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.

No, 4kwh is about the daily amount of sun hitting 1 square meter. Solar panels can capture about 20% of that

If I understand many of my colleagues gripes about their days in graduate school, the PI basically told them to make it work, so they did. Either by manipulating procedures, using the one study out of 5 that worked, or by photoshopping images. I’d say manipulation is absolutely rampant in his lab, this is just one way they were doing it and they got caught.