HYDROGEN IS GAINING MOMENTUM as the zero-emission fuel of the future for aviation, but the technology requires massive investment in new infrastructure as well as completely new propulsion systems or aircraft designs if it is to be used to its full potential. Aviation H2, an Australian startup that has set the aggressive goal of flying the country's first hydrogen-powered aircraft by mid-2023, has selected an alternative decarbonization path it says will allow use of existing engines, aircraft and infrastructure. The company plans to use liquid ammonia as a carbon-free fuel. Anhydrous ammonia has less than half the specific energy of kerosene, which reduces payload and range capability, but it is lighter and easier to transport and store than hydrogen. Ammonia brings its own challenges, however.
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