Time-varying losses in material flows of steel using dynamic material flow models

- Statistical dynamic material flow models have been developed and applied for the steel eco-cycle.
- This statistical method eliminates the need for adjustable model parameters.
- The lifetime of steel was shown to be between 28 and 35 years in 2012.
- The redundant time of steel in society was calculated to be between 4 and 11 years.
- The results indicates the lifetime of steel values are largely influenced by socioeconomic factors.

A method for annual evaluation of recycling rates in material flows was established to enable a consistent analysis of resource utilizations. The algorithm to calculate the time-varying losses was derived based on a sound statistical approach that would be viable for both historical data and future predictions. This method eliminates the need for adjustable parameters and is solely based on input data of the material consumption and scrap collection. This article describes the model methodology and the calculation procedures to classify the societal scrap reserve from the amounts of losses, based on statistics. These statistical models contribute to establish a standardized method to obtain consistent results. Based on the method the lifetime of steel data was for the first time calculated on an annual basis for the steel usage as well as for the end of life scrap amount. This was done for the Swedish steel consumption and the global steel consumption between 1900 and 2013 as well as for future predictions between 2013 and 2060. The lifetime of steel was calculated to be higher in an industrialized country such as Sweden compared to the global average value. More specifically, the service lifetimes of EOL steel in Sweden and in the World were calculated to be 35 and 28 years in 2012, respectively. This novel approach of using system specific data on the lifetime of steel on an annual basis enables a possibility to evaluate recycling trends and potentials to increase the recycling rate.