One's Trash, or 'Biomass,' Is Another's Energy

Rochester, MN, leaves nothing to waste when burning city garbage for power.

Garbage just might be the ultimate renewable energy resource. Get rid of it, and more just piles up. It collects in bins, bags, and Dumpsters in cities everywhere and must be hauled away, incinerated, or sometimes buried in precious open space.

But with a waste-to-energy program that began 22 years ago, Rochester, MN, has been successful heating and cooling public spaces like the 150,000-sf Mayo Civic Center with energy reclaimed from incinerated garbage. "We were green before green was cool," said Brad Jones, executive director of the Rochester Convention and Visitors Bureau.

The energy produced by one ton of garbage (the apt term is "biomass") is equal to that created by 500 pounds of coal. Rochester estimates that by turning biomass to energy, the burning of 450,000 tons of coal is avoided, but the process is not entirely clean. "Each ton of garbage that's incinerated produces 300 pounds of ash, some of it containing high concentrations of metals—textile dyes, for example," said Jones. Tight control of what is allowed into the incinerators produces a cleaner ash that can be used for roads, cement blocks, and even to make artificial wreaths. Some of the ash is landfilled. The goal is to reuse 100 percent of the ash someday, he said.

Meeting planners who are concerned about their groups' carbon footprint can feel good about booking the Mayo Civic Center (it has five main halls and 25 breakout rooms). Jones said the CVB is starting to get the word out that the building will use green energy and participate in a strict recycling program.

He added that the skyways connecting the civic center to about 2,000 hotel rooms are all heated by waste energy, too.

In 1987, Rochester had one of the first waste-to-energy plants. Now, there are about 90 around the country, said Jones. Operating cost is high, at about $55 million thus far; $33 million has been allocated to double capacity in 2009-10.

Special incinerators reduce the garbage to ash and send the steam to a turbine that produces energy, which heats 27 public buildings, cools 14, and provides electricity for 12.With the public library, some university buildings, the government center, city and county headquarters, and a federal prison-medical center all using the energy, significantly less trash is landfilled.

Originally published March 9, 2009