A review in redressing challenges to produce sustainable hydrogen from microalgae for aviation industry

The global depletion of fossil fuel reserves and associated environmental crisis have led researchers to explore microalgal biomass which has been proven could be a promising potential as a renewable energy feedstock. Biofuels such as biodiesel, bioethanol and hydrogen can be produced from microalgae. Indeed, microalgae are best employed for hydrogen generation because the microalgal cells have high growth rate, can grow in diverse habitats and non-arable lands, can solve the fuel versus food conflicts as well as can capture and assimilate the atmospheric carbon dioxide. Hydrogen that is produced from microalgae is a clean and sustainable option to replace or complement the fossil fuel demands. The combustion of hydrogen produces only water and no greenhouse gases emission which will assuage the untoward effect on the environment. Moreover, it can also be used directly to generate electricity in fuel cells and engines. Another sector that is looking into hydrogen as a replacement for fossil fuels, is transportation inclusive of the aviation industry. The use of hydrogen as an energy carrier in airplanes offers several advantages, the burning of hydrogen in the jet engines would produce water vapour which will eliminate carbon-related emissions. However, this also comes with limitations such as new designs and larger tanks for hydrogen storage. Besides, the mechanisms of hydrogen production from microalgae are also sporadic and not well documented systematically, pre-empting researchers from exploring this new energy source inclusively. The factors affecting the microalgal hydrogen production are as well essential, but still poorly conceived, leading to the low outputs in terms of hydrogen yields from microalgae. Accordingly, this article reviews various mechanisms and methods employed for producing hydrogen from microalgae as well as the pre-treatment procedures for enhancing the rates of hydrogen production from microalgae. Furthermore, the enhancement of hydrogen yields through state-of-the-art techniques and genetic engineering the microalgal strains are also unveiled to materialize the hydrogen production at an industrial scale. This review intents to shift the paradigm from typical hydrocarbon biofuels to green hydrogen adoption, hastening the carbon neutrality target that benefits the natural environment the most.