What will LEGO do when all the crude oil on earth is used? When crude is no longer available (which is in 53.3 years) what will LEGO do, since oil is needed in order to make plastic? Is there a plastic alternative, or another type of material that is strong and durable like ABS plastic?
They're working on it! Should be ready in 15 years.

http://www.nbcnews.com/science/environment/no-more-plastic-legos-company-searches-sustainable-material-n379976