Mark Scheffler

Municipal wastewater treatment plants (WWTPs) are potential sites for decentralized water electrolysis because they combine water availability, operational infrastructure, and local integration options for electrolysis coproducts. This review evaluates three downstream pathways for electrolytically produced gaseous hydrogen (H₂): onsite energetic use, trailer-based compressed gaseous H₂ export, and pipeline-based delivery. The system boundary extends from the H₂ handover point downstream of the electrolyzer to the WWTP-side utilization or transfer interface. A process-chain-based techno-economic synthesis identifies pathway-specific technical functions, interfaces, and cost-relevant components, including gas conditioning, compression, storage, reconversion, transport infrastructure, metering, control, and safety systems. For onsite use, PEMFC operation is associated with flexible, electricity-oriented reconversion, whereas the investigated modular H₂ CHP configuration represents comparatively steady cogeneration with simultaneous electricity and heat supply. For trailer-based export, compression, storage configuration, payload, utilization, and transport distance are key technical and economic drivers. For pipeline delivery, throughput, distance, pressure management, and pipeline sizing determine system performance. A directly comparable transport study indicates that trailer-based delivery is favored at lower H₂ throughputs, whereas pipeline transport becomes more favorable at higher throughputs, with the crossover strongly dependent on transport distance. The synthesis supports site-specific assessment of gaseous H₂ utilization pathways in WWTPs.

Municipal heat planning is becoming a mandatory element of local climate policy in Germany, yet many smaller municipalities lack geospatial tools that are transparent, reproducible and aligned with the German Heat Planning Act (WPG). This paper presents F|Heat, an open-source QGIS extension that supports early-stage municipal heat planning by automating data acquisition, building-level heat-demand preparation, heat-density and heat-line-density analyses, preliminary district-heating network routing, pipe dimensioning, heat-loss estimation and load-profile generation. The method is demonstrated for a district in Barntrup, North Rhine-Westphalia, Germany. The case study connects 268 buildings with an annual heat demand of 11.9 GWh and generates a 9.1 km preliminary network. Simulated annual heat losses amount to 1.6 GWh with standard insulation and 1.4 GWh with enhanced insulation. Using DN-specific network investment assumptions, the annualised network cost contribution is estimated at 0.042 EUR·kWh-1. The results show that F|Heat can provide a reproducible GIS-based workflow for suitability assessment, status-quo analysis and preliminary district-heating area assessment. The tool does not replace detailed techno-economic optimisation, heat-source assessment or engineering design, but narrows the gap between statutory heat planning requirements and the data-processing capacity of municipalities.