Texas joined Nebraska's latest action against the EPA, along with Alabama, Florida, Georgia, and several others. Photo by Sander Yigin/Unsplash

A large group of Republican attorneys general on Monday took legal action against the Biden administration and California over new emissions limits for trucks.

Nebraska Attorney General Mike Hilgers is leading the group of GOP attorneys general who filed a petition with the U.S. Court of Appeals for the District of Columbia Circuit to overturn an Environmental Protection Agency rule limiting truck emissions.

Texas joined Nebraska's latest action against the EPA, along with Alabama, Florida, Georgia, and several others.

A separate lawsuit against California claims a phased-in ban on internal-combustion trucks is unconstitutional and will hurt the U.S. economy.

Hilgers in a statement said the EPA and California rules “will devastate the trucking and logistics industry, raise prices for customers, and impact untold number of jobs across Nebraska and the country.”

“There’s not one trucking charging station in the state of Nebraska,” Hilgers later told reporters. “Trying to take that industry, which was built up over decades with diesel and fossil fuels-based infrastructure, and transforming it to an electric-based infrastructure – it’s probably not feasible.”

EPA officials have said the strict emissions standards will help clean up some of the nation’s largest sources of planet-warming greenhouse gases.

The new EPA rules are slated to take effect for model years 2027 through 2032, and the agency has said they will avoid up to 1 billion tons of greenhouse gas emissions over the next three decades.

Emissions restrictions could especially benefit an estimated 72 million people in the U.S. who live near freight routes used by trucks and other heavy vehicles and bear a disproportionate burden of dangerous air pollution, the agency has said.

A spokesperson for the EPA declined to comment on the legal challenge to the new rules Monday, citing the pending litigation.

California rules being challenged by Republican attorneys general would ban big rigs and buses that run on diesel from being sold in California starting in 2036.

An email seeking comment from California’s Air Resources Board was not immediately answered Monday.

California has been aggressive in trying to rid itself of fossil fuels, passing new rules in recent years to phase out gas-powered cars, trucks, trains and lawn equipment in the nation’s most populous state. Industries, and Republican leaders in other states, are pushing back.

Another band of GOP-led states in 2022 challenged California’s authority to set emissions standards that are stricter than rules set by the federal government. The U.S. Court of Appeals for the District of Columbia Circuit last month ruled that the states failed to prove how California’s emissions standards would drive up costs for gas-powered vehicles in their states.

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Houston earns No. 3 spot among cities with most Fortune 500 headquarters

biggest companies

Houston maintained its No. 3 status this year among U.S. metro areas with the most Fortune 500 headquarters. Fortune magazine tallied 26 Fortune 500 headquarters in the Houston area, behind only the New York City area (62) and the Chicago area (30).

Last year, 23 Houston-area companies landed on the Fortune 500 list. Fortune bases the list on revenue that a public or private company earns during its 2024 budget year.

On the Fortune 500 list for 2025, Spring-based ExxonMobil remained the highest-ranked company based in the Houston area as well as in Texas, sitting at No. 8 nationally. That’s down one spot from its No. 7 perch on the 2024 list. During its 2024 budget year, ExxonMobil reported revenue of $349.6 billion, up from $344.6 billion the previous year.

Here are the rankings and 2024 revenue for the 25 other Houston-area companies that made this year’s Fortune 500:

  • No. 16 Chevron, $202.8 billion
  • No. 28 Phillips 66, $145.5 billion
  • No. 56 Sysco, $78.8 billion
  • No. 75 Conoco Phillips, $56.9 million
  • No. 78 Enterprise Products Partners, $56.2 billion
  • No. 92 Plains GP Holdings, $50 billion
  • No. 143 Hewlett-Packard Enterprise, $30.1 billion
  • No. 153 NRG Energy, $28.1 billion
  • No. 155 Baker Hughes, $27.8 billion
  • No. 159 Occidental Petroleum, $26.9 billion
  • No. 183 EOG Resources, $23.7 billion
  • No. 184 Quanta Services, $23.7 billion
  • No. 194 Halliburton, $23 billion
  • No. 197 Waste Management, $22.1 billion
  • No. 214 Group 1 Automotive, $19.9 billion
  • No. 224 Corebridge Financial, $18.8 billion
  • No. 256 Targa Resources, $16.4 billion
  • No. 275 Cheniere Energy, $15.7 billion
  • No. 289 Kinder Morgan, $15.1 billion
  • No. 345 Westlake Corp., $12.1 billion
  • No. 422 APA, $9.7 billion
  • No. 443 NOV, $8.9 billion
  • No. 450 CenterPoint Energy, $8.6 billion
  • No. 474 Par Pacific Holdings, $8 billion
  • No. 480 KBR Inc., $7.7 billion

Nationally, the top five Fortune 500 companies are:

  • Walmart
  • Amazon
  • UnitedHealth Group
  • Apple
  • CVS Health

“The Fortune 500 is a literal roadmap to the rise and fall of markets, a reliable playbook of the world's most important regions, services, and products, and an indispensable roster of those companies' dynamic leaders,” Anastasia Nyrkovskaya, CEO of Fortune Media, said in a news release.

Among the states, Texas ranks second for the number of Fortune 500 headquarters (54), preceded by California (58) and followed by New York (53).

3 Houston energy companies rank among most innovative startups in Texas

report card

Three Houston companies claimed spots on LexisNexis's 10 Most Innovative Startups in Texas report, with two working in the geothermal energy space.

Sage Geosystems claimed the No. 3 spot on the list, and Fervo Energy followed closely behind at No. 5. Fintech unicorn HighRadius rounded out the list of Houston companies at No. 8.

LexisNexis Intellectual Property Solutions compiled the report. It was based on each company's Patent Asset Index, a proprietary metric from LexisNexis that identifies the strength and value of each company’s patent assets based on factors such as patent quality, geographic scope and size of the portfolio.

Houston tied with Austin, each with three companies represented on the list. Caris Life Sciences, a biotechnology company based in Dallas, claimed the top spot with a Patent Asset Index more than 5 times that of its next competitor, Apptronik, an Austin-based AI-powered humanoid robotics company.

“Texas has always been fertile ground for bold entrepreneurs, and these innovative startups carry that tradition forward with strong businesses based on outstanding patent assets,” Marco Richter, senior director of IP analytics and strategy for LexisNexis Intellectual Property Solutions, said in a release. “These companies have proven their innovation by creating the most valuable patent portfolios in a state that’s known for game-changing inventions and cutting-edge technologies.We are pleased to recognize Texas’ most innovative startups for turning their ideas into patented innovations and look forward to watching them scale, disrupt, and thrive on the foundation they’ve laid today.”

This year's list reflects a range in location and industry. Here's the full list of LexisNexis' 10 Most Innovative Startups in Texas, ranked by patent portfolios.

  1. Caris (Dallas)
  2. Apptronik (Austin)
  3. Sage Geosystems (Houston)
  4. HiddenLayer (Austin)
  5. Fervo Energy (Houston)
  6. Plus One Robotics (San Antonio)
  7. Diligent Robotics (Austin)
  8. HighRadius (Houston)
  9. LTK (Dallas)
  10. Eagle Eye Networks (Austin)

Sage Geosystems has partnered on major geothermal projects with the United States Department of Defense's Defense Innovation Unit, the U.S. Air Force and Meta Platforms. Sage's 3-megawatt commercial EarthStore geothermal energy storage facility in Christine, Texas, was expected to be completed by the end of last year.

Fervo Energy fully contracted its flagship 500 MW geothermal development, Cape Station, this spring. Cape Station is currently one of the world’s largest enhanced geothermal systems (EGS) developments, and the station will begin to deliver electricity to the grid in 2026. The company was recently named North American Company of the Year by research and consulting firm Cleantech Group and came in at No. 6 on Time magazine and Statista’s list of America’s Top GreenTech Companies of 2025. It's now considered a unicorn, meaning its valuation as a private company has surpassed $1 billion.

Meanwhile, HighRadius announced earlier this year that it plans to release a fully autonomous finance platform for the "office of the CFO" by 2027. The company reached unicorn status in 2020.

Tech entrepreneur turned climate investor is on a mission to monetize carbon removal

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The climate conversation is evolving — fast. It’s no longer just about emissions targets and net-zero commitments. It’s about capital, infrastructure, and execution at industrial scale.

That’s exactly where Yao Huang operates. A seasoned tech entrepreneur turned climate investor, Yao brings sharp clarity to one of the biggest challenges in climate innovation: how do we fund and scale technologies that remove carbon without relying on goodwill or government subsidies?

In this episode of the Energy Tech Startups Podcast, Yao sits down with hosts Jason Ethier and Nada Ahmed for a wide-ranging conversation that redefines how we think about decarbonization. From algae-based photobioreactors that capture CO₂ at the smokestack, to financing models that mirror real estate and infrastructure—not venture capital—Yao lays out a case for why the climate fight will be won or lost on spreadsheets, not slogans.

Her message is as bold as it is practical: this isn’t about saving the planet for the sake of it. It’s about building profitable, resilient systems that scale. And Houston, with its industrial base and project finance expertise, is exactly the place to do it.

The 40-Gigaton Challenge—and a Pandemic Pivot

Yao’s entry into climate wasn’t part of a long-term plan. It was sparked by a quiet moment during the pandemic—and a book.

Reading How to Avoid a Climate Disaster by Bill Gates, she came to two uncomfortable realizations:

  1. The people in power don’t actually have this figured out, and
  2. She would be alive to suffer the consequences.

That insight jolted her out of the traditional tech world and into climate action. She studied at Stanford, surrounded herself with mentors, and began diving into early-stage climate deals. But she quickly realized that most of the solutions she was seeing were still years away from commercialization.

So she narrowed her focus: no R&D moonshots, no science experiments—just deployable solutions that could scale now.

Carbon Optimum: Where Algae Meets Infrastructure

That’s how she found Carbon Optimum, a company using algae photobioreactors to remove CO₂ directly from industrial emissions. Their approach is both elegant and economic:

  • Install algae reactors next to major emitters like coal and cement plants.
  • Feed the algae with flue gas, allowing it to absorb CO₂ in a controlled system.
  • Harvest the algae and convert it into valuable commodities like bio-oils, fertilizer, and food ingredients.

It’s a nature-based solution, enhanced by engineering.
One acre of tanks can capture emissions and generate profit—without subsidies.

“This is one of the few solutions I’ve seen that can scale profitably and quickly,” Yao says. “And we’re not inventing anything new—we’re just doing it better.”

The Real Problem? It’s Capital, Not Carbon

As an investor, Yao is blunt: most climate startups are misaligned with the capital markets.

They’re following a tech startup playbook—built for SaaS, not steel. But building climate infrastructure requires a completely different approach: project finance, blended capital, debt structures, carbon credit integration, and regulatory incentives.

“Climate tech is more like real estate or healthcare than software,” Yao explains. “You don’t raise six rounds of venture. You build a stack—grants, equity, debt, tax credits—and you structure your project like infrastructure.”

It’s not just theory. It’s exactly how Carbon Optimum is expanding—through partnerships, offtake agreements, and real-world deployments. And it’s why she believes many climate startups fail: they don’t speak the language of finance.

Houston’s Role in the Climate Capital Stack

For Yao, Houston isn’t just a backdrop—it’s a strategic asset.

The city’s deep bench of project finance professionals, commodity traders, lawyers, and infrastructure veterans makes it uniquely positioned to lead the deployment phase of climate solutions.

“We’ve been calling it the wrong thing,” she says. “This isn’t just about climate—it’s an energy transition. And Houston knows how to build energy infrastructure at scale.”

Still, she notes, the ecosystem needs to evolve. Less education, more execution. Fewer workshops, more closers.

“Houston could be the epicenter of this movement—if we activate the right people and get the right projects over the line.”

From Carbon Capture to Circular Economies

The potential applications of Carbon Optimum’s algae platform go beyond carbon capture. Because the output—algae biomass—can be converted into:

  • Renewable oil
  • High-efficiency fertilizers (critical in today’s geopolitically fragile supply chains)
  • Food ingredients rich in protein and nutrients
  • Even biochar, a highly stable form of carbon sequestration

It’s scalable, modular, and location-agnostic. In island nations, Yao notes, these systems can offer energy independence by turning waste CO₂ into local energy and fertilizer—without needing to import fuels or food.

“It’s not just emissions reduction. It’s economic sovereignty through circular systems.”

Doing, Not Just Talking

One of Yao’s key takeaways for founders? Don’t waste time. Climate startups don’t have the luxury of trial-and-error cycles stretched over years.

“Founders need to get real about what it takes to scale: talent, capital, storytelling, partnerships. If you’re not ready to do that, maybe you should be a CSO, not a CEO.”

She also points out that founders don’t need to hire everyone—they need to tap the right networks. And in cities like Houston, those networks exist—if you know how to motivate them.

“It takes a different kind of leadership. You’re not just raising money—you’re moving people.”

Why This Episode Matters

This conversation is for anyone who’s serious about scaling real solutions to the climate crisis. Whether you’re a founder navigating capital markets, an investor seeking return and impact, or a policymaker designing the frameworks — Yao Huang offers a grounded, urgent, and actionable perspective.

It’s not about hope. It’s about execution.

Listen to the full episode of the Energy Tech Startups Podcast with Yao Huang:


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Hosted by
Jason Ethier and Nada Ahmed, the Digital Wildcatters’ podcast, Energy Tech Startups, delves into Houston's pivotal role in the energy transition, spotlighting entrepreneurs and industry leaders shaping a low-carbon future.