Hydrogen production from biomass
There are many ways to produce hydrogen, of which we have already presented the seawater process. But hydrogen can also be produced from biomass, as researchers at the École poyltechnique fédérale de Lausanne (EPFL) have shown using the principle of photo pyrolysis. The process can convert biomass into the fuels hydrogen, biochar and other hydrocarbon compounds. The process also works much more simply and quickly than in the conventional experimental setup.
The process of photo pyrolysis is based on biomass pyrolysis. In this process, the biomass is treated under high pressure of five bar at temperatures between 400 and 800 degrees Celsius. The end products are biochar and syngas. Syngas is a gas mixture consisting mainly of hydrogen, but also containing carbon monoxide and methane. Since the chemical process must take place at high temperatures and high pressure, the process is also technically complex and expensive.
In the new process developed by the researchers in Lausanne, the biomass is flashed with a xenon lamp to provoke a photo-thermal reaction. Xenon lamps are special lamps powered by xenon gas, whose luminosity is generated by gas discharge. For the biomass, the researchers used banana peels, orange peels, coffee beans, corn cobs and coconut shells in the experiment. These were first dried at 105 degrees Celsius for 24 hours and then pulverized. The powder was applied in a thin layer in a stainless-steel vessel. To prevent oxidation, hot argon replaced the air in the vessel. The xenon lamp was then used to flash the powder at 13.1 joules per square centimeter for 14.5 milliseconds. The reaction takes place under normal atmospheric pressure and at room temperature.
"Each kilogram of dried biomass can produce about 100 liters of hydrogen and 330 grams of biochar, which is up to 33 percent by weight of the original mass of the dried banana peels," explains Bhawna Nagar, who worked on the study. (pv-magazine)
After deducting the energy used for drying and flashing the biomass, the process achieves a positive calculated energy result of 4.09 megajoules per kilogram of dried biomass. In addition to fuel, biochar can also be used as fertilizer or electrode material. The method could provide a starting point for processing industrial waste into hydrogen and biochar in the future.
pv-magazine, article by Marian Willuhn (3/2/2022):
https://www.pv-magazine.de/2022/03/02/neues-blitzlicht-verfahren-zur-gewinnung-von-gruenem-wasserstoff-aus-bananenschalen-entwickelt/, accessed: 3/6/2022 at 2 p.m.
article by Gianluca Riccio (2/28/2022):
https://de.futuroprossimo.it/2022/02/il-politecnico-di-losanna-ha-un-metodo-per-estrarre-idrogeno-dalle-banane/, accessed: 3/7/2022 at 10 a.m.