In recent decades, the high consumption of energy from fossil fuels has contributed to a massive increase in greenhouse gas emissions around the world. To solve this problem, scientists have researched alternative and renewable energy sources.
One of the main candidates is hydrogen produced from organic waste, or biomass, from plants and animals. Biomass also absorbs, removes and stores CO2 from the atmospherewhile biomass decomposition can also give us ways to remove negative emissions or greenhouse gases.
EPFL researchers have developed a way to maximize hydrogen yields from bio-waste within milliseconds. The method uses rapid photopyrolysis to convert dry biomass powderslike banana peel, into valuable gases and solids, including hydrogen and biochar.
The new method developed by EPFL scientists for the photopyrolysis of biomass not only produces valuable syngas, but also solid carbon biochar that can be reused in other applications. Syngas is a mixture of hydrogen, methane, carbon monoxide and other hydrocarbons, and is what is used as “biofuel” to produce energy, while biochar is often considered a solid carbon waste, although it can be used in agricultural applications.
The process performs pyrolysis using a xenon lamp, commonly used to cure metallic inks for printed electronics. The team has also used the system in recent years for other purposes, such as nanoparticle synthesis.
The idea is to generate a powerful flashlight blast that absorbs the biomass and instantly triggers a conversion of the photothermal biomass into syngas and biochar. The banana peels were first dried at 105°C for 24 hours then crushed and sieved into a fine powder. The powder was then placed in a stainless steel reactor with a standard glass window at ambient pressure and under an inert atmosphere. The xenon lamp flashes and the whole conversion process is completed in milliseconds.
“Each kg of dry biomass can generate around 100 liters of hydrogen and 330 g of biochar, which is up to 33% by weight of the original dried banana peel mass,” says Bhawna Nagar, who worked on the study. The method also obtained a positive calculated energy result of 4.09 MJ·per kg of dry biomass.
The two end products of the method, namely hydrogen and solid carbon biochar, are valuable. Hydrogen can be used as green fuel, while carbon biochar can be buried and used as fertilizer or used to make conductive electrodes.
“The relevance of our work is enhanced by the fact that we indirectly capture CO2 stocks from the atmosphere for years,” Nagar explains. “We turned it into useful finished products in a very short time using a xenon flash lamp.”