Identification, Classification and Definition of KPI Indicators for the Evaluation of the Green H2 Combustion Process in the Aluminium Industry

The quantitative assessment of industrial decarbonization technologies is essential to objectively compare different processes and to facilitate the transfer of successful decarbonisation solutions across Hard-to-Abate Industries (HTAIs). However, existing Key Performance Indicator (KPI) frameworks differ considerably in KPI selection and definition, calculation methodologies, reporting units, and system boundaries, limiting direct comparison between different technologies and industrial sectors. This work proposes a harmonised KPI framework for the assessment of hydrogen combustion technologies in HTAIs. The framework integrates and harmonises relevant existing indicators while introducing specific KPI formulations and developments tailored to hydrogen combustion assessment. Its development was based on information from the scientific literature, European strategic initiatives, industrial reference documents, and the requirements of the H2AL and HYINHEAT EU projects. A total of 29 KPIs were identified, harmonised, and organised into six assessment categories: energy efficiency, material efficiency, atmospheric emissions, waste and by-product generation, product quality, and competitiveness. The applicability of the framework was initially assessed using industrial data from an aluminium high-pressure die-casting (HPDC) process employing natural gas–air combustion. The results demonstrated the applicability of the proposed framework under real industrial conditions and established an industrial baseline for future comparison with hydrogen combustion technologies. The proposed framework provides a practical and harmonised methodology for the assessment and future comparison of hydrogen combustion technologies across HTAIs.