In situ resource utilization (ISRU) is essential for several of NASA's future flagship missions. Currently envisioned ISRU plants include production of oxygen from hydrogen reduction of lunar regolith and extraction of water from Martian regolith or asteroid material. These ISRU processes require heating of the regolith to high reaction temperatures. Once the reaction is complete, most thermal energy exits the system in the spent regolith batch and is therefore wasted. Creare proposes to recover this heat and use it to preheat fresh regolith prior to entering the reactor. Our novel heat recovery design is purely passive, robust, and compact to accommodate tight mass and volume constraints. Our heat exchanger promises to recover 80% of the otherwise wasted thermal energy. This energy savings can either be used to reduce the power plant size or speed up the production rates of the ISRU system. The Creare team has firsthand knowledge of the current ISRU research status and has the necessary background in mechanical design, heat exchanger design, as well as the facilities and commercialization expertise, to make this project a success.