MINNEAPOLIS (WCCO) —  It’s that time of year to rake the leaves — bags upon bags can be seen lining the streets.

Heather from Eagan, and Joanne from Richfield e-mailed WCCO to ask: Where do the leaves go?

Good Question.

The good news is that Mother Nature makes sure your hard work raking will come back to you, full circle.

“You’d be surprised, when you have four maple trees and two ash trees, how many leaves you accumulate on the ground,” WCCO Reporter John Lauritsen said.  “Thirteen, 14, 15 bags and that’s just about 10 percent of the lawn so far, so we got a ways to go here.”

Like many, Lauritsen has been busy in his yard. His 15 bags of leaves are put in eco-guard, 100 percent biodegradable material.

A new state law mandates everybody in the metro area use biodegradable bags for their leaves.

What happens once those bags are picked up?

“It’s not uncommon to see 6-8,000 tons of material,” said owner of Organic Technologies Inc. Greg Austin.

Austin says the leaves are first dumped at a transfer site in Minneapolis.

“We grind it,” he said. “We grind it so that we stop the spread of emerald ash borer.”

Next, the ground material is hauled up to a composite site in Elk River.

“We have wind rows set up here, that wind row will heat up and temperatures will increase, and that material will break down,” Austin said.

Temperatures in the piles can get up to 160 degrees, even in the winter. Bacteria grows when it’s hottest; bacteria that’s helpful.

“It’s kind of why people like to see worms in their garden, it’s a good thing,” Austin said.

With bacteria comes more and more nutrients. Much of that nutrient rich material is then delivered to Minneapolis community gardens that grow their own fruit and vegetables.

The whole process takes nine months from the time you rake up your leaves, to the time it’s made into useable compost.