[hommelix]

There is already some trash flying around in space from decommissioned satellites. Reentering the atmosphere needs some energy to initiate the process and that was/is not always planned for. The combustion during reentry is producing CO2. This CO2 emission will scale up when the number of satellites is scaled up.

The alternative of collecting debris in space is discussed by some space agencies. I really don't think it is a good behavior from SpaceX to put more trash in space and let public money take care of the cleanup later.

[GMoromisato]

Satellites below 500 km do not need energy to reenter. Their orbits will naturally decay from friction with the upper atmosphere.

CO2 emissions from reentering satellites is far lower than CO2 emissions from terrestrial datacenters. If you need 1,000 tons of satellite for a 100 MW of compute, you're not going to get more than 1,000 tons of CO2. In fact, you'll get much less since metal doesn't release CO2 when it melts.

1,000 tons of CO2 is negligible compared to 40,000 tons at launch and invisible compared to 1.5 million tons for a terrestrial datacenter.