This feels like the difference between science and engineering. Although to be fair to you, this paper really feels like somewhere on that spectrum and not fully on the side of science. It's similar to how every battery advancement doesn't always make it to manufacturing.

To address the things that you thought of off the top of your head: * Anything done on land will be less carbon intensive as we transition to renewables. * Trains are incredibly efficient at transport, and depending on the quarry might already be established. * Boats are so good at shipping heavy weights because of those hydrodynamics, so as long as some reduced returns are okay (reduced cargo space), there's plenty of space on those cargo ships. The real limiter is stability of steering in canals and depth of ports/canals.