A U.N. report concluded carbon capture could offset fossil fuels’ effect on climate change. Two decades later, the process has failed to meaningfully scale up, and it’s proving hard to take the promises back.

In the spring of 2005, the United Nations convened more than 100 of the world’s top scientists in the medieval town of Oviedo, Spain. They were there to finish writing a paradigm-shifting report about a technology that they hoped could help stop climate change.

To celebrate the report’s impending completion, the meeting’s hosts handed out bottles of cava, Spanish sparkling wine, with tongue-in-cheek labels stating that they were to be opened only by those who truly believed it could work.

Belief was necessary because the technology — carbon capture and storage, or CCS — had barely been tested. The idea was simple: strip carbon dioxide from smokestacks before it could flow into the air and warm the planet. Then pump it into a porous part of the Earth’s crust and leave it there. Forever.

The experts in Oviedo had stacks of papers proving that parts of the process worked. But major questions remained about how much space exists inside the Earth to store the CO2, how effectively it could be monitored and whether the poisonous, concentrated gas would reliably stay underground.

The researchers were in Oviedo only because Saudi Arabia and other oil-exporting countries had pressured the U.N. to write the report despite the paucity of evidence, according to U.N. officials and records. The oil, gas and coal industries had spent years casting doubt on climate change while quietly fretting that policies to address it would one day put them out of business. The industry, documents show, saw CCS as a way to forestall that outcome, allowing the world to keep burning fossil fuels while simply burying the pollution underground. A U.N. report would bring the technology into the mainstream.

In turn, the U.N. hoped such a report would draw the oil-producing nations into its search for climate solutions. So despite objections from some nations and environmental organizations, which warned that the report would distract from the imperative to phase out fossil fuels, the U.N.’s preeminent climate science authority, the Intergovernmental Panel on Climate Change, went ahead. And for the first time, it invited a large contingent of industry researchers to join the scientists in writing the report, as well as several representatives from environmental groups. Benson’s chapter included authors and editors from Shell, Chevron and Saudi Aramco.

But 21 years after Oviedo, a staggering gap lies between expectations for the technology and its operational reality. Since 1996, just 12 large-scale geological storage projects have been constructed. Collectively, they bury less CO2 than a single power plant can emit in a year, according to our analysis of sites listed in an International Energy Agency database. Seven of them have faced technical, financial or performance issues. An investigation by Drilled and ProPublica found there’s reason to doubt carbon capture and storage will ever succeed at the scale needed to offer a significant climate solution.

History is full of audacious technological leaps — moments when visionary engineering solved seemingly intractable problems. Scientists told Drilled and ProPublica that they have devoted themselves to studying CCS in that spirit, hoping a grand techno-fix could help the world solve the climate crisis without a painful overhaul of the global energy system.

But that ambition did not exist in isolation. It was bankrolled in large part by companies that stood to profit from its success.

Industry documents show that oil company executives have long seen CCS as a way to hedge against climate regulation, greenwash their brands and preserve their core business. Internal Exxon documents obtained by Drilled and ProPublica show that in 1988, the company determined that any climate research Exxon supported should serve the dual purposes of protecting the value of its oil, gas and coal while preserving the company’s business options; the company would eventually become one of the world’s major funders of CCS research.

But even while oil industry leaders have pushed the world to embrace CCS, behind closed doors, they have remained skeptical of its potential as a climate solution.