NATIONAL MATERIALS FLOWS AND THE ENVIRONMENT

The functioning of modern societies requires large flows of materials to satisfy human wants both directly and indirectly; for example, 50 k g per day per American. The nature of these flows determines their imp act on the natural environment. We develop and test a comprehensive fr amework to order materials flows in the US economy, We assess and quan tify inputs to the national economy, outputs, foreign trade, and waste s from resource extraction, using mass measures of these flow componen ts. The bulk of materials inputs satisfies demand for energy, construc tion, and food. Atmospheric emissions and materials embedded in long-l ived structures dominate outputs, with smaller contributions from soli d wastes and dissipated materials. Trade, accounting for approximately 10% of US materials flows, is dominated by bulk commodities such as f uel, food, and chemicals. Extractive wastes from fuel and nonfuel mine rals account for more than double the amount of inputs and mostly rema in at the site of generation, Metrics based on a consistent, periodic accounting of physical materials flows can provide a powerful means to assess environmental performance at the national level. Improvements in the collection and organization of the data supporting national mat erial accounts will further their utility.