TL;DR
Yard debris is ground, screened, and composted in long windrows for a few months, then sold as compost and mulch. Woody material too coarse to compost becomes hog fuel or landscape bark instead. Almost none of it is buried.
Yard waste is the cleanest recycling stream most households produce, and it stays that way only because facilities reject contaminated loads aggressively.
The First Stop Is a Tipping Floor
Collection trucks and homeowner trailers dump on a concrete pad at a compost facility or a transfer station. Before anything is processed, a spotter walks the pile and pulls out what does not belong.
Plastic bags, plastic pots, landscape fabric, rocks, dirt clods, bricks, hoses, and treated lumber all come out by hand. So does anything metal, because a bolt or a length of wire fence destroys grinder teeth.
Loads that are badly contaminated get rejected outright and redirected to landfill at a much higher tipping rate. That is the mechanism keeping the stream clean, and the cost flows back to whoever brought the load.
Grinding and Screening
Clean green waste goes through a horizontal grinder or a tub grinder, which reduces branches, brush, and leaves to a rough uniform size in a single pass.
Ground material then goes over a screen. The fine fraction, which is leaves, grass, small twigs, and shredded material, heads to the compost pad. The coarse oversize fraction, which is chunks of branch and stump wood, gets separated for a different use.
Sizing matters because compost microbes work on surface area. Material that is too coarse will not heat, and material that is too fine mats down and goes anaerobic.
Windrow Composting, Step by Step
The fine fraction is built into long triangular piles called windrows, typically several feet tall and hundreds of feet long.
Microbes go to work immediately, and the pile heats. Active composting runs hot, well above the temperature of a backyard pile, which is what kills weed seeds and pathogens. Facilities monitor temperature and are usually required to hold specific temperatures for a set number of days as a condition of their permit.
Turning machines flip the windrow on a schedule, which reintroduces oxygen and moves the outside of the pile to the inside so everything gets the same heat treatment. Water is added when the pile dries out.
After several weeks to a few months of active composting, the pile is moved to a curing area where it finishes more slowly. Finished compost is screened again and sold in bulk to landscapers, farms, and garden centers, or bagged for retail.
What Happens to the Woody Oversize
The coarse fraction has three common destinations.
| Product | End use |
|---|---|
| Hog fuel | Boiler fuel at mills and industrial plants |
| Landscape bark and mulch | Sold in bulk, sometimes dyed |
| Bulking agent | Recycled back into the next compost batch for structure |
Hog fuel is a Pacific Northwest term you will hear at any yard debris facility here, and it reflects how much of the regional wood residue stream historically fed mill boilers. Stumps and root balls are usually handled separately because they carry a lot of embedded dirt and rock that wrecks grinders.
Coarse clean wood from construction is a related but distinct stream, described in scrap wood disposal options.
Why Bagging Hurts
Plastic bags are the single biggest contaminant in yard debris, and they cause a problem at every stage.
A bagged load has to be opened by hand or run through a debagger, which adds labor. Bags that survive into the grinder come out as thousands of plastic shreds that are impossible to screen out and end up as visible plastic flecks in finished compost. That is a quality defect buyers reject.
Paper yard waste bags are fine and break down with the material. Reusable tarps and bins are better still. Compostable plastic bags are a judgment call, because they only break down at commercial temperatures and many facilities still refuse them.
If your program uses a cart, load material loose. If you are hauling to a drop-off yourself, tarp the trailer rather than bagging, which is also the simplest approach in fall yard waste cleanup.
What Does Not Belong in Yard Debris
The accepted list is narrower than people assume.
Yes: leaves, grass, weeds, prunings, branches under the diameter your program specifies, garden plants, and small amounts of untreated wood in some programs.
No: dirt and sod, rocks and gravel, pet waste, treated or painted lumber, pallets, plastic pots and trays, landscape fabric, hoses, wire, root balls with soil attached, and diseased plant material in some jurisdictions.
Blackberry canes, ivy, and other aggressive species are usually accepted, because commercial composting temperatures kill the propagules that a backyard pile would not. That is one real advantage of the municipal route over composting invasive species at home. If you are unsure what your program takes, the practical breakdown is in getting rid of yard waste.
FAQ
Does yard debris really get composted, or does it just go to the landfill?
At a permitted compost facility it genuinely gets composted, because the facility sells the finished product and has a permit built around the process. What gets landfilled is contaminated loads and material the facility rejects at the gate. The wider recycling picture is covered in what happens to recycled junk.
Why can't I put dirt in the yard debris cart?
Soil adds enormous weight, wears out grinder and screen equipment, and dilutes the organic content that makes compost worth selling. Sod is the same problem with grass attached. Clean fill dirt has its own disposal route, usually a fill site or a landscape supplier.
Are branches limited to a certain size?
Most programs cap branch diameter and length, commonly a few inches across and a few feet long, so material fits the cart and feeds the grinder. Larger limbs and trunk sections usually need a separate drop-off or a hauler. Check your program's stated limits.
Can I put weeds with seeds in the cart?
Yes. That is precisely what commercial composting handles better than a backyard pile. Sustained high temperatures across the whole windrow kill weed seeds reliably, which is why municipal compost does not sprout the way a home pile can.
What about grass clippings treated with herbicide?
Some broadleaf herbicides persist through composting and can damage sensitive crops in the finished product. If you have recently treated a lawn, read the product label for guidance and consider leaving clippings on the lawn for a few mowings instead of sending them off.
Is there a difference between yard debris and green waste?
They are the same thing under different names. Some programs use green waste to also include food scraps collected in the same cart. Whether food goes in your yard debris cart depends entirely on your city, so check the accepted-materials list rather than guessing.
When It Is More Than a Cart's Worth
A single overgrown lot, a storm limb-down, or a full landscape tear-out produces far more than a yard debris cart holds, and hauling it in a sedan is not a real plan. See junk removal, and ask whether clean green material is routed to a compost facility. Pile it somewhere reachable, keep the plastic out of it, and get a quote.
