Clean Technologies and Environmental Policy

, Volume 8, Issue 4, pp 233–249

Switchgrass as an alternate feedstock for power generation: an integrated environmental, energy and economic life-cycle assessment

  • Xiaoyun Qin
  • Tanya Mohan
  • Mahmoud El-Halwagi
  • Gerald Cornforth
  • Bruce A. McCarl
Original Paper

DOI: 10.1007/s10098-006-0065-4

Cite this article as:
Qin, X., Mohan, T., El-Halwagi, M. et al. Clean Techn Environ Policy (2006) 8: 233. doi:10.1007/s10098-006-0065-4

Abstract

An environmental biocomplexity analysis is done on the environmental, energy, economic and technological implications of using switchgrass (Panicum virgatum) to replace coal in power generation. We evaluate cost, environmental impact and net greenhouse gas emissions. In the analysis, alternatives for production and transport are considered. The analysis shows that the most effective technologies for switchgrass preparation are harvesting loose material for hauling and chopping and then compressing it into modules and transporting. The GHG emission mitigation is found to be substantial with the mitigation contribution under cofiring found to be greater per ton of switchgrass than for switchgrass fired alone. This paper also analyzes the implications of switchgrass use under alternative cofiring ratios, coal prices, hauling distances and per acre yields.

Keywords

Biomass utilization Switchgrass Life cycle analysis Greenhouse gases Carbon tax 

List of Symbols

BFc

Burning fraction of carbon which is 99% (as used by USEPA)

BFc,coal

Burning fraction of carbon of coal

BFc,sw

Burning fraction of carbon of switchgrass

Ccoal

National average cost of coal

CGHG

Emission price in $ per metric ton of carbon dioxide equivalent

Cmodi

Cost of modification of plant to cofire switchgrass with coal

\({{C_{\rm SO}}_{\rm x}}\)

Cost of allowance of SOx reduction

Csw

Cost of switchgrass (includes preparation and delivery)

\({E}_{\rm CH_{4,co}}\)

Emissions of CH4 in cofiring

ECO,co

Emissions of CO in cofiring

\(\hbox{EF}_{\rm CO_{2}}\)

Emission factor for carbon dioxide

\(\hbox{EF}_{\rm SO_{x,MO}}\)

Emission factor of SOx for coal

\(\hbox{EF}_{\rm SO_{x,sw}}\)

Emission factor of SOx for switchgrass

EGHG,co

Emissions of greenhouse gases during cofiring

EGHG,co,lc

Greenhouse gas emissions during cofiring (lifecycle)

EGHG,coal,bn,lc

Greenhouse gas emissions from coal burnt alone (lifecycle)

EGHG,sw,lc

GHG emissions from switchgrass burnt alone (lifecycle)

\({E}_{\rm SO_{x,co}}\)

Emissions of SOx during cofiring

HHVfuel

High heating value of fuel

HHVsw

High heating value of switchgrass

MWc

Molecular weight of C

\(\hbox{MW}_{\rm CaSO_{4}}\)

Molecular weight of CaSO4

\(\hbox{MW}_{\rm CO_{2}}\)

Molecular weight of CO2

MWs

Molecular weight of sulfur

\(\hbox{MW}_{\rm SO_{x}}\)

Molecular weight of SOx

NPHRfuel,co

Net plant heat rate of fuel cofired

NPHRsw,bn

Net plant heat rate of switchgrass burned alone

NPHRsw,co

Net plant heat rate of switchgrass cofired

Pash,coal

Ash content in coal

Pash,sw

Ash content in switchgrass

Pc

Carbon content in fuel

Pc,coal

Carbon content in coal

Pc,sw

Carbon content in switchgrass

Ps,coal

Sulfur content in coal

Qelec

Electricity generated

Qelec,co

Electricity generated by cofiring

Qsw,bn

Electricity generated by burning switchgrass alone

\({R}_{\rm CaCO_{3}/SO_{x}}\)

Ratio of CaCO3 to SOx in SOx treatment

Rsw,co

Switchgrass cofiring ratio

Rsw,thermal

Switchgrass cofiring ratio (thermal input)

\({W}_{\rm CaCO_{3}}\)

Weight of CaCO3

\({W}_{\rm CaSO_{4}}\)

Weight of CaSO4

\({W}_{\rm CaSO_{4}}\)

Weight of CaSO4

Wcoal,bn

Weight of coal burnt alone

Wcoal,co

Weight of coal used in cofiring

Wfuel,co

Weight of the fuel cofired

WSOx,co,credit

Weight of SOx used in cofiring that is credited

WSOx,contr

Weight of SOx controlled

Wsw,bn

Weight of switchgrass burnt alone

Wsw,co

Weight of switchgrass used in cofiring

Wwaste,co

Total amount of waste from cofiring

Wwaste,reused

Weight of waste that can be reused

Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  • Xiaoyun Qin
    • 1
  • Tanya Mohan
    • 1
  • Mahmoud El-Halwagi
    • 1
  • Gerald Cornforth
    • 2
  • Bruce A. McCarl
    • 2
  1. 1.Department of Chemical EngineeringTexas A&M UniversityCollege StationUSA
  2. 2.Department of Agricultural EconomicsTexas A&M UniversityCollege StationUSA

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