A comparison of environmental benefits of transport and electricity applications of carbohydrate derived ethanol and hydrogen

It may soon become possible to produce hydrogen from hydrolysed carbohydrates instead of ethanol via fermentation and distillation, employing aqueous phase reforming. The environmental merits of these two different energy products and their uses are compared on a life cycle basis, based on expanded systems in the context of a coal-intensive energy economy. Eight industrial options are defined: ethanol for peak power generation with or without heat integration, hydrogen for peak power generation with and without heat integration, ethanol for use in a flexi-fuel vehicle and a fuel cell vehicle, and hydrogen use in an internal combustion engine vehicle and a fuel cell vehicle. Aqueous phase reforming to produce hydrogen is shown to generally out-perform the corresponding fermentation–distillation ethanol options. Peak power generated from ethanol would be a preferred short-term option, with peak power from hydrogen in the medium term ceding to the environmentally preferred option of hydrogen fuel cell vehicles in the long-term.