Trash trackers: The secret life of garbage 16 September 2009 by Catherine Brahic

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Trash trackers: The secret life of garbage

  • 16 September 2009 by Catherine Brahic

  • Magazine issue 2726.

Tracking device

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SO YOU diligently separate your cardboard from your glass, rinse your tins and tear the staples off paper. You fill your various bins and put them out for the men in bright overalls to take away along with the remains of this week's meals and domestic debris. And then, safe in the knowledge that you've done your bit for the environment, you forget all about it.

In fact, the life story of your weekly garbage is just beginning. Your aluminium can, for example, could have a variety of fates. It might be crushed and sent back to the canning factory to be turned into new cans. Or it could end up in the nearest landfill, or get shipped to distant shores to be either recycled or dumped. The truth of the matter is, no one can be sure where an individual piece of trash will end up or how the junk in a landfill got there.

Now, though, New Scientist has teamed up with researchers at the Massachusetts Institute of Technology to find out. In a pilot project in July and August, the MIT team tracked 60 pieces of trash as they made their way around Seattle. As the first results roll in (see "The Seattle experiment" and map), the next phase of the experiment kicks off. Next month, 1000 more pieces of garbage are being tagged and thrown away in New York, Seattle and London and tracked for two months. We are offering 10 readers the chance to join in and find out where their garbage goes to die (see competition details). "With the Trash Track project, the invisible waste system comes to life," says Assaf Biderman, associate director of MIT's SENSEable City Lab.

The experiment is more than just an attempt to satisfy our curiosity about where trash ends up. The idea is to help pave the way for an ideal world of waste disposal, where nearly everything gets recycled or reused and materials are sent to landfill no faster than the planet is able to produce them.

Tracking trash could pave the way for an ideal world of waste disposal, where nearly everything gets recycled or reused and very little is sent to landfill

Right now, that green utopia is a distant dream. Part of the problem is that we don't know what we are dealing with. While a lot of effort has gone into creating green supply chains to bring products to consumers, almost nothing is known about what goes on in the "removal chain". Waste is monitored of course, but only to see how many tonnes of different kinds of garbage arrive at a sorting centre, landfill or incinerator, and how many leave. These are tallied up under vague categories such as electronic or household waste. "It's fairly well measured in terms of mass," says. Valerie Thomas, a sustainability expert at the Georgia Institute of Technology in Atlanta and a member of the US Environmental Protection Agency's science advisory board. "It is not well measured in terms of content."

And in terms of environmental impact, it is the content that matters. Within the harmless-sounding category of "household waste", for example, lurks everything from carrot peelings to used diapers to mercury-containing low-energy light bulbs, each of which throws up a very different set of environmental challenges. In our ideal world, each should be dealt with separately.

Before that can happen, though, we need to get a clearer picture of the life cycle of different kinds of waste, and that's where the "trash trackers" come in. The team, made up of engineers, designers and life cycle assessment researchers at MIT's SENSEable City Lab, have designed tags that can be fixed to all kinds of rubbish. These tags beam out their location every 15 minutes for up to two months. Each is built around a cellphone SIM card and battery, and a motion sensor (see diagram). A low-power microprocessor keeps track of the motion sensor and, when the sensor registers movement it switches on the SIM card, triggering a search for nearby cellphone towers. The SIM then sends an SMS containing this information to MIT, where custom software compares it with standard maps of signal strength fingerprints to determine the position of the tag.

The tags aren't precise to the metre, explains Lewis Girod, who designed them. In cities, where there is a dense network of cellphone towers, the team can locate an object to within 100 to 500 metres. In rural zones, that goes up to 1 kilometre or more. "We infer the object's location from correlations and rough final locations," Girod says. "For example, during a first test in Massachusetts, we inferred a tag that was last seen in Lawrence went to an incinerator in Haverhill, which is nearby."

Telltale tags

The MIT group compares the approach to injecting a radioactive substance into a patient's bloodstream in order to find blockages that might be causing health problems. It could, for example, identify places where recyclables are being tossed into landfill, or where hazardous waste is illegally shipped overseas. It could also be used to compare different methods of disposing of the same kind of waste - whether by land, sea, air or a combination of all three. By estimating the energy efficiency and greenhouse gas emissions for certain types of waste in each removal chain, it might be possible to identify the leanest, most efficient removal chain.

For Thomas, there is also a more fundamental reason to tag trash: to find out where society stores the materials that it mines from the Earth and temporarily turns into products. Today's landfill sites are positively glittering with metals, including gold, aluminium, nickel, copper, lead, zinc, cadmium and mercury - in many cases at higher concentrations than natural ore deposits - plus huge quantities of recyclable glass and plastic. As commodities become increasingly scarce, we may have to mine landfills for their riches (New Scientist, 1 October 2008, p 34), and that means finding out exactly where to start digging.

This level of detail is beyond the scope of the trash tracking experiment - clearly it would be impossible to add cellphone-based tags to every product ever made and keep track of it all from cradle to grave. Other groups, however, are looking into cheap and easy ways to keep track of every product, and the components they contain, to make sure they are disposed of properly.

Thomas, for example, proposes adding barcodes or radio frequency identification (RFID) tags to each product and its recyclable components so that they could be scanned and sorted precisely and automatically. "In the same way as products that are made and retailed have barcodes and a whole associated system to help a product get from where it's manufactured to where it's sold, we will need to use the same approach to get all our products recycled again," she says. Thomas has calculated that the cost of such a system would be offset by the economic and environmental benefits (Resources Conservation& Recycling, vol 53, p 400).Hewlett-Packard and Wal-Mart have expressed interest in such a system, while the governments of South Korea and Japan are investigating using RFID tags to track and reduce e-waste.

This kind of hyper-efficient waste-free society is still some way off. To sustain our current rate of consumption, the planet would have to grow by more than a third, according to the United Nations Environment Programme (UNEP). And if all humans consumed at the same rate as the average American, we would need five planets to support us.

To make this wasteful way of life a thing of the past we first need to know where all the stuff we consume goes. Tracking our trash is just the beginning.

The Seattle experiment

In July and August the Trash Track team from MIT's SENSEable City Lab scattered 60 pieces of tagged garbage around the city of Seattle. Perhaps surprisingly, only two pieces found their way to Seattle's main landfill in Arlington, Oregon, more than 300 kilometres away.

Of the rest, 11 pieces, including a Spiderman shoe, a keyboard and laptop battery, started scattered over a 700-metre radius of Seattle, and ended up centred in the vicinity of two recycling facilities.

One facility, Total Reclaim, processes electronic waste, so it seems likely that the computer keyboard and battery went there. Most of the waste processed by Total Reclaim is separated into raw materials, such as plastic, glass, steel, copper and aluminium, which are then sold on to be reused as feedstock for new products.

Since Seattle's municipal recycling is delivered to the other facility, Allied Waste's recycling centre, it is reasonable to presume that the non-electronic waste ended up here. "From there, it is sold to markets all over the Pacific Rim, Canada and the US," says Brett Stav of Seattle Public Utilities.

One of the items that probably ended up at Allied Waste on 15 July, a fabric gardening glove, was placed in the same recycle bin on 11 July as a tagged bottle of motor oil that later popped up on 23 July, near Newberg, Oregon, travelling in the direction of the landfill site. This suggests both items went to Allied Waste and were sorted. The tracking device in the bottle of motor oil survived the sorting process, while the gardening glove's was probably destroyed or placed in a container that blocked its signal.

Three bits of trash ended up in shipping yards. The signal from a tracker attached to a blue hooded sweatshirt was picked up on 25 July in amongst shipping containers in one of Seattle's shipping yards. The two other items, a large plastic drinks bottle and an old tyre, ended up in a shipping yard in Tacoma, south-west of Seattle.

The journeys of other objects were more difficult to decipher. A toy truck left in a recycle bin in western Seattle on 12 July, for example, was last spotted five days later on a hill south of the city, near the small town of Maple Valley. A Pyrex measuring jug appeared to be in Lake Washington, but could also have been in transit on the bridge, or on either shore of the lake.

The results of those that could be traced, however, suggest that Seattle's waste sorting strategy is working. Even so, nearly 200,000 tonnes of Seattle's recyclable and compostable material ended up in the Arlington landfill site in 2008, according to Seattle Public Utilities.

This was apparently the destination of one of our pieces of tracked trash: three days after it was thrown in a recycling bin in Seattle, a Styrofoam takeout box turned up within 20 kilometres of the facility.

Citizen recycling

At 1.58 pm on 12 July, Musstanser Tinauli, a project leader for the Trash Track project at MIT's SENSEable City lab, threw New Scientist feature editor Caroline Williams's digital camera into a roadside garbage can in south Seattle. The camera was five years old and worked perfectly well, but was surplus to requirements thanks to a gift of a new, better-equipped one.

Caroline wanted to know whether, if thrown out rather than given away, it would end up in landfill, be recycled, or perhaps sent to a developing country to be re-sold. In the event, its fate was entirely different. Two days later, it turned up just 2.6 kilometres away in a residential area to the south of the city. It seemed to have been dug out of the bin and taken to a new home.

It wasn't the only bit of electronic kit that went through an adoption process. Two days after a TV set was left kerb-side in the north-eastern suburb of Westwood it turned up just over a kilometre away in another residential street.

An ancient Dell laptop belonging to New Scientist reporter Ewen Callaway was donated to the Computer Recycling Service store in the suburb of Green Lakes, north of the city. Within a few days it seemed to have found a new home less than half a kilometre away. Since 500 metres is close to the limit of the tags' accuracy, however, this particular movement is difficult to confirm.

This kind of impromptu recycling is another unknown quantity in the waste stream. "If in passing your stuff to other people you're avoiding somebody else buying new things, then you're reducing the amount of stuff that goes to landfill and reducing the total demand for resources," says Phillip Ward of WRAP, the Waste and Resources Action Programme, a waste advisory body to the UK government. But, he adds, "nobody really knows how long you keep things out of landfill with this process".

Competition: Track your trash

What happens to your garbage once you send it out into the world? Enter our exclusive competition to find out.

New Scientist has teamed up with researchers from MIT's SENSEable City Lab to launch the British arm of their Trash Track experiment. If you live in the UK and would like to get involved, go to and tell us, in no more than 75 words, what you would like to tag and why. The best suggestions will win a tag and the chance to follow the trail of your trash.

The results of this unique experiment will feature in a forthcoming issue of New Scientist magazine and on

Due to the nature of the experiment this competition is open to UK residents only. For full terms and conditions please visit

Catherine Brahic is New Scientist's environment news editor

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