A framework for the evaluation of anthropogenic resources: the case study of phosphorus stocks in Austria

Due to a predicted shortage of raw materials, increasing attention is drawn to the utilization of anthropogenic resources through recycling and urban mining. However, in order to assess the availability of anthropogenic resources as potential raw materials, a consistent concept for categorizing anthropogenic materials into reserves, resources and other occurrences is needed. This study presents a framework for the evaluation of anthropogenic resources, derived from the standard procedure for resource and reserve identification, evaluation, and classification of the U.S. Geological Survey for natural stock resources. The framework was applied to a case study on phosphorus (P) stocks in Austria. Results indicate that only 10% of the anthropogenic P stocks in Austria (one million tons in total) are extractable at subeconomic levels with production costs 5-10 times above the market price for P fertilizer. 70% of P stocks are not technically extractable and 20% of such a low grade that recovery is not practically feasible. Based on the assessment, it is found that the extractable amount of P could have been much higher if P-rich materials were not mixed with low-grade materials during landfilling. Although the evaluation of anthropogenic P stocks in Austria was performed on a screening level, the application of the framework highlights that a consistent method for the evaluation of anthropogenic resources can provide a basis for enhanced utilization of anthropogenic resources. In future, further case studies are needed to demonstrate the application of the evaluation framework for various resources and in consideration of environmental, technological, and societal factors.