Extracting Hydrogen Fuel From Banana Peels.

*biochar — древесный уголь.

As the world’s energy demands increase, so does our consumption of fossil fuels. The result is a massive rise in greenhouse gases emissions with severely adverse environmental effects. To address this, scientists have been searching for alternative, renewable sources of energy.

A main candidate is hydrogen produced from organic waste, or “biomass,” of plants and animals. Biomass also absorbs, removes, and stores CO2 from the atmosphere, while biomass decomposition can also bring us ways to negative emissions or greenhouse gases removal. But even though biomass heralds a way forward, there is still the question of the best way to maximize its conversion into energy.

Scientists led by Professor Hubert Girault at EPFL’s School of Basic Sciences have developed a new method that produces not only valuable gas, but also a biochar of solid carbon that can be repurposed in other applications.

The method performs is using a Xenon lamp, commonly used for curing metallic inks for printed electronics. The lamp’s white flash light provides a high-power energy source as well as short pulses that promote photo-thermal chemical reactions. The idea is to generate a powerful flash light shot, which the biomass absorbs and which instantaneously triggers a photothermal biomass conversion into syngas and biochar.

This flashing technique was used on different sources of biomass: banana peels, corn cobs, orange peels, coffee beans, and coconut shells, all of which were initially dried at 105°C for 24 hours and then ground and sieved to a thin 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 over in a few milliseconds.

Each kg of dried biomass can generate around 100 liters of hydrogen and 330g of biochar, which is up to 33wt.% of the original dried banana peel mass.

What stands out in this method is that both its end products, hydrogen and solid-carbon biochar, are valuable. The hydrogen can be used as green fuel, while the carbon biochar, can either be buried and used as a fertilizer or it can be used to manufacture conductive electrodes.