METRO
Solid Waste Department
600 NE Grand Ave.
Portland, OR 97232-2736
(503) 797-1650
Fax (503) 797-1795
Markets for yard debris compost were strong in 1993, marking the third consecutive year recovery of this material increased significantly. The quantity of yard debris recycled in the Metro area, and the percentage of all yard debris generated that was recycled, has more than doubled since 1990.
Increased recovery is due primarily to expanded curbside collection, expanding processing capacity and strong demand for finished compost product. New curbside collection programs came on line in Washington County in 1993. Universal Wood Recycling began accepting yard debris at two locations. Amazon Vegetation and C.L. Danner also opened yard debris processing operations. Wilsonville Waste Wood Processing resolved a permitting issue with Clackamas County and resumed operations. The Metro region adopted yard debris compost product standards.
Graphic: Estimated Tons of Yard Debris Recovered from Metro Area (1986-1993) [(See Source Document)
162,072 tons(1)
[FOOTNOTE 1: Generation equals tons recycled plus disposed in the Metro area. It does not include source reduction through home composting.]
105,483 tons = 68%(2)
[FOOTNOTE 2: This estimate is for material recovered from the Metro area in calendar year 1993. It is based on Metro's annual Recycling Level Survey. The term "yard debris" includes yard waste from wood, leaves and grass clippings. It does not include large stumps from land clearing at construction sites.]
Metro area
Metro area
$14-$54(3)
[FOOTNOTE 3: This is the range of fees processors charged for incoming material in July 1994. Some charge by weight while others charge by volume.]
Increasing steadily
Recovery leveling off
Yard debris is recovered primarily from the residential sector, although some is generated and recovered through maintenance of commercial and public property. This material is recovered through a number of different programs. Most cities in the region now have curbside collection. Haulers, landscapers and the public also self haul material directly to processors. Metro transfer stations do not accept source-separated yard debris for landfill disposal. The size, sophistication and quality control requirements of yard debris processing businesses vary greatly.
Most yard debris recovered in the Metro area is composted. Many chipping services also use raw, uncomposted chips as ground cover. Some composted material is sold as a soil amendment without additional processing. Much is screened and sold as mulch and soil amendment available in coarse, medium and fine sizes. This material is used in a variety of gardening applications and for erosion control. All local compost products currently are sold in bulk. Yard debris compost also is being tested as potting soil, horse stall bedding, and as a filtration medium for storm water runoff and aerosol can residues.
All processors compost recovered material on-site. Incoming loads are inspected and visible contaminants are removed by hand. Most facilities grind and screen ground yard debris to size specifications. Simple "piling" and turning with front-end loaders is the most common composting method utilized, although several processors plan to use "windrows" in the future. "Piling" literally means lumping recovered material into a pile and turning it with a front-end loader. The term "windrow" refers to rows of ground yard debris that can be aerated more effectively than a single pile, thus reducing total composting time. Ground material is watered and turned regularly to expedite the composting process.
Local processors have the capacity to handle more recovered yard debris, and their sales will support an increased supply of this material. While demand for compost products may have been constrained due to concerns about variable product quality, it has been sufficiently strong to enable processors to charge tipping fees that are less than half the Metro tipping fee for mixed municipal solid waste.
Yard debris compost products compete primarily with bark dust and peat moss, and secondarily with composted manure and mushroom compost. Prices for bark dust -- a byproduct of timber product industries -- are increasing in response to timber harvesting restrictions.(4)
[FOOTNOTE 4: Timber harvesting from U.S. Forest Service and Bureau of Land Management forest land has decreased 75 percent since 1988, according to an August 1993 study of alternative markets for recovered wood conducted for Metro by the engineering consulting firm - International Resources Unlimited of Eugene.]
Prices for peat moss -- a nonrenewable resource -- are high compared to compost products.
Processing and marketing costs can be minimized in several ways. Good quality recovered material, for example, typically costs less to process and market than poor quality recovered material, so educating waste generators and collectors about contamination issues can be effective. Processing costs also can be improved through technological advancements and process refinements.
Good quality recovered yard debris is relatively simple to compost. However, grinding, moving and watering this material is somewhat energy, capital and labor intensive. It is common for incoming loads of recovered material to contain large chunks of metal or wood that can damage and/or "choke" processing equipment, thus increasing operations and maintenance costs. The process of moving compost in different stages of maturity around processing sites -- which is done with front-end loaders -- is only semi-automated.
Quality control also is a significant cost component of compost processing. Heat generated during the composting process reduces or eliminates plant diseases, weed seeds, pesticide residues, and toxins. However, visible contaminants such as plastic and glass degrade the quality of compost products. Foreign materials in loads increase processing costs because they have to be "cleaned up" -- mostly by hand. Processors can remove most metal contaminants relatively inexpensively using magnets, but this technique does not capture all unwanted material; some manual quality control steps usually are necessary. The only effective way to remove plastic and other nonmetal contaminants is by hand.
Consumers are becoming increasingly environmentally conscious, and the look and benefit to clay soil of using compost products is becoming increasingly popular. Fine grade, uniform compost products that are free of weed seeds and pathogens are the most appealing to buyers. Oversized material is less marketable. Metro area processors produce a variety of different grades of compost that sell for varying prices.
In 1993, a Metro technical committee made up of experts in soil science, landscaping and yard debris processing adopted yard debris compost product standards. These standards are intended to address consumer doubts about variable compost product quality. Under this voluntary program, compost products that meet standards for pH, heavy metals, pesticide residue, plant nutrients, foreign materials, salts and seeds can be marketed as "Earth-Wise" products. Products marketed as Earth-Wise are tested twice a year to ensure they meet these new standards.
Recovery of yard debris is expected to continue to increase in 1994 and 1995, but increases are not expected to be as dramatic as in previous years. Sales trends indicate a steady market for this material. Regional population, employment and housing levels are projected to grow steadily through 2010. This would suggest growth in the economy with accompanying increases in building and landscaping activity.
Government procurement preferences for yard debris compost will expand demand, and there are a number of emerging applications for this material. Recent adoption of compost product standards should reduce consumer doubt about compost quality and consistency. Ongoing public education and promotion about the merits of compost products should also spur additional recovery.
Last Updated: November 1, 1995