Scientists have discovered an innovative source for renewable energy, this time by blasting banana peels with a powerful lamp.
This new method of extracting hydrogen could be a significant way of boosting supplies of the gas from biomass. This could also be applied to other food waste, such as corn cobs, coffee beans and coconut shells.
Renewable hydrogen can be made from biomass (plant and animal matter) as long as certain sustainability criteria are met, according to EU’s hydrogen policies. However, the team of Swiss-based scientists explain that all of the products from their photo-thermal (light and heat based) technique can be captured, including CO2, making it economical and climate safe.
“The relevance of our work is further heightened by the fact that we are indirectly capturing CO2 stores from the atmosphere for years,” writes Dr Bhawna Nagar, one of the authors from the École polytechnique fédérale de Lausanne (EPFL). “We have converted that into useful end products in no time using a xenon flash lamp.”
At present, there are two primary methods of chemically converting biomass using heat: pyrolysis and gasification. Through gasification, the organic material is heated to temperatures of 1000 ºC, and converted into syngas, a mix of hydrogen, methane, carbon monoxide, and carbon dioxide. This is used as biofuel, and biochar is left behind.
On the other hand, pyrolysis employs temperatures of 400-800 ºC and containers without oxygen to decompose the biomass. But this requires very specific reactors that can handle high temperatures and pressures, the scientists explain in Chemical Science.
Now, photo-pyrolysis, a simpler method is available using a xenon lamp – which emits a bright white light. One powerful flashlight shot can trigger biomass conversion in just a few milliseconds.
First, the banana peels must be dried at around 100 C for 24 hours, then ground and sieved to a fine powder before being placed in a stainless steel reactor.
“Each kilogram of dried biomass can generate around 100 litres of hydrogen and 330g of biochar, which is up to 33 weight per cent of the original dried banana peel mass,” says Dr Nagar.
This method splits natural biomass into gas and charcoal to produce hydrogen production. The charcoal can be added to soil to improve plant health, or stored as a carbon capture strategy.
The team of scientists have high hopes for their method, and believe it could be applied to industrial waste such as tyres. It could even pave the way for solar photo-pyrolysis – harnessing the sun’s energy to be even more sustainable.
