The aim of the Trash Track program, developed by the MIT SENSEable Ciy Lab, is to find out how much energy needs to be expended to make the waste generated in cities disappear. The project consisted of mapping the paths taken by the waste produced in two North American cities - New York and Seattle - until it accumulates in landfills or is recycled. This mapping can be calligraphed thanks to the digital tagging of thousands of objects, which have been chosen to give an adequate account of the type and quantity of waste. Based on cell phone technology, the litter markers are able to collect, over a long period of time, the position of each object, transmitting the data to a tracking station where the migration patterns of the litter are formalized. (For more information, see senseable.mit.edu/trashtrack/).