Biodiesel is has an even better net energy ratio than we thought. Older studies said biodiesel had a 3.2 to 1 energy ratio, but a comprehensive study by the NREL and USDA have shown a positive net energy ratio of 3.5 to 1. This is big news and puts to bed the idea that it takes nearly as much energy to make biofuels as we get out of the biofuels. Corn ethanol? Yeah, not particularly efficient (1.3 to 1). Biodiesel? 3.5 to 1.

This means that for every one unit of energy (say, gallon of fuel) it takes to make biodiesel, we get 3.5 gallons of biodiesel. Where does the extra energy come from? That's easy: the sun. Plants take the sun's power and convert it to energy better than the best solar panels do.

Here's the National Biodiesel Board's press release.

Feb. 6, 2008

  Biodiesel Yields Even Higher Energy Balance
New Study Shows 3.5 Units of Energy Gained For Every Unit Needed to Produce Biodiesel

ORLANDO, Fla.– A new analysis shows that the energy balance of biodiesel is a positive ratio of 3.5-to-1. For every unit of fossil energy needed to produce the fuel over its life cycle, the return is 3.5 units of energy, according to new research conducted at the University of Idaho in cooperation with the U.S. Department of Agriculture (USDA). The announcement of the increase—up from 3.2—was made today at the National Biodiesel Conference & Expo in Orlando.

The Department of Energy National Renewable Energy Lab (NREL) and USDA had produced the first comprehensive life cycle inventory for biodiesel in 1998. That landmark research found a 3.2 energy balance for biodiesel, while petroleum diesel yielded only 0.83 units of energy per unit of fossil energy consumed. The many changes that have occurred in the U.S. biodiesel and agricultural industries since the 1990s prompted researchers at the University of Idaho to update the study in cooperation with the USDA. Both the 1998 and 2007 study are based on biodiesel production from soybeans, which according to U.S. Census data is responsible for more than 80 percent of 2007 estimated biodiesel production. Biodiesel’s energy balance improved in the 2007 study even though the new analysis is more comprehensive than previous work, and even extends to the energy required to manufacture the farm machinery used to produce soybeans.

“The bottom line is that the energy balance of biodiesel has definitely improved in the last decade,” says University of Idaho Department Head of Biological and Agricultural Engineering Jon Van Gerpen, who credits Assistant Professor Dev Shrestha and graduate student Anup Pradhan for their work on the study. “The increase in soybean yields and a decrease in herbicide use greatly contributed to the increased energy balance. Meanwhile, energy used for crushing soybeans is significantly lower than what was reported in the NREL study.”

The researchers found national soybean yield data from 1975 to 2006 shows that the yield has increased at the rate of 0.6 bushels per acre per year. Yet, the fertilizer application rate has essentially remained the same and the herbicide application rate has declined to one-fifth of its rate in 2000. Reduced herbicide applications have the added benefit of requiring less diesel for field spraying.

At the processing level, technology improvements at soybean crushing facilities led to 55 percent less energy needed than what was reported in the NREL study. Although transesterification to convert soybean oil into biodiesel has also become more energy efficient, this process only contributes a small fraction of overall energy in the lifecycle analysis.

Today’s announcement came during a conference session highlighting promising feedstock developments, ranging from higher oil content in soybeans to new feedstocks, like algae. The NBB has launched a feedstock development initiative to help the market spur additional sources for biodiesel.

“As demand for biodiesel climbs, having enough feedstock available at a competitive price will continue to be an important issue,” said Ed Hegland, NBB chairman and a Minnesota soybean grower. “Soybean oil will continue to play an important role, but we are also excited about the prospect of algae and other feedstocks on the horizon. A rising tide lifts all boats.”

Biodiesel is a cleaner burning alternative fuel that can be used in any diesel engine. A domestically produced, renewable fuel, it can be made from animal fats or vegetable oil. The use of biodiesel in a conventional diesel engine results in a substantial reduction of unburned hydrocarbons, carbon monoxide, and particulate matter.