Advances in biohythane: Integrating biohydrogen and biomethane for sustainable fuel solutions

Hydrogen is regarded as the fuel of the future due to its high energy density and zero carbon emissions. However, hydrogen's high flammability and risk of metal embrittlement complicate its bulk storage, transportation, and distribution. Nonetheless, hythane is generated upon blending hydrogen (10–30 %) with methane (70–90 %). As a hybrid biofuel, hythane offers key benefits including high energy density and combustion efficiency, reduced emissions, and ease of storage and distribution. This article reviews the optimization, intensification, and application of synthetic biology in photo/dark fermentation and anaerobic digestion for producing biohydrogen and biomethane, respectively, from biowaste, as well as considerations for strategic integration of these bioprocesses to generate biohythane. Depending on the blending ratios of hydrogen and methane, hythane demonstrates superior fuel properties, including high energy density, burning velocity, flame temperature, ignition temperature, flammability range, and low diffusivity. • Hythane is a blended gaseous fuel composed of hydrogen and methane. • Hythane can leverage existing natural gas infrastructure while reducing emissions. • Hydrogen fraction in hythane enhances flame speed, energy content and combustion stability. • Biohythane can be produced by integrating photo/dark fermentation and anaerobic digestion. • Optimization of bioproduction and hydrogen/methane blending can improve the fuel attributes of hythane.