EVERY SPRING, MILLIONS OF AMERICANS mow their lawns and bag up the clippings, only to sigh in frustration when the grass grows back a week later. Thanks to a nationwide increase in yard waste recovery, however, people can feel good about all the grass, leaves and brush they rake up every year.
Across the nation, states and local governments have made great strides in the recovery and reuse of green waste. And as long as grass keeps growing and wood is discarded, green waste recovery should remain a viable and beneficial option.
A Growing Market
Yard waste continues to be one of the largest components of the municipal waste stream. In 2003, the last year for which the U.S.(EPA) has provided data, 236 million tons of municipal solid waste (MSW) was generated, with yard trimmings and food scraps together accounting for about 24 percent. Wood waste contributed another 6 percent. Yard and wood waste are also significant contributors to the nation's MSW recovery rate, which now stands at just more than 30 percent. In 2003, the amount of MSW recovered for recycling rose to more than 55 million tons, a 3 percent increase over 2002. About 56 percent — or more than 16 million tons — of yard trimmings were composted, representing almost a quadruple increase since 1990.
EPA estimates that about 60 percent of MSW produced in the United States, including paper, is compostable. Compost provides a variety of environmental benefits. In addition to saving landfill space through diversion, compost reduces the production of methane and acidic leachate in landfills, enriches soil, absorbs volatile organic compounds and toxic material in contaminated soil, and protects against erosion. Economically, compost can serve as a low-cost alternative to landfill cover and artificial soil amendments, and it can reduce the use of water, fertilizer and pesticides in agricultural and other land-use applications.
With the widespread adoption of landfill bans on yard waste (23 states ban or restrict its disposal), the composting industry has steadily grown over the last decade. Curbside yard waste collection programs are increasing, and drop-off locations for brush and bulkier wood waste are commonplace. More than 3,800 composting facilities exist nationwide, according to EPA.
Ohio, for example, is one of many states with a ban on yard waste in landfills, which enabled the state to recover 3.8 million tons of clippings in 2003, a full 62 percent of the total tonnage recycled in the state that year. New Jersey, Oregon and Washington also are leaders in yard waste recovery. In each of these states, yard and wood waste recovery accounts for more than 40 percent of the total material recycled.
“As disposal and collection costs increase, there are more dollars on the table for program directors to design programs that capture resources like yard waste,” says Kate Krebs, executive director of the Washington-based National Recycling Coalition (NRC). “While I don't like to see disposal costs increase, it gives you more flexibility as a waste manager. Yard trimmings are a big part of the waste stream, [and] the yard waste composting figure [from 1990 to 2003] represents one of the highest recycling growth rates. And that doesn't necessarily include backyard composting, which is so hard to quantify.”
In 1990, the North Dakota Legislature, for example, encouraged yard waste recovery as part of a statewide waste-reduction program. To comply, the city of Fargo established 13 drop-off locations with large green roll-offs where yard waste could be deposited from the spring through fall. Between 1990 and 2005, the city collected 86,000 tons of yard waste from the drop-off sites alone, and another 31,000 tons were collected from surrounding communities and private haulers through separate contracts.
“People can bring their yard waste, grass, leaves and organics, but not food waste,” explains Angela Boeshans, the city's recycling coordinator. “Then, every spring and fall, we offer residents a yard-full of compost and wood chips, and that's created from the yard trimmings we collect and the chips that come from our forestry program, including brush and pallets.” The waste is composted at the city landfill, which maintains a 22-windrow operation. The city has also contracted with the ADM sunflower processing plant in Enderlin, N.D., which uses the wood waste as fuel in its boiler. Biomass fuel continues to be the largest market for recovered wood wastes.
“We appreciate that the diversion saves space in our landfills,” Boeshans says, “but also that we can provide a product that benefits people's yards and the local economy.”
In California, thanks to the statewide diversion law AB 939, local governments have launched concerted efforts to recover more green waste. Since 1997, the California IntegratedBoard, Sacramento, has deemed the recovery of organic materials a top priority. Cities such as San Francisco and Bakersfield have established programs that collect and process yard waste and other organics to produce compost.
Modesto, for example, provides residents with a 90-gallon container in which to collect yard waste and brush, and it also receives biosolids from a wastewater treatment facility. The city's windrow compost facility produces two products, “Mo-Gro Pro,” a compost made from yard trimmings that is sold to landscapers and farmers, and “Mo-Gro Magic,” a co-compost made of biosolids and yard-trimmings and sold in bags. The program has helped the city reduce its waste stream by 12 percent, recovering about 24,000 tons of yard waste each year.
In 1992, the Sonoma County Waste Management Agency (SCWMA), Santa Rosa, Calif., was established to manage MSW for nine cities in the county and the county itself. The agency operates programs for yard debris composting, wood waste chipping, household hazardous waste collection, source reduction and education that collectively divert about 37 percent of waste from the county's landfill. Yard waste, trimmings, leaves, grass and small tree limbs — but not dimensional lumber or wood products — are accepted in a weekly curbside program. Waste is processed at a 25-acre composting facility at the landfill. The facility handles about 75,000 tons of yard waste a year. In addition, the county collects about 11,000 tons of wood waste a year from haulers that transport it directly to the facility.
“We have calculated that we have reduced the amount of green waste in our landfills from 15 percent in 1990 to about the 3-percent range right now,” says Ken Wells, director of SCWMA. “Of the green waste that gets discarded, 93 percent gets into our green waste program. We attribute that to the longevity of our weekly program. Residents get used to the regularity of putting that yard waste in the can.”
Through a partnership with the Sonoma Compost Co., Petaluma, Calif., the resulting compost is sold as a soil mix to vineyards, nurseries, landscaping companies and other organizations. Wood waste is reused as mulch and biomass fuel. Sonoma Compost also has participated in composting research projects, including an effort to determine if mulch derived from partially composted yard trimmings could successfully reduce soil erosion in hillside vineyards. The yard trimmings were ground through a 1.5-inch screen, composted for at least 15 days and kept at a moisture content of 40 to 50 percent. By the second year, soil loss was reduced by 78 to 98 percent in mulched vine rows compared to rows that had no mulch and little cover.
Looking ahead, the agency now is studying the feasibility of adding more food waste to the green waste recycling program.
Green waste recovery may be lucrative for many cities and counties, but it also can suffer during economic downturns. Houston, for example, ran a successful yard and wood waste recycling program for years. In fiscal year 1999, the city composted nearly 29,000 tons of yard waste, saving $463,149 in landfill fees, according to a Houston Chronicle report.
In addition to collecting yard waste at the curb, the city contracted with private companies to sort wood waste from heavy trash and convert it for use as mulch, soil amendments and boiler fuel. At one point, wood waste comprised about 32 percent of the more than 125,000 tons of heavy trash the city collected each year.
Nearly four years ago, the city was forced to temporarily suspend the yard and wood waste program because of budget cuts. The city then collected yard waste only sporadically before the program was suspended again last year during the hurricane season. The storms strained the city's general budget and its waste management resources specifically.
The suspension of the green waste programs is a contributing factor to Houston's poor overall recycling rate, which some reports have said is less than 3 percent.
Ed Chen, deputy director of the city's solid waste department, says that he and his colleagues are determined to reinstate the yard and wood waste recycling program as soon as possible. Chen has proposed to the city that the wastes be collected only in odd months.
Going forward, NRC's Krebs believes that communities must pay more attention to the recovery, processing and end-use development of wood waste. In addition to its use as a biofuel and in pulp and paper applications, numerous secondary uses exist for recovered wood waste, but markets are highly variable. The end uses include animal bedding, interim road beds, mulch and soil amendments and bulking agents for compost.
Although recovering green waste has tangible environmental benefits, having an economically viable end use is often the major selling point for city officials and participants, according to Krebs. “What creates methane in landfills? [Mostly] yard debris and trimmings,” she says. “If you don't put the yard trimmings in, you don't produce as much methane, and you reduce greenhouse gas. But it's a hard sell when you're looking at something as big as greenhouse gas production. When you can produce compost or fuel that creates new jobs and that has benefits, both environmentally and economically, that's all the better. The front-end benefits are nice, but the back end is nice too.”
Kim A. O'Connell is a contributing writer based in Arlington, Va.
GREEN WASTE EQUIPMENT SNAPSHOT
- Tub grinder from DuraTech Industries, Jamestown, N.D.
- 20-yard rolloffs from International Truck & Engine Corp., Chicago; Ford, Dearborn, Mich.; and Galbreath, Winamac, Ind.
- Compost loader from Caterpillar, Peoria, Ill.
- Compost turner from Wildcat, Freeman, S.D.
Sonoma County, Calif.:
- Tub grinder from Zehr Manufacturing, Caldwell, Idaho
- Front-end loader from Volvo Construction Equipment North America, Asheville, N.C.
- Screen from Erin Systems USA, Portland, Maine
- Compost turner from Scarab Manufacturing, White Deer, Texas