Proposed federal mandates for ethanol and advanced biofuels under the federal law requiring certain levels of renewable fuels  to be blended with gasoline seem to have few supporters and many critics.

The U.S. Environmental Protection Agency announced on May 29 its proposed targets for cellulosic biofuels, biomass-based diesel and advanced biofuels to be blended with gasoline for 2014-2016 under the Renewable Fuel Standard (RFS).

Ethanol and other biofuel blends for transportation vehicles were initially heralded in some quarters as a way to reduce greenhouse gas emissions in the transportation sector.

But some environmental groups contend that corn ethanol increases, rather than reduces, greenhouse gas emissions.

EPA postponed releasing targets in 2014, and some industry officials say that the lack of certainty about the Obama administration’s support for biofuels has hampered construction of new biofuel refineries at a time when they were poised to take off.

Brent Erickson, Biotechnology Industry Organization executive vice president, said that uncertainty over the RFS mandates has stalled $13.7 billion in investments the industry needed to expand capacity. “The chill in investment has had the heaviest impact on cellulosic biofuel developers,” he said in a statement.

EPA is proposing to increase amounts of biofuels—which include ethanol—to be used in coming years compared with historic levels.

For example, the proposed 2016 standard for cellulosic biofuels—those that generate the lowest amounts of greenhouse gas emissions—is more than 170 million gallons--or six times--higher than actual 2014 levels, EPA says. 

However, the mandates are lower than what was originally envisioned when Congress first approved the RFS in 2005.

That’s largely because of reduced demand for gasoline, deeper cuts in greenhouse gas emission levels through tightened fuel economy standards for cars and trucks, and the realities of the current marketplace, which saw “lower than expected development of the cellulosic biofuel industry,” Janet McCabe, head of EPA’s Office of Air and Radiation, told reporters on May 29.