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We held a one-week design sprint to build a smart trash chute. Here’s what we learned

The path to a more sustainable city goes right through the multi-family waste room.

By Jesse Shapins and Matt Breuer

The trash room in a typical apartment building might not seem like an obvious venue for innovation (for an air freshener, yes). Here's the thing: the multi-family waste chute is actually a gateway to a more sustainable city. Of the roughly 136 million tons of garbage that Americans dump into landfills every year, over half consists of papers, plastics, and various other materials that could be recycled.

A major challenge with recycling comes down to accountability. Suburban areas have made progress on this problem with pay-as-you-throw programs, which incentivize waste reduction by charging single-family households based on the amount they throw away --- effectively turning trash into a utility, just like electricity. In single-family neighborhoods, where every trash bin corresponds to an individual household, pay-as-you-throw has achieved great success. A program in Boulder, Colorado, increased landfill diversion rates over 30 percentage points, with many other cities showing substantial gains.

Cities have struggled to adopt similar programs in multi-family settings, in large part because trash chutes in apartment buildings don't know who's tossing what. Sidewalk has been exploring this challenge as part of a broader effort to reimagine urban waste in more sustainable ways, with other investigations around anaerobic digesters and autonomous removal (more on that in a future post). We think a combination of the right incentives and, yes, trash chute innovations can enable pay-as-you-throw to take hold in apartment buildings---and, over time, improve landfill diversion and recycling rates in cities.

Recently, Sidewalk held a week-long design sprint to prototype a "smart chute" that could serve as a proof point, bringing together environmental policy experts, building managers, designers, and software and hardware engineers. We wanted to share a bit about what we learned and where these explorations might go next.

Prototyping a smart chute

The sprint began with an expert briefing on the dynamics of pay-as-you-throw programs, as well as insights gleaned from interviews with apartment residents and building managers. With a shared understanding of the challenges, the sprint moved into a brainstorm phase for how to address them. The most promising ideas took a tech-lite approach that tried to enable pay-as-you-throw without imposing too many demands on tenants --- who, after all, want to spend as little time in the waste room as possible.

The prototype that emerged had three main components:

Automatic chute door. Interviews and general observation made it clear that people don't like touching a waste chute handle. (Some go so far as to wear rubber gloves into the trash room.) Cleanliness aside, chutes are heavy by design for reasons related to fire safety, making it difficult to hold a waste chute open with one hand while depositing a bag with the other. A touchless system would be welcomed by all, so the prototype used an automatic chute door that opened and closed via a tablet.

Tablet interface. Most people want to recycle, but they don't always know how or have the right incentives to do so. The prototype tried to address this challenge through messaging on the tablet. To open the chute door, users punched in their apartment number and the number of bags they were depositing. The tablet then showed how many bags this particular unit had discarded compared to neighbors. Studies have shown that people are more likely to engage in sustainable behavior when they know others around them are doing more to help the planet.

Enforcement. Our research revealed that when taking out the trash, residents often carry nothing else, so you can't count on people to bring a key card or a smartphone into the trash room. At the same time, waste accountability requires some method of enforcement. The prototype explored the use of a trash room cam, which could potentially help building managers ensure that people were not abusing the system --- for example, by punching in a different apartment from their own. At the same time, waste is revealing, so people are sensitive to being tracked; privacy is critical.

Testing and takeaways

With the prototype built, it was time to test the system. We gave about 10 pilot participants a bag of trash to throw away with no other guidance on how to use the smart chute. The test group included an older co-op tenant, a younger tenant, a building super, and a facilities manager at a local university. Here are some of the key lessons:

The digital experience added initial friction but was ultimately more satisfying. People aren't used to pushing a button to open a trash chute. That created a little confusion for users; many instinctively looked for a chute handle only to find there wasn't one. Automatic chutes may involve a behavioral learning curve --- not unlike push-button ignition in cars. The sprint team implemented a quick design hack to facilitate usage, covering the chute with a big red sign that read: "Use tablet to open chute." Once users got the hang of it, watching the chute open became a magic moment. One participant loved the idea of bringing his toddler into the chute room to press the button and watch the door open. (Who says trash can't be exciting?)

The point-of-throw was not an effective place to shape incentives using data. The ultimate goal of a pay-as-you-throw program is to increase recycling rates. In this prototype, we didn't introduce payment as an incentive, and instead tested simpler behavioral nudges of showing people how much trash they threw away in comparison with neighbors. But since pilot participants were so focused on using the chute, they ignored or failed to perceive this information when it was displayed on the tablet. Follow-up emails showing individual-usage versus neighbor-usage proved more promising in terms of behavioral change.

The prospect of accountability is promising. Trial users were comfortable with the enforcement camera --- most apartment buildings already have cameras for security --- and building managers saw it as a way to handle violations. Other ideas could also be promising for identification purposes, such as a selfie. Building managers and residents were both excited about the prospect of waste room accountability. One manager said the smart chute could help shed light on building waste behavior ("Why is the 17th floor producing more recycling versus the 2nd floor?") and encourage particularly wasteful units to recycle. Residents, meanwhile, expressed a desire for their fellow tenants to be accountable for cleanliness.

Moving forward

A smarter trash chute is just one step toward more sustainable cities. Any success requires cities to make pay-as-you-throw a policy priority. Chute rooms might be difficult environments to maintain electronics, and power or connectivity outages could lead to frustration. Above all, it's clear that recycling behavior starts in the home, so incentive programs must figure out how to go beyond the trash room and into the apartment unit.

We're planning to pilot the smart chute in a real building soon. At this stage, we remain focused on the fundamental first step: making trash individually measurable within a multi-family setting. If we can do that, we'll enable cities and buildings to pursue the types of incentive programs that can improve landfill diversion rates. We'll also unlock more advanced capabilities, such as chutes with optical sensors that can automatically detect (and potentially even sort) recyclables or organics. It all starts with seeing the trash chute not as an afterthought but as an opportunity for climate action.

The authors wish to recognize the other members of the smart chute sprint team: Rohit T. Aggarwala, Anand Babu, Marie Buckingham, Michael Mattheakis, Craig Nevill-Manning, Dan Vanderkam, and Violet Whitney.