636
N. Nakatsuka et al.
biomass gasification system were 0.163 MJ/MJ and 0.137 kg CO 2 -eq/MJ, respectively, which reaffirmed the advantages of such a system over coal-fired power plants
in terms of clean energy and environmental impact. Jeswani et al. (2019) conducted
a life cycle assessment and life cycle costing to evaluate the life cycle environmental
and economic sustainability of poultry litter gasification and showed that energy
from this system had lower impacts than the fossil-fuel alternatives in 14 out of 16
impact categories, and that even without subsidies, the cost of generating heat and
electricity from poultry litter was 37–66% lower than the cost resulting from the use
of fossil fuels. However, it was concluded that without subsidies, the system would
not be economically viable, as the payback period would increase to 25 years. Wang
et al. (2019) conducted life cycle environmental and techno-economic assessments
within a boundary ranging from agriculture residues collection and transportation
to energy conversion and final use of bioenergy products and showed that directcombustion power generation, gasification power generation, and briquette fuel are
the most sustainable technologies in both an environmental priority situation and an
economic priority situation based on their integrated-dimensions performance.
As described above, there have been multiple studies involving economic and
environmental assessments of woody biomass energy use based on energy balance.
There are, however, few approaches that include a dynamic simulation that takes
into account daily fluctuations in energy demand to evaluate the annual cost and
environmental load associated with a woody biomass gasification CHP system. It
should be noted that while Li et al. (2018) considered hourly energy demand to find
the optimal operation strategies for a CHP system, a comparative analysis of different
system configurations has not yet been undertaken. Furthermore, there are very few
case studies focused on Japan, despite the fact that forest areas account for 67%
of the country’s surface area, which suggests a huge potential for woody biomass
utilization.
42.3 Modeling Energy Conversion Systems for Woody
Biomass
42.3.1 Approach
We evaluate the annual cost and annual CO 2 emissions of energy conversion systems
for woody biomass by modeling each facility process (e.g., chipping, pelletizing, and
gasification). The modeling approach uses the abovementioned LCS (Umeda et al.
2000), which is a system that simulates a product life cycle flow based on the inputoutput relation between two processes throughout the life cycle. A key characteristic
of LCS is its capability to describe any type of process by defining the procedure (i.e.,
the calculation formula connecting input and output parameters) of each process. In
this study, we apply LCS to the material and energy flow of woody biomass, rather
than product life cycle flow, taking into account dynamic changes in heat demand.
N. Nakatsuka et al.
biomass gasification system were 0.163 MJ/MJ and 0.137 kg CO 2 -eq/MJ, respectively, which reaffirmed the advantages of such a system over coal-fired power plants
in terms of clean energy and environmental impact. Jeswani et al. (2019) conducted
a life cycle assessment and life cycle costing to evaluate the life cycle environmental
and economic sustainability of poultry litter gasification and showed that energy
from this system had lower impacts than the fossil-fuel alternatives in 14 out of 16
impact categories, and that even without subsidies, the cost of generating heat and
electricity from poultry litter was 37–66% lower than the cost resulting from the use
of fossil fuels. However, it was concluded that without subsidies, the system would
not be economically viable, as the payback period would increase to 25 years. Wang
et al. (2019) conducted life cycle environmental and techno-economic assessments
within a boundary ranging from agriculture residues collection and transportation
to energy conversion and final use of bioenergy products and showed that directcombustion power generation, gasification power generation, and briquette fuel are
the most sustainable technologies in both an environmental priority situation and an
economic priority situation based on their integrated-dimensions performance.
As described above, there have been multiple studies involving economic and
environmental assessments of woody biomass energy use based on energy balance.
There are, however, few approaches that include a dynamic simulation that takes
into account daily fluctuations in energy demand to evaluate the annual cost and
environmental load associated with a woody biomass gasification CHP system. It
should be noted that while Li et al. (2018) considered hourly energy demand to find
the optimal operation strategies for a CHP system, a comparative analysis of different
system configurations has not yet been undertaken. Furthermore, there are very few
case studies focused on Japan, despite the fact that forest areas account for 67%
of the country’s surface area, which suggests a huge potential for woody biomass
utilization.
42.3 Modeling Energy Conversion Systems for Woody
Biomass
42.3.1 Approach
We evaluate the annual cost and annual CO 2 emissions of energy conversion systems
for woody biomass by modeling each facility process (e.g., chipping, pelletizing, and
gasification). The modeling approach uses the abovementioned LCS (Umeda et al.
2000), which is a system that simulates a product life cycle flow based on the inputoutput relation between two processes throughout the life cycle. A key characteristic
of LCS is its capability to describe any type of process by defining the procedure (i.e.,
the calculation formula connecting input and output parameters) of each process. In
this study, we apply LCS to the material and energy flow of woody biomass, rather
than product life cycle flow, taking into account dynamic changes in heat demand.