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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