Re: Disposible like BIC or Gillette razors
There will be a crossover point. Based on 300t of carbon per starlink launch and 8kg of carbon per km of fibre laid overland, that's equivalent to 37.5Mm of fibre but some 5.7Gm of fibre for Internet connectivity was sold in the UK in 2021 alone and, by 2022, that only yielded (in conjunction with existing fibre) 42% of homes on full fibre broadband.
https://www.gov.uk/government/news/new-measures-protect-uks-88m-optical-fibre-cables-industry
Obviously, there's the potential for multiple strands to be laid in the same trench and all of it may not have been laid yet but, assuming it were laid singly, doing so would emit more carbon than 150 Falcon 9 launches. Perhaps in a very densely populated country like the UK, almost everyone could be connected up for less carbon emissions than Starlink but there will be outliers and there are plenty of sparser countries.
I would suggest that no one method is "best" for everyone and the ideal solution is to find the balance point where the lowest carbon solution can be applied. If fibre works out best for one customer, use fibre, if Starlink or similar works out best for another customer, use that. In the meantime, while the fibre barons are stalling, perhaps Starlink and other similar services which might arise later could fill the gap, because Internet connectivity is important.
Geostationary isn't ideal because, in addition to latency, it takes a lot more energy to get the satellites up there and they take a lot longer to come down (long after they become broken or obsolete).