A $1 billion project to harness CO₂ emissions from a Texas coal plant suffered chronic mechanical problems and routinely missed its targets before it was shut down this year, according to a U.S. Department of Energy report.

The Petra Nova plant's performance was seen as a major test of emerging efforts to capture planet-warming gases and store them below ground, a technology considered crucial to companies and governments hoping to fight climate change.

The joint venture project between NRG Energy Inc. and Japan's JX Nippon had received a $190 million grant from the U.S. government. Before being mothballed, it was the only U.S. project capturing carbon from a coal-fired power plant.

Since Petra Nova started up in 2017, it suffered outages on 367 days, according to a Department of Energy technical report compiled in March. Issues with the carbon-capture facility accounted for more than a quarter of the outage days, followed by problems with the plant's dedicated natural gas power unit, according to the report.

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The facility also missed its carbon capture targets by about 17%: It captured 3.8 million short tons of CO₂ during its first three years, shy of the 4.6 million short tons developers had expected.

The plant was designed to capture 33% of the carbon emissions from one of four units at the W.A. Parish coal plant southwest of Houston, and pipe it 81 miles to the West Ranch oil field in Jackson County, Texas, where it would push more oil to the surface.

Department of Energy spokeswoman Shaylyn Hynes said the department believes that, despite the outages outlined in the report, the project had been generally successful, and that NRG had idled the project “due to the pandemic and the low price of oil, not failed technology.”

"DOE remains committed to CCUS technology as it is critical to meeting our nation’s emission reduction goals,” she said, referring to carbon capture, utilization and storage.

NRG idled the facility on May 1, saying a collapse in the price of oil prompted by the coronavirus pandemic made it uneconomical.

NRG would not comment on the plant's technical performance, but said it could be brought back online when economic conditions improve.

"We are proud of the work we have done to demonstrate that carbon capture could be installed on an existing coal-fired generating station and operated as designed," NRG spokesman Chris Rimel said in a statement.

Petra Nova's shutdown "highlights the deep financial risks" facing other carbon capture and storage (CSS) projects in the works, according to a report by the Institute for Energy Economics and Financial Analysis.