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Posts Tagged ‘ethanol’

Let’s take a second and consider what a sensible energy policy would look like. I know, in the current political climate it’s a bit like talking about the tooth fairy’s hair color. But here it is:

I have a big problem with the implicit idea in current energy policy that ethanol is the new holy grail of fuels. What makes ethanol so great? Specifically, compared to an existing fuel (say gasoline), how does ethanol compare. On the plus side, ethanol has a high octane number. That’s about it.

On the negative side, as Stein pointed out, ethanol has only 2/3rds of the energy (per unit volume) that gasoline has. Ethanol burns with a colorless flame (dangerous!), which is why E85 contains 15% gasoline. The problem is that ethanol increases the vapor pressure of the mixture, leading to more evaporative loss and emissions. Ethanol also has this nasty habit of absorbing water, causing all sorts of corrosion issues. Hence, you need to replace pretty much the entire fuel-related infrastructure (storage tanks, pipelines and vehicles) for widespread ethanol use. Before Uncle Sam starts signing those checks, it is worth asking: Is there an alternative? Let me rephrase that: What does the ideal fuel of the future look like?

Well, of course, the ideal fuel would be renewable, and available in significant quantities, unlike any food-based fuel. It should also be miscible with existing fuels; in other words, it shouldn’t do any of the things ethanol does. It should also not change the physical properties of the blended fuel; unlike the way, biodiesel can cause gelling even at low fractions. In a word, the ideal fuel looks like something we are all familiar with: gasoline (or better yet, diesel).

Hang on, you say, gasoline isn’t renewable. No, but it can be. And it looks increasingly like (plain old crude-based) gasoline is at least as renewable as corn ethanol. Clearly, the challenge is not to come up with some new fuel: Ethanol! Biodiesel! Bio-butanol! Or the dumbest of all: Hydrogen! No, the real challenge is to make pretty much the same fuels from a different feedstock than crude. Preferably a renewable feedstock. So, what does the ideal feedstock look like?

The ideal feedstock should be plentiful, cheap, and renewable. And by renewable, I mean that using it should not involve taking the food of somebody’s (anybody’s) table. BTW, it does not have to be carbon-free. Even Al Gore will agree, as long as it’s renewable you are only returning CO2 to the atmosphere that was there to begin with. And, as our ideal fuels showed, there are many benefits to carbon-based fuels.

Here’s the good news: the ideal feedstock is everywhere. It is often cheaper than zero dollars per gallon: we typically pay people to take it off our hands. The ideal feedstock is WASTE. And other than metals, glass and other inorganics, any waste would work. So how much waste are we talking about?

ethanol_fuel_diagram.gif

According to USEPA (quoted indirectly) Americans dump 232 million tons of municipal solid waste a year. If you add up paper, food waste, wood and yard trimmings, the renewable (biomass) fraction is ~61%. Seeing as “other” includes rubber and textiles, the bulk of that would be organic (if not renewable). So subtracting metal and glass, the organic fraction is just over 87%. The EPA estimates that approximately 6.9 million [dry] tons of sewage sludge biosolids were generated in 1998. Then there is of the order of 35 million tons per year of manure. Lots of waste.

I know what you are thinking, and here I have to disappoint. All these wastes combined can only produce about half the oil the country uses. Still, it’s a lot of oil.

Critics may point out that much of these wastes go to composting and other recycling facilities. It should be remembered that even after one has converted these wastes to liquid fuels, much of the fertilizer value remains in the char – available for use.

And no, this isn’t perpetual motion. We are not going to waste our way to independence from our “allies” in OPEC. For every kWh (or BTU if you must) of waste that goes into waste, one can only recover ~60% as liquid fuel, at best. So, conservation still beats any other alternative.

By now, you should be thinking: yeah, but where is the technology that’s going to do all this? Surprisingly, the technology is at least as developed as cellulosic ethanol (I know, that sets the bar pretty low. I just couldn’t resist).

In the town of Carthage, MO, is a stinking plant that converts turkey waste (all the inedible) into a heavy diesel fuel. They used to refine it to a vehicle fuel quality, but as you can imagine, at 500 bbl/d you can’t operate a refinery at a profit. The cost? $80/bbl. And that’s after paying the equivalent of $20-30/bbl for the feedstock. We really should stop feeding this crap to farm animals.

In Freiberg, Germany, a company by the name of CHOREN, is building a facility that will produce ~2,000 bbl/d of diesel from forestry waste.

In Soperton, GA, Range Fuels is busy building a facility that will convert forestry waste into mixed alcohols (including some ethanol). For political (subsidy?) reasons they are calling it cellulosic ethanol. But the process is miles away from the inefficient fermentation-distillation process that most cellulosic ethanol researchers are working on.

You should also bear in mind that none of this will work if oil sells for $10/bbl. So, as I tried to explain in a previous post, we really need expensive oil for renewable energy to fly.

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