Application of thermoelectricity to industrial waste-heat has been put forth as a possible mean to increase energy efficiency of industrial operations. However, no materials are available to date at the scale and cost compatible with high temperature, large-scale materials processes like steel or glass making. Indeed, such reactors are characterized by large surface area and low heat fluxes, calling for inexpensive thermoelectric devices. Chalcogenides, like SnS, are materials with lower costs than traditional thermoelectric materials, and can exhibit semiconducting behavior in the molten state. In this work, it is shown that these features that can be used to harvest electric power from high temperature heat flux via thermoelectricity. In a second time, the materials properties that control the energy efficiency and scalability of such molten thermoelectric are discussed, along with some of the results obtained for SnS.