Seattle ? Where does that coffee cup, disposable razor or unwanted television end up once it’s tossed to the curb?

Using an electronic tracking device about the size of a matchbook, MIT researchers are tagging about 3,000 pieces of Seattle trash to get people thinking about what they throw away and where it ends up.

“Seeing where your trash goes allows you to change your behavior,” said Assaf Biderman, associate director of MIT’s SENSEable City lab and a project leader. “Will you refill a cup instead of throwing away a disposable one?”

Researchers are visiting the homes of hundreds of Seattle volunteers to affix electronic tags on about 10 to 15 pieces of their household trash, such as pizza boxes, Styrofoam cups, slippers and scrap metal. The volunteers will dispose of the item as they normally would.

The battery-operated smart tags rely on cell phone technology to send information back to MIT computers, allowing researchers — and the public — to monitor the trash in real-time as it moves through the waste stream to its final destination.

The public will be able to follow the trash migration at an exhibit that opens at Seattle’s Central Library Sept. 18.

Jennifer Giltrop of Seattle said she’s curious to see what happens to the empty wine bottle, a used printer cartridge and a plastic bag that she recently had tagged.

“We know where we purchase our items from, but we’re not always as aware of what happens when we throw things away,” said Giltrop, 38, who is assistant director of Seattle’s main library. “We’re aware of recycling, but what’s the process?”

Biderman said the project will allow researchers to study in detail how efficiently, or inefficiently, the waste removal system works.

Does recycling end up being recycled rather than in the landfill? Does it take weeks rather than hours or days for trash picked up from one Seattle neighborhood to get to the transfer station?

In Seattle, about 789,608 tons of waste is discarded each year. About half of that ends up in the landfill, while the rest is recycled, reused or composted.

But about two-thirds of the city’s garbage that ends up in the landfill, including food and yard waste, can be recycled, according to the latest figures from 2006.