Environmental Engineering Reference
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Biomass Fuel Quality Enhancement
and Respiratory Quotient (RQ)
for Ranking Fossil and Biomass Fuels
Based on CO 2 Emissions
Siva Sankar Thanapal, Dustin Eseltine, Kalyan Annamalai
and Devesh Ranjan
Abstract Torrefaction is one of the thermo-chemical pretreatment techniques used
to enhance the properties of biomass fuels. An inert environment is maintained
during torrefaction process. Effect of using carbon dioxide (CO 2 ) as torrefaction
medium for mesquite and juniper woody biomass was investigated in the current
study. CO 2 torrefaction resulted in improved grindability and comparable energy
retention in the case of mesquite and juniper. A three component model based on
independent parallel reactions was developed to model the torrefaction process.
Effect of torrefaction on behavior of the three components in the biomass: hemi-
cellulose, cellulose and lignin was studied. Kinetic parameters for the three biomass
components were obtained from literature. Results from the TCM were compared
with the results obtained from TGA experiments carried out on mesquite and
juniper samples. Further, concept of respiratory quotient (RQ) used in biological
literature was applied to combustion applications. Global warming potential (GWP)
of different fuels were estimated based on respective RQ. Higher the RQ of fuel,
higher is its GWP. A term RQ P ROCESS ,B IOMASS was introduced to estimate the amount
of CO 2 produced during processing a renewable fuel for combustion applications.
Keywords Torrefaction
Lignocellulosic biomass
Pyrolysis
Carbon dioxide
emissions
Respiratory quotient
Thermo gravimetric analysis (TGA)
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