For the first time, researchers at TU Graz and Rouge H2 Engineering have created high-purity hydrogen straight from methane in a biogas plant.
Decentralized green hydrogen may be created from biogas using the “Chemical-Looping Hydrogen-Method,” a sustainable approach for decentralized hydrogen generation. The biggest issue in implementation right now is not the price per kilogram of hydrogen generated, but rather its delivery and subsequent usage.
Researchers from Graz University of Technology collaborate with process engineer Viktor Hacker to produce high-purity hydrogen from genuine biogas at an existing biogas plant in one of the world’s largest industrial demonstration plants. The “Chemical-Looping Hydrogen-Method,” a sustainable approach for decentralized hydrogen generation, serves as the foundation. “We show that a chemical looping system can be implemented into an existing biogas plant,” says Viktor Hacker of TU Graz’s Institute for Chemical Process Engineering and Environmental Technology. “Not just in the lab, but on an industrial scale, high-purity hydrogen for fuel cells is created from genuine biogas.”
The biogas originates from the South Styrian kostrom Mureck GmbH, which produces methane gas from pig dung, glycerine phase, silage maize, and grain wastes. An extra pillar has sparked a lot of interest: “Of course, the possibility of our biogas generating green hydrogen for sustainable transportation in addition to power is incredibly exciting for us,” says Managing Director Karl Totter.
The demonstration system was erected in the summer of 2021 on the company’s Mureck premises and will be in use for testing until the end of October 2021. Around 1% of the biogas flow (around 30 liters per minute) is diverted to the 10 kilowatt system, which mixes it with water vapor. The mixture is pumped into the reactor of the facility. Biogas is reformed and synthesis gas is created there. The iron oxide is subsequently reduced to iron by this gas. The iron is subsequently reoxidized to iron oxide by passing steam through the reactor. Hydrogen is emitted with a purity of 99.998 percent, according to Graz University of Technology.
This iron-steam process has a 75 percent efficiency. “We could even have a 3 megawatt hydrogen generation plant if we routed the full biogas flow from the Mureck biogas plant (about 480 cubic meters per hour) via a suitably scaled-up chemical looping facility instead of the one percent.” “This indicates the technology is now suitable for commercial application,” says Gernot Voitic, project manager for Rouge H2.
According to technological and economic studies, the hydrogen price for this decentralizedly produced hydrogen would be 5 euros per kilogram. In comparison to electrolysis (5-12 euros / kg), this makes the method cost-effective. For comparison, hydrogen costs roughly 10 euros per kilogram at the gas station.
The difficulty, according to many participating in the initiative, is not in the manufacturing of green hydrogen, but rather in how that hydrogen is dispersed and used. Hydrogen-powered cars must now be refueled at 700 bar pressure, while the chemical looping system only creates hydrogen at a pressure of up to 100 bar, according to specifications. That’s a lot, but it’s not enough to refuel directly.
It can also be utilized in fuel cell automobiles, where a lower pressure is adequate, to consume hydrogen without extra compression. These could theoretically travel at a pressure of only 2 bar, but only a short distance. As a result, decentralized hydrogen production in biogas plants for shorter excursions, such as hydrogen tractors or hydrogen-powered storage vehicles like forklifts, Hacker concluded.