Biodiesel, Green Diesel, and Jet Fuel

It is annoying to me that the definition of cellulosic ethanol has now been officially coopted in last year’s energy bill to include gasification processes. To me, that’s like redefining the definition of ‘birds’ to include ‘bats.’ This is all about marketing the ‘new’ cellulosic brand. But cellulosic ethanol has a 40-year history, and is distinct from biomass gasification (as I explained here).

Lately I have seen the definition green diesel made from hydrocracking processes creeping into the definition of biodiesel. While green diesel is a ‘bio’-diesel, it isn’t biodiesel. I have explained the differences here. But I just saw the distinction blurred again today in a story:

Using Plants Instead of Petroleum to Make Jet Fuel

Chemical engineers in North Dakota have successfully turned oil from plants—canola (rapeseed), coconuts and soybeans—into jet fuel indistinguishable from the conventional kind, according to U.S. government tests. Working with the U.S. Department of Defense’s Defense Advanced Research Projects Agency (DARPA), scientists at the Energy & Environmental Research Center (EERC) at the University of North Dakota turned these plant oils into fuel that had a similar density, energy content and even freezing point.

“It’s got a freeze point of –47 degrees Celsius (–52.6 degrees Fahrenheit). Anyone familiar with biodiesel can tell you that’s no small feat,” says chemical engineer Chad Wocken, EERC environmental technologies research manager. “It’s processed so that it contains only the same hydrocarbon molecules present in petroleum fuel.”

Although he declined to explain the exact details of the process, Wocken says it is thermocatalytic—in other words, the engineers heat the plant oils in the presence of an undisclosed catalyst to create a slew of petroleum products. In fact, the process is not unlike conventional oil refining in that it produces everything from the kerosene used as aviation fuel to regular gasoline.

It’s no small feat primarily because it isn’t biodiesel. Don’t count on getting a tax credit for it, though. Congress in their infinite wisdom decided to continue giving conventional biodiesel priority over hydrocracked green diesel. But don’t get me started.

While I don’t want to downplay what these guys have done, there is a history here. Neste, Petrobras, and ConocoPhillips have been producing green diesel via hydrocracking vegetable oils or animal fats. Green diesel has also been produced via biomass gasification/Fischer-Tropsch by Choren. Further, Neste is already producing the fuel commercially, and is in the process of expanding production.

The novelty of what is being reported upon in the story seems to be the jet fuel aspect. The freeze point of conventional biodiesel is quite high, which makes it unsuitable for use as jet fuel. Green diesel has a much lower freeze point, and while I am not sure if Neste or Petrobras have produced jet fuel (which needs an even lower freeze point than diesel) with their hydrocracking process, they certainly could do so.

3 thoughts on “Biodiesel, Green Diesel, and Jet Fuel”

  1. The part that gets me is the discussion on algal biodiesel. As if you could only make biodiesel out of algae. The discussion is usually complete with references to the challenges with growing high-lipid algae.

    To me that approach is DOA, due to (1) the cold-flow properties (or lack thereof) for biodiesel, (2) the inherent processing costs for making biodiesel (feedstock required: clean lipids, methanol and unreusable catalyst, (3) the fact that even for the high-lipid species you are still tossing 50%+ of the biomass, (4) the fact that growing one uncompetitive species at large scale will eventually prove totally unsustainable.

    Can we take the blinkers off, already? The only way algal biofuel is going to get of the ground, is as an ocean-based system (ask King about investment required for any land-based system, especially those cute clear plastic tubes), with gasification that would allow 100% use of the available biomass, and be unlimited by which species dominate.

    And, as I said before, the step before that needs to be waste gasification, you know, the type our elected prosti… I mean, representatives just decided they won’t fund as long as there is a powerful (vote for me!) Ag lobby around.

  2. NREL, our national center for renewable energy research, in Golden CO, is sadly subjected to the same funding structure that our legislators sell. That’s why innovation doesn’t get very far there. I did an internship there, I used to think liberally about funding alt energy research, now I’m all for leaving it to private funding. When is the last time an innovative process or application that took flight came from NREL? If a process ever does come from NREL, it is essentially given away for free. That would be beneficial, if anything would ever get developed there, in spite of the buracracy. Also, collaboration seems distant from the fenced nerd compound in Golden. That place needs a change!

  3. They can lower biodiesel's melting point to roughly -60F by either heat removal fractionation, or even some special filters to remove the high gelling compounds. This way it's usable in any climate, and it totally tax credit applicable. The only disappointing part is either method obviously uses energy, which reduces the biodiesel's EROI. Gotta crack some eggs to make the omelet I guess (and not hydrocrack! :).

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