Credit: Photo: Minnesota Pollution Control Agency
This aerial photo of the Crow Wing County Landfill shows the spray application of treated leachate on the compost area, on the landfill crown. About 620,000 gallons of leachate were applied to this area in 2005.
Credit: Photo: Portland Bureau of Maintenance
A Portland, Ore., worker pushes leaves to the end of a city block for pick-up. Leaves are then are moved to the recycling facility by dump truck.
Waste diversion is a buzzword across the country, and we're not just talking plastic and glass anymore. Green waste is being composted and re-used in increasing amounts in many municipalities, and many are doing it as part of their normal waste collection. “We provide a free drop off area for our residents to drop off their leaves and grass clippings,” said Douglas R. Morris, Crow Wing County (Minn.) solid waste coordinator. “We also take their brush for free. We do charge commercial [business owners] a fee if they bring in brush. This is to prevent them from clearing off land and bringing us all the trees and brush.”
Crow Wing County falls right in line with the nationwide trend of accepting yard waste, either by picking it up as part of trash collection or by providing drop-off sites for residents to haul in their own waste. About 15 years ago, a little more than 20 states had some sort of yard waste disposal ban. Today, there are nearly 3300 yard trimmings composting sites, according to a 2004 report by BioCycle magazine. The largest facilities process well over 100,000 tons per year of yard trimmings.
Minnesota statutes ban yard waste from being placed in a landfill, said Morris. “Since the county operates a landfill for our county residents/business, we track this closely,” he said. In 2004, the site collected more than 18,000 cubic yards of waste, and that number is expected to continue to rise each year, even though many county residents do their own composting.
Yard trimming compost that is screened and free of plastic can be used for mulching around trees and flower gardens, for fertilizer on athletic fields and golf courses, or as a component in nursery mixes. A mature compost product is critical in these applications. Many municipally operated yard trimmings facilities have programs where compost is given away or sold to residents at a fairly low price. Other municipalities have chosen to market the compost to landscapers and other buyers for a fairly competitive price. Private companies almost always sell the compost and create a variety of blends for various applications.Reducing Landfill Waste
Though Crow Wing County does not place green waste in the landfill, it currently is using compost on its landfill. “As part of the county's Recirculation to Energy project, a yard waste composting area was established on the bermed intermediate crown of Cells 1 and 2 of the Crow Wing County Landfill in 2002,” said Morris. “Annually, the landfill operator transfers the accumulated yard waste to Cells 1 and 2, placing a 3- to 6-foot lift. Pre-treated leachate from the leachate ponds is then sprayed over the yard waste, three times per month, from May through September. A typical application is about 40,000 gallons.” The leachate is applied with a trailer-mounted spray gun.
Once the compost is mature, it's removed from the landfill crown and stockpiled for later use as a topsoil supplement on landfill construction projects and for erosion control. “This product has been very beneficial since the site is extremely topsoil poor,” said Morris. One growing season is required to generate a mature product. Testing completed by the county verifies that the compost has a high nutrient content with no concern of contamination. Fresh yard waste is subsequently applied on the landfill crown to renew the composting process.
Portland, Ore., also has a strong “green” emphasis in its recycling program. In November and December of each year, the Portland Leaf Collection Program swings into high gear. The leaves are picked up in the streets, helping reduce slippery road conditions and clogged drain inlets. Plus, the leaves collected become compost, saving the city some money down the line.
“Leaves collected by these programs become part of the city's recycling effort and are turned into compost,” said Jill Jacobsen, program manager for the city's bureau of maintenance (BOM) in the office of transportation. “Only leaves are collected. Leaf removal crews will not pick up yard debris, nor will they accept it at leaf depots. For the last several years, BOM has collected approximately 25,000 cubic yards of leaves and turned them into about 5000 cubic yards of compost.”
The city also is looking at a unique way to compost its street sweepings. About 25,000 tons of debris are swept from city streets each year, much of which is green waste. In a pilot project, the BOM is pursuing the option of using this debris as alternative daily cover material at local landfills, after it is treated with enzymes.
“Another use of the finished material might include composting the debris and making a compost material that could be used as fill or cover material in the right of way,” said Jacobsen. “The viability of this proposal will continue to undergo testing and evaluation in the near future.”