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TL;DR: A novel method for converting pistachio nut shells into biofuel and activated carbon electrodes for batteries has been developed. The process involves pyrolysis and activation of bio-char, resulting in additional biofuel production and a functional electrode.

Abstract: Even while the argument continues to rage over the environmental merits of powering cars by biofuels or electricity, Mark Grinstaff and his colleagues at Boston University in the USA have found a way to combine the two. They have developed a method for converting pistachio nut shells into both a biofuel and activated carbon electrodes for batteries.1 Their method involves first heating the shells at 450°C in the absence of oxygen. Known as pyrolysis, this process converts the shells into a mixture of a liquid bio-oil, flammable gases such as methane and hydrogen, and a solid bio-char. Usually, the bio-oil and gases are the desired products from this process, with the bio-char mainly just used as a soil additive. Instead, Grinstaff and his colleagues decided to try turning the bio-char into activated carbon for use in batteries. Th is required making the bio-char more porous, which they did by treating it with potassium hydroxide and then heating it again to 450°C. As a bonus, this process also generated yet more bio-oil and fl ammable gases, amounting to 25% extra. With the resulting biocharderived carbon, Grinstaff and his colleagues fabricated an electrode and showed that it could be used in a working lithiumion supercapacitor, a type of battery that stores energy via the separation of charge rather than chemical reactions. 1. Goldfarb JL, Dou G, Salari M and Grinstaff MW, Biomass-based fuels and activated carbon electrode materials: An integrated approach to green energy systems. ACS Sust Chem Eng DOI: 10.1021/ acssuschemeng.6b02735 (2017). BRASSICA OILSEEDS