Consequently, the protons abstracted from MSW by sulfur are shuttled first to H 2 S, then to H 2 O before forming the H 2 gas product. SO 2 -depolarized electrochemical cells generate H 2 from water molecules with a minimum cell potential of 0.158 V, approximately 8x lower than the direct electrolysis of water, potentially reducing energy costs significantly. If the electricity used to drive the SO 2 -depolarized cell comes from renewable sources, and if the co-produced biochar is sequestered, this process may be considered carbon-negative. The cycle is completed by regenerating elemental S through an exothermic reaction between excess SO 2 and H 2 S, known as the catalytic Claus process, such that no sulfur is released. In sum, we describe here a carbon-negative multi-step chemical reduction pathway using MSW for the regeneration of SO 2 feedstock from H 2 SO 4 generated in a SO 2 -depolarized electrochemical cell for the production of H 2 gas.