Today (July 17th) I spent some time on the phone with POET's VP of Science and Technology Dr. Mark Stowers. (I was also invited up for a visit, but I couldn't swing that just now). Joining us on the call was Matt Merritt, POET's Media Relations Specialist. We covered a lot of ground on the call. Key interests of mine in assessing fuels of any kind are the energy inputs – what kind, how much – and the related topic of logistics. Therefore, I probed this area in some depth, as I consider that the key to the whole thing.

First a bit of background on POET. They are the largest ethanol producer in the world, producing more than 1.5 billion gallons of ethanol each year from 26 production facilities across the country (each with its own nuances, I was told). They recently started up a 20,000 gal/yr pilot-scale cellulosic ethanol plant, which uses corn cobs as feedstock. Plans are to commercialize the process in 2011. They have named this effort Project Liberty.

Dr. Stowers is in charge of company R&D, which includes corn and cellulose to ethanol, as well as the investigation of novel processes for utilizing waste to power their facilities.

My questions and Mark's answers below are paraphrased, but as I told them if they spot anything that I got wrong they can notify me and I will correct it. The format below includes questions, answers, and comments from me. Where the comment was part of the interview, it will appear as a prelude to a question or a comment in the follow-up as "RR: Comment.... Mark's answers will appear as "MS: Comments..." To distinguish from additional comments I might interject, I will indicate those with [RR: Comment...]

I started off by voicing my skepticism that cellulosic could ever make a huge impact, due to logistical issues and energy requirements. That was going to be a major thrust of the interview, but I started off with a related comment/question.

RR: Conditions in Texas have been really dry. We have had over a week with temperatures exceeding 100 degrees each day. There are a number of corn fields near my house, and the fields appear to be dead. How are conditions up north?

MS: Actually this will probably will have one of the best years ever. We got rain when we needed it. Corn grew 6 inches overnight recently. In Sioux Falls right now the temperature is 77 degrees.

RR: OK, let's move on to you process. Can you start by walking me through your cellulosic ethanol process?

MS: Our cellulosic process is based on corn cobs. We have harvested 25,000 acres over the past couple of years. We are currently still trying to work out harvesting and storage. The yield is 0.65 tons/acre, and we can collect commingled with grain with a modified combine. Or we can collect them with stover coming out of the back of the combine. The bulk density for cobs is higher than for stover, and that makes it easier to separate. We store at the farm field edge currently and can collect over the next 6-9 months. We make sure sufficient stover is left on the field for erosion control and nutrition. We are not focused on stover because the bulk density for cobs is better, and cobs have 16% more carbohydrates than the stover. We believe that the nationwide potential is for 5 billion gallons of ethanol if all cobs collected.

RR: OK, I am going to walk through some numbers here. As you may know, I have been skeptical about the potential of cellulosic ethanol to scale very well. I feel that there are niches in which it will work, but I don't think it works well as a large scale solution. From information gathered around cobs (some of which came directly from POET news releases), average cob yields are 0.65 bone dry tons (1300 pounds) per acre.

I have a reference that says the heating value of cobs is about 7900 BTU/lb, so the total BTU value of the cobs on an acre is about 10 million BTUs/acre. The amount of ethanol that equates to 10 million BTUs is 135 gallons of ethanol per acre (ethanol at 76,000 BTU/gal). So that would seem to be an upper limit on a gasification type process that could (theoretically) capture 100% of the BTUs. But of course enzymatic processes are not going to convert lignin, and there will be some inefficiencies. My guess is that you probably need 20 pounds or more of cobs to produce a gallon of ethanol, putting the actual yield at around 65 gallons per acre. I saw someone (not POET) who recently claimed cellulosic from corn cobs would increase per acre yields by about 110 gallons per acre, but based on the BTU value I don't think that's possible.

MS: Yes, I think that 110 gal/acre number looks too high. The 20 pound number you came up with looks approximately correct. We get 85 to 110 gallons of ethanol per ton. We are drying and burning the lignin for fuel, but in addition to the cellulose we are also converting the hemicellulose to ethanol.

RR: What is the percentage of cellulose and lignin in the cobs?

MS: The cellulose plus hemicellulose is upwards of 60%. Lignin is about 15%.

RR: One of the keys to success for a cellulosic ethanol process is to increase the concentrations of ethanol in the crude product. Historically this has been in the 3-4% range, and I don't believe that will be commercially practical. The energy required to purify a solution in that range would be comparable to the energy contained in the ethanol. [RR: Of course with waste heat or very cheap BTUs, you might be OK to do it anyway]. So can you discuss the sorts of ethanol concentrations you are getting?

MS: First of all, I agree with your comments on ethanol in the 3-4% range. While we have not released information on our titers, they are lower than those for corn ethanol. On the other hand we have some of the highest titers in the business; we can achieve greater than a 20% ethanol solution from corn. We are better than the 4-5% range for our cellulosic process. Also, there is sufficient energy in the solid waste stream and the liquid stream to provide more than enough energy to power our cellulosic process.

RR: Don't you have problems with the enzyme activity diminishing at higher ethanol concentrations?

MS: We do not see enzyme activity as a rate limiting step with respect to ethanol tolerance.

RR: Beyond the energy required to process the cellulosic ethanol, there is the fuel required to gather and transport the corn cobs. Along those lines, one of my readers wondered about the radius to the plant in which the logistics be economical? His comment was that he heard that shipping costs for cobs are twice as costly as the grain because they are so bulky.

MS: We can go out to a 25-35 mile radius; about the same as corn.

[RR: I suspect if you did the analysis for cobs by themselves, collecting cobs and transporting them from 35 miles away might not be worth the fuel value of the subsequent ethanol produced.]

RR: Do you have a feel for how many BTUs of energy is required to produce a BTU of cellulosic ethanol?

MS: We have some idea of those numbers, but haven't released them. [RR: I think he said they are waiting for more results from their pilot plan, and they are working on getting better numbers.]

RR: Another question from a reader: "Will they contract with producers and what will the terms be?" I think I know the answer to this, because I read an article yesterday in which Poet spokesman Nathan Schock said that this hasn't been determined. [RR: Here is the article: Iowa plants to offer farmers cash for corn cobs.]

MS: Nathan was correct; we have contracted with some farmers for fall harvest but we don't know where the economic sweet spot for everyone involved is going to be.

RR: I would think you would hold those numbers close anyway, or all farmers will be holding out for the highest published price.

MS: Yes, that is a key point.

RR: (I asked if a reason for focusing on cobs over stover was related to concerns about soil depletion. I also incorporated another question from a reader:) "Ask POET what they think of cellulosic from corn stover. They seem to say that stover has too many collection and handling problems (dirty, low density, etc), and that is one reason they are concentrating on cobs only. Many others assume corn stover will be the primary source of cellulosic feedstock."

MS: We don't have to leave all stover behind necessarily; we have just chosen to focus on cobs. How much one can remove depends on soil type, location, and tillage practice. Cobs take those variables away.

RR: Is your ethanol purification compatible with existing corn ethanol infrastructure? I would think that with a higher water concentration you could go into your corn ethanol distillation system, just at a lower feedpoint.

MS: A cellulosic plant will be a bolt on to an existing corn ethanol plant. But we will have a better efficiency if we don't intermingle the streams with corn ethanol because we don't want to get things like lignin in our corn ethanol distillation train. So it is better to have separate distillation trains. The infrastructure will be more of what you see in common (utilities, logistics in and out, etc.).

RR: Why not just use the cobs as fuel for the corn ethanol process? Have you done comparative studies on that?

MS: We are doing that today as well. We are using other renewable biomass to fuel a solid fuel boiler at Chancellor, South Dakota. This is a 100 million gal/yr facility. We are also using landfill gas in a multi-purpose boiler.

RR: What is the quality of the methane from your digestor?

MS: We have two applications for our biogas. One is for overall energy, and the other is feedstock for the dryers. We are just finishing up 3rd month of operation. The boiler that we have developed can handle the biogas that is produced.

RR: How many engineers on Project Liberty?

MS: Between the lab and pilot plant, we probably have 25 scientists and engineers.

RR: Is your pilot unit fully integrated? Is the pilot process fully connected?

MS: We are completely integrated from cob collection through ethanol production and recycle streams. We have a 24/7 operation with 4,000 data points collected. The pilot plant has been running since about Nov 18, 2008.

RR: One of the things that I strongly believe is that if the corn ethanol industry is ever going to break free from endless subsidies, you have to get the fossil fuels out of the process to the greatest possible extent. The sugarcane guys are more immune to the ups and downs of fossil fuel prices because of the large role bagasse plays in providing fuel for the process. So it feels like you are headed down the right path here. However, it can be that you might have enough waste energy to fuel your process, but most of the BTUs are used up in the conversion, leaving very little ethanol. So then the question becomes, "Are you left with a small net amount of ethanol, or a very small net amount of ethanol?"

MS: The energy from our waste streams should be sufficient to power the 25 million gal/yr cellulosic plant and nearly power the 50 million gal/yr starch plant next door.

[RR: To me this was the most significant statement he made during the interview. If an added benefit is that you are also powering your corn ethanol plant with the energy produced from the cellulosic process, you have a very powerful synergy.]

RR: When you are out front with a technology, there are always risk factors. What are some of the risk factors that you have identified that might keep you from meeting your goals?

MS: First is the absence of a market for cellulosic ethanol. The blend wall from E10 really limits the cellulosic market.

RR: OK, that's market risk. How about technical risk?

MS: We must have farmers and equipment manufacturers engaged; we need a solution in which both sides can make money. We need programs early on to help biomass collectors overcome the risk. How many cobs can you get in a truck? The logistics become important. There is also the issue of inventory management. The annual supply of cobs for a 25 million gal/yr cellulosic plant would require a silo the size of the Empire State Building. We need to decentralize this, and we need as high a throughput into the reactor as possible.

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