The iron and steel industry represents an important case for industrial ecology due to its ability to accept waste-derived inputs and due to the generation of useful by-products. With the objective of supporting environmentally conscious decisions regarding resource use and waste management, a life cycle assessment (LCA) tool for ironmaking was developed. The tool combines mass flow-based process models with an LCA database to assess the use of alternative resources in ironmaking, considering various process configurations. The article contains a description of the tool and a case study illustrating two areas of application. In the first part of the case study, an inventory analysis focused on the effects of feedstock recycling of waste plastics in ironmaking on heavy metal distribution is presented. It is demonstrated how uncertainties in input heavy metal concentrations and mass transfer can be incorporated into the model to predict the heavy metal loads in the process outputs. In the second part, the substitution of coke with a range of alternative reducing agents are assessed with regard to impact on climate change and fossil resource depletion. It was found that the use of sustainably sourced charcoal and waste-derived reducing agents is beneficial both with respect to the impact on climate change and fossil resource depletion at the respective calculated coke replacement ratio, whereas the results for heavy oil, coke oven gas, and raw tar indicate that trade-offs between impact categories occur. The results also highlight the importance of considering the avoided impacts of alternative treatments for waste-derived resources.