Green Waste, Where Do All The Grass Clippings Go?

May 14, 2015

Where those tree branches, grass clippings and leaves you meant to rake up last fall go all depends on what bin you put it in.

In the past, green waste was burned or went in the garbage with everything else. However, Utah State University Extension Assistant Professor Rebecca Mills said the organic materials can do so much more when composted.

“If it goes to the land fill it will decompose eventually, but the environments at the landfill aren’t appropriate for it to decompose in its most beneficial way," Mills said. "Because in the landfill, when it composts it creates greenhouse gases, but in a compost bin it composts naturally, and quickly and it creates a heat that then creates a usable material that you can add back to your garden,” Mills said.

Green waste is kind of what it sounds like, leaves, grass and branches, but it can also be organic kitchen matter like banana and avocado peels, coffee grounds and onions. Like the pile of yellow ones I saw when I first arrived at the Logan City Landfill.

To the east of the landfill itself is the city’s composting facility. This is where my tour with Landfill Manager Carl Francis began.

“We divert somewhere between 10,000 to 14,000 tons of material from our regular landfill,” Francis said.

Green waste at the landfill consists of stuff people put in their green bins, along with grass clippings from yard maintenance groups and city spring street side pickup. The piles are huge—the size of a building. The woody materials are separated out from the other things— bound to become wood chips. Another thing that has to be separated out, Francis tells me as a huge construction truck drives by, is garbage.

“We’ve got a lot of stuff to process today, so he’s just going through this material and looking for garbage," Francis said. "We wanna get the garbage out, get the metal, the rocks, those are bad for our equipment. When he gets it separated out, he’ll pile up a lot of the garbage, the stuff we don’t want to process, and we have to take that back up to the landfill,” Francis said.

Green waste makes up 27 percent of all of the waste generated in the U.S., and about 58 percent of it is composted by city landfills.

Many cities around the state of Utah now offer curbside green waste pick up, but Mills says at-home composting is a recent trend that’s picking up steam. Besides just composting in a bin in the backyard, more and more people are turning to smaller, under the sink forms of green waste disposal.

“You can actually compost in your home, like say under your kitchen sink or in a closet, with worms. It’s called vermicomposting.

Mills is currently teaching a class about this kind of composting.

“The course that I’m developing is called the kitchen compost garden, where you have your kitchen scraps and you feed them to your worms, and they make compost that you can then put on your garden so that you can grow good fruits and vegetables, to eat, to compost, to garden, to eat, see how it goes in a circle like that.

Back out at the landfill, Francis said at-home composting isn’t much different than the work he does here—minus the larger machinery.

“So we take all the materials from the mixed pile, and we’ll grind those up and we’ll use that plus some grass, maybe some leaves, and some straw and manure, and lately we’ve been watering the material before we lay it out. If we get the right moisture content and we can probably make compost within four months,” Francis said.

The city is pretty scientific about the compost making process. The materials are turned often to keep oxygen concentration up—and weeds down.

“We need to get the temperature up to 140 degrees for two weeks consecutively, and the reason for that is, if we can get it up to that temperature, it’ll kill the weed seed that’s in the compost.

After 4-8 months of turning and watering, the volume of the compost piles at the landfill will have shrunk by about 50 percent. This dark, earthy smelling material is then put into a sorter to make sure that the end product is of the right consistency.

Logan City has made a business out of green waste, selling the organic materials back to city residents as compost and woodchips for their gardens and yards. Francis says this is a service that he couldn’t see his customers letting go of any time soon.