YARD WASTE INCLUDES grass, leaves, and tree and brush trimmings. By weight, grass is the biggest component of yard waste, averaging half of the total generated. 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 is a relatively small component of landfilled MSW by volume.

The amount of yard waste and its MSW disposal market share have declined dramatically in the past four decades while the composting rate has soared. Variable-rate programs have promoted backyard compost piles and grasscycling. State and local composting requirements have 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 between 132 degrees F and 140 degrees F, moisture content of 40 percent to 60 percent and an adequate carbon-to-nitrogen ratio are required for composting. Improper operation can cause odors and allow the growth of a fungus (aspergillus fumigatus) that causes health problems.

Chaz Miller is state programs director for the National Solid Wastes Management Association, Washington. E-mail the author at: cmiller@envasns.org.

Sources:

Biocycle, January 2004, www.biocycle.com

“Municipal Solid Waste in the United States: 2001 Facts and Figures,” U.S. EPA, Office of Solid Waste, 2003, www.epa.gov/osw

Composting Council, Amherst, Ohio, www.compostingcouncil.org

Cornell Waste Management Institute, www.cfe.cornell.edu/compost

“Measurement Standards and Reporting Guidelines,” National Recycling Coalition, Alexandria, Va., www.nrc-recycle.org

Yard Waste Municipal Solid Waste (MSW) Facts:

Generated:

  • 27.98 million tons or 12.2% by weight.*

  • 196.5 pounds (lbs.) per person.*

  • 90% is from homes, 10% from businesses.



Composted:

  • 15.8 million tons or 56.5%*

  • 3,227 yard waste composting facilities.

  • Ohio leads in yard waste composting facilities.

  • Compost can be produced in as little as three months.



Incinerated or Landfilled:

  • 12.16 million tons or 7.5% of discarded MSW.*

  • 2,876 Btus per pound versus 4,500 to 5,000 Btus for 1 lb. of garbage.

  • Several states ban the burning of yard waste piles.

  • 23 states ban or restrict yard waste disposal.



Landfill Volume:

  • 21.7 million cubic yards (cu. yds.) in 1997.

  • 5.1% of landfilled MSW in 1997.



Density:

  • Uncompacted is 250 to 500 pounds per cubic yard (lbs./cu. yd.)

  • Landfilled is 1,500 lbs./cu. yd.



Source Reduction:

  • Grasscycling (“leave it on the lawn” programs) and backyard composting combined to make yard waste the most source-reduced item in the waste stream.

  • Brush can be shredded into mulch.

  • Xeriscaping (landscaping with plants that need little water and produce small amounts of waste) reduces yard waste.



Composting Markets:

  • Not a fertilizer, yard waste compost 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 mulch.

  • Compost can be used as a landfill daily cover.

  • Compost processors often charge a tipping fee.



End-Market Specifications:

  • Vary by market.

  • Keep non-organic materials out.

  • Tests show little heavy metal contamination.