The major takeaways of this work are:
(1) For specific workloads, clusters of repurposed phones are cheaper and more carbon efficient than traditional servers.
(2) More broadly, scavenging unwanted equipment shows excellent potential for building economic and carbon-efficient systems, especially when renewable energy is plentiful.
(3) Sustainability has operational and manufacturing facets; manufacturing dominates as operating trends towards zero with cleaner energy mixes.
(4) Accurate LCA information is essential for carbon-based analyses; it would be beneficial if more ICT manufacturers published this information, including cloud providers who build custom systems. Our work highlights the need for more holistic analyses of the environmental impact of computing. With the substantial carbon cost of manufacturing and the difficulties of responsible recycling, the energy efficiency of a device may be the least significant component of its environmental and human impact.
I use Home Assistant, and install that on all my old, re-purposed smartphones (usually as cheap CCTV). Each phone is plugged into a smart power socket.
I then use automation to turn a phone’s charger off when it hits 80%, then back on when it reaches 50%. No overcharging, no overheating, and actually helps keep the batteries in good shape.
You can do that with root and ACCA instead of being complex like that
I already use Home Assistant for a number of other things, so not really complex. Also, you’re assuming Android only.
Because I assume that iOS devices become e-waste a few years after discontinuation, unless you write custom software on some outdated xcode+MacOS combo