Back when I worked in a refinery, I used to spend a lot of time thinking about how biomass would behave in certain refining processes. A fluidized catalytic cracker (FCC), for instance, takes oil and subjects it to heat and a catalyst to fracture larger hydrocarbons into smaller ones that can serve as gasoline blending feedstock (among other things). Another refining unit is a delayed coker. Very heavy oil is subjected to even higher temperatures than in the cracker, and once again the hydrocarbon chains are cracked into smaller molecules useful for further processing into gasoline and diesel. Petroleum coke, similar in appearance to coal, is also produced.
Given the extreme conditions of these units, either of them should be able to break biomass down into much smaller fragments. I wondered about this for several years, but then in 2007 I saw an interesting announcement that a Vinod Khosla-backed company called KiOR was actually working on this sort of approach:
Khosla Ventures and BIOeCON form KiOR to commercialize cellulosic ethanol
I had forgotten about the misleading title of that particular story. While I used to wonder about what would be formed if biomass was fed to a catalytic cracker, I knew one thing that wouldn’t be formed: Cellulosic ethanol. This was a bit more of the marketing craze that caused all sorts of biomass conversion processes to be called “cellulosic ethanol.” Regardless of the misleading title, the story was intriguing. I blogged about it at the time:
After that, I continued to think a lot about the process itself, but didn’t hear much more until this past week, when suddenly a number of people e-mailed to ask about this:
“Biofuel company Kior said on Monday it has secured a $75 million loan to build five plants in Mississippi that will convert wood chips into a petroleum replacement.
The Pasadena, Texas-based company expects to build three of five planned facilities over the next five years. The package from the state also includes state assistance on infrastructure and worker training.
Kior stands out from many biofuels companies in that it is making a petroleum replacement, rather than ethanol. That means its product, which it is now making at a demonstration plant in Texas, can be shipped in pipelines and treated in existing refineries to make gasoline or diesel equivalents.”
So, they have decided they won’t be making ethanol after all. Now, in fact, they are highlighting that point.
So what will they make, and what are the potential stumbling blocks? Let’s dive into that.
When biomass is heated up rapidly to 500 degrees C, fast pyrolysis occurs. The cellulose, lignin, and hemicellulose break down in seconds into a pyrolysis oil and char. The char can be burned to provide the heat for the process, which means the process could be run with little to no fossil fuel inputs.
The pyrolysis oil that is produced is distinct from hydrocarbons, such as those that make up crude oil. Whereas hydrocarbons are composed of just hydrogen and carbon (methane, the simplest hydrocarbon, is CH4; one carbon atom with four hydrogen atoms attached to it), the compounds of pyrolysis oil contain a lot of oxygen. These compounds include aldehydes, carboxylic acids (like acetic acid), ketones, alcohols, sugars, and pyrolytic lignin, and their volumetric energy content tends to be far lower than that of petroleum.
Pyrolysis oil has some characteristics that make it challenging to use as a fuel. Pyrolysis oil is quite acidic, with a pH ranging from 1.5 to 4. The oil also polymerizes over time unless it is stabilized. However, some companies have managed to overcome these challenges, and pyrolysis oil has some promise for electricity production. One company in Canada, Dynamotive, incorporated a 2.5 megawatt turbine to produce electricity from pyrolysis oil at a plant in Ontario, but it isn’t clear whether that approach has been successful (Source).
Pyrolysis oil may also be upgraded into transportation fuel. The company UOP, which among other things licenses technology to refineries for upgrading crude oil, entered into a joint venture in 2008 with Ontario-based Ensyn Corp. (one of the leading pyrolysis companies) to upgrade pyrolysis oil to transportation fuel. The joint venture is called Envergent Technologies, and was selected as a recipient of a $25 million DOE grant to demonstrate pyrolysis oil upgrading technology at a Tesoro refinery outside of Honolulu. (See this press release).
Pyrolysis oil components tend to be relatively short, and when the oil is processed in a cracker the chains get even shorter. So about half of the oil is lost to carbon dioxide and water, another 15% to light gases, only about 30% is converted to gasoline, and another 8% to diesel (these are published results from UOP). Given that the biomass yield to pyrolysis oil is about 75%, that puts the biomass to gasoline yield at 22.5% (by mass) — and that is with the addition of 5 weight percent hydrogen. Still, that is around 70 gallons per ton of biomass, which is comparable to several other biomass conversion technologies.
KiOR’s process reportedly impregnates catalyst within the biomass, and when it is fed to the FCC it cracks the biomass and then partially upgrades the oxygenated components to hydrocarbons. So what they reportedly produce is not a conventional pyrolysis oil, but instead a pyrolysis oil that has at least been partially upgraded.
Questions for KiOR
In order to evaluate KiOR’s technology, there are some specific questions to ask. First, what is the composition of the oil coming out of cracker? How does this compare to conventional pyrolysis oil? (KiOR’s U.S. Patent Application number 20100105970 says that most, but not all, of the oxygen has been removed). What is the biomass cost assumption built into the model that says the oil is competitive with $70 crude oil?
How small do the particles need to be before feeding into the cracker? (The energy required to grind biomass to fine particles can be substantial; KiOR’s U.S. Patent Application number 20100209965 mentions the use of circulating sand to reduce the size of the biomass). How is the catalyst impregnated into the biomass (feeding crude oil into an FCC is one thing; having to impregnate biomass and then feed it in will be more costly and time-consuming)?
One potential issue is the need to transport the oil from the FCC to a refinery. In a conventional oil refinery, the product that comes out of the cracker goes right into the other process units. I think that’s the model that KiOR would like to adopt, because if they have to ship the oil off-site for processing, that will seriously hurt the economics of the process.
I have also seen a great deal of misinformation in various press releases about KiOR’s process. For instance, I came across this:
“KiOR wants to take biomass – in this case wood chips from local timber – and use a catalyst to chemically turn it into a near-perfect match to crude oil in a matter of seconds. The product then can go through existing crude refineries and be used to make standard gasoline or diesel fuel.
“They’re going to do what it takes millions of years for Mother Nature to do in a matter of seconds,” Gov. Haley Barbour said.
KiOR officials say one barrel of the new oil can make more gasoline and diesel than standard crude, and it will burn cleaner, releasing just 25 percent of the amount of emissions into the air.”
Something may have been lost in the media translation, but there are several things wrong with this short excerpt. First off, it isn’t a “near-perfect match to crude oil.” It is partially upgraded pyrolysis oil, which will be quite different from crude oil. Second, one barrel of this oil can’t possibly make more gasoline and diesel than standard crude. This isn’t just something I doubt, it isn’t physically possible.
Biomass contains far too much oxygen, and that ends up as a lot of carbon dioxide and water during the upgrading process. This is why UOP’s yields to transportation fuel are in the 20% range instead of the 80% range. Conventional crude oil is almost pure hydrocarbon, so almost all of the barrel (90% or more) is turned into finished products (gasoline, diesel, jet fuel). The gasoline yield from crude oil will certainly be much higher than the gasoline yield of the KiOR process. (That’s not a knock against the process; just a misconception that should be corrected).
Finally, gasoline from biomass doesn’t release just 25% of the emissions relative to gasoline from oil. Whether gasoline is produced from biomass or fossil fuels, the release of emissions into the air when they are burned will be about the same. The difference is that the biomass incorporated recently atmospheric carbon dioxide during the growing cycle (whereas oil incorporated ancient carbon dioxide), so the net impact can be lower emissions — depending on how much energy it took to process the biomass. But it seems to be a common misconception that the emissions themselves from gasoline derived from biomass would be lower.
Does the process have potential? Yes, I would have to say that it has potential and this is one of the more promising approaches that Vinod Khosla has helped to develop. Is there a lot of hype and misinformation in the press releases? Yes, there is. What I have attempted to do in this essay is explain some of what is going on, and also to point toward the questions to ask when evaluating the process. Ultimately, the factors that will determine their success are the logistics of getting biomass into the plant and getting their oil processed into transportation fuel, the quality of the oil they produce, and the capital cost of the plant. (FCC units aren’t cheap, and this process adds steps to the conventional FCC process).
Can they compete with well-established companies like Ensyn or BTG-BTL companies that already have operating units? Ensyn has a big advantage in this space, having run pyrolysis units for over 20 years (one of which I have visited in Ontario). With Ensyn’s partnership with UOP to upgrade their pyrolysis oil — and over 20 years of pyrolysis oil experience under their belts — they are several steps ahead of KiOR in the path to commercialization.
On the other hand, KiOR’s use of catalytic cracking is a different spin on conventional pyrolysis, and success versus an Ensyn will ultimately be determined by any economic advantages of the oil KiOR produces. Both Ensyn and KiOR require further upgrading of their oil to transportation fuel, so the cost of upgrading KiOR’s oil will have to be substantially less to warrant the extra capital outlay for the catalytic cracker.