LA PORTE — Just off of Highway 225 past the refineries and coal stacks that line the freeway, one small plant is proving that generators can make electricity without emissions. Nothing that turns into acid rain. Nothing that makes it hard to breathe. Nothing that contributes to climate change.

Distinguished from the other industrial sites only by a green leaf on its sign, the demonstration plant has been testing operations for just under a year to prove a power technology that, instead of emitting carbon dioxide, heats it to drive the turbines that make electricity. All but 3 percent of the carbon dioxide is recycled to produce more electricity; the rest can be captured and stored, ready for pipelines to customers in the oil and gas and other industrial industries.

“This is a game changer for the way we make power,” said Ramanan Krishnamoorti, chief energy officer at the University of Houston and a chemical engineer. “It’s a beautiful engineering feat, but it also makes it a clean system that is energy efficient and capital efficient.”

The plant, developed and operated by a company called NET Power, soon will begin selling power into the grid as it completes the final phase of its operational testing over the next few months. The next step, building plants that can produce power on a commercial scale, should get underway in the early 2020s, company officials said.

NET Power’s technology is considered among the most promising for the energy industry searching for ways to reduce carbon emissions as concerns about climate change grow and governments around the world move to increase the regulation and cost of emitted greenhouse gases. The power and transportation sectors are the biggest sources, each accounting for about 28 percent of the nation’s greenhouse gas emissions, according to the Environmental Protection Agency.

Many analysts and industry officials view carbon capture as critical to the long-term survival of companies that produce fossils fuels — oil, natural gas and coal — but so far developing commercially viable, affordable systems remains elusive. NRG Energy, the power company headquartered in Houston and Princeton, N.J., installed a carbon capture system at its W.A. Parrish coal-fired plant in Fort Bend County, but the cost reached $1 billion.

Heat and mass

NET Power, backed by a North Carolina investment firm 8 Rivers Capital and other investors, such as the Houston oil company Occidental Petroleum, uses a technology called the Allam power cycle, which heats up carbon dioxide in a combustion chamber to an extremely high temperature — a point known as supercritical carbon dioxide, at which the C02 gas becomes like a liquid. The process uses the heat and mass of supercritical carbon dioxide to turn the turbines. The carbon dioxide, still very hot, then cools and is recycled through the plant.

The excess carbon dioxide generated by the process could be captured at the correct pressure and quality to be easily transported via pipeline. Normally, in air combustion, sequestration of carbon dioxide is difficult because it is expensive to separate the carbon from the air, and then bring it to the correct pipeline pressure. The Allam power cycle removes the need for this separation.

This is potentially a big deal for Texas, where carbon dioxide that can be transported via pipeline is in demand from its energy and chemical industries. Oil and gas companies can pump carbon dioxide into aging oil wells to increase production, a process known as enhanced oil recovery. It can also be used to make cement.

The $140 million demonstration plant, on West Fairmont Parkway in La Porte, will have the capacity to produce 25 megawatts of electricity, enough to power about 5,000 Texas homes on a hot summer day. Construction on the plant began in March of 2016; it began testing operations in May.

“We have a (technology) that isn’t spewing (carbon dioxide) into the atmosphere,” said Bill Brown, the CEO of NET Power and 8 Rivers Capital.

NET Power estimates that commercial versions of the plant, which would have a generating capacity of about 300 megawatts, could produce power for $20 per megawatt hour, assuming the federal tax credits that provide incentives for storing carbon dioxide stay in place. That prices also assumes the company can sell their pipeline-ready carbon dioxide for $15 per ton, as well as the nitrogen and argon they produce.

NET Power estimates a combined natural gas cycle produces power at about $44 per megawatt hour, assuming a price of about $2.96 per thousand cubic feet of natural gas. NET Power estimates that 450 of its power plants could replace all the new fossil fuel power plants needed from now until 2040 in the U.S.

The first fire: Experimental no-emissions power plant in La Porte fired up successfully

Brown said he believes the Allam power cycle will prove to be economically and environmentally competitive, but he admits it’s a difficult industry to revolutionize. For example, he said, renewable technologies have not been nearly as consequential as people would have hoped. Wind energy, for example, generates a little over 6 percent of the nation’s electricity, according to the Energy Department.

“It’s hard to predict how a disruption will happen in the energy industry,” Brown said. “We see it happen with the tech industry, but with something like this … it’s slow.”

Skeptics’ view

Rice University energy economist Peter Hartley is skeptical that a carbon capture revolution is imminent. It’s expensive to pipe the carbon dioxide and store it, he said. He also is uncertain of how many buyers there are carbon dioxide, which is key to lowering the net costs of carbon capture.

“More breakthroughs are needed (in the technology),” Hartley said.

Both the federal government and the energy industry appear to realize that. The fossil-fuel friendly Trump administration allocated $36 million in federal assistance to advance carbon capture technology in September of 2017, and in January announced it would fund at least two front-end engineering and design studies for commercial-scale carbon capture systems on coal and natural gas power plants.

As shareholders turn up the pressure on energy companies to address climate change, the industry, too, is financing carbon capture research and development. NET Power’s investors, in addition to 8 Rivers and Occidental, include Exelon Corp., a power company headquartered in Chicago and McDermott International Inc., a Houston oil and gas services company.

RELATED: University of Houston courts oil and gas for work on carbon management

Occidental’s interest in the NET Power’s technology is two-fold. First, the company is looking for a way to shrink its and the energy industry’s carbon footprint. Second, the company needs a source of carbon dioxide for its operations: The company injects over 50 million tons of carbon dioxide into its oil and gas reservoirs per year to boost production by as much as 20 percent.

Chevron, the nation’s second largest oil company after Exxon Mobil, also uses carbon dioxide to boost production. Chevron has invested over $1 billion in carbon capture, utilization and sequestration projects, and $75 million in research and development over the past decade, according to its February climate change report.

Texas, and particularly West Texas’ Permian Basin, would be an ideal location for a commercial scale plant, said Brown. First, the oil field would provide ready customers for the carbon dioxide produced and captured by the plant. Second, it would provide a steady supply of cheap natural gas burned to heat the carbon dioxide to its supercritical state. (Carbon dioxide produced by burning the natural gas would be captured and recycled with the rest of the C02.)

Rapid advances

Engineers say most carbon-based fuels, including gasified coal or biomass, could substitute in the NET power plants for natural gas. This could make the technology viable in regions across the globe. For example, in the Middle East, where sour natural gas is plentiful, a NET Power plant could run on the lower quality natural gas with high carbon dioxide content without producing greenhouse gas emissions, Brown said.

Experts, including Krishnamoorti, believe the cooperation of the oil and gas industry on carbon management is vital if the United States wants to make meaningful strides toward solving climate change. While commercial-scale carbon capture, utilization and sequestration projects may be at least a few years out, Krishnamoorti said, the urgency for such technology is growing.

“These are things that are advancing pretty rapidly,” Krishnamoorti said, “and over the next five to seven years will be transformative.”

erin.douglas@chron.com

Twitter.com/erinmdouglas23

The article was updated to clarify the process of heating carbon dioxide to its supercritical state.