Optimal integration of a biomass-based polygeneration system in an iron production plant for negative carbon emissions

The iron industry is an energy-intensive sector and a major contributor to global carbon dioxide emissions. With the projected increase in the demand for iron as raw material, the industry seeks ways to improve sustainability. The incorporation of a biomass-based polygeneration system (BBPS) is a sustainable approach to generate the needed utilities of the iron plant. Biomass can be converted thermochemically into fuel gas for use in the plant, while the resulting biochar can be utilized for carbon sequestration. A multiobjective optimization model using fuzzy linear programming (FLP) is developed to seamlessly integrate a BBPS in an iron plant while obtaining negative carbon emissions. The FLP model simultaneously satisfied the product demands while maximizing the annual profit and minimizing the carbon footprint of the iron manufacturing plant. A sensitivity study is performed to gauge the effects of uncertainties of the prices of product streams and capital costs together. The best configuration of the integrated BBPS and the iron production plant are determined using this approach, resulting in 2.7 million tons CO₂ y⁻¹ of negative carbon emission. The reduction of the carbon footprint upper threshold target by 80% has shown a 34.15% improvement on the negative carbon footprint and 1.81% enhancement on the annualized capital cost of the plant. The change in the biomass price had a significant effect on the Pareto frontier of the level of satisfaction compared with the change in the coal and iron ore prices. The varied capital cost of the gasification had a relatively significant influence to the annualized profit of the plant compared with the varied capital cost of the other polygeneration processes.