Many Ames residents don’t know where their garbage goes, and perhaps many don’t care. However, Ames residents can rest assured their garbage, most of it anyway, is put to good use.

In Ames, it is helping to light and perhaps heat your home, thanks to the Ames Resource Recovery (ARR) facility located in east Ames.

The facility receives Story County garbage and turns about 70 percent of it into fuel for the Ames coal power plant, said John Pohlman, assistant superintendent of the ARR facility.

The Ames power plant burns 90 percent coal and 10 percent refuse recovered from the garbage, called refuse derived fuel (RDF).

“As a coal-fired power plant they burn the material at a much higher temperature than a regular fire would be,” Pohlman said. “They have a much better efficiency that way.”

When the garbage reaches the ARR, the burnable material, mostly paper, is separated from ferrous metals and other non-burnables. Ferrous metals are recycled out daily. The remaining material goes to the Boone County Land Fill.

“Since we are a college town we have a higher than the national average of paper or paper products in the waste stream,” Pohlman said. “Plastic is a relatively small percentage. There may be some fiber material and very small amounts of wood.”

After the ARR processes the garbage, it is put in a bin between the ARR and the power plant. The power plant extracts it out of the bin and processes it for its burning needs.

Although garbage is only 10 percent of the fuel used at the power plant, Pohlman said this is not insignificant.

In addition, burning garbage uses up less land fill space. Pohlman said although a land fill is still necessary, the life of the land fill is increased dramatically by burning garbage.

The ARR was built in 1975 as a result of concerns about fossil fuel availability and to reduce the need to build an additional landfill for Story County garbage.

The purpose at the time was to avoid building a new landfill in a high-cost agricultural state and during a time when the cost of energy was becoming very expensive (mid-70s energy crisis).

“The life expectancy of the plant equipment originally was 20 years,” Pohlman said. “Toward the end of the 20 years there was a study done to see if we should not do this any more or to continue it. Essentially, it was determined through that study that we would continue this facility.”

Last year the facility was close for modifications.

Pohlman said there were some concerns with dust, and facility managers were concerned with general safety.

The efficiency of moving the garbage through the facility was increased, cutting down on manhours.

The modifications were originally planned to take three months. The facility was shut down for about six months due to some construction difficulties. Some of it was weather related.

“Now we are back in operation after the modifications,” Pohlman said. “We have a very good dust collection system.”

The ARR was the first municipally owned and operated plant of this kind in the country.

In the U.S. there are “130, plus or minus 10, similar type facilities that are waste-to-energy-type facilities,” Pohlman said.

Some of these are “mass burners” that burn everything and do separation of the metals afterwards. Others process out the non-burnables first, like Ames facility does.

The ARR receives an annual average of 175 tons of refuse per day, which varies seasonally, Pohlman said. Iowa State students in Ames have an impact on the waste stream.

He said when students leave and return to school there are variations in the waste stream as people clean up, move out and throw things away.

Seasonal changes and weather have an impact too. Wet weather causes the energy value of the burnable refuse to go down, Pohlman said.

The city of Ames operates both the power plant and the ARR. Pohlman said other similar operations have started up and have had difficulties in finding customers for their finished product because they do not have this kind of arrangement.

“The city owns and operates both of us,” Pohlman said. “We have worked over the years to make it a workable arrangement.”

A tour of the Ames Resource Recovery facility will be held today from 2 to 3:15 p.m. Interested students, faculty and staff should sign up in Room 2025 in Black Engineering.

The tour is sponsored by the American Society of Mechanical Engineers International.