At this year’s Taste of Chicago, billed as the world’s largest food festival, people weren’t the only ones digesting. Steps from the stands operated by city restaurants serving up delights like crawfish boils and turtle soup, red wigglers slithered in bins filled with rotting lettuce and carrot peels.

Volunteers from the University of Illinois brought the worms to the Taste to teach city dwellers how to make nutrient-rich soil from table scraps.

“People living in high rises can’t have compost bins, their neighbors won’t let them,” said Bill Rattan, who is studying to become a master gardener at the University of Illinois and was one of the volunteers who brought the worms to the 10-day feast.

“With a box of worms that they can put in their kitchen or on their balconies, they can turn their garbage into soil.”

Worm lovers say the practice — called vermicomposting — is environmentally sound because it saves fuel used to cart garbage to landfills. And the soil made by the worms is so full of nutrients it can replace chemical fertilizers.

The U.S. Environmental Protection Agency says one pound of red wigglers, or about 800 to 1,000 of the worms , can eat up to half a pound of vegetable scraps a day.

Worms are good composters because their guts kill bacteria harmful to plants, also eliminating foul smells, and their castings, or excrement, are loaded with beneficial bacteria.

Cities on the West Coast like Seattle that have mandated reductions in their trash streams have been vermicomposting for years.

“The last four or five years have just been phenomenal, said Debbie Anderson at Rising Mist Organic Farm in Kansas who has sold worms and vermicomposting products for 7 years. “I’m just rushing to keep up with orders.”

Over the last two years her orders for worms have been growing from New York city. “Doormen see on the packages that tenants are getting worms and pretty soon more people from the same apartment building want worms,” she said. “It’s all part of recycling becoming more mainstream.”

The farm sells bags of pure worm castings for $21.50 per 10 pounds. It recently sold two tractor trailers worth of castings to the University of Wisconsin.