Yard waste includes grass, leaves, and tree and brush trimmings. By weight, grass is the biggest component of yard waste, averaging 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 municipal solid waste by weight but is a relatively small component of landfilled MSW by volume.
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 (132-140 F), moisture content (40-60 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), which causes health problems.
The amount of yard waste and its MSW disposal market share declined dramatically in the last four decades while the composting rate soared. Backyard compost piles and grasscycling programs have reduced yard waste generation. State and local composting requirements increased the number of commercial composting operations.
Yard Waste MSW Facts
- 32.9 million tons, or 12.7% of MSW by weight.
- 216.4 pounds (lbs.) per person per year.
- 21.3 million tons or 64.7%.
- 3,500 yard waste composting facilities, mostly in the Northeast and the Midwest.
- Average daily throughput is 57,300 tons.
- Compost can be produced in as little as three months.
- Yard waste compost accounts for one-fourth of U.S. recycling rate.
Incinerated or Landfilled:
- 11.6 million tons or 7.0% of discarded MSW.
- Percentage sent to disposal has steadily declined for the last three decades.
- 2,876 Btus per lb. vs. 4,500-5,000 Btus for a lb. of garbage.
- Several states ban the burning of yard waste piles.
- 24 states ban or restrict yard waste disposal.
- 21.7 million cubic yards (cu.yd.) in 1997.
- 5.1% of landfilled MSW in 1997.
- Uncompacted is 250-500 lbs./cu.yd.
- Landfilled is 1,500 lbs./cu.yd.
- Grasscycling (“leave it on the lawn” programs) and backward 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 little waste) reduces yard waste.
- Composted yard waste is a 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.
- Premium compost is used as a soil amendment or mulch.
- Compost useful as landfill daily cover.
- Processors often charge a tipping fee.
End Market Specifications:
- Vary by market.
- Keep non-organic materials out.
- Tests show little heavy metal contamination.
“Municipal Solid Waste Generation, Recycling, and Disposal in the United States: Facts and Figures for 2008,” U.S. EPA, Office of Solid Waste, 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 Recyling Coalition, Washington, www.nrc-recycle.org
* Data is from 2008 EPA estimates, except where noted.