A hybrid fuzzy AHP-TOPSIS multi-criteria-based decision-making for evaluating waste-to-energy processes for mixed municipal solid waste in India

India's municipal solid waste (MSW) management system is predominantly characterized by unsegregated mixed waste streams, comprising heterogeneous organic and inorganic fractions such as food waste, plastics, and paper. The lack of source-level segregation presents significant challenges for conventional waste treatment pathways and highlights the need for context-specific waste-to-energy (WTE) processes. This study applies a hybrid multi-criteria decision analysis (MCDA) framework, integrating the Fuzzy Analytic Hierarchy Process (FAHP) and the Fuzzy Technique for Order Preference by Similarity to Ideal Solution (FTOPSIS), to systematically evaluate five WTE processes: incineration, anaerobic digestion (AD), pyrolysis, gasification, and hydrothermal liquefaction (HTL). Eighteen evaluation criteria covering elemental, environmental, energy, economic, and socio-economic aspects were identified and weighted using Fuzzy AHP, with environmental impacts emerging as the highest priority (∼34%), followed by elemental and energy recovery efficiency (∼30%), economic feasibility (∼19%), and socio-economic considerations (∼7%). The weighted criteria were then used within the Fuzzy TOPSIS model to rank the technological alternatives. The results indicate that HTL is the most promising WTE process for India's mixed MSW, followed by gasification, pyrolysis, incineration, and AD. The hybrid MCDA framework employed provides a robust and adaptable decision-making process for policymakers and stakeholders to identify optimal WTE process options in regions facing high waste heterogeneity and inadequate waste segregation infrastructure.