Green hydrogen may soon be matter of waste recycling in major cities, as researchers from the Hong Kong University of Science and Technology have created what they describe as an “ultra-fast” green hydrogen production method using municipal wastewater.
The research team tested a modular forward osmosis-water splitting (FOWS) system that integrated a thin-film composite FO membrane for water extraction with alkaline water electrolysis.
Published in the open-source journal Nature, the team’s research demonstrated the system was capable of generating high-purity hydrogen directly from wastewater at a rate 14-times faster than state-of-the-art electrolysis, with very low energy consumption compared to industry standards as well.
Addressing water constraints
One of the core logistical challenges of green hydrogen production is the vast amount of clean water required to achieve it – one kilogram of hydrogen requires about 9 kilograms of water to produce.
In areas of the world – like Australia – that experience water scarcity, the supply of clean water for electrolysis is limited and can become a source of conflict within communities.
Substituting clean, potable water for wastewater as in the Hong Kong University team’s experiment could offer a far more sustainable water source for use in energy generation.
“Using wastewater effluent is crucial for sustainable H2 production in regions where seawater is unavailable or freshwater resources are scarce, especially as H2 projects are rapidly expanding amid the foreseeable intensified worldwide water stress,” the paper reads.
The team’s findings also point to a 46% reduction in capital costs associated with water treatment compared to traditional processes, with potential to capture both additional energy produced during the process, and clean water from the hydrogen cells themselves as by-products of the technology.
All in all, the research could lead to wastewater-based green hydrogen production that is cleaner, cheaper, and more efficient.