Analytical Techniques for Heavy Metal Monitoring in Environmental Samples Related to Biogas Producing Systems: A...

The accurate quantification of heavy metals or trace elements in biogas-producing systems supports sustainable energy pathways. At present, criteria guiding the selection of analytical techniques for heavy metal determination in biogas studies remain fragmented. This study applied the Analytical Hierarchy Process (AHP), Multi-Criteria Decision-Making Analysis (MCDA), and Simple Multi-Attribute Rating Technique (SMART) to evaluate the analytical techniques using eight defined criteria. A systematic literature review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) framework, covering publications from the past 25 years retrieved from the Scopus database through a refined search string. The results from the integrated MCDA-AHP framework indicate that XRF-based technologies demonstrated strong overall suitability across multiple operational and analytical requirements, particularly for rapid screening and field-based monitoring applications. The four highest-ranked criteria were multi-element analysis (0.258), low detection limit (0.238), cost (0.188), and matrix tolerance (0.119). Handheld XRF achieved the highest aggregate score (72.2%) within the evaluated framework. However, ICP-based techniques remain important for applications requiring ultra-trace quantification and higher analytical sensitivity. Although ICP-OES remains widely applied, four scenario tests continued to prioritize XRF-based methods, with only scenario 4 ranking ICP-OES second. The proposed framework provides a transparent and reproducible basis for selecting analytical techniques for monitoring heavy metals in biogas systems.