Houston startup gears up to deliver geothermal energy

ready to drill

Criterion Energy Partners is aiming to be a next-gen energy company. Photo via Getty Images

Sean Marshall and Danny Rehg founded Criterion Energy Partners in 2020 with the hope that geothermal energy could be the cleaner, safer wave of the future. Less than three years later, the team is close to making their plan a reality thanks to a geothermal well that they hope to drill this year.

Entrepreneurship wasn’t always part of the plan for either partner. When Marshall enrolled in the MBA program at Rice University’s Jones School of Business in 2016, he had a successful career at Credit Suisse and had his eye set on a future political career. But then he met classmate Rehg, whose background was in petroleum engineering. Their wives were both attorneys in the Houston district attorney’s office and the couples became fast friends. They also realized that, as Marshall now puts it, Rehg knew how to drill wells and he knew how to make deals.

In the ensuing years, both Rehg and Marshall's careers evolved and, eventually, the pair started looking for other opportunities. That’s when they read an article in Rolling Stone about geothermal energy.

“It was really a place where it really felt like this was something we were put here to do,” says Marshall.

Marshall and Rehg spent the ensuing months “like rats in a dumpster” learning about the players and opportunities in the geothermal industry and built from there. They learned about Pleasant Bayou Power Plant, a 1989 geothermal energy project based in Brazoria County that was backed by the U.S. Department of Energy.

Last summer, Criterion Energy Partners, a member of Greentown Houston, closed on a 10,000-acre lease around the site of Pleasant Bayou.

"We hope by the end of this year we will be generating electrons,” says Marshall.

Though the company has a patented technology that connects wells to the grid, called Criterion Geothermal System, Marshall says that some of the best advice he’s gotten was, “Don’t fall in love with your technology; fall in love with the problem.” The 2021 Texas freeze reminded the founders what that was.

“People were looking for cleaner, lower-emission power sources and [there was] a need for energy resiliency,” says Marshall, explaining that the freeze created an ideal situation for the company, as people began to think more outside the grid.

The year 2022 was a big one for Criterion Energy Partners. Oil and gas powerhouse Patterson-UTI invested in the company, followed by funding from the Department of Energy. The money not only allowed Criterion Energy Partners to lease their land, they are also now paying 12 salaries, including those of the founders. The team offices in The Cannon’s Esperson coworking space.

“Our mission is to make geothermal commercially viable everywhere,” says Marshall. “I still believe in that.”

However, Criterion Energy Partners may be even bigger than proving an alternative energy source. Marshall says that geothermal is the foundation on which they are building “a next-generation energy company.” Criterion Energy Partners could be the more stable basis for a whole new energy system.

Sean Marshall and Danny Rehg founded Criterion Energy Partners in 2020. Photos courtesy

------

This article originally ran on InnovationMap.

Ad Placement 300x100

Ad Placement 300x600

CultureMap Emails are Awesome

Property Showcase

Investors close partial acquisition of Phillips 66 subsidiary with growing EV network

M&A activity

Energy Equation Partners, a London-based investment firm focused on clean energy companies, and New York-based Stonepeak have completed the acquisition of a 65 percent interest in JET Tankstellen Deutschland GmbH, a subsidiary of Houston oil and gas giant Phillips 66.

JET is one of the largest and most popular fuel retailers in Germany and Austria with a rapidly growing EV charging network, according to a news release. It also operates approximately 970 service stations, convenience stores and car washes.

“We are delighted to complete this acquisition and to partner with Stonepeak and Phillips 66 to take JET to the next level,” Javed Ahmed, managing partner of Energy Equation Partners, said in a news release. “This investment reflects EEP’s commitment to investing in established players in the energy sector who have the potential to make a meaningful impact on the energy transition, and we are excited to work alongside the entire JET team, including its dedicated service station operators, to realize this vision.”

The deal values JET at approximately $2.8 billion. Phillips 66 will retain a 35 percent non-operated interest in JET and received about $1.6 billion in pre-tax proceeds.

“Under Phillips 66’s ownership, JET has grown into one of the largest fuel retailers in Germany and Austria," Anthony Borreca, senior managing director and co-head of energy at Stonepeak, added in a news release. "We are excited to join forces with them, as well as Javed and the EEP team, who have long-standing experience investing in and operating retail fuel distribution and logistics globally, to support the next phase of JET’s growth.”

6 must-attend Houston energy events in December 2025

Event Guide

Editor's note: The year is coming to a close, but there are still exciting energy events to attend in Houston this month. Mark your calendar now for pitch days, seminars, networking, and Reuters Energy LIVE 2025.

Dec. 4 — Resiliency & Adaptation Sector Pitch Day

Join innovators, industry leaders, investors, and policymakers as they explore breakthrough climate and energy technologies at Greentown Labs' latest installment of its Sector Pitch Day series, focused on resiliency and adaptation. Hear from Adrian Trömel, Chief Innovation Officer at Rice University; Eric Willman, Executive Director of the Rice WaTER Institute; pitches from 10 Greentown startups; and more.

This event is Thursday, Dec. 4, from 1-3:30 p.m. at the Ion. The Ion Holiday Block Party follows. Register here.

Dec. 8 — Pumps & Pipes Annual Event 2025

The annual gathering brings together cross-industry leaders in aerospace, energy and medicine for engaging discussions and networking opportunities. Connor Grennan, Chief AI Architect at the NYU Stern School of Business, will present this year's keynote address, "Practical Strategies to Increase Productivity." Other sessions will feature leaders from Cena Research Institute, NASA Ames Research Center, ExxonMobil, Southwest Airlines, and more.

This event is Monday, Dec. 8, from 8 a.m.-5 p.m., at TMC Helix Park. Register here.

Dec. 9 — Energy in Action Seminar

The Energy Transition Institute hosts a monthly Energy in Action Seminar focused on the digitization of the global energy transition. This month's topic is "Exploring AI’s Impact on the Fuels & Petrochemicals Industry," featuring speaker Leo Chiang, Senior Director of Corporate Technology at The Lubrizol Corporation. The event includes a one-hour talk followed by an hour of networking.

This event is Dec. 9 from 4-6 pm at the University of Houston.

Dec. 9-10 — Energy LIVE 2025

Energy LIVE is Reuters Events' flagship conference and expo that brings the full energy ecosystem together under one roof in Houston to solve the industry's most urgent commercial and operational challenges. The event will feature 3,000-plus senior executives across three strategic stages, a showcase of 75-plus exhibitors, and six strategic content pillars.

This event is Dec. 9-10 at NRG Park. Register here.

Dec. 11-12 — Fundamentals of The Texas ERCOT Electric Power Market

This two-day seminar provides a comprehensive overview of the structure, function, and current status of the Texas ERCOT ISO. Attendees will gain an understanding of the dynamic Texas wholesale and retail competitive markets, and learn how these markets interface with ERCOT ISO energy auctions and ISO operations. This two-day event will also address the rapidly expanding new market opportunities in Texas renewables, distributed generation, demand response, and demand side management, and more.

This event is Dec. 11-12 at the Courtyard Marriott Houston near the Galleria. Register here.

Dec. 9-11 — AST Conference & Trade Show

The 18th Annual National Aboveground Storage Tank (AST) Conference & Trade Show is the premier event for professionals in storage tank and terminal operations. Join industry leaders and experts for a three-day conference providing regulatory updates, technical insights, hands-on learning, and networking opportunities.

This event is Dec. 9-12 at The Woodlands Waterway Marriott. Register here.

Houston scientists develop 'recharge-to-recycle' reactor for lithium-ion batteries

reduce, recharge, recycle

Engineers at Rice University have developed a cleaner, innovative process to turn end-of-life lithium-ion battery waste into new lithium feedstock.

The findings, recently published in the journal Joule, demonstrate how the team’s new “recharge-to-recycle” reactor recharges the battery’s waste cathode materials to coax out lithium ions into water. The team was then able to form high-purity lithium hydroxide, which was clean enough to feed directly back into battery manufacturing.

The study has major implications for the electric vehicle sector, which significantly contributes to the waste stream from end-of-life battery packs. Additionally, lithium tends to be expensive to mine and refine, and current recycling methods are energy- and chemical-intensive.

“Directly producing high-purity lithium hydroxide shortens the path back into new batteries,” Haotian Wang, associate professor of chemical and biomolecular engineering, co-corresponding author of the study and co-founder of Solidec, said in a news release. “That means fewer processing steps, lower waste and a more resilient supply chain.”

Sibani Lisa Biswal, chair of Rice’s Department of Chemical and Biomolecular Engineering and the William M. McCardell Professor in Chemical Engineering, also served as co-corresponding author on the study.

“We asked a basic question: If charging a battery pulls lithium out of a cathode, why not use that same reaction to recycle?” Biswal added in the release. “By pairing that chemistry with a compact electrochemical reactor, we can separate lithium cleanly and produce the exact salt manufacturers want.”

The new process also showed scalability, according to Rice. The engineers scaled the device to 20 square centimeters, then ran a 1,000-hour stability test and processed 57 grams of industrial black mass supplied by industry partner Houston-based TotalEnergies. The results produced lithium hydroxide that was more than 99 percent pure. It also maintained an average lithium recovery rate of nearly 90 percent over the 1,000-hour test, showing its durability. The process also worked across multiple battery chemistries, including lithium iron phosphate, lithium manganese oxide and nickel-manganese-cobalt variants.

Looking ahead, the team plans to scale the process and consider ways it can sustain high efficiency for greater lithium hydroxide concentrations.

“We’ve made lithium extraction cleaner and simpler,” Biswal added in the release. “Now we see the next bottleneck clearly. Tackle concentration, and you unlock even better sustainability.

View All Listings

ENERGYCAPITALHTX EMAILS ARE AWESOME