Methane is produced by methanogens in landfills, methane is not really part of the carbon cycle. The cycle itself isn’t self contained, so all the carbon dioxide and methane join all the rest in the atmosphere. We want to reduce any greenhouse gas sources as much as possible, whether it’s “carbon neutral” or not.
They can’t just use any type of sand for construction, beach sand is out of the question as it’s not rough enough. It’s coming to the point that it’s hard to find sources of sand that don’t have negative ecological impacts, so replacing that component with something else is a good idea.
I’d be willing to guess that they already tested using bio char as a replacement and saw that it worked well in concrete, then started looking at waste sources of starting material that had sandy texture, then boom coffee grounds.
I use nextcloud tasks and deck for keeping track of things. Tasks is great for checklists, calendar integration, reminders, etc., I use it for simple reminders like trash day, and things I don’t want to bother with making a calendar event for. You can have it make a calendar event, but I don’t. Deck is a kanban style thing with calendar integration as well, it’s a bit more job-task oriented so I use it to help me juggle tasks when I have a lot of projects that need keeping up with. Setting up nextcloud is way overkill for just those features, though. If you’re not looking for the other features of nextcloud, I don’t think it’d be worth it.
It is pretty easy to set up if you go the nextcloudpi route on Debian, you don’t need a raspberry pi. Any computer running Debian can do it, but you may need to install a few dependencies if you’re on minimal Debian that aren’t listed anywhere, at least last time I set it up they weren’t. But again, if you aren’t looking to use the rest of nextcloud, I wouldn’t go that route.