Researchers at Japan’s Kyushu University have developed a microwave-assisted technique that significantly speeds up the conversion of biomass into hydrogen and other useful gases, a breakthrough that could improve renewable fuel production and support the transition to cleaner energy.
The study found that microwave radiation creates microscopic high-temperature regions on nickel catalyst nanoparticles, allowing biomass to break down much faster than with conventional heating while using less energy, Techxplore reported.
Biomass such as wood, straw and agricultural residues is considered a renewable alternative to fossil fuels. It is commonly converted into gases, liquids and solid carbon through pyrolysis, a process in which biomass is heated in the absence of oxygen. However, conventional heating is slow because heat gradually moves from the outer surface to the interior of the material.
The researchers found that microwave heating transfers energy directly to the catalyst, creating localized hot spots on nickel nanoparticles while the surrounding material remains relatively cool. These high-temperature regions accelerate chemical reactions and improve hydrogen production.
The research team, led by Professor Shuntaro Tsubaki of Kyushu University’s Faculty of Engineering, collaborated with scientists from The University of Osaka, Institute of Science Tokyo, High Energy Accelerator Research Organization (KEK) and International Christian University. Their findings have been published in the Chemical Engineering Journal.
To understand how the process works, the researchers used a solid-state microwave generator and mixed cellulose and bamboo powder with a commercial nickel catalyst. They monitored the catalyst during the reaction using advanced X-ray absorption fine structure (XAFS) and X-ray diffraction (XRD) techniques, allowing them to observe changes in the catalyst in real time.
The experiments showed that microwave-assisted heating increased hydrogen production by more than six times compared with conventional heating.
The XAFS analysis revealed that nickel particles became as much as 80 degrees Celsius hotter than the surrounding material during microwave irradiation. XRD measurements also showed that the nickel particles underwent sintering at bulk temperatures of 350-400°C under microwave heating, whereas the same process normally requires temperatures above 1,000°C using conventional heating. The findings suggest that the actual temperature at the catalyst surface is much higher than the externally measured temperature.
“Our findings provide rare, experimentally grounded insight into how microwaves interact with catalytic nanoparticles during reactions,” Professor Tsubaki said.
The researchers believe the technology could enable rapid, electricity-driven production of hydrogen and other light gases from agricultural and forestry residues, reducing the need for large industrial furnaces.
They also said the microwave-assisted approach could be applied to other high-temperature industrial processes, including converting mixed plastic waste into useful hydrocarbons and producing advanced carbon materials from biomass.
According to the researchers, the technology has the potential to improve both sustainable energy production and the development of advanced materials while making biomass conversion faster and more energy efficient.
