Generation of renewable hydrogen from sewage sludge — Quantitative and energy-based technology evaluation

The paper presents a critical analysis of a commercial pre-feasibility study for hydrogen generation from sewage sludge generated in a wastewater treatment plant sized Population Equivalent (PE) = 160,000 Three commercial offers based on hydrothermal carbonization, gasification/plasma gasification and gas separation, are analysed and validated in terms of chemical reactions and energy balance. The obtained hydrogen yield equals 10 kg H₂/Mg sludge for Technology#2 and 5.5 kg H₂/Mg sludge for Technology#3, while the process efficiency equals 31.4% and 41.2%, respectively. The offer for Technology#1 is inconsistent. The potential market can be built in the transport sector, based on buses (8–12/day) or locomotives (1–2/day) and complemented by passenger cars (16–22/day). Hydrogen surplus can be disposed into the natural gas network at a city gate station, with target concentration <2%. Alternatively, it is possible to install a fuel cell unit for on-site electricity generation of 1780 MWh/a sold to the public grid.