34 4 Produce Leaner What if all the matter extracted for building materials was used somewhere in the supply chain? To mine resources much more mass is extracted from the earth—typically two to three times more—than the amount used. For some resources, as a deposit is quarried, this ratio continues to increase, requiring more and more extraction for the same output. Reuse of by-products is already part of the material supply chain. Timber production, for example, incorporates several forms of reuse. Shavings are used to produce particleboard, and sawdust can be used to fire kilns used in the lumber- drying process. Improving the production chain of building materials could greatly reduce the amount of raw materials consumed by urbanization, increasing material efficiency. Or, perhaps the question should be stated more radically: Could materials be produced without any raw- material extraction at all? Higher material efficiency could have advantages for all actors. Reduced material costs could be an incentive for manufacturers to improve product supply chains— savings that should be passed on to users.