Nearly 80 percent of Americans live in municipalities with a population exceeding 20,000. This steady growth in urban population has exacerbated yard waste problems for many communities. Central to the issue is the enormous problem of grass clippings and their disposal.
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Large-scale facilities often use the agitated bed method to aerate and keep microbes working in the production of compost.
As increased handling costs affect local tax rates, city planners and government officials are establishing ordinances to limit their exposure to yard waste. Most cities across the country, and half the states, have passed statutes forbidding the dumping of clippings into public landfills.
According to Chaz Miller, programs director, National Solid Wastes Management Association, "By weight, grass is the biggest component of yard waste, averaging half of all yard waste."
Composting yard waste at a commercial composting facility has emerged as the primary alternative. However, a few communities continue to allow commercial clippings at municipal sites.
Green View Landscaping, with operations in several municipalities in Illinois, must comply with various ordinances. Ashley Haffner, marketing director, says, "In Champaign-Urbana, we do not bag clippings, we pay to recycle all the yard debris. In Bloomington-Normal, it is all taken to a compost site provided by the city free-of-charge. In Dunlap, Ill., we do a combination of all three methods."
When decomposing, clippings expel foul odors and are slow to break down, and they must be bundled with brush or other woody plantings. Barnes' compost is a combination of yard debris, grass and food wastes.
Grass clippings only become waste products when taken to landfills. As they decompose, nutrients are lost to ground water contamination. The standing pools of yellowish and blue water found in landfills often finds its way into groundwater. Grass clippings comprise 10 to 20 percent of the solid waste collected by communities on a year-round basis. Curbside collection of grass clippings increases trash tonnage, handling, hauling costs, taxes and can consume valuable landfill space.
Many communities, such as Dublin, Ohio, utilize private hauling companies to pick up curbside yard waste. Collected waste is then disposed of in private composting facilities. Ronald L. Burns, director of streets & utilities for Dublin, Ohio, says, "The city of Dublin does not have an ordinance prohibiting landscape contractors from leaving the yard waste from a Dublin resident's property at the curb for disposal by the city; however, the city does encourage contractors to dispose of yard waste off-site."
Kurtz Brothers, Inc., operating composting facilities in North Royalton and Elyria, Ohio, has been at the forefront in compost technology. Greg Malone, research and product development director, explains, "Our primary source of raw material comes from brush, yard trimmings, leaves and grass clippings. The perfect combination is most difficult to acquire during summer and late fall. That makes it difficult to reach the ideal carbon to nitrogen ratio of 30:1."
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Washington State University, Pullman, Wash., composts about 25,000 cubic yards of organic waste annually on a four-acre asphalt surface.
PHOTOS COURTESY OF PLANT SERVICES DEPT. OF THE UNIVERSITY OF WASHINGTON
Springtime collection of clippings reaches its peak and so there is often an overabundance of nitrogen. Managing inflow of proper materials can be a real challenge for composting facilities.
A tipping fee is charged to landscape companies at commercial sites. A few cities, such as Defiance, Ohio, maintain seasonal municipal composts sites. However, commercial disposal is prohibited. They offer their finished municipal compost free-of-charge to residents.
Waste Management Services (WMI), the nations largest curbside waste disposal service, has invested heavily in ongoing composting operations. In Illinois, the company's compost is retailed under the brand names Organic Valley and Nature's Helper. WMI also built a facility to process pre-consumer commercial food waste and yard waste at its Vista landfill in Apopka, Fla.
More than 100 cities now offer "curbside composting." Plastic refuse bins are placed at each home to recycle a combination of grass clippings and food refuse. Several energy companies are using clippings and discarded food for anaerobic digestion, a fermentation process that creates biofuels.
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These bins are relatively common in the landscape trade. At this facility blowers force air into the material to keep the composting process going.
Having access to a variety of materials is essential to establish proper composts piles. Landscape companies offering a myriad of services, such as tree pruning and stump grinding, often have the most access to necessary compost elements. The area of a compost pile must be large enough to prevent dissipation of heat and moisture, yet small enough to allow good air circulation and oxygen content. As composting proceeds, the C/N ratio gradually decreases from 30:1 to 10 to 15:1 for the finished product.
Recipes for Success
Some landscape companies produce their own compost. Though not a fertilizer, yard waste compost is a useful soil conditioner. However, managing the decomposition process is not an easy task. As mentioned above, the proper ratio of carbon to nitrogen is 30:1. To reach and maintain that mix, the composts manager must have a basic understanding of the C/N of key elements.
Here are some ratios to emphasize that point: Carbon:Nitrogen Ratio -Food Wastes, 15:1; Wood, 700:1; Sawdust, 500:1 Straw, 80:1; Grass Clippings, 19:1; Leaves, 60:1; Fruit Wastes, 35:1; Rotted Manures, 20:1; Cornstalks, 60:1; Alfalfa Hay, 12:1
Microbial breakdown of organic material produces heat. The amount of heat depends on the size of the pile, its moisture content, aeration and C/N ratio. Lack of proper oxygen levels produces the rotten-egg smell, familiar to most landscape professionals. Monitoring oxygen content often requires active aeration, provided by turning or mixing the compost ingredients on a regular basis.
A moisture content of 45 to 55 percent is considered optimum for composting. Often the same materials that are high in nitrogen also have a good moisture content. A soil moisture-sensor should be used to measure the compost regularly. Experienced managers sometimes rely on a daily squeeze test, whereby the compost mixture is squeezed in a closed fist. Composts should feel damp to the touch.
Nick McCullough, CEO of McCullough's Landscape and Nursery LLC, New Albany, Ohio, says they sometimes compost on a customer's property. "We're fortunate that a few of our properties are quite large and we have composting areas on the estates we maintain, eventually retuning the compost to the gardens."
Homemade compost can be used in flowerbeds, when overseeding a lawn and as an amendment to turf soil. Raw clippings recently treated with pesticides should not be used as a mulch immediately after mowing, but can be harvested for compost. Most pesticides degrade rapidly in compost piles because of the high temperatures and moister content.
To bag or not to bag
The most effective use of grass clippings, and perhaps the most responsible, is to simply allow them to decompose. Termed "grasscycling" by proponents, this method is less costly and more environmentally friendly. When left on the lawn to decompose, grass clippings decompose rapidly. Clippings feed soil organisms, recycle nutrients and contribute organic matter. As a result, water is conserved and less fertilizer is needed.
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Compost produced at the Washington State University site is only sold as a wholesale product to nurseries and retailers in large quantitites of 50 cubic yards or more.
Dave Peabody, president, Peabody Landscape Group, Inc., Columbus, Ohio, explains that leaving the clippings is always the first option. "Only if we have to, do we bag the clippings, if the grass is too wet or the grass is really long, especially in the spring. No question that a lawn that has been bagged has a nicer appearance, however, it costs additional money, and two days following the site-visit the customers forget how nice the lawn looked or if the clippings were bagged anyway."
The "Don't Bag It" campaign started in the early 1990s by Dr. Bill Knoop at the University of Texas A&M, not only encourages landscape companies not to bag clippings, but explains how other factors such as over-watering and over-fertilizing contributes to the problems associated with disposing of grassclippings (www.arlingtontx.gov/environmentalser vices/pdf/grassclippings_dontbagit.pdf).
In conjunction with any crusade to allow clippings to decompose on a client's lawn, is the one-third rule. Allowing grass to grow to about 2 to 3 inches and setting mowing depth at one-third of the blade height.
Like most professional landscape companies, Garrick-Santos Landscape Co., Malden, Mass., handles clippings as volume and conditions dictate. "We do dispose of grass clippings off-site and we also use mulching decks during June, July and August," said Anita Garrick CLP, MCLP. "Depends on weather and site conditions though. We don't bag it to send to recycling centers, it goes by the truck or dumpster full, daily."
With a U.S. population now in excess of 315 million people, most crowding into ever-growing metro areas, programs to recycle clippings either at private composting facilities, such as Barnes Nursery, Kurtz Brothers or Waste Management, or by composting at the individual landscape facilities or "Grasscycling" remain the most effective choices available. However, new technologies, such as anaerobic digestion are advancing as municipalities search for better alternatives to keep disposal costs down.
Jackie Ingles is a writer, editor and freelance partner with her husband, Mike. She lives and works in Columbus, Ohio, and can be contacted at <45 light="" oblique="">firstname.lastname@example.org>