Grass is Greener in Composting

by Diana Barnum


Most yard waste composting facilities in the U.S. use windrow technology, as shown here.

Composted grass may not be a pretty shade, but the money coming from yard waste composting sure is. This is one area where the grass is definitely greener on the other side…of the compost facility, that is.
“The composting and organic recycling industry is doing well despite the economy today,” according to Dr. Stuart Buckner, executive director of the U.S. Composting Council. “One area of significant growth is yard trimmings composting projects. The number of facilities that handles this nationwide has grown from about 650 in 1988 to over 3,800 today.”
Why the increase? Two reasons: content and bans. A shift from mainly leaf composting to mixed yard waste that includes grass clippings and brush caused an increased need for facilities to handle the material. But the main reason is local and regional bans on yard waste disposal in landfills created a sudden need for facilities. At the time of Dr. Buckner’s research, presented in a report entitled, “The Current Status Of Organics Recycling And Composting In The United States,” 22 states had these bans in effect.
Yard waste generates the most waste, approximately 28 million tons last year, of which 45% is recovered with composting. However, Buckner notes that yard trimmings are down. He reported 35 million tons in 1990 compared to 30 million in 1999.

A handful of compost enriched soil.

“The number of facilities may have plateaued, but growth is expected to continue at a slower rate,” said Buckner.
He noted that components of growth and non-growth are due to an increase in demand for composted projects and an increasing demand for sources. Successful reduction campaigns like “grasscycling” or leaving the clippings on the lawn is also a factor.
A negative factor in the industry is odor control. But Buckner found that successful facilities are site-specific in design, process management, material handling and odor control throughout their entire operations.
Equipment and Technology Most yard waste composting facilities in the U.S. use windrow technology. Some use static piles. Generic pieces of equipment that are required at most facilities include shredding machinery, front- and back-end machinery, aerating or turning machines and bagging equipment. Exact models of equipment depend upon the type of waste (some facilities handle biosolids and other materials), mixture, how it is delivered, quantity delivered, regulatory requirements such as speed and proximity to neighbors and the site’s size.
“The U.S. Composting Council can help determine equipment needs,” advised Buckner.
He did note two new models of equipment that have enhanced the industry lately; logger shredders and varied screens. Logger shredder manufacturers are expanding the shredder’s ability with a variety of sizes and shapes. And screen manufacturers are designing a variety of sizes and speeds. These new models help meet the different facility sizes out there, as some handle leaves and grass, some also include brush and others add in stumps.
Some of these new screens were chosen by Kevin Tritz, president of the U.S. Composting Council and multi-facility operator for Specialized Environmental Technologies, Inc. of Bloomington, MN. Tritz is a subcontractor who manages 11 compost sites for NRG Energy Center in Minneapolis with 72 employees. His group is known as the Resource Recovery Division.
On one NRG site that handles yard waste, organics are also taken in. A standard picking line checks the content of materials that arrive with a horizontal Mueller unit. They use a 7400 Peterson Pacific Unit horizontal shredder for grinding yard waste and organics go into biodegradable bags.
Tritz participates in a pilot program that sends the balance of materials to the energy plant to make fuel for electricity. He began hauling 10,000 tons per year or 40 tons per day in 1998 for the program. Now the amount is 150 tons per day. Transportation is a problem, though.
“We’re going through pilots with some haulers to collect organics,” said Tritz. “Receiving material and transporting materials economically is a large problem to overcome.”
Biodegradable bags with co-mingled waste are hopefully in the future.
“It’s the evolution of recycling,” Tritz explained.
The U.S. Composting Council listed more than half a dozen markets and applications for compost. The demand of more than 1 billion cubic yards per year goes to:
• Retail and homeowners for landscape and garden needs
• Sports turf
• Nurseries for growing plants
• Landscaper Companies
• Agriculture for crops and soil
• Silviculture for seedlings and mulch
• Topsoil blenders to amend soil
• Landfills for cover
• Roadsides for erosion control and growing solutions.
An estimated 500,000 cubic yards of compost used in 2000 by the states’ Departments of Transportation alone, and a projection of more than 18 million cubic yards needed per year, equals a lot of revenue. Grass could very well be greener on the other side of the compost facility.
For more information and composting solutions, contact Dr. Stuart Buckner at the U.S. Composting Council, 200 Parkway Drive South, Suite 310, Hauppauge, NY 11788. Call: (631) 864-2567; or fax inquiries to: (631) 864-3796. Kevin Tritz can be reached at Specialized Environmental Technologies, Inc., 8585 W. 78th Street, Suite 240, Bloomington, MN 55438. Call: (952) 946-6999; or fax inquiries to: (952) 946-7975.