“Nothing has changed with regard to ethanol production costs or efficiencies. The only change has been abject failure of the rail system to adequately address the needs of all its customers,” RFA wrote. “The U.S. economy is suffering as a consequence.”

In a recent email, AAR spokeswoman Holly Arthur blamed the delays on the cold.

“As you can imagine, record cold temperatures, snow and ice have impacts on rail operations — from having to deal with snow and ice on infrastructure and equipment, to limits on how long employees can be outside,” Arthur said. “Railroads are doing all they can to address any service disruptions.”

The Renewable Fuels Association, which represents ethanol producers, has asked AAR to respond to questions on the steps railroads are taking to reduce the logjam.

It has also asked the railroad association to address how much the growth in crude oil rail transport has affected transportation of ethanol.

“The railroads have attributed this lackluster performance and inefficiency to winter weather. But they seem to have forgotten that winter comes every year,” RFA wrote in the letter today. “Indeed, a more plausible explanation for the severity of the current epidemic is the explosive growth in railcar shipments of Bakken and Canadian crude oil.”

Crude oil, though, represents just 1.4 percent of rail traffic, according to AAR.