Mechanical Engineer II - Stack Engineering

About Travertine Travertine is an Industrial Transformation company based in Boulder, CO, that is rapidly scaling a technology for sulfur-decoupled production of critical minerals, starting with phosphate. Our technology enables large-scale circularity in extractive industries while simultaneously decarbonizing building materials. We do this by electrochemically recycling chemical byproducts, sulfate wastes, into sulfuric acid and valuable mineral co-products. Sulfuric acid is the world's most used inorganic chemical and is vital for producing a wide range of critical elements including phosphate, lithium, copper, nickel, and rare earth elements. Travertine's technology solves the dual problems of sulfur supply vulnerability and large-scale chemical waste disposal. Our transformative process changes the fundamental material balance of critical mineral production, laying the groundwork for an industry liberated from fossil inputs and their legacy impacts. Since founding, Travertine has raised over $29M in capital, including over $5M in US Federal and State government grants. We are an accomplished and driven team recognized by C&EN 10 startups to watch in 2022, Bloomberg NEF Pioneers in 2023, RMI Third Derivative 1st Gigaton Captured program in 2024, Mining Cleantech Challenge in 2026, and are a founding member of the Carbon Removal Alliance. Travertine designed, built, and successfully operated our core technology Demonstration Plant in Rochester, NY for over 3,000 hours, and delivered the project on-time and on-budget. We are now developing our first commercial plant, which will be the only new phosphate plant built on US soil in over 50 years.

The Role The Mechanical Engineer II - Stack Engineering will support the design, prototyping, and testing of stack hardware for Travertine's electrochemical systems. This role will work closely with cross-functional teams to advance mechanical design from early-stage concept and rapid prototyping through to functional mass-produced parts and assemblies. The engineer will also contribute directly to the design, fabrication and operation of electrochemical test systems.

This role will contribute to the development of features critical to electrochemical performance. These features include components for optimizing flow distribution and mass transport, thermal management, durable sealing methods and reduction of ohmic and faradaic losses. Our process is well suited to scale rapidly as it combines three industrialized unit operations in a novel way: salt-splitting electrolysis, hydrometallurgy, and caustic direct air capture of CO 2 . This is the perfect opportunity for an ambitious and creative mechanical engineer to contribute to complex development efforts and rapidly take a technology from pilot to full-scale.

Critical to this role, will be working closely with our Electrochemical R&D and Process Engineering teams to identify areas for mechanical and electrochemical design improvement, develop prototypes, and fine-tune validation procedures to translate those results into engineering design. This role will also interface with external consultants, manufacturers and integrators to bring concepts and prototypes toward commercial success.

Key Responsibilities Design & Prototyping: Create detailed CAD models, drawings, and physical prototypes for electrochemical cells, test stands, and mechanical fixtures.

Testing & Validation: Design and execute experimental testing to characterize hardware performance, resistance, pressure limits, and fluid/thermal properties.

Data Acquisition & Automation: Implement instrumentation, sensors, controls, and data acquisition tools to validate system performance.

Cross-Functional Collaboration: Work with R&D, process development, and senior engineers to translate technical requirements into robust hardware solutions.

Fabrication & Sourcing: Interface with local machine shops, vendors, and internal fabrication tools to build custom components and assemblies.

Design for Manufacturability: Optimize the design of parts and assemblies to reduce cost and improve reliability, manufacturing cycle time and yield.

Qualifications Bachelor's degree or greater in Mechanical Engineering.

Educational or industry background in electrochemistry preferred.

2+ years of hands-on mechanical design and rapid prototyping experience in hardware, startup, or industrial environments.

Proficiency in 3D CAD modeling, drafting, and mechanical design principles.

Experience with machine shop operations (milling, turning, welding) and safe chemical/laboratory practices.

Compensation & Benefits This role is onsite and based in our Boulder, CO headquarters.

Salary range is highly dependent on skill set and experience $100,000-$120,000 per yr.

Benefits

Competitive pay

Stock options

Health, Dental, Vision, Life Insurance

401k with 100% match up to 3% of salary

Flexible time off policy