the main outlet for selling the compost (either in bulk or by the bag); however, the city's farmers market also volunteered to sell the material on Sat-urdays. The city gave some of the composted material to the parks department to determine its value as an additive in flower beds.
By mid-April 1994, the city sold approximately 175 yards of compost to the public. By July 1994, leaf compost sales totaled $3,975. Overall, public demand for the product was good, but sales slowed after the spring planting season. The leftover compost will be used in the 1995 composting program.
The net cost of composting leaves in the pilot program was $38.42 per ton (see chart), including collection, processing and marketing costs (minus income from the sale of the compost).
The pilot program had the following results:
* Cost-effectiveness. The cost of composting leaves exceeded the income from sales even when using low-tech methods. However, at $38.42 per ton, the costs were far less expensive than an earlier city composting pilot program.
* Product quality. Compost made from low-tech methods is comparable in quality to compost made using specialized equipment. The city experimented by mixing the leaves with different additives, including newspaper, wood mulch and vegetable food waste.
* Leaf compost attributes. Gar-deners prize compost made from leaves as a high-quality soil amendment. However, marketing compost by its nutritional content is a mistake: It is a soil amendment, not a fertilizer.