"Forty-five thousand families would face undue financial hardship and stress simply at the hands of EPA catering to big oil. And they aren't satisfied – they won't be satisfied until you repeal it altogether," Branstad said.
Still others suggested that the EPA proposal could not only eliminate jobs and rural economic growth, but also have an impact on future development.
Jan Koninckx, Global Biofuels Business Director for DuPont, said the proposed rule would undo the progress the industry has made over the past several years.
"It sends a signal to investors that the U.S. can't play the long game anymore, that as a nation we cannot envision a better future and stick with it long enough to see it through – that we're not serious about opening a marketplace for new fuel technologies, and that perhaps, the money is better spent somewhere else," Koninckx said.
Ethanol by-products became a common topic, too. Fuel companies and ethanol supporters argued that fuel plants can produce thousands of tons of feed through marketing of by-products. Dried distillers grain, argued Iowa livestock producer Mark Leonard, costs 80% of the price of corn while providing 20% more energy and 300% more protein.
"When you see all the facts you realize ethanol is good for your vehicle, it's good for the economy and we need to keep the RFS," he said.
Artificial market and higher prices
But nearly every comment from an RFS proponent was countered at some point by an RFS opponent. Many said a major drawback of the RFS is the "artificial market" it creates.
Congressman Bob Goodlatte, R-Va., an outspoken opponent of the RFS, said the policy unnecessarily drives up the price of corn, feed for animals and food prices for consumers. And he noted, 169 bipartisan House members agreed by signing on to a letter to oppose the RFS.
"We appreciate that the EPA has imposed a slight reduction," Goodlatte said, but "it is not enough to provide the much need relief businesses farmers and consumers need."