Cellulosic Ethanol Primer: Let’s Call it “Celluline”

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Sheesh. It seems that everybody and their brothers are ethanol experts these days. But what drives me nuts is that when people are talking about ethanol, they don’t seem to know what type of ethanol they’re talking about.

It’s sad because the widespread misinformation and misunderstanding is killing popular opinion for biofuels in general right now and, in particular, mercilessly destroying the good name of the second generation of ethanol — cellulosic ethanol.

The truth of the matter is that cellulosic ethanol will be made from non-food sources (miscanthus, switchgrass, wood waste, and even garbage) that can be grown on marginal land or is already a waste byproduct of society.

The production of cellulosic ethanol could have huge benefits beyond energy independence:

Q: So, If cellulosic ethanol has so much promise, why is it being beaten down by public opinion before its even left the starting gate?

A: Because only a very small portion of society actually understands that there’s a huge chasm of difference between cellulosic ethanol, and ethanol made from corn or petroleum.

If we start our analysis at the beginning, I believe one of the main barriers to public acceptance of cellulosic ethanol is its name — it’s meaningless, incomprehensible and virtually unpronounceable to anybody but scientists, policy wonks and the companies that are driving the change.

As a result, it gets lumped into a broad “ethanol” category, because at least the word “ethanol” is pronounceable and generally understood by somebody not completely geeked out, or on the money making side of the venture.

So, here and now, I’m proposing that we stop calling it cellulosic ethanol and start calling it “celluline.” I know my name has no basis in science or nomenclature whatsoever, but who cares? As long as everybody can pronounce it and it has a specific meaning with specific associations, let’s go for it.

Now that we’ve got that out of the way, what the hell is celluline anyways and why is it so different from corn ethanol or petroleum ethanol?

Any kind of plant out there has four basic microscopic building blocks: lignin, cellulose, starch, and sugar. On a microscopic level, these four building blocks are all made of the same compounds and atoms, just arranged in different ways.

  • Lignin: Made up of super long and complex microscopic organic chains that take forever to decompose. A tree that’s been rotting in the forest for hundreds of years is mostly leftover lignin. No animals can digest lignin, but a very few types of microbes can.
  • Cellulose: Made up of “kind of long” organic chains that are not nearly as complex as lignin. Grasses are mostly cellulose. Humans can’t digest cellulose. Some animals, like cows, have specialized microbes in their guts that turn the cellulose into starches and sugars (see below) which the animal can then digest.
  • Starch: Very short chains of linked sugar molecules. Humans can digest starch. Think corn kernels.
  • Sugar: Very simple single or double molecules of carbon, hydrogen and oxygen. Almost anything can digest sugars.

These four building blocks are put together in the plant using energy from the sun, carbon from the atmosphere and nutrients from the soil.

Currently, most of the ethanol in the US is made from corn and a small portion is made from petroleum. This is the way its been for a long time. It seems obvious to me why making ethanol from petroleum is a bad idea, so I won’t cover that.

Corn ethanol is considered a first generation ethanol. A corn kernel is 50% starch when dry. It’s really easy to make ethanol from starch, but not so good because of the food vs. fuel debate and the fact that only a very small portion of the plant is being used to make the fuel.

On the other hand, celluline is made by taking plants with lots of cellulose and lignin (i.e. non-food plants) and turning them into ethanol. This process uses most of the plant with comparatively little waste.

So how is celluline made?

In a nutshell, making celluline is much like making beer (or any other alcohol for that matter). Sugars and starches are fermented into ethanol following these steps:

  • Harvested plant material arrives at the celluline facility.
  • Plant material is pretreated to remove lignin and enrich cellulose. This usually involves some amount of heat and/or acid.
  • The left-over cellulose needs to be turned into fermentable sugars. This involves enzymes (reaction accelerators). The enzymes break the cellulose chains into small sugar bits.
  • The resulting sugars are fermented into ethanol by microbes including bacteria and fungi.

There you go. The underlying celluline process is not hard to get a grasp on. All you need to remember are two sets of four to be able to talk the talk:

  • Lignin, cellulose, starch and sugar
  • Harvest, pretreatment, enzymes, and fermentation

Hope that helps. Obviously there’re a myriad of new developments and company trade secrets that alter the process some, but in the end it doesn’t really deviate from the general outline given above by much.

Right now, celluline is in the research and development stage for the most part, but there are several companies working to start commercial production sometime in the next year, and many companies that are opening pilot test plants in the same time frame.

So, my friends, it won’t be very long before second generation ethanol is replacing corn ethanol with all its promise. In the process, I truly hope that we’ll get rid of the “cellulosic ethanol” tongue twister of a name and adopt something else that clearly indicates the difference between first and second generation ethanol.

Obviously I’m partial to “celluline,” but I could probably be persuaded to get behind another equally simple and catchy name. Anybody have any suggestions?

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Image Credit: Photo from petrr‘s Flickr photostream. Used under a Creative Commons license.

Nick Chambers

Not your traditional car guy.