An air quality permit was approved Friday afternoon for the huge new Volkswagen auto assembly plant at Enterprise South Industrial Park, though - to meet current EPA requirements to deal with paint fumes - greenhouse gas emissions from the facility will be high. Also, there will be nitrogen dioxide emissions contributing to the local ozone problem.

Some six thermal oxidizers that will burn natural gas will have to be installed at the plant to control emissions from the paint shop.

Officials said the entire plant will emit 128,000 tons of carbon dioxide per year as well as 80 tons each of nitrogen dioxide and carbon monoxide.

Bob Colby, Air Pollution Control Bureau director, said the paints used at the plant will use low-VOC (volatile organic compound) waterborne coatings except for the clearcoating operation, which is used to seal the undercoating of paint. The sealant paint will be solvent-based.

Mr. Colby said under existing EPA rules that the oxidizers will be necessary to neutralize hazardous materials in the sealant paint that is designed to preserve the paint shine and prevent chipping.

But he acknowledged that the oxidizers are heavy greenhouse gas emitters and utilize large quantities of natural gas.

Mr. Colby said, "We do have some concern that the oxidizers will create large amounts of carbon dioxide gas and use a finite energy source when it may not give us any significant environmental benefit. Those are the rules now and we have to abide by them.

"But there may come a point when the policymakers may need to change that policy."

He said the oxidizers will control VOC emissions contributing to ozone, but he said the oxidizers will bring the nitrogen dioxide "that in this area is an even more significant contributor to the ozone problem."

Mr. Colby said he does not believe that the VW plant will be a significant contributor to the local ozone problem, which required the area to be placed under an Early Action Compact. It included establishment of vehicle emission stations and implementation of open burning restrictions.

However, Mr. Colby noted that the EPA has just lowered the ozone level standards from 86 parts per billion to 75 parts per billion.

He said Hamilton County most recently was at 79 parts per billion.

Mr. Colby said the county will have until 2016 to fully comply with the new requirement.

He said he expects the ozone problem here to continue to improve with upgrades to area coal-fired power plants and other clean air advances.

Officials said the oxidizers cost up to $1 million each and cost up to a half million dollars a year each in natural gas costs to operate.

The Air Pollution Control Bureau held a special session on Friday to consider the request. Jody Baker, longtime attorney, said it was the first time a request had been considered that was not a part of a regular board meeting.

Mr. Colby said the report was prepared and approved in record time.

It was filed Aug. 8, and a public comment period was Sept. 4-Oct. 6.

The only comments received were from the EPA and the U.S. Forest Service.

Mr. Colby said the plant emissions should not affect visibility in the closest park service tract at the Cohutta Wilderness.

Environmental Resources Management of Brentwood, Tn., prepared the air quality permit application with a host of staff members working long days and weekends. The application weighed six pounds.

Lem Stevens of ERM said his staff made few changes from the plans submitted by VW because he said they were designed to be environmentally friendly and were within current EPA guidelines.

He noted that the paint process used by Volkswagen eliminates an intermediate "guidecoat" layer of paint used by other automakers.

Mr. Colby said a powder-based clearcoating is used at one plant, but he said Volkswagen and other automakers say it is inadequate. VW officials said it causes problems with controlling the thickness of the application and there are problems with chip resistance, dirt in the clearcoating, lower appearance quality and yellowing of the paint. Mr. Colby said the oxidizers would not have been required had the powder-based paint sealant been used.

Mr. Colby said with use of the oxidizers that 56 percent of the solvent-laden air will be captured in the clearcoat spray booth and routed to a regenerative thermal oxidizer to control the emissions. He said emissions from the clearcoat ovens (approximately 39 percent of the sprayed clearcoat) will be controlled by the oven thermal oxidizer. He said approximately five percent of the clearcoat VOC emissions is expected to evaporate in the inspection zone and will be exhausted to the atmosphere.

The plant will be heated by boilers and space heaters that operate on natural gas.

Attending the meeting were officials of Volkswagen, ERM as well as SOSE, which is designing and building the plant.

No members of the Air Pollution Control Board asked any questions at the brief meeting at the Development Resource Center on South Market Street.