National Materials Flows and the Environment

Abstract

The functioning of modern societies requires large flows of materials tosatisfy human wants both directly and indirectly; for example, 50 kg perday per American. The nature of these flows determines their impact onthe natural environment. We develop and test a comprehensive frameworkto order materials flows in the US economy, We assess and quantifyinputs to the national economy, outputs, foreign trade, and wastes fromresource extraction, using mass measures of these flow components. Thebulk of materials inputs satisfies demand for energy, construction, andfood. Atmospheric emissions and materials embedded in long-livedstructures dominate outputs, with smaller contributions from solidwastes and dissipated materials. Trade, accounting for approximately10% of US materials flows, is dominated by bulk commodities such asfuel, food, and chemicals. Extractive wastes from fuel and nonfuelminerals account for more than double the amount of inputs and mostlyremain at the site of generation, Metrics based on a consistent,periodic accounting of physical materials flows can provide a powerfulmeans to assess environmental performance at the national level.Improvements in the collection and organization of the data supportingnational material accounts will further their utility.