According to new research from Princeton Engineering, wastewater can substitute for clean water in hydrogen production, overcoming a key limitation of hydrogen fuel and cutting water treatment costs by up to 47%.
Published in the journal Water Research, the study represents progress toward making hydrogen a viable option for decarbonizing hard-to-electrify industries like steel and fertilizer production.
Turning Wastewater into a Resource for the Hydrogen Economy
Senior author Z. Jason Ren noted that conventional hydrogen production depends on clean water, increasing costs and straining local supplies. His team investigated whether treated water from wastewater plants could serve as a substitute.
“Hydrogen infrastructure often competes with local freshwater supplies,” said Ren, a professor of civil and environmental engineering at the Andlinger Center for Energy and the Environment. “However, every community has a wastewater treatment plant, providing a widely distributed water source for the hydrogen economy.”
Green hydrogen, produced using renewable energy, relies on electrolysis to split water into hydrogen and oxygen. In this process, water enters an electrolyzer, where electric current drives hydrogen ions through a membrane to the cathode, forming hydrogen gas.
A Lower-Carbon Alternative Powered by Natural Gas
In the United States, most hydrogen is produced as blue hydrogen, where natural gas powers the process and some of the resulting carbon dioxide is captured and stored underground, making it a lower-carbon option compared to using natural gas directly.
Green hydrogen, produced via electrolysis using renewable electricity, generates far fewer carbon emissions. However, it typically needs ultrapure water, produced from tap or groundwater—often via reverse osmosis—to remove impurities that hinder electrolysis.
Testing Reclaimed Wastewater for Hydrogen Production
The Princeton team explored using treated wastewater instead of tap water to skip the purification step. This approach “reclaims” wastewater, treating it for safe discharge into aquifers or use in irrigation and industrial cooling.
Although this method had been attempted before, it typically failed after a short period, Ren noted. Ph.D. student Lin Du investigated this using a proton exchange membrane water electrolyzer, the same technology used commercially with ultrapure water.
Du and colleagues used electrochemical testing and advanced microscopy to compare pure water and reclaimed wastewater in electrolyzers. They found that the system’s performance quickly declined with reclaimed water, while it remained stable with pure water.
Further experiments and modeling identified calcium and magnesium ions—the minerals that cause scale—as the main culprits. These ions adhere to the membrane, blocking ion transport and turning the porous membrane into a solid barrier.
Acidic Solution Enables Stable Hydrogen Production
To solve this problem, the researchers devised a straightforward approach: adding sulfuric acid to the water. The resulting acidic buffer provides an abundance of protons that outcompete other ions, preserving ion conductivity, sustaining the electrical current, and enabling continuous hydrogen production.
“It’s costly to remove all those ions to produce ultrapure water for the electrolyzer,” said Ren. “With a bit of acidification, you can use ion-rich water in the electrolyzer, and it operates for over 300 hours without noticeable issues.”
The team estimated that replacing purified water with reclaimed wastewater could cut water treatment costs for hydrogen production by roughly 47% and reduce the energy needed for treatment by about 62%.
Importantly, Ren noted, “this acid is recirculated, so it never leaves the system,” which benefits both the environment and costs. Similarly, calcium and magnesium ions stay dissolved and don’t disrupt circulation.
Scaling Up and Expanding to Seawater Applications
Ren and his team are working with industry partners to test their method at larger scale and with pretreated seawater. Last year, they identified U.S. sites near wastewater plants to optimize hydrogen production and reduce costs.
“We aimed to thoroughly explore the potential of using reclaimed water to support a national hydrogen strategy,” Ren said. “Our work combines in-depth technical research with broader analytical studies to address both scientific and industry needs.”
Read the original article on: Tech Xplore
Read more: Ways In Which Digital Technologies can Enable a Circular Economy