A wide-ranging climate change bill with the potential to significantly affect Iowans faces a key vote as early as today in Congress.

Meanwhile, last-minute changes have been written into the plan to try to entice support from farm state legislators.

The House is scheduled to vote on the 1,200-page cap and trade bill today. The plan would cap carbon emissions and set up an open market to trade credits permitting emissions.

It also would move the country away from fossil-based fuels and toward renewable energy.

The bill's authors say it's needed to combat global climate change.

The legislation has been particularly controversial in Iowa, where farm groups have worried it will push up their costs.

Some congressional offices say they've gotten hundreds of calls on the matter.

Also, MidAmerican Energy Co., the state's largest utility, has run a barrage of newspaper and television ads saying it will boost household utility bills by at least 25 percent.

"I'm very pleased to see as this bill has moved forward it's improved," said U.S. Rep. Bruce Braley, D-Iowa, a member of the House committee that wrote the bill. "This is a transformational energy bill that's going to create jobs in our state."

Earlier this week, the bill's authors agreed to a compromise that will delay proposed federal regulations that would factor in land-use changes in implementing biofuel mandates. Farm groups say the new rules will hurt the biofuels industry.

Also, the U.S. Department of Agriculture would be given responsibility for implementing part of the climate bill, rather than the Environmental Protection Agency. Rural legislators wanted the change.

Still, there is opposition from farm groups. The Iowa Farm Bureau Federation applauded the compromise Thursday but said the overall bill still would raise producers' costs.

The Iowa Corn Growers Association, meanwhile, voted to oppose it.

"Everybody's rather nervous the way it is right now," said Dean Taylor, a Jasper County farmer and association director.

The association's national office has taken a neutral stand, he said.

The compromise is expected to draw farm state support to the bill, however. U.S. Rep. Leonard Boswell, D-Iowa, said late Thursday he will support the bill. Boswell previously had been on the fence. A spokesperson for U.S. Rep. Dave Loebsack, D-Iowa, said Thursday he hadn't decided yet.

U.S. Rep. Phil Hare, D-Ill., plans to vote for the bill, a spokesman said.

Also Thursday, an Iowa-based group criticized MidAmerican for its opposition to the climate change bill. The Iowa Policy Project, a liberal group, said the bill will help Iowans, not hurt them.

"Critics of the current proposal present a false choice between protecting the environment and protecting consumers," said David Osterberg, executive director.

The group noted a Congressional Budget Office study last week said the cost of the cap and trade program would be $175 per household in 2020.

A MidAmerican spokesperson responded by reiterating its estimates, saying its costs will go up $280 million in 2012 and more after that.

The Senate hasn't acted yet on a climate change proposal, which is a top priority for President Barack Obama.