Communications of the ACM

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Tracking Garbage

By Samuel Greengard
Communications of the ACM, March 2010, Vol. 53 No. 3, Pages 19-20
10.1145/1666420.1666429
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In a world where the movement of goods—everything from pallets of breakfast cereal to computer components—is tracked with precision, it's nothing short of remarkable that trash and recyclables are generally discarded without a thought. Worldwide, humans generate more than 2 billion tons of waste annually. In the U.S., each individual produces about 1.5 tons of solid waste per year. Unfortunately, no one knows exactly how all the waste flows, where it goes, and how it can be managed more effectively.

This situation may soon change, however. Researchers are now focusing on the so-called "removal chain" in an attempt to address a long-standing problem: how to save landfill space, improve recycling rates, and trim the flow of toxic materials into the environment. Using barcodes, passive and active radio frequency identification (RFID) tags, cellular transmitters, and other technologies, they're putting a high-tech spin on what has long been a low tech and mostly unmanageable problem.

It's certainly more than a throwaway idea. Trash-tracking technology provides a number of benefits, including the ability to follow individual items, components, and subcomponents through the disposal process to ensure that they are recycled or disposed of correctly; gauge how effectively curb-side recycling programs work and use incentives to boost participation rates; and weigh trucks as they go to landfills to better understand loads and how to establish more efficient routes and service patterns.

"The study of what we could call the 'removal chain' is becoming as important as that of the supply chain," states Carlo Ratti, director of the SENSEable City Laboratory at the Massachusetts Institute of Technology (MIT). Ratti and a select group of researchers are among those tagging trash and exploring how society can deal with it more effectively. Notes Valerie Thomas, associate professor in the School of Public Policy at Georgia Institute of Technology, "Waste is a topic that society must address more effectively. We must find ways to reduce waste and make recycling easier and more streamlined."

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Trash Gets Smart

The idea of giving trash brains is ultimately about dollars, yen, euros, and good sense. At present, it's often next to impossible to assure that trash is routed to the best possible destination for disposal or recycling. "The problem with the current system is that there is little understanding or control of the waste stream. In many cases, trash and recycling materials don't wind up where they are supposed to go to," observes Lewis Girod, a research scientist at MIT who designed the tags for the SENSEable City Laboratory project.

That may soon change. The SENSEable City project, in place in New York and Seattle, aims to better understand the removal chain and boost recycling rates. A system called TrashTrack uses hundreds of small, smart, and location-aware tags as a first step toward the deployment of "smart-dust" networks of tiny locatable and addressable micro-electromechanical systems. Researchers attach the tags to different types of trash in order to follow objects through a city's waste management system. This reveals the final journey of items in a series of real-time visualizations. MIT displays the information at the Seattle Public Library and the Architectural League of New York.

So far, researchers have tagged more than 3,000 pieces of Seattle and New York City garbage with electronic-tracking devices that use a GSM chipset, SIM card, and cellular radio contained within a 2-inch-long device. The units—chosen because of the low cost and ubiquity of GSM—rely on an algorithm to shut off when they haven't moved for a few minutes, and a timer and motion sensor to wake them up when movement is detected. When tags come into contact with a new cell tower they send a status report via SMS. Researchers match the time stamps with the reports to create a movement map. The method of using cellular signals is accurate to about 100 meters, which is sufficient for tracking trash movement.

Over the short-term, the units have proved effective. However, because they draw from a 900-milliamp lithium ion battery, they do not provide a long-term solution to trash tracking. At most, they can last about six months. Another challenge, Girod says, is ensuring that the antennas attached to the individual pieces of trash have exposure to the sky so that they can transmit continuous signals during the transport process. In some instances, other objects, vehicles, or facilities have obscured the units. The transmitters are enclosed in a small fiberglass shell to help them survive movement and possible compacting. Girod says the use of 3G GSM will provide better signal accuracy and dependability.

MIT isn't the only group to experiment with trash tagging. Georgia Institute of Technology's Thomas has examined tagging technology as well. She has focused on using conventional barcodes and RFID tags to track items as they move through the waste stream. The primary value, she says, is for managing items like batteries, toys, electronics, office equipment, shop equipment, household tools, garden equipment, and even clothes. "Many of these items can be recycled but they often aren't," says Thomas. "Some of them—including household chemicals, light bulbs, and fixtures—may contain toxic substances that could be more easily tracked and removed."

She advocates placing barcodes and more advanced optical barcode labels on items, and using passive and active RFID tags for situations where automated scanning and tracking makes sense. "Right now, one of the biggest problems is the way items are packaged," Thomas notes. "There is often a barcode on the package when something is sold, but the actual appliance or device—and its subcomponents—are not identified." Claudia Binder, a professor at the University of Zürich's Institute of Science, Innovation, and Sustainability Research, has studied the use of RFID in trash tagging and believes it is feasible and could play an important role in changing behavior and improving environmental awareness. RFID, she says, speeds data collection and eliminates line-of-sight issues. It would almost certainly "lead to an improvement in the current recycling rate," she says.

Nevertheless, tagging garbage presents a few obstacles. For one, there's the cost of adding labels, tags, and readers to the removal chain—something that could boost per-item costs from a few cents to a few dollars. Tags themselves would have to be recycled, and privacy issues could enter the picture, Binder says. Without adequate protection, someone could glean details about a person's life and consumption habits. Finally, Binder worries that too much automation could have the unintended consequence of decreasing environmental awareness and shifting responsibility away from recycling.

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Waste Not, Want Not

Despite the challenges, the idea of using technology to track and manage trash is gaining momentum. In Aspropyrgos, Greece, a suburb of Athens, city officials implemented a three-month pilot study in 2007. Altogether, 15 of the 2,500 city-supplied garbage bins used by residents and businesses were equipped with an RFID tag mounted near the base of the bin. Each of the city's 15 garbage-collection trucks was equipped with an RFID reader and when workers emptied any of the tagged bins into the truck, the antenna picked up a unique ID encoded to the bin's tag. The system allowed the town's sanitation department to optimize routes and manage vehicles more efficiently. It also helped the city gauge the productivity of crews in the field.

In Philadelphia, an RFID-based recycling system called RecycleBank (developed by Texas Instruments) was piloted in 2006. A high-tech bin measures the volume of recyclables contained within it and when a truck picks up the items, it transmits the data to an onboard computer. Households receive cash awards based on the amount of plastic, glass, and other materials they contribute. Recycling participation rates among the 2,500 residents who initially subscribed to the program rose from 25% to 90%. Moreover, the average household increased the volume of recyclables from less than 5% to more than 50%.

An effective removal-chain system would eventually create a more efficient disposal system and slash landfill requirements, Thomas says. It would also create new economies and opportunities. Ultimately, Thomas would like to see a system where items that cannot be recycled—everything from banana peels to soiled napkins—can be composted and combusted, with the latter method producing power. MIT's Girod believes a better understanding of waste would lead to important changes in public behavior and public policy.

In fact, governments are beginning to take notice, Girod says. In the United Kingdom, the Department for Environment, Food and Rural Affairs is studying trash tagging in order to better understand waste flow and how to trim refuse collection costs, improve recycling rates, and lessen the environmental impact of garbage, including hazardous waste. In the U.S., the Environmental Protection Agency has indicated interest in boosting compliance, and tagging would likely create a viable framework for managing consumption from purchase to landfill.

"There's no question that tracking trash has economic and social benefits," concludes Thomas. "It will likely play an important role in the future. We must become more efficient in the way we dispose of waste."

 Further Reading

MIT Trash | Track Web site
http://senseable.mit.edu/trashtrack/

Saar, S. and Thomas, V.
Toward trash that thinks. Journal of Industrial Ecology 6, 2, January 2002.

Smart trash cans (video and text)
ScienceDaily, October 1, 2006.
http://www.sciencedaily.com/videos/2006/1001-smart_trash_cans.htm

Binder, C.R., Quirici, R., Domnitcheva, S. and Stäubli, B.
Smart labels for waste and resource management. Journal of Industrial Ecology 12, 2, April 2008.

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