Why Circularity Fuels Started with Diamonds to Scale Sustainable Jet Fuel

Dr. Stephen Beaton is Co-founder and CEO of Circularity Fuels, which develops compact reactors that turn waste carbon streams into high-value fuels and chemicals. Rather than compete with fossil fuels from the start, Stephen identified high-purity methane for lab-grown diamonds as a beachhead market—where Circularity’s product is 80–90% cheaper than incumbents while proving the core technology needed for clean liquid fuels.

Stephen earned a chemistry PhD at Oxford and built deep expertise in synthetic fuels during his U.S. Air Force career, including overseeing jet fuel quality control in the Middle East and launching the Air Force’s e-fuels program. His insight: build a fuels company that doesn’t begin with fuel.

Today, Circularity Fuels operates demonstration reactors in diamond facilities and is scaling toward biogas-to-SAF production using the same reactor platform. The company has raised $3M in venture funding, including from DCVC, plus $5M in grants from ARPA-E, NSF, and the California Energy Commission. MCJ is proud to be an investor.

Episode recorded on Aug 12, 2025 (Published on Sept 16, 2025)

In this episode, we cover: 

• [03:09] Dr. Beaton’s background in clean fuels
• [07:31] His work with Air Force petroleum in the Middle East
• [10:12] A brief overview of hydrocarbons
• [13:08] ESAF as resilience for Pacific operations
• [16:22] What e-SAF really means and why it matters
• [19:24] Circularity Fuels’ origin story
• [21:20] The company’s three principles
• [23:04] High-purity methane for diamonds as a beachhead
• [27:46] Recycling diamond exhaust with microwave-sized reactors
• [30:40] Building a fuel company without fuel as the initial product
• [34:35] Hardware sales vs metered methane service model
• [39:05] Biogas-to-SAF pathway via Fischer-Tropsch
• [42:38] Circularity’s progress to date
• [44:01] Competing with fossil jet and carbon removals
• [48:41] How Circularity secured non-dilutive funding

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*Editing and post-production work for this episode was provided by The Podcast Consultant