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Processing - Windrows of Opportunity

The most common approach to processing yard waste is the windrow-and-turn method Leaves and grass clippings are formed into long narrow piles, called windrows. The piles should be 6 to 8 feet high and 12 to 16 feet wide. The length of the windrows will depend on the size of the composting facility.

Windrows should be formed within one day of receiving yard waste at the facility and should be formed perpendicular to the slope of the site to prevent water from ponding around the base. If leaves and grass will be composted together, the materials should be mixed prior to windrow formation. The yard waste should be fluffed to break up clumps. Water should be added to dry leaves to achieve the optimum 50 percent moisture content and aid in the composting process.

Windrows should be turned regularly to ensure proper oxygen levels in the piles and to help control the temperature. Turning can be accomplished with:

• Front-end loaders that scoop and fluff materials in a cascading fashion;
• Windrow turning attachments used with front-end loaders or tractors;
• Self-propelled windrow turners that straddle the windrows and turn materials.

Windrows should be turned after the first one or two weeks of composting, then periodically (at least twice per year) after that. Leaf windrows should not be turned during frigid weather because heat losses can slow the composting process. If grass and leaves are composted together, a more frequent turning schedule may be needed to prevent odor problems.