Researchers hacked 15-year-old smartphones into tiny servers that outperform Raspberry Pi at a fraction of the cost.
A team at the University of Tartu’s Institute of Computer Science has shown that obsolete mobile phones can be wired together to do the sort of heavy data processing normally reserved for expensive server farms while keeping thousands of handsets out of landfills.
Led by associate professor of pervasive computing Huber Flores, the engineers stripped the batteries from four discarded Google Nexus devices, fitted them with 3-D-printed holders, and powered them from an external source. The cluster cost about €8 (US$9.20) per phone, yet comfortably outperformed popular single-board computers such as the Raspberry Pi for image-analysis and website-hosting chores.
“Innovation often begins not with something new, but with a new way of thinking about the old, reimagining its role in shaping the future,” Flores said.
From trash cans to tiny cloud
More than 1.2 billion smartphones roll off factory lines each year, and the WEEE Forum estimates that 5.3 billion of them are simply discarded annually. Even when a handset is recycled, only the precious metals, gold, palladium, and the like, tend to be recovered. Plastics and circuit boards are often burned or buried, releasing toxins. By turning the handsets into computing nodes, the Tartu group hopes to extend their working life and cut the environmental toll of e-waste and new server construction.
“Smartphones are really well designed for high-energy processing,” Flores told IEEE Spectrum in an article, which is a part of their Journal Watch series. “They are also very well optimized not to overheat and are very efficient in handling heavy data processing applications.”
Even 15-year-old models carry multi-core CPUs, fast RAM, Wi-Fi and Bluetooth radios, and flash storage, ingredients that form a miniature cloud when linked by open-source software.
To create that cloud, one phone is designated as a “master” that receives jobs from sensors or user commands and parcels them out to three “worker” phones. The researchers replaced Android with the Linux-based PostmarketOS, which let them control the hardware directly and patch known security holes.
Field test at 25 meters
The team’s proof-of-concept went well beyond the lab. During an eight-hour dive off Madeira, the smartphone rack, housed in a watertight bubble and attached to a high-resolution camera, identified and counted fish 25 meters below the Mediterranean’s surface.
The same setup could sit at a city bus stop, crunching passenger counts from infrared sensors so transit planners can adjust schedules in real time, or ride on a ground robot that processes aerial footage beamed in by swarms of drones.
“These phones, you can just get them from the trash,” Flores said. “Then you install the open-source system … and you have a tiny data center that can be useful for many applications.”
Colleague Ulrich Norbisrath argues that such quick hacks embody a broader shift: “Sustainability is not just about preserving the future! It’s about reimagining the present, where yesterday’s devices become tomorrow’s opportunities.”
Obstacles and a policy nudge
There are limits. The Nexus line’s modular design made battery removal and board access straightforward, whereas modern phones are glued shut with proprietary chips and are harder, sometimes impossible to repurpose.
“If it’s too difficult to hack and repurpose the phones, then the whole thing becomes more costly,” Flores cautioned in the IEEE Spectrum report. He believes regulation rather than market forces will be needed to make future gadgets more reuse-friendly. “Manufacturers are not going to do it unless there are guidelines telling them so.”
The World Health Organization lists discarded electronics as one of the fastest-growing waste streams. About 62 million metric tons were discarded in 2022, with only 22 percent properly recycled. By proving that even decade-old handsets can tackle AI-class workloads for the price of a pizza, the Tartu prototype suggests one modest but practical route toward shrinking that mountain of toxic trash.
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