Bio-based electricity: How biomass resources can support renewable electricity policies
Matt Kocoloski and Paulina Jaramillo
Carnegie Mellon University
Tepper School of Business
RenewElec Workshop Presentation
October 22, 2010
Overview
• Biomass may be used to generate low-carbon energy compared to fossil fuels
• Policies encourage use of biomass for both transportation fuel (RFS, LCFS) and electricity (RPS)
• Project will examine benefits of using different biomass feedstocks and conversion technologies to meet different types of electricity demands in order to inform renewable electricity policies
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Feedstock Characterization
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500 Mtons of biomass ~ X million kWh
Feedstock Characterization
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Switchgrass: perennial, low-input grass; potential energy crop
Photo courtesy sciencedaily.com
Feedstock Characterization
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Photo from Glassner (1998)
Corn Stover: portion of plant remaining once
crop has been harvested
Feedstock Characterization
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Forest residues: generated by logging operations, timberland clearing, or thinning measures
Photo from nrcs.gov
Feedstock Characterization
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Photo from EIA
Primary mill residues and municipal solid waste: wood wastes generated by industrial or urban operations
Feedstock Characterization
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Feedstock Type
Cost Potential Supply
Currently Available
Alkali Content
Feedstock Impurities
Switchgrass High High No High No
Corn Stover Medium Medium Yes High No
Forest Residues
High Medium Yes Low No
Urban/Mill Residues
Low Low Yes Low Yes/No
Conversion Options
• Cofiring biomass with coal– Biomass blended at low-
levels with coal and used in current boilers
– Limited capital costs, but limited potential (5 – 10% in regions with coal-fired capacity)
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Figure from Morrow (2008)
Conversion Options
• Dedicated biomass combustion– Requires boiler replacement, but may be option for older
coal plants to meet emissions regulations
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Diagram from EERE
Conversion Options
• Biomass gasification– Biomass converted
into syngas, which powers a gas turbine
– High capital costs, but may be better suited to load-leveling and CCS
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Diagram from Rhodes (2005)
Conversion Options
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Conversion Technology
Capital Cost
Generation Potential
Regional Limitations
Adds Capacity
Ramping/Load-Leveling Ability
Cofiring with coal
Low Low Yes No Low
Dedicated combustion
Medium Medium Yes No Low
Gasification High High No Yes High
Research Questions
1. What types of electricity demand should be met using biomass? Should biomass be used primarily to meet base load demands, peak demands, or coupled with intermittent renewable technologies (such as solar and wind generation) to act as a load-leveler?
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Research Questions
2. What technologies should be used to convert biomass into electricity? Should conversion to electricity be accomplished through cofiring biomass with coal, dedicated biomass gasification or combustion, or in a combined heat and power system?
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Research Questions
3. How does uncertainty in biomass feedstock availability impact electricity generation options? How does regional variability in electricity generation infrastructure impact conversion options?
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Summary
• Biomass may make a positive contribution to meeting environmental goals for electricity generation
• Interesting decisions regarding:– Feedstock type– Conversion technology– Electricity demand type
• Project intends to explore these interconnected decisions with the goal of informing renewable electricity policies
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