For years, the toymaker Lego has been trying to figure out how to make its plastic building blocks out of sustainable materials. It’s experimented with all kinds of things — Brazilian sugarcane, for instance, which worked, at least for some pieces. It also tried recycled plastic bottles, which … didn’t work. The company said Monday it’s abandoning an effort to make its bricks out of recycled PET, the plastic found in many of our bottles and food containers.