May 24, 2005 | General


BioCycle May 2005, Vol. 46, No. 5, p. 70
New method developed by Agricultural Research Service simplifies process by eliminating an expensive step in synthesizing the fuel.

IN THIS COUNTRY, soybean oil is the most prevalent starting material for biodiesel, although other vegetable oils, animal fat and waste grease are used as well. But soybean oil’s relatively high cost makes biodiesel expensive – discouraging wider adoption of this renewable fuel.
Now Agricultural Research Service (ARS) scientists in Wyndmoor, Pennsylvania have developed a method that eliminates a step – and an air polluting chemical – from the process of synthesizing biodiesel. Michael Haas, a biochemist with the ARS Fats, Oils and Animal Coproducts Research Unit and colleagues have come up with a different approach.
In biodiesel production, hexane – a colorless, flammable liquid derived from petroleum – is used to extract the oil from soybeans. But hexane is an air pollutant, and its release is regulated by EPA. Working with a biologist and chemist, Haas eliminated hexane from the process by skipping the oil extraction step. Instead, soybean flakes are incubated with methanol and sodium hydroxide, the same agents that would be used to process extracted oil.
Explains Haas: “In the new method, soybean flakes are incubated in alkaline methanol, eliminating the need to isolate and purify the oil before transesterification.” (“Transesterification” is a reaction between fats and alcohol that forms the simple fatty acid esters that are biodiesel.)
The researchers then noticed that their new method used considerably more methanol than is typically needed in biodiesel synthesis. They reasoned that the moisture naturally present in soybeans, as much as 10 percent in soy flakes, could be the reason behind the high methanol requirement. They found that by drying the flakes before starting the biodiesel synthesis, they could greatly reduce the required methanol volume. As a result, estimated cost went down to $1.02 per gallon.
Haas and his colleagues are presently refining their economic model to account for income from selling the lipid-free, protein-rich flakes left after the biodiesel reaction for use as animal feeds and to account for cost differences between refined-oil and flaked-soybean starting materials.
According to Jim Core of the ARS Information Staff, ARS has filed a patent application on the process. Haas is exploring use of this new method to produce biodiesel from the lipids in corn coproducts from ethanol plants that use corn as a starting material. He’s also investigating the suitability of canola seeds and meat and bone meal.
IN MID-APRIL, a bill introduced into the U.S. House would set a renewable fuels standard (RFS) requiring use of eight billion gallons of renewable fuels, like biodiesel and ethanol, by 2012. The Senate introduced similar legislation this year.
According to results of a national survey of registered voters, 74 percent support establishing an eight billion gallon per year RFS to reduce U.S. dependence on foreign oil and improve air quality. Support for the RFS is strong regardless of party affiliation or geographic location.
The same survey also found that 79 percent of registered voters support extending the current biodiesel federal tax incentive to encourage biodiesel use in the U.S. Last fall, Congress approved a two-year tax incentive for biodiesel that took effect January 1, 2005.

Sign up