Beyond Ethanol
November 4, 2010 § Leave a comment
A recent article in the Economist describes an important new direction for biofuels, namely the pursuit of drop-in fuels. These are synthesized hydrocarbons and can be used directly in any proportion for engines running on gasoline, diesel or jet fuel. The last two cannot be served by ethanol.
As we have discussed in the past, ethanol has about 33% less energy than the same quantity of gasoline. This calorific penalty decreases as we move to higher alcohols. The article discusses ongoing work on the production of butanol. It has 4 carbons compared to 2 in ethanol, so it has more calories. It is very similar to gasoline in calorific content and less corrosive and water absorbent than ethanol, and so a better substitute.
Most of the story is directed to the production of alkanes from sugar. These are straight chain compounds with the formula CnH2n+2. Conventional oil derived fuels have this formula as well. The number n is about 7 to 9 for gasoline and about 12 to 16 for diesel and a bit higher for jet fuel. So, alkanes with the right number are for all practical purposes direct drop-ins for these conventional fuels.
Herein lies the attraction. Also, being tailored, often through genetic engineering, the composition will be predictably uniform. This is not the case for the input to refineries from a variety of crude oil sources. In fact oil refineries today are forced to be very picky about the mix of crude they will accept. Seed based oils also suffer from this variability.
No small wonder, therefore, that many of the leading players in the drop-in biofuels space are supported by major oil companies. The list includes ExxonMobil, Shell and Total – all heavy hitters.
The reliance on sugar as feed stock is of note. Today, Brazil is the only source for economical sugar for this purpose. Tariffs apply only for ethanol; at least for now. So the long term potential for this feed stock can be debated.
One company is even reported to be using sugar to grow algae for diesel. This is quite a departure from the original allure of algal diesel. It was seen as using sunlight and waste carbon dioxide, a sustainability home run of sorts. Now we see folks going to the dark side of algae, literally. These algae are grown in the dark! The photosynthetic part is transferred to the growing of sugar. So we still have the sunlight and carbon dioxide (from the air in this case) put to use.
An interesting twist is the use of existing ethanol plants by some of these companies. This is a good trend, to deploy assets created by a flawed national policy and subsequently idled by realities.
So, what of corn and cellulose? Both are challenged by the fact that the chemical structure renders them more difficult to convert to alkanes. Of the two, corn, while simpler to react, is the worse in part because of water usage. Cellulosic materials such as grasses offer the promise of draught resistance. Price of Brazilian sugar over the long haul will be a determinant.
An interesting avenue for biomass in general is pyrolysis such as practiced by RTI International under DOE funding. This produces a liquid akin to crude oil. Close enough to merit inclusion as a portion of the feed to a refinery. This is the pre-refinery analog to a post-refinery drop-in fuel. Requiring no modification to current practices. A chemical plug and play, as it were.
Finally, the Economist story discusses the place of electric cars in this context. They opine that while alcohol will get trampled, drop-in fuels will survive. In the next thirty years, gasoline will continue to be used to a significant degree. So, ethanol will continue to be used as a means of assuring complete burn of the fuel. This use as an oxygenate came about from the outlawing of MTBE, but is only needed at the 6% or so level. Beyond that, ethanol is a liability on many grounds and will probably fade away.
But drop-ins will hang around a lot longer. The Beyond Ethanol story will feature electric cars but drop-ins will get serious second billing.
Flexi-Fuel Fairy Tale
December 11, 2008 § Leave a comment
The Utopian State, known the world over as the US, was in the throes of a dilemma. Much maligned for not doing enough to limit carbon dioxide emissions, it developed a plan that seemingly in one fell swoop tackled global warming associated with automobile emissions while at the same time reducing import of oil from nations, some of whom were deemed unfriendly, at least in the rhetoric of elections.
This solution was known as the 20/10 plan. The goal, to replace 20 percent of gasoline with ethanol in 10 years, was seen as visionary, if for no other reason as that 20/10 was about as good as one got with vision. However, even before vast quantities of alcohol had been consumed, a hangover of major proportions was in the making. Therein lies the tale.
The Utopian State, as befitted its name, was inclined to believe that the public would recognize a really good thing when they saw it. They especially believed in the maxim: If You Build it, They Will Come, because said maxim was irresistibly derived from the powerful combination of Kevin Costner, the National Sport and mysticism.
So they built it, a complex web of subsidies to farmers, automobile companies and refiners, and tariffs on imported ethanol, all designed to produce domestic ethanol to blend with gasoline, and vehicles that would run on the stuff. In a nod to perceived consumer preferences, they incentivized the auto companies to make flexi-fuel cars, capable of using regular gasoline and also E85, a blend with 85% ethanol.
They even created demand for these cars by ordering their agencies to use them and mandating the use of the new fuel. Waivers to the mandate were given generously, no doubt in the Utopian belief that said waivers would not be sought if not merited. It seems that some of these outfits are seeing a net increase in gasoline usage (Washington Post: Problems Plague U.S Flex-Fuel Fleet, Oct. 23, 2008), a result contributing in no small measure to the aforementioned hangover.
At the core of Utopian belief is that folks will “do the right thing.” So, purchasers of flexi-fuel vehicles were expected to purchase E85, even from filling stations some distance away, ignoring the fuel consumption getting there and back. Then word filtered through that E85 delivered 28 percent fewer miles per gallon. In short, it was more expensive to use and harder to find. They started filling up with regular gasoline because the flexi-fuel vehicle allowed that; filling stations noted the drop in volume and stopped stocking E85.
In time, it became apparent that the federal policy and legislation underestimated, or ignored, the fact that even in the US only market-based policies function. Into this nightmare scenario stepped in Prof. Wunderbahr from a prestigious eastern university, with an engine design that delivered a small car running on E85, delivering fuel economy and the muscle of a larger vehicle. The design took advantage of the high octane number of ethanol (113 versus 87 for regular gasoline), which allowed effectively high compression ratios, which in turn improved the efficiency of combustion. The result was elimination of the gas mileage penalty from using ethanol, increased power for an engine of given size, and retention of the improved emissions associated with ethanol usage.
Auto makers vied with each other to retool and produce these cars without any federal incentive because the public actually wanted them. Fuel distributors rushed to install E85 pumps and realized that this was simply achieved by eliminating one grade of fuel. They came to the realization that all vehicles on the road today specify either 87 or 91 octane. A third grade was not needed, and the third pump was now available with modification to dispense E85. The US government, not wanting to be left out of this, set policies to further these steps. Ethanol from sources non competitive with agriculture became cheaply available. All was well again.
And then they elected a new President who resolved never again to set policy that was not market-based. The country united behind him on this and it was never quite the same again. The country was henceforth known as the United States.
Research Triangle Energy Consortium 