“Making Advanced Biofuels from Cellulosic Biomass Is Not an Illusion: It is About to Happen”, a Biofuels Digest special report on advanced biofuels
By Biofuels Digest special correspondent Tim Sklar
Overview
On April 4, 2009, C. Ford Runge, a professor of applied economics and law at the University of Minnesota published an “opinion piece” on TwinCities.com website titled “The biofuel illusion”. This article was cited in Biofuels Digest and available to thousands of its readers through a hyperlink. Dr. Runge’s opinions should be of concern to all who are involved in developing biofuels, as many of his assessments appear to be inadequately researched and many of his conclusions, ill founded.
This article highlights those assessments that are most damaging and provides information that can be used to rebut many of the conclusions Dr. Runge has reached.
A case is then made for accelerated development of biorefineries that can convert wood waste into advanced biofuels, as wood waste is a significant and readily available untapped resource and the technology for converting it to biofuels is well advanced. In making this case, issues are presented that will have to be addressed and recommendations made as to what it will take to achieve this objective
The purpose in making this case is to re-enforce the argument that producing 2nd generation biofuels is about to happen, especially if concerted efforts to convert wood waste into biofuels are given high priority.
Revisiting Runge: Assessments and Rebuttals
Runge: “Despite the prospect of technical breakthroughs, none (of the six DOE backed pilot projects using cellulosic materials) have produced biofuels on commercial terms”
Rebuttal: By definition, pilot projects are much smaller than commercial scale projects and are not designed to have produced biofuels on commercial terms. According to a leading venture capital firm, pilot biorefineries on average cost ~$12 million and process 1 ton per day of biomass, demonstration biorefineries on average cost ~$50 million and process 50 tons per day of biomass and commercial scale biorefineries on average cost ~$150 million and process at least 1,000 tons per day of biomass. Only commercial scale plants can produce biofuels on commercial terms, and to date, there are no 2nd generation biorefineries of commercial scale in operation.
Runge: Cellulose sounds good… (but it) has physical properties that make it hard to digest, and digestion is what fermentation into fuel is all about.”
Rebuttal: Cellulosic biomass can be converted into biofuels without fermentation, using a thermo-chemical pathway. This is discussed in some detail as the preferred pathway for processing wood wastes. Further, bio-chemical pathways that use hydrolysis and fermentation are undergoing significant improvements, as new enzymes that are just becoming available are demonstrating much-improved yields and processing efficiencies.
Runge: “Cellulosic ethanol is roughly twice as expensive to produce as corn-based (ethanol)…”.
Rebuttal: Not wholly true. Although it can be conceded that starch-based ethanol is still more economical to produce than cellulosic ethanol at this point in time, most experts believe that increases in conversion efficiency of 2nd generation biorefineries will happen in a few years time. Under development are a number of 2nd generation process improvements that are expected to increase average biofuels yields by as much as 50% while significantly lowering capital costs. Because there are so many promising research and development projects being undertaken and so many recently announced new pilot plants being built, such improvements appear inevitable.
The assertion that cellulosic ethanol is now twice as expensive as corn ethanol may hold true in specific instances, but much has changed. As more 2nd generation biorefineries become commercial scale operations, this alleged cost disparity will surely disappear.
Runge: “…despite decades of research and lots of money, no method of converting cellulose to fuel comes close (emphasis added) to the cost effectiveness of converting either sugar…or corn (to ethanol)”.
Rebuttal: Although at this point in time, no technology of choice has emerged for cellulosic biofuels, there are more than twelve 2nd generation biorefinery projects that are either under construction or about to commence construction in the next two years, having already received funding. These projects use 11 technology variants of three different conversion pathways. Data obtained with respect to the cost of building and operating these types of facilities, combined with the yields that can be expected, indicate that the per-gallon costs of biofuel produced will be competitive to corn ethanol’s cost per gallon. Because the mix and yield of biofuels that can produced by these plants is not uniform, it will be hard to compare their cost effectiveness to one-another let alone to 1st generation biorefineries that use corn. But as shown in the following summary of biorefining pathways, it is highly likely that 2nd generation biorefineries will be cost-effective. The following are approximate metrics that have been calculated for the three established pathways used in producing advanced biofuels:
• The “Flash Pyrolysis” pathway produces bio-oil and is the cheapest process to build and operate, costing ~$2 per mmgpy at an operating cost of ~$1 per gallon. This pathway produces a high yield of bio-oil (170 gpdt), but bio-oil is a low value fuel, with an average selling price 50% less than gasoline.
• The “Two-staged Acid Hydrolysis w/ Fermentation” bio-chemical pathway produces ethanol and furfural and costs ~$5 per mmgpy to build and has an operating cost of >$3 per gallon. This pathway produces an average ethanol yield, of 65 gpdt, but the average ethanol-selling price is 30% less than gasoline.
• The “Two-staged Enzyme Hydrolysis w/ Fermentation” bio-chemical pathway produces ethanol and no secondary products and costs ~$8 per mmgpy to build and has an operating cost of ~$2.50 per gallon. This pathway produces an average ethanol yield, of 75 gpdt, and the average ethanol-selling price is 30% less than gasoline.
• The Thermo-chemical” pathway that uses “Gasification with Gas-to-Liquids Conversion” can produce high value fuels such as ultra-clean diesel and jet fuel and costs ~$7 per mmgpy to build and has an operating cost of ~1.50 per gallon. This pathway produces an average bio-fuels yield, of ~60 gpdt and the average selling price for advanced fuels produced is 50% more than gasoline and 80% to 100% more than ethanol.
Runge: “…who, exactly will grow…switch grass…to supply (cellulosic plants ethanol, given $4 corn?…(and)…Why would farmers…convert their fields to exotic, unproven and sometimes noxious alternatives?”
Rebuttal: These questions suggest that there are no reasons why farmers would grow switch grass in lieu of corn and evinces a lack of understanding about switch grass as a potential source of biofuel.
Dr. James R. Frederick runs an ongoing switch grass research program at Clemson University’s Pee Dee Research Center in Florence, South Carolina. Findings he and his research team have reported provide insights that Dr. Runge has not taken into account. For instance, according to Clemson’s switch grass study findings:
• Switch grass is cheaper to produce than corn, as it requires fewer inputs to produce and is perennial.
• In the first year, most of the costs of producing switch grass are incurred in the establishment of a switch grass crop, the year that yields are minimal, and farmers can be expected to operate at a loss; and,
• By the 2nd year profits will be realized as yields obtained in the 2nd year have been demonstrated to be at least 6 tons per acre, and is predicated on the assumption that the delivered price per ton obtained for switch grass will be the same as wood waste and comparable on a BTU basis to the price of coal.
Dr. Runge remarks suggest that all of the folks that are investing in biorefineries designed to use switch grass will have a hard time being supplied and therefore must be ill-advised. In the next two years there will be at least six biorefineries on line capable of making cellulosic ethanol from biocrops such as switch grass.
(In a review of Biofuels Digest’s fifty hottest biofuels projects a list of sixteen biorefinery projects that are most likely to immediately succeed had been compiled, based on three factors: $ yield/dry ton; maturity of technology being used; and, length of time pilot or demonstration units have been in successful operation. It was found that 6 of these 16 projects would shortly be able to process switch grass into cellulosic ethanol on a commercial scale).
Once these biorefineries are announced, their demand for switch grass will provide the incentive for farmers to grow this crop, and Dr. Runge failed to mention any of them.
Runge: ”There are also bulk handling issues.” And Runge suggests that in order to provide switch grass instead of corn to a biorefinery in amounts needed to produce an equivalent amount of ethanol, it is estimated that “a semi-trailer load every six minutes (would be needed), 24 hours per day”.
Rebuttal: Clemson’s research indicates that the cost of transporting switch grass to biorefineries could be problematical. But they are studying this problem and have concluded that switch grass can be best prepared for transport if it is first shredding, pelletizing or made into briquettes. It appears that the Clemson team is considering the same transportation strategies to reduce transportation costs as those being adapted by timberland harvesters. If this strategy works, switch grass transportation costs would be comparable to the cost of transporting wood waste.
The Case for Converting Wood Wastes Into Biofuels
The primary reason for accelerating development of biorefineries that can convert wood waste into advanced biofuels is to take advantage of this readily available material and a proven technology to produce significant amounts if biofuel in the shortest period of time. The primary source of wood waste that can immediately be used is the 1.2 gtpa of forest residue and pre-commercial thinnings that are left behind each year in the process of timberland harvesting. The most likely candidates for exploiting this waste are pulp mill operators who have access to this material and can take advantage of hosting a biorefineries that can make advanced biofuel. A recently completed pre-feasibility study that we had undertaken demonstrated the efficacy of this approach and there are two DOE sponsored like projects that are being developed at two pulp mills. In addition, there are a few stand-alone biorefineries in the developmental stage that are successfully producing biofuels from wood waste and there are a number of processes undergoing testing that should offer improvements in the cost-effectiveness of currently available technologies and processes. And although there are still a number of issues to address and obstacles to overcome, we still believe in an acceleration in current efforts to develop more wood waste-to-biofuels biorefineries. The following is a list of a number of findings that have been developed from our studies and research.
Findings
Forest residue and pre-commercial thinnings are an immediate abundant and sustainable source of woody biomass that could be used to produce large quantities of advanced biofuel as well as provide bioenergy, a use that will more than likely receive government provided incentives.
Other wood wastes that could economically be collected, pre-processed and delivered to biorefineries that are designed to use timberland harvest wastes could be best used as a supplemental feedstock, especially if they can be obtained at lower cost.
The cost to harvest timberland harvest wastes is comparable to harvesting sawmill logs, but large scale harvesting of these wastes will only occur, if a higher end use can be found. Such an end use could be as a feedstock to produce high value biofuels.
There is significant evidence and expert opinion to support the contention that when converting wood wastes into advanced biofuels, thermo-chemical pathways currently offer significant advantages over bio-chemical pathways.
Bio-chemical pathways could be used to process other forms of wood wastes if they can be gathered close to a biorefinery that processes municipal solid waste.
The use of wood chips from logs could be used to make biofuels, but an even higher value is obtained when used in forestry products and paper. Use of this source of carbonaceous material would only make sense in periods of significantly depressed prices for forestry products and paper.
There are a number of problems in handling and storing untreated wood chips. Pre-processing using torrefacation offers opportunities to overcome these problems at a reasonable cost. But torrefacation processes have yet to be commercially demonstrated.
in selecting a thermo-chemical pathway, decisions have then to be made as to the best gasifier technology to use, as some gasifier technology is not as well suited as others in gasifying wood waste.
The decision making process in selecting a specific type of gasifier for a specific biorefinery is further complicated by the fact that the more advanced gasification and syngas clean-up systems are likely to be more capital intense, but the operating efficiencies needed to justify the added capital expenditure have to be evaluated on a project specific basis. And, if a biorefinery is expected to be able to obtain significant quantities of lower cost agri-waste or MSW, this would impact upon pre-treatment, gasifier and gas clean-up systems selections.
Further assessment, testing and project-specific evaluation will be needed to for each thermo-chemical biorefinery that is to be undertaken. Likewise, deciding on pre-treatment options will also be a project-specific exercise, as there are trade-offs to be considered with respect to capital costs, operating costs and operating efficiencies.
Commercial scale gasifiers used in thermo-chemical biorefineries have to be continuously fed and certain gasifiers require the feedstock to be pulverized to resemble pulverized coal. And there is a need to develop better material handling and gasifier-feeding systems, specifically designed to handle wood waste.
There is not enough data available to suggest that removal of significant amounts of contaminants through treatments such as torrefacation, significantly reduce the requirements for gas clean up. Much more research has to be done in order to justify the cost effectiveness of torrefacation in reducing syngas clean up requirements.
Significant technological advances are being realized in perfecting bio-chemical pathways and thermo-chemical pathways and developers of 2nd generation biorefineries will need to remain cognizant of changes that could render their biorefineries non-competitive.
Conclusion
• Making advanced biofuels from cellulosic biomass is not an illusion, it is about to happen.
• Significant advances in 2nd generation biorefinery technologies have been made, and more are expected, that will permit cellulosic ethanol and other advanced biofuels to be cost competitive.
• Switch grass will become a valuable biocrop, as more 2nd generation biofuels plants reach commercial stage,
• Development of wood waste to biofuels plants could and should be undertaken at an accelerated
Tim Sklar can be reached at Sklar and Associates or at sklarincdc@aol.com
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