As we have mentioned above, one difficulty to be overcome for the practical and extensive use of biomass-derived ethanol as a hydrogen source to fuel-cell systems is supplying the energy needed to distill and/or vaporize the H2O/ethanol mix­tures, and that related to the endothermicity of the steam reforming reaction.

Recently, Dumesic and coworkers have shown that methanol, ethylene glycol, glycerol, and sorbitol can be reformed in the aqueous phase to H2 and CO2 at temperatures near 500 K and at pressures between 15-50 bar [57-59]. On the basis of these studies, the reforming of ethanol in the aqueous phase appears as a new approach to be considered for the production of H2 from ethanol reforma­tion. This process would have several advantages over steam reforming: i) it does not need energy to vaporize alcohol and water before the reaction; ii) the operating temperatures and pressures are suitable for the water-gas shift reaction, so it may be possible to generate hydrogen with low amounts of CO in a single step; and iii) the step of H2 purification or CO2 separation is simplified because of the pressure range of the effluent.

Another possibility that merits greater study is the operation under autother­mal conditions with ethanol/water/air mixtures. Here, the goal is to maximize the hydrogen yield, while minimizing the total combustion and the formation of by-products and carbon deposits on the catalysts. For both steam reforming and oxidative steam reforming, future research is needed to develop more stable, active, selective, and inexpensive catalytic systems that operate under the required final experimental conditions.

Finally, the integration of the ethanol reformation in an energetically favored total process is also an area, which, still in our day, remains to be completed from a technological point of view.

Efforts in the above-mentioned areas could lead to the practical use of ethanol as H2 supplier to generate clean electrical power in the not-so-distant future.