Urban Digestive Systems. Towards the Sentient City. - MIT ...

to operate for 20-30 hours when constantly inmotion, and from 3-6 months in sleep mode.— We noticed that about 20% of the tags eitherreported very short traces or failed to senda report at all. Tags could have failed for anynumber of reasons: destruction during thewaste removal process, arriving somewherethe transmission signal was blocked, hardwaremalfunctions of the tracking device, or humanerrors resulting from volunteers not disposingof the tagged item. We found that failure ratesdepended heavily on the packaging strategyand type of trash; battery failure turned out tobe less of a problem than physical destruction.— The location reports we received had limitedresolution in time, due to the power-conservingmeasures explained earlier. However, theresolution was sufficiently high for inferencesabout the route and the mode of transportation.The accuracy for GSM based localization canbe estimated at about 250 m. GPS localizationsignificantly improved this accuracy. However,since the GPS signal required a clear view ofthe sky, this feature was not always available.DeploymentsThe blend of technology, information systems,and my own lack of concrete knowledge aboutwhere trash goes were the primary catalysts.A strong feeling that I wanted to influenceothers in the Seattle area to get involved at thelocal level was a secondary — but still important— motivation.— Trash Track volunteer survey***Over several phases of the Trash Track project,we distributed a total of 3,000 sensors inthe cities of Seattle, New York, and London.The initial field test of trash tags took placein June 2009 in Seattle, Washington. Our primarygoal was to test the tags’ performanceonce they had entered the waste removalstream. We also wanted to sample data from awide distribution of disposal locations acrossthe city. Driving to these target locations, wefound many objects simply lying around onstreets and empty lots. Examples includedbeverage containers and newspapers, toysand batteries, cell phones and computers, applianceslarge and small, furniture and clothing,and hazardous materials and car parts.We tagged each of these found items, tryingout different techniques for attaching themsecurely. Tagged objects were then droppedinto public garbage bins, brought to recyclingcenters, returned to retailers via take-back programs,dropped on the curbside of residentialhomes, or, in a single case, left provocativelyin public space. We quickly realized that additionalmeasures were necessary in order toprotect the tags from physical damage, ensureproper signal transmission, and conceal themto prevent manual removal. In order to achievethese partially conflicting goals, we experimentedwith different methods for protectingthe sensitive devices.This turned out to be an assembly problemof a very peculiar kind, since we neededto be able to secure a tag to a wide range ofmaterials and geometries. Encasings of latexmold rubber and carbon fiber provided effectiveprotection, but were too complicatedand time-consuming to produce on the site ofdeployment. We settled on a process whichcovered the sealed tag with a 1-2 inch thickshock-absorbing layer of sturdy foam basedon epoxy resin, a quick-setting material alsoused for insulating and patching boat hulls.For some electronic waste, tags could alsobe embedded into the interior circuitry ofthe object. Special care was given to deviceswith metal cases, to prevent Faraday cagesfrom blocking of blocking wireless signals.***The following August, we distributed an additional600 tags in the city of Seattle, usinga threefold approach. A portion of the tagswas distributed during a public event at theSeattle Central Library, at which volunteerseach brought to us an object to be tagged,which they would then disposed of. For asecond portion of tags, our team arranged tovisit volunteers at their homes, attaching tagsto their prepared garbage objects and havingthe volunteers dispose of them as they normallywould. Finally, the remaining tags weredeployed directly by our team across the metropolitanarea, covering the full range of materialsand garbage types (such as plastic, metal,e-waste, etc.), different geographic areas, anda variety of garbage disposal methods.We were struck by how strongly the publicresponded to the project. Within two days ofsending out a newsletter announcement inSeattle calling for volunteers, we had receivedmore than 200 responses - far beyond ourexpectations. It suggested just how engagedthe general public could become in researchingwhere trash goes. This also contributed to ourdecision to set up subsequent deployments ofmany tags with expanded involvement by localvolunteers. Following our August experiment inSeattle, two smaller experiments were carriedout in the cities of New York City and London.In September of 2009, preliminary resultsfrom these efforts were shown to the publicin exhibitions at the Seattle Public Library andthe Architectural League of New York. In bothexhibitions, a real-time visualization based oncollected sensor data provided a compellingportrait of the journey of the tracked garbage,item by item. Each representation includeda photo with the description of the disposedobject, where and when it was thrown away,and an animated view of the object’s trajectorythough the waste system. These data visualizationswere combined with a video composedby German artist Armin Linke for this exhibition,which showed scenes from the insideof waste management facilities, juxtaposingclean abstract data with the brute physicalityof waste.***In October 2009, building on experiencesfrom this initial phase and the exhibitions, weprepared for our largest deployment to date.In order to launch 2,200 location sensors in themetropolitan area of Seattle, we extended ourcollaboration with local citizens. We recruitedvolunteers through an open call in local media,in which we asked them to provide garbageitems from their own households according toa wish list of items. From the pool of volunteerswho registered through our web site, weselected around 100 homes to visit, in orderto achieve an even geographic distribution ofdisposal points across the whole region.During the following three weeks, fourmobile deployment teams visited the homesof selected volunteers, elementary and highschools, and private institutions. The SeattleCentral Library served as a base of operationsfor preparing the tracking devices and thematerials necessary for the deployment, aswell as for training lead volunteers who joinedus during visits to homes. On site, the team attachedtags to trash using layers of protectiveepoxy foam, and documented each item, itsmaterial properties, and the time and locationof its disposal.In order to achieve a diverse and representativeselection of household wastes, weprepared a ‘wish list’ and some guidelines forwhat we were looking for. Two main factorsshaped the selection of trash for tagging:— Primarily, the list was based on the taxonomyused by the Environmental ProtectionAgency to divide municipal solid waste intocategories based on contained materials(Office of Solid Waste 2008b). These materialcategories include organics, paper and paperboard,glass, plastics, metals, and rubber,leather and textiles.—The second important influence in selectingproducts was the nature of the waste collectionsystem in Seattle. In this system, differentmechanisms capture different types of waste;for example, single-stream curbside recyclingcollects aluminum cans, while food and yardwaste collection handles organic scraps, andfluorescent light bulbs are collected at householdhazardous waste centers (Seattle PublicUtilities n.d.).Extra consideration was given to emergingwaste categories such as discarded cell phones,computers, fluorescent bulbs, and other householdhazardous waste, which are increasinglyprevalent in the waste stream (Office of SolidWaste 2008a). These emerging waste sourceshave an array of disposal mechanisms, many ofwhich are provided by private sources, such asmanufacturer take-backs, store drop-offs, andmail-in programs. The collection rates throughthese mechanisms, as well as their environmentalimpacts and trade-offs, are not asestablished as those of municipal solid waste.***While we varied and refined our proceduresthroughout the project, each of these deploymentsactively involved local citizens. Besidescreating public awareness about the project,its goals, and the questions it raises, this alsoensured that we could distribute our tags in away that closely matched how people in thatcity actually disposed of their trash. Recruitedvolunteers came from local neighborhoods,schools, public libraries, institutions, andcompanies, collectively providing an incrediblearray of garbage items. Volunteers also98-99 MIT Senseable City Lab Trash Track