Using Biomass at Ethanol Plants for

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1 Using Biomass at Ethanol Plants for Combined Heat and Power (CHP) Vance Morey Professor Bioproducts and Biosystems Engineering i Using Corn for Energy at Ethanol Plants July 11, 2011 Project Support Xcel Energy Renewable Development Fund University of Minnesota Initiative for Renewable Energy and the Environment Project Cooperators AMEC E&C Services Inc. LLS Resources, LLC 1

2 Biomass for Electricity and Process Heat at Ethanol Plants 2

3 Motivations for Using Biomass Reduce fossil energy inputs, i.e. improve energy balance Reduce natural gas costs Decrease net greenhouse gas emissions Generate renewable, dependable (base load) power that complements power from renewable sources that are variable such as wind and solar 3

4 Conventional Dry-grind Ethanol Process Energy Ratio: 1.7 4

5 Energy Ratio: 1.7 Combined Heat and Power (CHP) Concept Simultaneous production of two or more types of usable energy from a single energy source (also called Cogeneration ) Use of waste heat from power generation equipment 5

6 Biomass Technology Options Process heat for the ethanol plant Combined heat and power (CHP) process heat plus generate electricity with a back pressure turbine CHP plus grid process heat plus generate electricity with an extraction turbine and condensing turbine Biomass integrated gasification combined cycle (BIGCC) process heat plus generate electricity with gas turbine and steam turbine. Biomass Fuel Properties Heating Type val.(dry), Btu/lb Ash Nitrogen Sulfur Chlorine % % % % DDGS Syrup* Corn stover Corn cobs Wood < *Syrup moisture 67%; other fuels 10-15% 6

7 Fluidized Bed Combustion Limestone bed material for reducing emissions Flexible for different types of fuels Rentech-SilvaGas Process Steam blown gasifier, atmospheric pressure Medium energy value synthesis gas Char combusted in combustor Gasifier heated by hot sand from combustor 7

8 Emissions Control Dryer volatile organic compounds (VOC) Route dryer exhaust air through combustor Particulate matter Cyclones Baghouse Sulfur and chlorine emissions Limestone sorbent bed material Flue gas semi-dry scrubbing NOx emissions Selective non-catalytic reduction (SNCR) ASPEN Plus Modeling Started with USDA model of a dry-grind fuel ethanol plant Used this model to understand the ethanol process and its energy requirements Added components to the model Biomass conversion (fluidized bed combustion or gasification) Electricity generation Emissions control (NOx, SOx, Chlorine) Modified drying system to use process steam (steam tube dryer) 8

9 Conventional Dry-grind Ethanol Process Steam Tube Dryers Used for drying co-products and biomass fuel Davenport Dryer Co. 9

10 Electricity Generation Steam Turbine Back-pressure Turbine Constant steam pressure at outlet Should use all outlet steam for process needs Extraction Turbine Extract steam at constant pressure for process Condense excess steam at low pressure Electricity Generation Combined Cycle 10

11 Corn Combustion CHP Corn Combustion: CHP + Grid 11

12 Syrup and Corn Combustion: CHP Integrated Gasification Combined Cycle 12

13 System Comparisons CHP, CHP + Grid, and BIGCC with corn stover and syrup and corn stover as biomass fuels Life-cycle GHG analysis for fuel ethanol based on Liska et al. (2009), Plevin (2009), and GREET (2009) Life-cycle GHG analysis excludes indirect land use change effects Power and Efficiency* System CHP Syrup & Corn CHP Corn CHP+G Syrup & Corn CHP+G Corn Fuel Input MW th Power System Power Gen. Total (Grid), Therm. Eff., Eff. % MW e % (2.8) (4.6) (9.6) (10.7) *50 million gallon/yr plant 13

14 Power and Efficiency* System BIGCC Syrup & Corn BIGCC Corn Fuel Input MW th Power Total (Grid), MW e Power Gen. Eff. % System Therm. Eff., % (24.7) (24.6) NGCC (30.3) *50 million gallon/yr plant g CO 2 e/mj Conventional Ethanol Plant Input Output Net Gasoline Conventional Plant Gasoline Gasoline Ethanol Net Coproduct Credit Biorefinery Other Denaturant 2% Vol. Fossil Electricity Natural Gas Corn Production U.S. Midwest average corn ethanol (Liska et al., 2009; Plevin, 2009) 14

15 g CO 2 e/mj CHP and BIGCC Input Output Net Input Output Net Gasoline CHP BIGCC Gasoline Gasoline Ethanol Net Renewable Elec. Credit Coproduct Credit Fuel Biorefinery Other Denaturant 2% Vol. Corn Production CHP, CHP+G, and BIGCC vs GHG Reduction 140% GHG Reduction (%) 120% 100% 80% 60% 40% 20% 38.9% 66.3% 79.1% 80.4% 91.8% 116.5% 124.1% 0% Natural CHP Gas Plant Syrup & (Liska) CHP Corn CHP+G Syrup & CHP+G Corn BIGCC Syrup & BIGCC Corn 15

16 BIGCC & NGCC vs GHG Reduction 140% GHG Reduction (%) 120% 100% 80% 60% 40% 20% 38.9% 116.5% 124.1% 93.4% 0% Natural Gas Plant (Liska) BIGCC Syrup & BIGCC Corn NGCC Natural Gas Electric Power Production Potential in Minnesota Approximately 1 billion gallons of annual corn ethanol production capacity 500 MW could be produced and sent to grid if biomass power generation were fully implemented at these plants Renewable, dependable (base load) power that complements power from renewable sources that are variable such as wind and solar 16

17 Estimated Capital Costs* System 50 Mil gal/yr 100 Mil gal/yr Ethanol Plant Conv. NG $75,000,000 $121,850,000 CHP Syrup & Corn $131,800,000 $214,100,000 CHP Corn $144,000,000 $233,900,000 CHP+G Syrup & Corn $146,650,000 $238,200,000 CHP+G Corn $162,000,000 $263,200,000 BIGCC Syrup & Corn $207,400,000 $336,900,000 BIGCC Corn $206,700,000 $335,800,000 NGCC Natural Gas $145,000,000 $235,550,000 *Estimated by AMEC E&C Services Inc. References De Kam, M.J., R.V. Morey, and D.G. Tiffany Integrating biomass to produce heat and power at ethanol plants. Applied Engineering in Agriculture 25(2): De Kam, M.J., R.V. Morey, and D.G. Tiffany Biomass integrated gasification combined cycle for heat and power at ethanol plants. Energy Conservation and Management 50: EPA Impact of Combined Heat and Power on Energy Use and Carbon Emissions in the Dry Mill Ethanol Process. Washington D.C.: Environmental Protection Agency. Available at: Accessed 14 December Kwiatoski, J.R., A.J. McAloon, F. Taylor, and D.B. Johnston Modeling the process and costs of fuel ethanol production by the corn dry-grind process. Industrial Crops and Products 23: Gielen, D CO 2 removal in the iron and steel industry. Energy Conversion and Management 44 (7): GREET The Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) Model. Ver. GREET 1.8c.0. Argonne, IL: Center for Transportation Research, Energy Systems Division, Argonne National Laboratory. Available at: Accessed 7 July Guinn, J.H Method for injecting carbon dioxide into a well. United States Patent No. 4,212,354. Dated 15 July Kaliyan, N., R.V. Morey, and D.G. Tiffany Reducing life cycle greenhouse gas emissions of corn ethanol by integrating biomass to produce heat and power at ethanol plants. Biomass and Bioenergy 35(3): Kheshgi, H.S., and R.C. Prince Sequestration of fermentation CO 2 from ethanol production. Energy 30(10): Liska, A.J., and K.G. Cassman Response to Plevin: implications for life cycle emissions regulations. Journal of Industrial Ecology 13(4): Liska, A.J., H.S. Yang, V.R. Bremer, T.J. Klopfenstein, D.T. Walters, G.E. Erickson, and K.G. Cassman Improvements in life cycle energy efficiency and greenhouse gas emissions of corn-ethanol. Journal of Industrial Ecology 13(1): McAloon, A.J., F. Taylor, and W.C. Yee A model of the production of ethanol by the dry grind process. Proceedings of the Corn Utilization & Technology Conference, Indianapolis, IN., June 7-9. Poster 58. Morey, R.V., D.L. Hatfield, R. Sears, D. Haak, D.G. Tiffany, and N. Kaliyan Fuel properties of biomass feed streams at ethanol plants. Applied Engineering in Agriculture 25(1): Morey, R. V., N. Kaliyan, D. G. Tiffany, and D. R. Schmidt A corn stover supply logistics system. Applied Engineering in Agriculture 26(3): Plevin, R.J Modeling corn ethanol and climate: a critical comparison of the BESS and GREET models. Journal of Industrial Ecology 13(4): Tiffany, D.G., R.V. Morey, and M.J. De Kam Economics of biomass gasification/combustion at fuel ethanol plants. Applied Engineering in Agriculture 25(3): USDA ASPEN Plus Model for Shelled Corn to Ethanol Process Analysis Dry Grind Starch Fermentation. USDA ARS. 17

18 Questions? Vance Morey