Lonnie O. Ingram, Director

Grand Challenge for Renewable Energy from Biomass

"To displace imported petroleum by increasing the cost-competitive production of fuels and chemicals from renewable biomass by at least 100-fold."

Emerging knowledge in functional genomics and molecular technologies provides new opportunities for the genetic tailoring of plants and microorganisms to produce novel materials, fuels, and chemicals. During the past century, plants have been extensively modified to vastly improve the production of food, feed, and fiber. An understanding of fundamental mechanisms that govern the physical limitations of plant efficiency will allow the design and control of many useful plant properties. These include the control and characterization of plant architecture and composition (lignin, cellulose, hemicellulose, starch, and oils), improvements in the energy-efficiency of plant production (reduced nutrients, water, and land requirements), and an expansion in the range of environments that can be used for cultivation (salt tolerance and stress resistance). Further advances in the fractionation of biomass into individual components using physical and chemical treatments offer a major opportunity for cost savings. Metabolic engineering of new microbial biocatalysts offers the potential to produce novel biomaterials and chemicals that will serve as renewable alternatives to current petrochemicals. These improved microbial biocatalysts are required to expand the range of useful conditions for industrial fermentations and reduce costs through process simplification. Substantial cost-savings can also be realized by the development of biocatalysts that produce enzymes (cellulase, xylanase, and others) for carbohydrate depolymerization as co-products during fermentation, eliminating the need for separate enzyme production facilities. Application of biochemical and genetic principles provide mechanisms for the rational design of improved enzymes concerned with the depolymerization of plant constituents. Recent expansion in genomic sequences from microbes and plants provides a vast tool kit of genes and enzymes that can now be recombined and used to provide clean and sustainable solutions to our current dependence on imported petroleum.

 

The modern industrial revolution has been powered by the use of solar energy from ancient plants and microalgae that formed vast deposits of petroleum, coal, and natural gas. The ancient photosynthetic processes that produced these reservoirs of fossil energy also shaped our climate and the composition of our atmosphere. Storage of carbon in relatively inert fossil forms reduced atmospheric carbon dioxide and other compounds associated with planetary heating, and produced our oxygen-rich atmosphere. The vast scale of biological conversion processes offers the opportunity to replace part of our dependence on fossil residues for energy with contemporary sources of renewable biomass. Biological transformations of renewable biomass materials also offer the opportunity to displace current petroleum-based chemicals and plastics using environmentally friendly processes. Co-production of these higher value chemicals from renewable biomass is essential to reduce the cost of liquid fuels such as ethanol or biodiesel from biomass.

Approximately 0.2% of the current U.S. energy needs are supplied by renewable biomass, principally direct combustion (heating or electricity) or ethanol as a fuel extender and oxygenate (2 billion gal per year; 1.3% of total automotive fuel). Both the areas of liquid fuels (ethanol, biodiesel) and combustion offer tremendous opportunities for expansion through the development of improved methods for the solubilization of plant constituents and the application of our emerging knowledge of plant and microbial genomics.

Near term expansion of research should focus on the development of improved bioconversion processes to produce chemicals (ethanol, longer chain alcohols, fatty esters, etc.) that can be blended with currently used automotive fuels (gasoline, diesel) and on the development of microbial processes for higher value co-products (commodity chemicals, bio-based plastics) that displace imported petroleum and increase revenues. Under-utilized residues from current agriculture and forestry with little or no current value should be used as feedstocks for this near term expansion. Approximately 30 million tons of corn is currently converted to fuel ethanol in the U.S. by a mature industry using very efficient processes that take advantage of the highly digestible nature of starch by microbial enzymes. While this can continue to expand and make an important contribution to the energy security of our nation, the energy intensive nature of corn farming and competing uses of corn as food and feed will prevent the substantial replacement of automotive fuel by ethanol from corn alone. In contrast, the use of under-valued lignocellulosic residues as feedstocks should have minimal impact on consumer costs for the primary products from agriculture (food, feed and fiber). This new use represents an expanded benefit with minimal investment of additional energy. Additional fuels from lignocellulosics can be blended with gasoline to reduce petroleum imports while maintaining the benefits of corn-based ethanol production.

The high capital cost and increased risk associated with process complexity have thus far blocked the industrial implementation of many promising new technologies. Much of this process complexity can be reduced through the genetic engineering of improved microbial biocatalysts, the genetic tailoring of the plants for specific applications, and by improvements in plant fractionation technologies that increase efficiency and reduce costs. Even with process simplifications, the barrier of risk associated with the first implementation of a novel technology should not be underestimated.

Many aspects of process complexity can be improved by the application of knowledge from microbial and plant genomics. Genomic sequences provide a catalogue of genes that can be used to alter cellular structure, composition, and function. These sequences provide a starting point for our understanding of integrated processes which limit the efficiency of water and nutrient use, the partitioning of photosynthate among cellular constituents, tolerances to extreme environments, and bioconversions processes by microorganism. A logical next step is to expand these genetic catalogues by adding fundamental knowledge concerning the integration of gene functions and physiological activities.

Cellulose depolymerization by enzymes is arguably the single most expensive step associated with the bioconversion of lignocellulose to fuels and chemicals. Increased understanding of the molecular mechanism of glycohydrolases may lead to creation of more efficient enzymes that resist product inhibition. Additional approaches include the co-production of glycohydrolases by the microbial biocatalysts during fermentation and the co-production of glycolydrolases in the tissues of plants prior to harvesting for bioconversion. Significant reductions in added cellulase will also be achieved by improved understanding of the fundamental chemical and physical processes involved in the fractionation and solubilization of biomass.

Our increasing facility and knowledge of plants should also support a more radical approach to biomass feedstocks, the genetic tailoring of plant composition for specific bioconversion processes. Continuing investigations of fundamental mechanisms that regulate the partitioning of photosynthate between carbohydrate polymers (cellulose, hemicellulose, starch), protein, lipid, and lignin should now allow rapid improvements in plant composition for fuels and chemicals equivalent to those which have been realized in food crops. For instance, increasing the lignin content with reduction in carbohydrate content would increase the energy density of plant residues intended for use in combustion. Alternatively, increasing the production of carbohydrate polymers that can be readily degraded by enzymes (starch, hemicellulose) and reducing the content of cellulose and lignin could eliminate the need for cellulases enzymes in bioconversion processes. Relatively small lignin and cellulose residues that remain after enzyme treatments of such materials could be burned to provide steam and power.

Broad implementation of biomass as a primary energy source in the U.S. and in the world will depend upon the genetic modification of plants to expand the range of soil environments for productive cultivation, to minimize nutrient requirements, and to increase crop productivity (tons/acre per year). These improved plants will become the feedstocks of the future. Areas of particular interest include salt tolerance, metal tolerance, and improved efficiencies for the use of water and nutrients. This is a longer term goal where sustained investment in fundamental research is essential. Again, genomics provides a wealth of information by cataloguing the genes. However, continuing fundamental studies are essential to understand the mechanisms that have evolved to control these macro functions in plants and microorganisms. Results from these investigations will serve as a guide for the rational design of future improvements using both traditional and molecular approaches.

The efficiency with which we have converted fossil biological energy sources into fuels and chemicals has allowed a tremendous expansion in population and improvement in the quality of life throughout the industrialized world. As we look toward a future that must rely upon alternative energy sources, the same fundamental biological processes which created fossil deposits and our oxygen-rich atmosphere can be harnessed to provide a renewable source of energy and chemicals. Traditional plant breeding coupled with chemical and microbial conversion processes has allowed 100 to 1000-fold increases in the production of food and food products over the past the century with small recent contributions from genomics and molecular methods. These new methods together with new advances in materials science and chemistry offer the opportunity for even greater improvements in biobased products over the next 50 years and provide the basis for the conservative estimate of a 100-fold increase in contribution of renewable biomass (20% of energy needs) to our national security.

References and Suggested Reading

1. “Biobased Industrial Products: Priorities for Research and Commercialization.” (1999). National Research Council. National Academy Press.
BP/Amoco. (2002).
2. Brown, P., and Parkinson, B. (2000). “Protecting the Climate While Safeguarding the Economy,” Backgrounder No.3, May.
3. Bull, T.E. (1999). “Biomass in the Energy Picture,” Science, 285:120.
4. Campbell, C. J. (1997) “The coming oil crisis,” Multi-Science Publishing and Petrochemical Consultants, Essex.
5. Campbell, C. J. (2002) “Peak oil: An outlook on crude oil depletion.”
6. Christison, B. (2002), “Oil and the middle east – Why U.S. policy has to change,” ASPO-ADAC Newsletter Number 17.
7. “Climate Change 2001: The Scientific Basis,” (2001). Intergovernmental Panel on Climate Change (Edited by J.T. Houghton, Y. Ding, D.J. Griggs, M. Noguer, P.J. van der Linden, X. Dai, K. Maskell and C.A. Johnson), Cambridge University Press.
8. “Conservative Reserve Program” (2002). USDA, Farm Service Agency.
9. Costanza, R., Daly, H., Folke, C., Hawken, P., Holling, C.S., McMichael, A.J., Pimentel, D., and Rapport, D. (2000). “Managing Our Environmental Portfolio,” BioScience, 50(2):149-155.
10. Deffeyes, K. S. (2001). “Hubbert’s Peak – The Impending Oil Shortage,” Princeton University Press, Princeton, NJ.
11. “Draft Report of the Seventeenth Session of The Intergovernmental Panel on Climate Change (IGCC).” Intergovernmental Panel on Climate Change. (2001). Nairobi, April 4-6.
12. “Energy Innovations: A Prosperous Path to a Clean Environment,” (1997). Alliance to Save Energy (with others), Washington.
13. “Federal Energy Research and Development for the Challenges of the 21st Century”. (1997) Energy Research and Development Panel, President’s Committee of Advisors on science and Technology. Office of Science and Technology, Executive Office of the President of the United States, Washington, DC, November.
14. English, G., Jr. and Ewing, T. W. (2002). “Vision for Bioenergy & Biobased Products in the United States,” U. S. Biomass Technical Advisory Committee (Biomass R&D Act of 2000).
15. Ford, W.C. Address to the 4th Annual Greenpeace Business Conference. October 5, 2000. London.
16. Giampietro, M., Ulgiati, S., and Pimentel, D. (1997). “Feasibility of Large-Scale Biofuel Production,” BioScience, 47(9): 587-600.
17. Greene, D. L., Jones, D.W., and Leiby, P.N. (1998). “The outlook for U.S. oil dependence,” Energy Policy 26:55-69.
18. Hawkin, P., Lovins, A., and Lovins, L.H. (1999). “Natural Capitalism: Creating the Next Industrial Revolution.” Rocky Mountain Institute. Little, Brown and Co., Boston.
19. Haseltine, D.M. (2000). “Exploring Our Energy Future,” Chemical Engineering Progress, 96(1):75-83.
20. Holdren, J. 2001. “Meeting the Energy Challenge,” Science. 291: 945.
21. Hypercar Inc. website
22. “The Impacts of Increased Diesel Penetration in the Transportation Sector.” (1998) SR/OIAF/98-02.
23. Kassler, P. (1994). “Energy for Development,” Shell International Petroleum Company, LTD, London.
24. Kennedy, D. 2001. “An unfortunate U-turn on carbon,” Science. 291: 2515.
25. Kerr, R.A. (1998). “The Next Oil Crisis Looms Large – an Perhaps Close.” Science, 281: 1128-1131. August 21.
26. “Land Idled by Federal Programs,” USDA, Farm Service Agency. (2000). Also see http://www.fsa.usda.gov/pas/default.asp.
27. “Light-Duty Automotive Technology and Fuel Economy Trends 1975 Through 2000,” USEPA (United States Environmental Protection Agency) Air and Radiation EPA420-S-00-003, (2000).
28. “Long-Term World Oil Supply: A Resource Base/Production Path Analysis,” Energy Information Administration. (2000).
29. Lugar, R.G., and Woolsey R. J. (2000). “The New Petroleum,” Foreign Affairs, 78:88-102.
30. Lynd, L.R. (1996). “Overview and evaluation of fuel ethanol from cellulosic biomass: Technology, Economics, the Environment, and Policy.” Annu. Rev. Energy Environ., 21:403-465.
31. Lynd, L.R., Jin, H., Michels, J.G., Wyman, C.E., and Dale, B. (2002). Bioenergy: Background, Potential, and Policy. Accepted for publication, Center for Strategic and International Studies, Washington, DC.
32. Lynd, L.R., Wyman, C.E., and Gerngross, T.U. (1999). “Biocommodity Engineering”, Biotechnol. Prog., 15(5):777-793.
33. McLaughlin, S.B., de la Torre Ugarte, D.G., Garten, C.T. Jr., Lynd, L.R., Sanderson, M.A., Tolbert, V.T., and Wolf, D.D. (2002). “Power in Prairie Grasses: An Ecological and Economic Perspective.” Environmental Science and Technology, 36: 2122-2129.
34. “National Energy Policy.” Report of the National Energy Policy Development Group, May 2001.
35. Pimentel, D., Rodrigues, G., Wang, T., Goldgerg, K., Staecker, H., Ma, E., Brueckner, L., Trovato, L., Chow, C., Govindarujul, U., and Boerke, S. (1994). “Renewable Energy: Economic and Environmental Issues,” BioScience, 44(8):536-547.
36. Pimentel, D., Stachow, U., Takacs, D.A., Brubaker, H.W., Dumas, A.R., Meaney, J.J., O’Neil, J.A.S., Onsi, D.E., and Corzilius, D.B. (1992). “Conserving Biological Diversity in Agricultural/Forestry Systems,” BioScience, 42(5): 354-362.
37. Pimentel, D., Wilson, C., McCullum, C., Huang, R., Dwen, P., Flack, J., Tran, Q, Saltman, T, and Cliff, B. (1997). “Economic and Environmental Benefits of Biodiversity,” BioScience, 47(11): 747-757.
38. “Powerful Partnerships: The Federal Role in International Cooperation on Energy Research, Development, Demonstration, and Deployment,” (1999). The office of Science and Technology Policy, Executive Office of the President of the United States.
39. Renewable Energy and Sustainable Energy WWW Links
40. “Report to the President of the Interagency Steering Committee on the Outcome of the Deliberations of the Policy Dialogue Advisory Committee to Assist in the Development of Measures to Significantly Reduce Greenhouse Gas Emissions from Personal Vehicles,” (1996). The White House, February. Available from Air Docket, U.S. EPA, 401 M St. SW, M-1500, Washington DC 20460; or Sierra Club, 408 C St. NE, Washington DC 20002 (202 547 1141).
41. Shell. (2002).
42. Stokes, D.E. (1997). “Pateur’s Quadrant: Basic Science and Technological Innovation,” Brookings Institution Press.
43. “The Science of Climate Change,” (2001). A joint statement issued by the National Academies of 17 countries. Science. 292:1261.
44. “The Timing of Climate Change Policy,” (2002). The Pew Center for Global Climate Change.
45. Turner, J.A. (1999). “A Realizable Renewable Energy Future,” Science, 285:687-689.
46. Wackernagel, M., and Rees, W. (1996). “Our Ecological Footprint: Reducing Human Impact on Earth,” New Society Publisher
47. Woolsey, R.J. “Defeating the Oil Weapon,” Chapter to appear in: “The Next American Century: Essays in Honor of Richard G. Lugar.” Rowman and Littlefield (publication expected December, 2002).
48. Yergin, D. (1992). “The Prize: The Epic Quest for Oil, Money and Power.” Simon & Schuster, New York.