Revisiting the Energy Return and Merits of Soybean Biodiesel

In the current issue of Scientific American, there is an article with nice multiple graphics to educate people about today’s higher cost of producing energy as measured by the EROI. Energy return on investment (EROI) is the value used to represent the energy obtained per unit of energy spent to obtain it. The article titled, “The True Cost of Fossil Fuels,” is written by Mason Inman, who is writing a biography of geologist M. King Hubbert, the “father of peak oil”.

Inman explains that even though much of the easy-to-extract oil is already gone, the average EROI of conventional oil, at 16, is still far higher than that of other liquid fuels. As we go after oil from more difficult places, however, that number continues to fall. He tells us that 5 to 9 is the minimum EROI required for industrial societies to function economically.

The following graphic (using Inman’s EROI values) puts some of today’s liquid fuel sources into perspective:

As shown, corn ethanol is on the bottom of the heap for the EROI of the included liquid fuels, at 1.4. Irrigated corn produced in Nebraska would be even lower. And corn ethanol is not even close to fitting into the 5 to 9 required economic range, which is why it would not survive without the infrastructure subsidies and mandates that it has been afforded. This is why I rail against it here so often, assuming that my readers are familiar with this low EROI fact. It is not good to do so much damage to our environmental and exhaust our agricultural resources to produce a product which offers us nearly nothing in return.

The point of the Scientific American article is to show us which energy sources are the most economically feasible, which are the most worthwhile to pursue, and which hold the most promise for a sustainable future. It also includes graphics on electrical production and vehicle mileage return on investment.

As our industrialized nations spend more and more for fuel, we have less to spend on other societal needs. If governments such as ours pick winners through mandates and politics, we find ourselves pouring valuable time, money, and natural resources into a poor EROI product like corn ethanol. For such a serious subject as energy, on which every aspect of our lives depend, wasted efforts are not what we need. In addition, the sobering related economic realities mean that it is not a good time to be blowing bubbles in our monetary policy or having to work through the aftermath of a debt crisis. Corn (and cellulosic) ethanol mandates have unfortunately been a political opportunistic sideshow, distracting and diverting resources away from solutions that might have better potential based on real energy physics.

Now, back to the point of this post, the energy return of soybean biodiesel.
Based upon an informal Google search that I did of recent articles on soybean biodiesel, it seems that the current energy return value of 5.5 for soybean biodiesel is poorly known, as it is common to continue to see values of 1.9 to 3 given, instead. The study reporting the FER value of 5.5 came out in 2011 from an American Society of Agricultural and Biological Engineers publication, Energy Life-Cycle Assessment of Soybean Biodiesel Revisited by A. Pradhan, et al. (FER stands for Fossil Energy Ratio which is the energy delivered to the consumer divided by the fossil energy inputs. Inman uses the FER value as “EROI” in the above graph.)

The 2011 ASABE paper cited above explains to us that the greater efficiency in the production of soybean biodiesel has been achieved through improvements in soybean yields, energy savings from using no-till, and more energy‐efficient soybean crushing and conversion facilities. It used 2006 data, which showed an improvement from 4.6 in a previous study that used 2002 data, and from 3.2 in the study prior to that which used 1990 data. If we had an up-to-date study, we’d be safe to assume that today’s energy return for soybean biodiesel —absent a drought— would surpass 5.5. And, according to, U.S. seed technology companies are projecting that current soybean yields will double by 2030.

While corn ethanol is struggling and never has made energy sense, there are conditions today which favor the increase of soybean biodiesel production. Soybean biodiesel is classified by the EPA as an advanced biofuel. Americans have watched with dismay as the EPA has had to erase its ongoing unrealistic mandates for the unscalable product, cellulosic ethanol, year after year. Might this failed policy redirect towards more soybean biodiesel production, since it qualifies as an advanced biofuel already?

Growing soybeans using no-till and a cover crop uses less water and fertilizer than input hungry corn, making it the lesser of two evils if you dislike monoculture crops.

As an added bonus, biodiesel can be used as heating oil.

The EPA requires that 1.28 billion gallons of biodiesel will be blended in 2013. About 60 percent of U.S. biodiesel feedstock is currently from soybeans. (Other feedstocks are industrial grade corn oil, canola oil, animal fats and tallow, and recycled cooking oils and grease.) This year’s biodiesel will require 11.6 million soybean acres, equivalent to 15 percent of all U.S. soybean acres. Compared to corn ethanol, the EPA’s mandated use for next year is 13.8 billion gallons, which will require approximately 32 million acres of corn. One acre of soybeans will produce about 63 gallons of biodiesel, whereas one acre of corn will produce 423 gallons of ethanol. In 2011, 29 percent of U.S. crop area was planted to soybeans and 35 percent to corn.

In the E.U., rapeseed provides two-thirds of the input for biodiesel production and the amount that soybeans can provide is capped at 1 million metric tons because of the food vs. fuel debate. Soybean biodiesel promoters argue that biodiesel is a valuable use of soy oil, and that the food portion of the bean is still entirely utilized as feed or food.

Obviously, the two products of ethanol and biodiesel are used differently, and each has its own set of challenges. Ethanol found its foothold as a replacement for MTBE, but as fuel it contains 34 percent less energy than the gasoline which it replaces. In comparison, biodiesel is just 8 percent less energy dense than petroleum diesel.

In conclusion, the sobering bottom line is this…. A 2006 Proceedings of the National Academy of Sciences study told us, “If all American corn and soybean production were dedicated to biofuels, that fuel would replace only 12 percent of gas demand and 6 percent of diesel demand.” That is why, when land use considerations are made, higher lipid dense micro-algae biodiesel holds far more promise than any other biofuel, but actually producing it on any kind of scale —so far— appears to be just another fairy tale.


How to Measure the True Cost of Fossil Fuels – As oil becomes more expensive, determining where to invest energy to get energy is increasingly important. By Mason Inman.

Behind the Numbers on Energy Return on Investment. A full listing of the sources and references behind the calculations in this EROI infographic. By Mason Inman.

6 thoughts on “Revisiting the Energy Return and Merits of Soybean Biodiesel

  1. Jardinero1

    One question: Were the soybeans in the study Roundup Ready?

    All kidding aside, I have a few observations and I welcome corrections if I am mistaken:

    1. Coal is conspicuously absent and it enjoys a mighty high EROI, higher than oil.

    2. EROI is a dynamic value. As refining and processing becomes more efficient, so rises the EROI. Increased refining and processing efficiency is a by-product of R&D and the money invested in R&D. So, at some point, all roads lead back to where a dollar of investment will provide the most yield on EROI. The proverbial, “most bang for the buck.”

    That being the case, it would make the most sense to invest R&D money in efficiency improvements where there already exists a high ROI, like oil and coal. As a hypo, if you can invest a dollar anywhere, and that dollar will buy you a ten percent improvement in EROI, wherever you invest it; then a dollar in coal or oil will buy you much more EROI, than a dollar invested in corn ethanol or soy bio-diesel.

    3. It also seems to me that the obverse of EROI, is the efficiency of the burn, on the consumption side. Higher fuel efficiency in autos, power generation, et cetera, multiply the EROI of any given fuel source. So again, instead of investing money on increasing the efficiency of corn ethanol production you might be better off investing R&D money in efficiency improvements on the consumption side of autos, power generation, et cetera.

    1. K. McDonald Post author

      Agreed. I’m coming at this subject while working with the known mentality of our policy makers, who are determined to produce biofuels at any cost. And I’m trying to anticipate where policy may be headed.

      Coal was listed by Inman in his graphic on electricity production EROI, by the way.

      Our greatest potential for gains in the near term lies in efficiency gains, however, something we haven’t been very good at until lately — like you say.

  2. D O'Connor

    The problem with these EROI analyses is that don’t compare like products.

    You can’t burn crude oil in a vehicle, so at the very least you need to include the refinery in the system, if not all of the tramsportation system for getting the crude oil to the refinery, the products distributed etc.

    If you do this properly you will find that gasoline and diesel fuels have an EROI of less than 5, which is outside of the supposed economic range. If you look at some oil sands to gasoline or diesel systems you find values of less than 2, and yet companies are investing billions of dollars into these resources with the expectation of getting an economic return.

    1. K. McDonald Post author

      Thanks for the link, Scott. You are the go to person to analyze the mathematics of how this policy plays out. The other idea is that biobutanol made from corn will enter the scene.


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