Yard waste includes 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 third largest component of generated MSW by weight after paper products and food waste. Yard waste is the fifth largest component of discarded MSW, after food waste, plastics, paper products and metals. Yard waste 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 degrees Farenheit), moisture content (40-60 percent) and an adequate carbon-to-nitrogen ratio are required for composting and to avoid fungal infestation.
The amount of yard waste sent to disposal went down by 50 percent in the last two decades and its MSW disposal market share declined by the same percentage. At the same time, the composting rate soared. State and local composting requirements increased the number of commercial composting operations.
Chaz Miller is state programs director for the National Solid Wastes Management Association, Washington. E-mail him at: [email protected]
Yard Waste Facts*
- 33.4 million tons, or 13.4% of MSW by weight.
- 216.1 pounds (lbs.) per person per year.
- 19.2 million tons or 57.5%.
- 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.
- 14.2 million tons
- or 8.6% of discarded MSW.
- Amount sent to disposal has been flat in the last decade after declining dramatically in the previous decade.
- 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.
- 25 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 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 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.
Biocycle, Oct. 2010, www.biocycle.com
“Municipal Solid Waste Generation, Recycling, and Disposal in the United States: Facts and Figures for 2010,” 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 2010 EPA estimates, except where noted.