Journal of Industrial Ecology vol:20 issue:4 pages:854-866
State-of-the-art technologies that implement the ‘Industrial Ecology’ concept only make it to the market if environmental gains and economic benefits are significant. Therefore, the paper investigates, in an interdisciplinary way, two innovative technologies that valorize Stainless Steel (SS) slags as block masonry (bricks): carbonation and thermo-alkali-activation. The technical, environmental and economic features of three SS bricks - solid bricks, perforated bricks and light-weight aerated blocks – are compared to commercially available construction materials. Although the produced bricks meet industrial standards, technical challenges such as optimization of alkali addition and use of metal molds should be dealt with before upscaling to industrial production. A cradle-to-gate Life Cycle Analysis (LCA) that aggregates the results of the various impact categories shows that the environmental impact of solid and perforated SS bricks is lower than the impact of conventional clay-baked bricks thanks to the avoidance of additives for slag stabilization and energy consumption for sintering clay. The impact of aerated SS bricks was found to be similar to the commercially available aerated blocks. More specifically, the CO2 uptake from carbonation reduces the overall environmental impact whereas use of alkalis increases the impact. A SWOT analysis highlights the economic advantages of SS bricks originating from lower energy requirements, reduced dependence on primary resources and improved metal recovery from slag. However, in order to apply the innovative technologies at industrial scale, challenges related to processing conditions, feedstock variability and potential competition from existing brick suppliers have to be overcome.