earthquake-proof*

* according to Yahaya Ahmed of Nigeria’s Development Association for Renewable Energies

Assuming they're using generic sand and not coarse-washed sand that is causing sand scarcity problems, I think concerns about digging may be overblown, but I can't imagine how a house built with circular plastic bricks joined with mud will hold up during an earthquake. That they're planning to build a 3-story house this way is kind of terrifying. I hope none of the load bearing walls are built like this.

For a better tested alternative, Earthships use vulcanized rubber tires filled with rammed earth for load-bearing walls, and reuse glass bottles as design elements in non-load-bearing walls.

Though it is possible to design bricks that mitigate these problems. Precious plastic has a system for building square hollow bricks that allow other materials to bear loads.