THESIS
2015
xiii, 73 pages : illustrations ; 30 cm
Abstract
This study investigates the replacement of coal with six types of woody biomass (i.e., farmed tree,
post-consumer wood, construction and demolition derived wood, forest residue, industrial
residue, and mixed wood waste) using four thermal technologies (i.e., biomass firing, co-firing,
biomass gasification, and co-gasification) for power generation. A fair parallel comparison is
conducted with respect to life cycle carbon footprint, energy input and the economic aspect in
order to identify the most environmentally friendly and cost-effective option. In this study, a total
of 20 scenarios covering four thermal technologies and six types of woody biomass are assessed
with coal firing as a reference scenario. The functional unit is defined as “one kilowatt hour
(kWh) of electricity...[
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This study investigates the replacement of coal with six types of woody biomass (i.e., farmed tree,
post-consumer wood, construction and demolition derived wood, forest residue, industrial
residue, and mixed wood waste) using four thermal technologies (i.e., biomass firing, co-firing,
biomass gasification, and co-gasification) for power generation. A fair parallel comparison is
conducted with respect to life cycle carbon footprint, energy input and the economic aspect in
order to identify the most environmentally friendly and cost-effective option. In this study, a total
of 20 scenarios covering four thermal technologies and six types of woody biomass are assessed
with coal firing as a reference scenario. The functional unit is defined as “one kilowatt hour
(kWh) of electricity generated”. Three aspects, namely life cycle carbon footprint, energy input
requirement and material acquisition cost, are evaluated for the 20 scenarios. Life cycle
assessment methodology is applied to quantify the life cycle carbon footprint with the system
boundary defined as “cradle-to-gate”. The energy input requirement and material acquisition cost
are quantified through multiplication of the feedstock consumption by the corresponding heating values and unit costs, respectively. The results of the three aspects are then normalized with
reference to coal firing to investigate the relative impact among the 20 scenarios. After the
quantification, it is found that biomass firing using forest residue with 100% woody biomass
allocation generates the least life cycle carbon footprint and requires the least material acquisition
cost. Additionally, co-firing using forest residue with 5% woody biomass allocation at energy
base has the least energy input requirement. Based on the normalized results of three aspects in
equal weight among the 20 scenarios, biomass firing using forest residue with 100% woody
biomass allocation has the relatively lower normalized values for life cycle carbon footprint,
energy input requirement and material acquisition cost of 0.01, 1.08 and 0.17, respectively. In
this study, biomass firing using forest residue with 100% woody biomass allocation is identified
to be the most environmentally friendly and cost-effective option. The results of this study
provide a decision support base for the selection of the appropriate thermal technology with the
specific type and allocation of woody biomass based on the environmental impact, energy input,
and economic aspects. Since it is assumed that the feedstock is locally provided with sufficient
supply in USA and there are existing power plants for each thermal technology, the supply
concern of each type of feedstock and the carbon footprint, energy input, and other costs caused
by the construction phase of the new power plants are not considered in this study.
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