Yard waste includes grass, leaves, and tree and brush trimmings. By weight, grass is yard waste's largest component, supplying an average of half of all yard waste. Leaves and brush each provide one quarter. By volume, leaves are the biggest component.
Yard waste is the largest single component of generated MSW by weight, but it is a relatively small component of landfilled MSW by volume.
The MSW generation and disposal market share of yard waste declined dramatically in the past four decades, while the composting rate soared. Variable rate programs promoted backyard compost piles and grasscycling. State and local composting requirements increased the number of commercial composting operations.
Composting is the controlled decomposition of organic matter by microorganisms into a humus-like product. Waste and carbon dioxide dissipate into the atmosphere. Up to 75 percent of the volume and 50 percent of the weight are lost through composting.
Aeration, temperature control (132 to 140 degrees F), moisture content (40 to 60%) and an adequate carbon-to-nitrogen ratio are required. Improper operation can cause odors and allow the growth of a fungus, aspergillus fumigatus, which causes health problems.
The columnist is director, state programs for the Environmental Industry Associations, Washington, D.C. E-mail the author at: [email protected]
Biocycle, December 2001 www.biocycle.com
“Municipal Solid Waste in the United States: 1999 Facts and Figures,” EPA, Office of Solid Waste, 2000
Composting Council, Amherst, Ohio
Cornell Waste Management Institute, Ithaca, N.Y.
“Measurement Standards and Reporting Guidelines,” National Recycling Coalition, Alexandria, Va.
*1999 EPA estimates
Yard Waste Municipal Solid Waste Facts:
- 27.7 million tons or 12.1% by weight.*
- 203.4 pounds per person.*
- 90% is from homes, 10% businesses
- 12.6 million tons or 45.3%*
- 3,846 yard waste composting facilities.
- Ohio leads in yard waste composting facilities.
- Compost can be produced in as little as three months.
Incinerated or Landfilled:
- 15.2 million tons, 9.1% of discarded MSW by weight.*
- 2,876 Btus per pound heating value vs. 4,500 Btus to 5,000 Btus for a pound of MSW.
- Several states ban the burning of yard waste piles.
- 23 states ban or restrict yard waste disposal.
- 21.7 million cubic yards in 1997.
- 5.1% of landfilled MSW in 1997.
- Uncompacted is 250 to 500 pounds per cubic yard.
- Landfilled is 1,500 pounds per cubic yard.
- Grasscycling (“leave it on the lawn” programs) and backyard composting used 11.7 million tons in 1996.
- Brush can be shredded into mulch.
- Xeriscaping (landscaping with plants that need small amounts of water and produce small amounts of waste) reduces yard waste.
- Yard waste compost is not a fertilizer. It is a useful soil conditioner that improves texture, air circulation and drainage, moderates soil temperature, enhances nutrient and water-holding capacity, decreases erosion, inhibits weed growth, and suppresses some plant pathogens.
- High-quality compost is used as a soil amendment and as mulch.
- Compost can be used as landfill daily cover.
- Compost processors often charge a tipping fee.
- Vary by market.
- Keep nonorganic materials out.
- Tests show little heavy metal contamination.