By The Kansas City Star Editorial Board

Congress has tried to create a charmed life for ethanol and Midwestern corn growers in recent years.

First came a hefty tax credit for producing the renewable fuel. And in late 2007 U.S. lawmakers passed a new standard that requires quadrupling the output of ethanol and other biofuels by 2022.

But this month the federal Government Accountability Office issued a sobering report that questioned the need for the tax credit because it’s not expected to boost ethanol production beyond already-mandated levels.

In reaction, Congress should scrap the 45-cent tax credit that artificially supports each gallon of ethanol.

The credit helps keep out cheaper ethanol from Brazil, boosting the cost of driving for American motorists.

More notably, the tax credit is no longer needed now that Congress has mandated such a large increase in production. Right now the credit is a source of easy profits for the industry.

The GAO report also correctly called for more rigorous examinations of ethanol’s long-term impact on the environment.

That’s a field ripe for study, mostly because farmers likely will be using more land, water and fertilizers to dramatically increase corn production. The GAO authors fairly point out that changes in crop yield and the use of water conservation techniques could lessen these environmental concerns.

Ultimately, new studies could help determine whether ethanol’s true effect on the environment is more harmful than now thought.

In the short term, getting rid of a tax credit costly to U.S. taxpayers is a needed first step in Washington.