The $9.4bn facility, owned by Formosa Plastics, would consist of 14 separate plastic plants in St James parish, known as Cancer Alley

The state of Louisiana has issued a series of key air quality permits for a gargantuan proposed petrochemical complex that would roughly double toxic emissions in its local area and, according to environmentalists, become one of the largest plastics pollution-causing facilities in the world.

The $9.4bn facility, owned by the Taiwanese chemicals firm Formosa Plastics, would consist of 14 separate plastics plants across 2,300 acres of land in St James parish, a largely African American community in the already heavily polluted area in southern Louisiana known as Cancer Alley.

Activists say the plant could release 13m tonnes of greenhouse gases a year, the equivalent of three coal-fired power plants, and would emit thousands of tonnes of other dangerous pollutants, including up to 15,400 pounds of the cancer causing chemical ethylene oxide.

The facility has been forcefully opposed by environmental groups and certain local campaigners.

The 16 permits issued by Louisiana’s state environment agency (LDEQ) essentially allow Formosa to begin construction, said the LDEQ spokesman Greg Langley. A spokeswoman for Formosa, which is operating the project under a subsidiary, FG LA, said the company would start “site preparation activities” in the first quarter of 2020. This first phase, including soil testing, could take up to a year to complete, the spokeswoman said.

The permits had not been made available to the public by Tuesday afternoon. Langley said this was because of the volume of documents, numbering more than 1,000 pages, which were still uploading to the department’s public website.

The announcement was met with derision by local campaigners. “We are fighting to protect our homes and our families from this monster, Formosa. We are not going to stop because of this bad decision by the state to grant air permits,” said Sharon Lavigne, the president of the campaign group Rise St James, in a written statement.

Environmental activists on Tuesday indicated they would continue to oppose the project, but withheld details of what their next steps would be until the permits were made publicly available.

“The state of Louisiana is wholly unprepared to provide proper oversight of this monster,” said Anne Rolfes, the founding executive director of the environmental organization Louisiana Bucket Brigade. “This approval signals that our state government is willing to sacrifice our health, our clean air and water to cheap plastics. The good news is that we, the people, do not accept this decision. The fight has just begun.”

The project has been endorsed by a number of senior state officials in Louisiana, including the governor, John Bel Edwards, citing job creation and tax revenues. It is expected to create 1,200 new permanent jobs with 8,000 temporary construction jobs.

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“FG is pleased to have completed the rigorous environmental permitting process,” said Janile Parks, the director of community and government Relations at FG LA. “Our team has worked diligently to design a facility that meets state and federal standards that protect the health and safety of our employees, community and the environment.”

Parks said that project would generate $362m in taxes for state and local governments during construction, with about $207m being “collected in the St James area”.

But local campaigners argue that the financial rewards should be seen as secondary to the project’s environmental impact.

At the end of last year, in addition to environmental and health concerns, it was revealed that the complex would be built over two suspected slave burial grounds. The news left residents in the mostly African American neighbourhoods surrounding the sites furious that the information had not been publicly disclosed to them during the application phase of the project.