Houston founder shares how he's using tech to make digital media more effective and equitable

houston innovators podcast episode 173

This month, Mark Walker is celebrating his company's one year anniversary of going public — only the ninth Black-founded business to accomplish this feat on a U.S. stock exchange. Photo courtesy

After working in both sides of the advertising world, Mark Walker thought he could reimagine a platform that would be more efficient and equitable.

Walker co-founded his company, Direct Digital Holdings, an adtech platform, after serving in several roles — from an early hire at Houston digital media startup Questia to business development director at NRG Energy and COO of EBONY Media. He shares on the Houston Innovators Platform how he took this experience in tech, advertising, and media to create his company's platform.

"NRG Energy gave me a top-down view of the value chain, and Ebony gave me a bottoms-up view of the value chain of how media is purchased," Walker says on the show. "At Direct Digital Holdings, we help companies buy and sell media — and we leverage technology to do it. It's really the culmination of both of those experiences."

With over 30,000 publishers on its platform, Direct Digital makes it easier for its core customers — middle market companies looking to buy into the digital media ecosystem — to tap into these opportunities without the tech know-how they might otherwise need. Walker explains that at EBONY, he saw how small to midsize publications — especially the multicultural ones — were being left out on the ad selling side of the equation. The Direct Digital platform bridges the gap on each end.

Founded in 2018 in partnership with Keith Smith, who went through similar professional experiences, Direct Digital went public exactly one year ago after growing the company through strategic M&A activity. Walker says the decision to IPO made the most sense for his company — though it wasn't an easy process. Direct Digital is only the ninth company founded by a Black entrepreneur to go public on a US stock exchange.

"If you think the process is hard — it actually is," Walker says on the journey to IPO. "We were a privately held company, and we knew we had a good growth trajectory and we looked a couple different options. We decided to go public in a very traditional way."

Walker explains there were some risks involved, but the co-founders ultimately decided to shy away from adding in investors who might not have the same ideas for the company's future.

Direct Digital has been a Houston company from the star — despite the city not being home to a booming adtech ecosystem. Instead, Houston — with its collection of Fortune 500 companies and rich diversity — has allowed the business to stand out.

"If you look at and reflect on how our company has been built — from our board of directors to our leadership and management team — we're a majority minority organization all the way across the board," Walker says. "Diversity is very important to us. It's the lifeblood of our business — especially because we're serving publishers in those communities in big way. And moreso, we think you get the best product, thoughts, and ideas from a diverse workforce, and Houston fits right into that mold for us."

Walker shares more about his company's future, advice on IPO, and what all he's watching in adtech — from AI to streaming — on the podcast. Listen to the interview below — or wherever you stream your podcasts — and subscribe for weekly episodes.


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Rice University's edtech company receives $90M to lead NSF research hub

major collaboration

An educational technology company based out of Rice University has received $90 million to create and lead a research and development hub for inclusive learning and education research. It's the largest research award in the history of the university.

OpenStax received the grant funding from the U.S. National Science Foundation for a five-year project create the R&D hub called SafeInsights, which "will enable extensive, long-term research on the predictors of effective learning while protecting student privacy," reads a news release from Rice. It's the NSF's largest single investment commitment to national sale education R&D infrastructure.

“We are thrilled to announce an investment of $90 million in SafeInsights, marking a significant step forward in our commitment to advancing scientific research in STEM education,” NSF Director Sethuraman Panchanathan says in the release. “There is an urgent need for research-informed strategies capable of transforming educational systems, empowering our nation’s workforce and propelling discoveries in the science of learning.

"By investing in cutting-edge infrastructure and fostering collaboration among researchers and educators, we are paving the way for transformative discoveries and equitable opportunities for learners across the nation.”

SafeInsights is funded through NSF’s Mid-scale Research Infrastructure-2 (Mid-scale RI-2) program and will act as a central hub for 80 partners and collaborating institutions.

“SafeInsights represents a pivotal moment for Rice University and a testament to our nation’s commitment to educational research,” Rice President Reginald DesRoches adds. “It will accelerate student learning through studies that result in more innovative, evidence-based tools and practices.”

Richard Baraniuk, who founded OpenStax and is a Rice professor, will lead SafeInsights. He says he hopes the initiative will allow progress to be made for students learning in various contexts.

“Learning is complex," Baraniuk says in the release. "Research can tackle this complexity and help get the right tools into the hands of educators and students, but to do so, we need reliable information on how students learn. Just as progress in health care research sparked stunning advances in personalized medicine, we need similar precision in education to support all students, particularly those from underrepresented and low-income backgrounds.”

OpenStax awarded $90M to lead NSF research hub for transformational learning and education researchwww.youtube.com

2 Houston startups selected by US military for geothermal projects

hot new recruits

Two clean energy companies in Houston have been recruited for geothermal projects at U.S. military installations.

Fervo Energy is exploring the potential for a geothermal energy system at Naval Air Station Fallon in Nevada.

Meanwhile, Sage Geosystems is working on an exploratory geothermal project for the Army’s Fort Bliss post in Texas. The Bliss project is the third U.S. Department of Defense geothermal initiative in the Lone Star State.

“Energy resilience for the U.S. military is essential in an increasingly digital and electric world, and we are pleased to help the U.S. Army and [the Defense Innovation Unit] to support energy resilience at Fort Bliss,” Cindy Taff, CEO of Sage, says in a news release.

A spokeswoman for Fervo declined to comment.

Andy Sabin, director of the Navy’s Geothermal Program Office, says in a military news release that previous geothermal exploration efforts indicate the Fallon facility “is ideally suited for enhanced geothermal systems to be deployed onsite.”

As for the Fort Bliss project, Michael Jones, a project director in the Army Office of Energy Initiatives, says it’ll combine geothermal technology with innovations from the oil and gas sector.

“This initiative adds to the momentum of Texas as a leader in the ‘geothermal anywhere’ revolution, leveraging the robust oil and gas industry profile in the state,” says Ken Wisian, associate director of the Environmental Division at the U.S. Bureau of Economic Geology.

The Department of Defense kicked off its geothermal initiative in September 2023. Specifically, the Army, Navy, and Defense Innovation Unit launched four exploratory geothermal projects at three U.S. military installations.

One of the three installations is the Air Force’s Joint Base San Antonio. Canada-based geothermal company Eavor is leading the San Antonio project.

Another geothermal company, Atlanta-based Teverra, was tapped for an exploratory geothermal project at the Army’s Fort Wainwright in Alaska. Teverra maintains an office in Houston.

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This article originally ran on EnergyCapital.

Houston investor calls for all angels to move the ecosystem forward

houston innovators podcast episode 233

One of the biggest components of a well-functioning startup ecosystem is inarguably access to capital, and Mitra Miller is dedicated to enhancing education around investment and growing Houston's investor base.

As vice president and board member of the Houston Angel Network, the oldest angel network in Texas and one of the most active angel networks in the country, Miller strives to provide guidance to new and emerging angel investors as well as founders seeking to raise money from them.

"Most founders have no idea or understanding of how investors think — we are not an ATM," Miller says on the Houston Innovators Podcast. "We are really partners you are getting married to for the next 5, 8, 10 years — sometimes longer. We need to bring your allies in every sense of the word."



HAN, a nonprofit, provides a unique opportunity for its members, as Miller explains. The group consists of around 100 individuals from all business backgrounds, so evaluating companies together brings more than just a wealth of capital — but also a wealth of knowledge.

"What HAN provides is access to investments," Miller says, adding that members have the benefit in evaluating companies together with people from different backgrounds. "Inside a group like HAN, we have extraordinary expertise."

In addition to educating both founders and investors in the process, Miller has dedicated herself to providing opportunities for students in low-income parts of Houston to learn about the startup world. Eight years ago, she founded Eagle Investors, an organization that provides a year-long program that culminates in a group of students participating as judges for the Rice Business Plan Competition.

"They spend a year learning about innovation, entrepreneurship, and investing by meeting local investors, entrepreneurs, and service providers. They go around Houston to get to visit and ... experience all of the ecosystem," Miller says.

At RBPC, the cohort of high school students evaluate the pitches and select a company to provide a $5,000 prize.

Miller herself has been a judge at RBPC for 20 years now, and she's had a front row seat for watching Houston develop as an ecosystem. She's seen the city make real progress, but has one major call to action.

"The piece that I am most aware of that I would like to see grow is activating more accredited investors who are interested in this asset class of early-stage companies and plugging in," Miller says. "They can also invest their time and knowledge to help companies in our region grow and scale."

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