644
N. Nakatsuka et al.
42.6 Conclusion
In this paper, we proposed a model to analyze woody biomass energy conversion
systems using life cycle simulation (LCS) (Umeda et al. 2000). The proposed model
considers fluctuations in hourly heat demand and provides the means to assess the
operation of the system and identify ways to improve its economic and environmental performance. In the hot bath case study, two scenarios were created to allow
for a comparative analysis of different configurations of energy conversion systems.
In scenario A, a heavy oil boiler was used to supply the required heat; in scenario
B, a gasification CHP system using woody biomass was assumed. Results showed
that, in scenario B, annual cost was lower by 23% and CO 2 emissions were lower
by 190% relative to scenario A. Sensitivity analysis revealed that the selling price of
electricity and the power generation efficiency of the CHP system are critical parameters in establishing the economic advantage of scenario B. As a matter of economic
sustainability, it is possible to raise the woodchip price by raising the electricity selling
price, which will increase the income of the forestry business operator providing the
woodchips. It was found that annual CO 2 emissions were highly sensitive to the
power generation efficiency of the CHP system in scenario B, and to heat demand
in scenario A. As a focus for future research, integrating scenario analysis methods
(e.g., Kishita et al. 2016) and the quantitative model proposed in this paper would
be of significant value in helping system designers derive better designs and proper
operational guidelines for energy conversion systems by taking into account both
long-term social changes (e.g., oil prices and electricity selling prices in the Feed-inTariff system) and short-term (e.g., hourly) energy demand fluctuations. Modifying
the timeline of the study (e.g., from 2019 to 2039), collecting more data to improve
the modeling of biomass gasification CHP systems, and verifying the simulation
results through experiments in real fields are also matters for future consideration.
Acknowledgements The authors are grateful to Mr. Takumi Tanaka, master’s student at Osaka
University, for his valuable contributions to the data analysis conducted here. We also would like to
thank Gojo City for providing valuable data and comments to conduct the case study. The contents
of this paper are the sole responsibility of the authors.
This study was supported by the Sumitomo Foundation Environmental research grant and the
Grant-in-Aid for Young Scientists (18K18233) and Scientific Research B (19KT0008) awarded by
the Japan Society for the Promotion of Science (JSPS).
References
Bracmort K (2016) Is biopower carbon neutral? Congressional research service, Washington, DC,
R41603. Available at: https://www.fas.org/sgp/crs/misc/R41603.pdf (Accessed 28 June 2019)
Cleary J, Wolf DP, Caspersen JP (2015) Comparing the life cycle costs of using harvest residue as
feedstock for small- and large-scale bioenergy systems (part II). Energy 86:539–547
Hasler PH, Nussbaumer T (2016) Gas cleaning for IC engine applications from fixed bed biomass
gasification. Biomass Bioenerg 6:385–395
N. Nakatsuka et al.
42.6 Conclusion
In this paper, we proposed a model to analyze woody biomass energy conversion
systems using life cycle simulation (LCS) (Umeda et al. 2000). The proposed model
considers fluctuations in hourly heat demand and provides the means to assess the
operation of the system and identify ways to improve its economic and environmental performance. In the hot bath case study, two scenarios were created to allow
for a comparative analysis of different configurations of energy conversion systems.
In scenario A, a heavy oil boiler was used to supply the required heat; in scenario
B, a gasification CHP system using woody biomass was assumed. Results showed
that, in scenario B, annual cost was lower by 23% and CO 2 emissions were lower
by 190% relative to scenario A. Sensitivity analysis revealed that the selling price of
electricity and the power generation efficiency of the CHP system are critical parameters in establishing the economic advantage of scenario B. As a matter of economic
sustainability, it is possible to raise the woodchip price by raising the electricity selling
price, which will increase the income of the forestry business operator providing the
woodchips. It was found that annual CO 2 emissions were highly sensitive to the
power generation efficiency of the CHP system in scenario B, and to heat demand
in scenario A. As a focus for future research, integrating scenario analysis methods
(e.g., Kishita et al. 2016) and the quantitative model proposed in this paper would
be of significant value in helping system designers derive better designs and proper
operational guidelines for energy conversion systems by taking into account both
long-term social changes (e.g., oil prices and electricity selling prices in the Feed-inTariff system) and short-term (e.g., hourly) energy demand fluctuations. Modifying
the timeline of the study (e.g., from 2019 to 2039), collecting more data to improve
the modeling of biomass gasification CHP systems, and verifying the simulation
results through experiments in real fields are also matters for future consideration.
Acknowledgements The authors are grateful to Mr. Takumi Tanaka, master’s student at Osaka
University, for his valuable contributions to the data analysis conducted here. We also would like to
thank Gojo City for providing valuable data and comments to conduct the case study. The contents
of this paper are the sole responsibility of the authors.
This study was supported by the Sumitomo Foundation Environmental research grant and the
Grant-in-Aid for Young Scientists (18K18233) and Scientific Research B (19KT0008) awarded by
the Japan Society for the Promotion of Science (JSPS).
References
Bracmort K (2016) Is biopower carbon neutral? Congressional research service, Washington, DC,
R41603. Available at: https://www.fas.org/sgp/crs/misc/R41603.pdf (Accessed 28 June 2019)
Cleary J, Wolf DP, Caspersen JP (2015) Comparing the life cycle costs of using harvest residue as
feedstock for small- and large-scale bioenergy systems (part II). Energy 86:539–547
Hasler PH, Nussbaumer T (2016) Gas cleaning for IC engine applications from fixed bed biomass
gasification. Biomass Bioenerg 6:385–395