Consider the following: you can run an SNES emulator off a 45-watt laptop from 2009, but you could also run the same software on a 1.2-watt Raspberry Pi. That's a 10-50x reduction in power consumption, which is hugely significant when it comes to reducing energy use. Conversely, we could take that same 45-watt laptop and melt down it's component parts, stripping it for the trace amounts of copper, aluminium and gold it contains, and turn it into 5 Raspberry Pis. I'm all-for reusing older equipment, but the overwhelming majority of trashed tech is not worth saving.

I really recommend doing your research before you hop into a project like this. I've worked on engineering teams with 20-30 people before, and I can tell you right now that managing your expectations is crucial for a project of this scale. Like I said earlier, you'd only really be turning trash into slightly more useful trash. Unless you've got some hard numbers here that I've somehow missed, I've got a hard time seeing how you'd put this together.