NEW YORK/HOUSTON (REUTERS) - The largest US oil refiners released tonnes of air pollutants into the skies over Texas this past week, according to figures provided to the state, as refineries and petrochemical plants in the region scrambled to shut production during frigid weather.
An arctic air mass that spread into an area unused to such low temperatures killed at least two dozen people in Texas and knocked out power to more than four million at its peak. It also hit natural gas and electric generation, cutting supplies needed to run the plants along the US Gulf Coast.
Shutdowns led to the refineries flaring, or burning and releasing gases, to prevent damage to their processing units.
That flaring darkened the skies in eastern Texas with smoke visible for miles.
"These emissions can dwarf the usual emissions of the refineries by orders of magnitude," said Ms Jane Williams, chairman of the Sierra Club's National Clean Air Team.
She said United States regulators must change policies that allow "these massive emissions to occur with impunity".
The five largest refiners emitted nearly 337,000 pounds (153 tonnes) of pollutants, including benzene, carbon monoxide, hydrogen sulphide and sulphur dioxide, according to preliminary data supplied to the Texas Commission on Environment Quality.
Valero Energy said in a filing with the commission that it released 78,000 pounds over 24 hours beginning last Monday from its Port Arthur, Texas, refinery, citing the frigid cold and interruptions in utility services.
The 118,100 pounds of emissions from Motiva's Port Arthur refinery from last Monday to Thursday were more than three times the excess emissions that it declared to the US Environmental Protection Agency for the whole of 2019.
Marathon Petroleum's Galveston Bay Refinery released 14,255 pounds over less than five hours on Monday, equivalent to about 10 per cent of its total releases above permitted levels in 2019.
Exxon Mobil said its Baytown Olefins Plant emitted nearly a tonne of benzene and 68,000 tonnes of carbon monoxide, citing in its disclosure the halting of "multiple process units and safe utilisation of the flare system". Exxon blamed the shutdown of two Texas refineries on the freezing weather and loss of natural gas supplies. A spokesman said its petrochemical plants in Texas and Louisiana had supplied 560 megawatts to local communities, helping power about 300,000 homes.
Valero did not have an immediate comment. Motiva did not respond to a request for comment.
"We don't typically provide comment on our operations beyond our filings," said Marathon spokesman Jamal Kheiry. "However, I can say that the safety of our workers, our neighbours and the environment are our top priorities as we operate our facilities."
Final figures on pollution releases are due to be submitted to the state in two weeks.
The flaring continued through the week as refiners kept plants out of service.
"We had six or seven flares going at one time. It's still happening now," Port Arthur resident Hilton Kelly said last Friday. Port Arthur is home to refineries operated by Motiva, Valero and Total.
Ms Sharon Wilson, a researcher at advocacy group Earthworks, said the releases were alarming, in part because "there is no safe amount of benzene for human exposure".
State data showing oil and gas producers were flaring methane this past week "is just making things worse and it could have been prevented" by winterising facilities, she said.
Texas oil and gas companies filed 174 notices of pollution releases above permitted levels between Feb 11 and Feb 18, four times the number the prior week.
Total pollution at Houston-area facilities during the cold snap totalled about 703,000 pounds, about 3 per cent of the total pollution over permitted amounts for all of 2019 and almost 10 per cent of 2018's releases, according to data from Texas Commission on Environment Quality analysed by advocacy group Environment Texas.