How to design a sailing ship for the 21st century?

I spend a lot of time thinking about how to make international shipping more planet-friendly. The bunker oil the ships burn is really bad stuff, and local regulations do little to stop what happens out in the ocean. I’m not smart enough to figure out how to bring sailing back, but it seems like the best way forward. Using old ship designs probably wouldn’t work due to the proliferation of containers. Of course, the easiest solution would be to just reduce international trade and have more stuff made locally.

I feel like the sailing ships of this century will have different sailing technology than square rigger. You don’t see a square rigger on an ocean racing yacht and the ships need to be competitive (somewhat) with other forms of shipping. They need to be able to handle bulk or container cargo (which means specialization in design) and thus the square rigger design is unlikely to accomodate that.