The US is unlikely to meet some specific biofuel mandates under the current Renewable Fuel Standard by 2022 unless new technologies are developed or policies change.
A new report from the National Research Council, requested by Congress, adds that the standard might anyway be ineffective at reducing global greenhouse gas emissions.
In 2005, Congress enacted the Renewable Fuel Standard as part of the Energy Policy Act and amended it in the 2007 Energy Independence and Security Act.
It now says that by 2022, consumption of renewable fuels should consist of 15 billion gallons of conventional biofuels; one billion gallons of biomass-based diesel fuel; four billion gallons of advanced renewable biofuels and 16 billion gallons of cellulosic biofuels produced from wood, grasses, or non-edible plant parts.
But, according to the NRC, no commercially viable biorefineries exist for converting cellulosic biomass to fuel - and nor will they, unless technology improves significantly.
In any case, it's uncertain how much using biofuels rather than petroleum will reduce greenhouse gas emissions. Dedicated energy crops will have to be grown, and will probably require conversion of uncultivated land or the displacement of commodity crops and pastures.
And cost estimates of cellulosic biofuel show it's not economical compared with fossil fuels when crude oil's price is $111 per barrel. Furthermore, there would need to be significantly more federal spending, mostly on grants, loans and loan guarantees.
And it's not even clear, says the NRC, whether there will be any environmental benefits. In fact, air-quality modeling suggests that production and use of ethanol to displace gasoline is likely to increase air pollutants such as particulate matter, ozone, and sulfur oxides. Biofuels also require more water to produce.
"Key barriers to achieving the renewable fuel mandate are the high cost of producing cellulosic biofuels compared with petroleum-based fuels and uncertainties in future biofuel markets," says the NRC.
"Biofuel production is contingent on subsidies, the nature of the mandate, and similar policies."