Your concerns are noble. 

And I agree cases better be made from recycled plastics, wood, or similar (and there are). While steal tin ain't that bad.
When Apple brought out their first Macbook with a massive aluminium case they actually proudly presented videos showing how it's 
milled from a massive block (not casted.) App.>85% of the material is removed until the frame is left, and I cried:"

 Are they mad?!" (They are. But that's another topic. 

) Sure, it's a very nice case. But the energy needed to recycle all this aluminium chippings is madness.
 
The cases are of no much consequences. The very electronics, the boards are what use most of the noblest resources. And those are hard to recycle: very energy consuming, so expensive, so it's way cheaper to dump it all on landfills in countries we look down at, and think how dirty they are.  Just duckduckgo for pictures "electronics landfill africa."
You don't need to only see the bare resources themselves. Furthermore the amount of energy needed to produce, manufacture, transport, and recycle are what concerns.
Switching to more environmental friendly, resources saving materials is right. But as long as our economy ain't interested in devices being used as long as possible, but there are such things like planned obsolescence, those are just marketing stunts, letters of indulgence, just to give everybody a good feeling about how exemplary "green" we are, buying even more, slightly more greener things. While neither the things nor we are, but in fact trashing up the planet even more.
My #1 example at this point are printers.
The new models are advertised with lower energy consumption, and lower CO2 emission. While their production and transportation eat up 
magnitudes of what you will save in its lifetime.
You use it for two to three years. Then this bugger also starts to mither you with fantasy-error-bullshit, until after four or five years you are close to throw that annoying piece of shit out of the window. So you buy a new one. And of course - naturally - any of your cartridges left won't fit into the new one anymore. And maybe another cable is needed,... But it feels so very good to buy and have a new, smooth, errorless working device again.
Until in two or three years the shit starts all over again. While technically the device is tip-top. It could last ten, fifteen, twenty years - then saving resources, and CO2.
By now I don't know a single study estimates the price you pay with losing your peace of mind with all this mithering error BS.
But we have this in all devices today. Our car beeps, flashes, and brings the strangest error messages while everything is mechanically tip-top. Yesterday our dishwasher gave up. Five years - time to buy the new model, with WiFi, of course.
The car and the dishwasher still can be repaired. But if not I do buy new things. Of course. What else shall I do?
But I don't buy anymore from the same company (which is not the same as the brand.)
"Fool me once or twice, shame on you. Fool me three or more times, shame on me."
And I'm no fool. At least I try not to.
Insofar FreeBSD (and also other BSDs, and Linux) help to save the planet.
You are not forced to buy new hardware every few years, but can do all your computering needs - real needs; excluding bleeding edge gaming - also on "old" hardware. 

