What happens to yard waste after it's left at the curb?

Ever wondered what happens to the leaves, grass clippings, twigs and other green waste you set on the curb for collection?

If you live in Columbus, it eventually may end up right back in your yard -- likely in the garden, as mulch, soil or compost.

Since 2010, Columbus residents have had two options for getting rid of yard waste, free of charge, regardless of the season. They can take it to a mulch facility themselves, or they can leave it at the curb in paper bags, or in plastic or metal containers, separate from trash or recycling.

The Solid Waste Authority of Central Ohio (SWACO) dedicates $1.5 million each year to provide the curbside pickup program for all Franklin County residents. SWACO pays composting facilities Kurtz Bros. and Ohio Mulch to receive, process and compost that waste.

The curb is where waste-hauler Rumpke will retrieve it, as long as drivers don’t see prohibited materials in the container, says Rumpke spokesperson Taylor Greely.

“If they find unapproved material at the curb and they’re aware that it’s unapproved material, they’re not going to collect it with the yard waste,” Greely said.

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When the drivers’ neighborhood routes are finished, they take the waste to an approved mulch facility.

Yard waste from the City of Columbus is taken to Kurtz Bros. Central Ohio, where the waste goes through a months-long process turning the cast-off twigs and greenery into compost and mulch sold to consumers.

Kurtz Bros. collects yard waste from Rumpke drop-offs, landscape companies and individual homeowners, and arranges it in piles dozens of feet high.

Operations supervisor Terry Speakman says that before anything else happens, his team removes any visible plastic that has made its way into the waste piles.

“In curbside pickup, 30 percent of it’s probably plastic,” Speakman said. “That’s a big problem."

Plastic is among the items no one should be throwing in with their yard waste because it can contaminate the end product. Unfortunately, plastic mulch bags and other items are common finds.

“Trash bags, chairs, furniture,” Speakman said. “You name it, we’ve had it.”

After visible plastic is removed from the mountains of yard waste, the piles sit for about two months, during which time the material begins to decompose.

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The waste then heads to one of several grinders -- large pieces of machinery that each cost more than half a million dollars -- which reduce the waste to a finer mix. As the waste is ground, it falls through giant steel sifters, which separate the smaller pieces of mulch from anything larger than an inch.

Speakman says the sifting process is how 80 to 90 percent of the stowaway plastic gets separated from the end product. The offending rocks, plastic and other large pieces remaining in the sifter get sent to a landfill.

The mounds formed by the freshly-ground yard waste sit at the facility for two to six months, depending on the final product being made, while it ages and darkens.

From there, the resulting mulch might be dyed red, black or brown before it’s bagged and sent back to consumers who can buy the mix at Kurtz Bros. locations.

>> Recyclable or not? Find out what you should and shouldn't put in that Rumpke recycling bin

Why recycle yard waste instead of throwing it in the trash?

“If we collect yard waste separately from trash or recycling, it diverts that volume from the landfill,” Rumpke's Greely said.

Throwing yard waste in your regular trash also is illegal. Leaves, grass clippings and similar biodegradable materials have been banned from landfills in Ohio since 1994.

A 1988 U.S. EPA report laid out guidelines for reducing the nation’s landfill waste by 25 percent by 1992. Ohio legislators responded by enacting a less-ambitious state law requiring communities to reduce landfill dumping by 25 percent between 1989 and 1994.

The EPA’s first recommendation for solving what it called a national “solid waste dilemma” was to emphasize composting.

Yard waste was an easy waste source to pinpoint -- in Columbus, that type of waste took up 17 percent of the city’s landfill at the time, even though there existed several alternative methods for disposing of and recycling it.

A recycling coordinator told The Dispatch in 1993 that leaves alone accounted for about half of the trash collected in central Ohio in late fall every year.

Thanks in part to landfills that enacted their own yard-waste bans about a year before the law went into effect, Ohio easily met that 25 percent reduction goal by early 1993.

How should yard waste be prepared for pickup?

Rumpke requires branches and Christmas trees to be cut to 4 feet or shorter and tied into bundles with string or twine, the bundles being no wider than 2 feet.

Loose material should be placed into biodegradable bags, such as the paper bags sold at hardware stores and other retailers. Rigid metal or plastic containers marked “Yard Waste” also work, but each bag, bundle or container should weigh 50 pounds or less when it's placed on the curb for pickup.

Plastic is the item that causes the most problems for Kurtz Bros. when they break down yard waste into mulch. But they have a few more guidelines to help homeowners prepare their waste.

Accepted by Kurtz Bros.:

• Tree branches
• Grass clippings
• Bushes
• Leaves
• Unpainted pallets (except at the Dublin Kurtz Bros. location)
• Old mulch
• Woodchips
• Logs
• Sod/edgings (though sod must be kept separate from other yard waste)
• Yard waste in paper lawn bags

Materials not accepted by Kurtz Bros.:

• Building materials
• Treated, painted wood
• Dirt
• Rocks
• Concrete
• Plastic
• Metal
• Food waste
• Sewer waste
• Railroad ties
• Root balls

Why are certain materials not accepted?

The concept is actually pretty simple, says Kurtz Bros. general manager Jerry Bennett. Would you want those materials returned to you or your neighbors in the form of mulch?

Treated wood, for example, contains chemicals that aren’t good for garden mulches. Concrete, plastic and metal don’t perform as mulch, either.

And food waste?

“You can compost and do that kind of stuff with food waste, but it comes up in a different class with the EPA,” Bennett said.

Because food waste attracts different types of vermin and insects, the EPA’s regulations for a facility like Kurtz Bros. are different from its regulations for a facility that handles food waste.

Still, the concept is simple:

“No one that I know takes food waste and mixes it with their mulch,” Bennett said.