Good Question: What Happens To Raked Leaves?

MINNEAPOLIS (WCCO) -- Are your arms tired from raking over the weekend? While we clean up our yards, Our cities and towns are getting ready to sweep up our streets.

All those leaves everywhere got Brian from St. Paul wondering: What happens to the leaves we leave at the curb?

As the leaves rain from the trees, filling our curbs and our lawns, the piles and piles of bags are mounting.

Every leaf bagged in Minneapolis and all 7,500 tons swept up by sweeper trucks end up at a transfer station.

Greg Austin owns Organic Technologies, Inc.

"Its somewhere in the range of 15,000, 20,000 tons per year," said Austin.

A new Minnesota law mandates biodegradable bags for leaves and grass clippings.

"They work well. They break down very fast," said Austin.

Minneapolis -- a big city with people speaking lots of languages -- is exempt. They get until 2013. So the bags have to be separated from the leaves.

"To make a good product you need to make sure that you don't have as much contamination in it," said Austin.

The transfer site is the first stop for our yard waste.

Twenty miles north, in Columbus, Minn., our fallen leaves get a new life.

"When you get done after turning them, you start to get this kind of product," said Austin.

Pure compost. It looks more like dirt or rich soil than anything else.

The leaves are piled up 12 feet high. That pressure creates heat, which bacteria like. In July, St. Paul firefighters said a huge stack of paper caught fire under the pressure of its own weight.

"You'll see temperature ranges out here, 140 to 160 degrees. We like seeing that. Even in the middle of the winter you'll see those temperatures," explained Austin.

It's the same process everywhere. By law, yard waste can't go into landfills. Our leaves fertilize the next generation of trees.

In most cities, it's against the law to rake your leaves into the streets. You have to bag them.

Lots of towns let you drop off your leaves at a compost site for free. Most private trash haulers will take away a certain number of bags for free.