To complete the cycle, SO 2 and water distilled from the refluxing sulfuric acid are added to the anode chamber, while the anolyte containing H 2 SO 4 may be fed back to the reflux chamber. Figure shows this entire process schematically using cellulose as a model feedstock, along with one possible implementation in a reactor design. While both reactions 1 and 1 are endothermic, reaction 1 is significantly more exergonic, so the free energy available to drive the additional reaction steps of the proposed cycle is increased. While many possible chemical pathways exist through which H 2 can be generated from biomass using sulfur intermediates, the cycle proposed here uses well known or industrially implemental technologies. In the following sections, the process parameters and thermodynamic analysis for each of the four reaction steps listed in figure will be discussed. Finally, a simple economic analysis of this reaction cycle is presented.