A 1998 estimate predicts that U.S. wastewater treatment systems generated nearly 8 million dry tons of sludge in 2005. This sludge requires significant energy to treat, ranging from 30-80% of total electrical input to a wastewater treatment system.
Since 2001 the University of Michigan’s Center for Sustainable Systems has developed a growing set of factsheets that cover topics including energy, water, food, waste, buildings, materials, and transportation systems. Each factsheet presents important patterns of use, life cycle impacts and sustainable solutions. They are designed to inform policymakers, business professionals, students and teachers. The factsheets are peer-reviewed and updated annually.