Review Reports - Perspectives on Biomass-to-Power for a Circular Bioeconomy in Taiwan

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The research focuses on the perspectives on biomass-to-power for a circular bioeconomy in Taiwan showing the biomass resources employed, the main renewable energies applied, and data related to the installed capacity and power generation (electricity) for the last years. Along the paper the English language has been correctly used, and the data search have shown a hard work, however they should be represented in a more a visual way and some examples of facilities working should be explained. The following are presented below some notes to keep in mind.

AN OVERVIEW OF RENEWABLE POWER IN TAIWAN

Lines 81 to 91: Perhaps the quantities facilitated of renewable energy type contribution and the installed capacity could be unified in the same paragraph because the percentages are similar for each renewable energy type.

Lines 92 to 100: the information expressed in these lines should be represented into a bar chart or other similar chart, it looks like clearly.

In Table 1 there is a mistake in the total percentage in 2021, it should be 100 %.

Challenges in the development of biomass-to-power in Taiwan

The biomass-to-power plant schematized in Figure 1 should be explained more extensively and another biomass-to-power plant for thermochemical routes. It is very important to show the actual state of biomass-to-power in Taiwan.

Comments for author File: Comments.pdf

Author Response

Q1. Lines 81 to 91: Perhaps the quantities facilitated of renewable energy type contribution and the installed capacity could be unified in the same paragraph because the percentages are similar for each renewable energy type.

Reply: Thank you for your suggestion. They are unified in the same paragraph due to the similarity for each renewable energy type.

Q2. Lines 92 to 100: the information expressed in these lines should be represented into a bar chart or other similar chart, it looks like clearly.

Reply: Thank you for your suggestion. A new figure (Figure 1) is added to make it clear.

Q3. In Table 1 there is a mistake in the total percentage in 2021, it should be 100 %.

Reply: It has been revised to make it correct.

Q4. The biomass-to-power plant schematized in Figure 1 should be explained more extensively and another biomass-to-power plant for thermochemical routes. It is very important to show the actual state of biomass-to-power in Taiwan.

Reply: That is a very good suggestion, thanks. The detailed description about the new biomass-to-power plant in the first paragraph of Sec. 4.1 has been added to take an actual case in Taiwan.

“……………………. In actual, this facility may be the first integrated biomass/waste-to-energy system in Taiwan, including thermal incineration treatment (design capacity: 660 metric tons/day, or 219,000 metric tons/year), anaerobic digestion (design capacity: 135 metric tons/day, or 49,275 metric tons/year), and sanitary landfill (design capacity: approximately 40,000 cubic meters). The local government aimed at developing it as a demonstration park for the biomass industry and resource recycling.”

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Dear authors, I believe this is an interesting perspective article that addresses the conversion of biomass into energy for a circular bioeconomy in Taiwan. In the current version, there are several areas for improvement, which, once addressed, will enhance the article's quality for reconsideration for publication. Below, I share several observations that will allow for improvements to the article:

The "Abstract" section can be improved. I recommend delving a little deeper into the differences between biochemical and thermochemical pathways for energy generation from biomass. The reasons behind the increase or decrease in this generation should be briefly explained, and how these developments are associated with the circular bioeconomy and how they are linked to sustainability should also be mentioned. This would improve its quality.
In section "1. Introduction", I recommend explaining the characteristics of the circular bioeconomy; more opinions on future projections of the topic should be included, as this will improve the quality of this section.
In section "2.1. Current status" I recommend exploring in more detail why certain sources dominate or what specific barriers might hinder other renewable energies. It would be appropriate to add a trend chart to make the section more engaging. It would also be interesting to include Taiwan's figures to contextualize the country's performance compared to international benchmarks, thus highlighting its global performance.
In section "2.2. Policy for promoting renewable power", I recommend that more detailed comments be made on why Taiwan is lagging behind in meeting these objectives. The actual effectiveness of these policies should be explored in greater depth, and possible disadvantages of the policies for biomass energy generation should be mentioned.
In section "2.3. Regulatory measures for promoting renewable power" I recommend delving deeper into the practical application of regulatory measures for the promotion of renewable energy, highlighting what has worked and what has not. It is also necessary to explain possible regulatory problems that slow down the process, as well as mention some conjectures about how these measures may evolve after 2025. This will allow for a better vision of the future of the topic.
In section "3.1. Current status", I recommend explaining the causes of the changes in the current state of energy generation from biomass in Taiwan. In addition, it would be interesting to compare the trends in Taiwan with Japan or South Korea; this will broaden the global perspective of the article.
In section "3.2. Biomass-to-power by anaerobic digestion" I recommend mentioning biological limitations that may slow down or interfere with the digestion process; this will improve the quality of this section.
In section "3.3. Biomass-to-power by thermochemical routes" I recommend delving deeper into some of the recent technological advances in cogeneration systems, as well as expanding on the idea of biomass co-combustion with fossil fuels, highlighting how this approach could reduce emissions.
In section "4.1. Biomass resource" the estimate of metric tons per year must be linked to a bibliographic source. I recommend addressing factors and the possible repercussions of climate change that alter the biomass supply; this will improve the quality and analysis of the section.
In section "4.2. Promotion incentives" I recommend expanding the discussion of Taiwan's food tariffs by comparing them with those of other countries, as well as the long-term sustainability of these subsidies; improving this would enrich the content of the section.
In section "4.3. Stationary air pollution" I recommend addressing more about the degree of compliance with these standards in practice, whether facilities carry out activities properly, and also discussing projections on how Taiwan could meet these emissions targets by 2050.
In section "4.4. Site land use requirements" I recommend including real-world examples of projects that have succeeded or failed due to land constraints, as well as exploring potential conflicts in populated areas. This will allow us to address the importance of energy objectives in relation to the needs of society.
In section "4.5. Units for meeting performance durability requirements" I recommend discussing in more detail the financial obstacles to generating energy from biomass, as well as addressing practical and specific recommendations for its proper development.
Section "5. Conclusions and future prospects" is rather brief. I recommend addressing more specific future scenarios, for example, how the gradual increase in energy production from biomass could reduce greenhouse gas emissions, as well as recommendations for policymakers on modifying incentives or simplifying regulations to allow for its proper development. This will improve the quality of the section and facilitate readers' understanding.

Author Response

Q1. The "Abstract" section can be improved. I recommend delving a little deeper into the differences between biochemical and thermochemical pathways for energy generation from biomass. The reasons behind the increase or decrease in this generation should be briefly explained, and how these developments are associated with the circular bioeconomy and how they are linked to sustainability should also be mentioned. This would improve its quality.

Reply: Thank you for your comment. The device used for SEM analysis was mentioned in the manuscript (S-3000N, Hitachi Co., Tokyo, Japan), which was written in section 2.4.

Q2. In section "1. Introduction", I recommend explaining the characteristics of the circular bioeconomy; more opinions on future projections of the topic should be included, as this will improve the quality of this section.

Reply: Thank you for your suggestion. As recommended, the characteristics of the circular bioeconomy and its future projections were included into the manuscript for better comparisons.

Q3. In section "2.1. Current status" I recommend exploring in more detail why certain sources dominate or what specific barriers might hinder other renewable energies. It would be appropriate to add a trend chart to make the section more engaging. It would also be interesting to include Taiwan's figures to contextualize the country's performance compared to international benchmarks, thus highlighting its global performance.

Reply: Thank you for your suggestion. As recommended, we included a new chart (Figure 1) for depicting installed capacity of renewable energy and its renewable electricity generation during the period of 2020-2024. In addition, we briefly described the regulatory promotion for solar photovoltaics (PV) and wind power.

Q4. In section "2.2. Policy for promoting renewable power", I recommend that more detailed comments be made on why Taiwan is lagging behind in meeting these objectives. The actual effectiveness of these policies should be explored in greater depth, and possible disadvantages of the policies for biomass energy generation should be mentioned.

Reply: That is a very good suggestion, thanks. We included the description about the main reasons in meeting these objectives behind.

Q5. In section "2.3. Regulatory measures for promoting renewable power" I recommend delving deeper into the practical application of regulatory measures for the promotion of renewable energy, highlighting what has worked and what has not. It is also necessary to explain possible regulatory problems that slow down the process, as well as mention some conjectures about how these measures may evolve after 2025. This will allow for a better vision of the future of the topic.

Reply: Thank you for your comment. We included the description about the practical application of regulatory measures for the promotion of renewable energy. In addition, we briefly addressed possible regulatory problems that slow down the renewable energy development in Taiwan.

Q6. In section "3.1. Current status", I recommend explaining the causes of the changes in the current state of energy generation from biomass in Taiwan. In addition, it would be interesting to compare the trends in Taiwan with Japan or South Korea; this will broaden the global perspective of the article.

Reply: Thank you for your comment. We included the description about the causes of the changes in the current state of energy generation from biomass in Taiwan. In addition, we briefly addressed the case of biomass-to-power systems using solid-type woody biomass in Japan for comparison.

Q7. In section "3.2. Biomass-to-power by anaerobic digestion" I recommend mentioning biological limitations that may slow down or interfere with the digestion process; this will improve the quality of this section.

Reply: Thank you for your comment. We included the description about the biological limitations that may slow down or interfere with the digestion process.

Q8. In section "3.3. Biomass-to-power by thermochemical routes" I recommend delving deeper into some of the recent technological advances in cogeneration systems, as well as expanding on the idea of biomass co-combustion with fossil fuels, highlighting how this approach could reduce emissions.

Reply: Thank you for your comment. We included the description about the recent technological advances in cogeneration systems, as well as expanding on the idea of biomass co-combustion with fossil fuels.

Q9. In section "4.1. Biomass resource" the estimate of metric tons per year must be linked to a bibliographic source. I recommend addressing factors and the possible repercussions of climate change that alter the biomass supply; this will improve the quality and analysis of the section.

Reply: Thank you for your comment. We included the bibliographic source about the biomass resource and the description about the biomass supply by the possible repercussions of climate change [24].

Q10. In section "4.2. Promotion incentives" I recommend expanding the discussion of Taiwan's food tariffs by comparing them with those of other countries, as well as the long-term sustainability of these subsidies; improving this would enrich the content of the section.

Reply: Thank you for your comment, however the purpose of the Perspective paper was not to delve into the discussion of Taiwan's food tariffs by comparing them with those of other countries. Regarding the long-term sustainability of these subsidies, it would be sustainable based on a 20-year FIT scheme. The budget for renewable energy development was officially offered by the central government.

Q11. In section "4.3. Stationary air pollution" I recommend addressing more about the degree of compliance with these standards in practice, whether facilities carry out activities properly, and also discussing projections on how Taiwan could meet these emissions targets by 2050.

Reply: Thank you for your comment. We included the compliance with these Stationary air pollution standards.

Q12. In section "4.4. Site land use requirements" I recommend including real-world examples of projects that have succeeded or failed due to land constraints, as well as exploring potential conflicts in populated areas. This will allow us to address the importance of energy objectives in relation to the needs of society.

Reply: Thank you for your comment. We included the successful cases in biomass-to-power plants due to land constraints and potential conflicts in populated areas.

Q13. In section "4.5. Units for meeting performance durability requirements" I recommend discussing in more detail the financial obstacles to generating energy from biomass, as well as addressing practical and specific recommendations for its proper development.

Reply: Thank you for your comment. We described the financial obstacles for generating energy (biogas) from biomass, including high-cost turbine-generator set and biomass feedstock collection & transport, and the system operation durability caused by inconsistent feedstock and potential hazards posed by the biogas-to-power plants.

Q14. Section "5. Conclusions and future prospects" is rather brief. I recommend addressing more specific future scenarios, for example, how the gradual increase in energy production from biomass could reduce greenhouse gas emissions, as well as recommendations for policymakers on modifying incentives or simplifying regulations to allow for its proper development. This will improve the quality of the section and facilitate readers' understanding.

Reply: Thank you for your comment. We included the description about the further promotion incentives in the energy production from biomass.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Manuscript: Perspectives on biomass-to-power for a circular bioeconomy in Taiwan

1)The manuscript does not articulate a scientific objective. It only states that it “updates” Taiwan’s biomass-to-power achievements.

The authors must explicitly formulate at least one research question, for example:

a) What limits biomass-to-power expansion in Taiwan?
b) How sensitive is deployment to FIT levels?
c) Is biomass availability sufficient to meet 2050 decarbonization goals?

Without such framing, the manuscript is only descriptive.

2)Although large volumes of biomass are listed (Section 4.1), the manuscript never computes their actual energy potential.

The authors must add:

a) Lower heating values (MJ/kg) of key biomass streams
b) Recoverable fractions
c) Conversion efficiencies
d) Resulting electricity potential (GWh/year)

This would allow readers to understand whether Taiwan’s biomass resources are marginal or strategic.

3)The paper shows that FIT increased and installed capacity increased, but this is only temporal coincidence.

The authors should add:

a) A regression or elasticity analysis between FIT and capacity growth
b) Or a counterfactual scenario (e.g., what capacity would be at constant FIT)

Without this, policy conclusions are not scientifically justified.

4)Table 2 shows that installed capacity decreased while electricity generation increased. This is scientifically important but completely ignored.

The authors must calculate:

a) Capacity factors (GWh / MW / year)
b) Performance trends
c) Possible efficiency gains or operational changes

This is essential for understanding system maturity.

5)The manuscript claims climate benefits but provides no CO₂ accounting.

The authors should include:

a) Emissions avoided per kWh of biomass power
b) Comparison with coal, gas, or solar

c)Life-cycle or at least combustion-stage CO₂ offsets

6)FIT values are listed, but no economic implications are derived.

The authors must estimate:

a) Revenue per MW
b) Typical CAPEX/OPEX ranges
c) Payback periods
d) FIT burden on the electricity system

Without this, policy sustainability cannot be assessed.

7)The paper is isolated in the Taiwanese context.

The authors must compare Taiwan with:

a) Japan
b) South Korea
c) China
d) EU biomass systems
e) Using metrics such as:

-MW per million inhabitants

-Biomass electricity per ton of waste

-FIT vs deployment efficiency

8)Tables 1–5 currently function only as data displays. They must be used to produce:

Derived indicators, Trends, Ratios and Performance metrics

9)Some percentage values in Table 1 are inconsistent (e.g., totals not summing to 100%). This must be verified and corrected.

Final Recommendation: Major Revision

Comments on the Quality of English Language

Substantial revisions to text or experimental methods needed

Author Response

Q1. The authors must explicitly formulate at least one research question, for example:

a) What limits biomass-to-power expansion in Taiwan?
b) How sensitive is deployment to FIT levels?
c) Is biomass availability sufficient to meet 2050 decarbonization goals?

Reply: Thank you for your comment. In the third paragraph of Introduction, we briefly included the description about the limitations of biomass-to-power expansion in Taiwan. In addition, the annual biomass amount (about 5 million metric tons, described in Sec. 4.1) and forest area (about 2.2 million hectares) in Taiwan are insufficient to meet 2050 decarbonization goals. In this regard, biomass energy is one of many available options for climate change mitigation.

Q2. Although large volumes of biomass are listed (Section 4.1), the manuscript never computes their actual energy potential.

The authors must add:

a) Lower heating values (MJ/kg) of key biomass streams
b) Recoverable fractions
c) Conversion efficiencies
d) Resulting electricity potential (GWh/year)

Reply: Thank you for your comment, however the purpose of the perspective paper was not to delve into the estimation of energy potential in Taiwan. As we mentioned in the Introduction that the insights were to provide the updated achievements of renewable power and biomass-to-power over the past five years (2020-2024) and some challenges of the biomass-to-power development. On the other hand, it was currently hard to compute the actual energy potential due to heterogeneity of biomass materials and limited data on their thermochemical properties.

Q3. The paper shows that FIT increased and installed capacity increased, but this is only temporal coincidence.

The authors should add:

a) A regression or elasticity analysis between FIT and capacity growth
b) Or a counterfactual scenario (e.g., what capacity would be at constant FIT)

Reply: Thank you for your comment. In Sec. 4.2, we briefly included the description about the analysis between FIT and capacity growth in Taiwan based on the data in Table 2 and Table 4.

Q4. Table 2 shows that installed capacity decreased while electricity generation increased. This is scientifically important but completely ignored.

The authors must calculate:

a) Capacity factors (GWh / MW / year)
b) Performance trends

c) Possible efficiency gains or operational changes

Reply: Thank you for your comment. In Sec. 4.2, we briefly included the description about the contradiction between the installed capacity decreased and electricity generation increased using the data in Table 2.

Q5. The manuscript claims climate benefits but provides no CO₂ accounting.

The authors should include:

a) Emissions avoided per kWh of biomass power
b) Comparison with coal, gas, or solar
c)Life-cycle or at least combustion-stage CO₂ offsets

Reply: Thank you for your comment, however the purpose of perspective paper was not to delve into the estimation of CO₂ accounting in Taiwan. As we mentioned in the Introduction that the insights were to provide the updated achievements of renewable power and biomass-to-power over the past five years (2020-2024) and some challenges of the biomass-to-power development. However, the estimation of GHG emission reduction can be briefly carried out by using the data in biomass-to-power (Table 2) and official electricity carbon emission factor for 2024 (i.e., 0474 kg CO₂-equivalent per kilowatt-hour).

Q6. FIT values are listed, but no economic implications are derived.

The authors must estimate:

a) Revenue per MW
b) Typical CAPEX/OPEX ranges
c) Payback periods
d) FIT burden on the electricity system

Reply: Thank you for your comment. In Sec. 3.1, we briefly included the description about the payback periods in the current state of biogas-to-power systems in Taiwan.

Q7. The paper is isolated in the Taiwanese context.

The authors must compare Taiwan with other countries

-MW per million inhabitants

-Biomass electricity per ton of waste

-FIT vs deployment efficiency

Reply: Thank you for your comment. In Sec. 3.1, we briefly included the description about the Japan’s case in the installed capacity of biomass-to-power systems by adopting the gasification of solid-type woody biomass based on a new reference [20].

Q8. Tables 1–5 currently function only as data displays. They must be used to produce:

Derived indicators, Trends, Ratios and Performance metrics

Reply: Thank you for your comment. We included the description about the trends by depicting a new chart (Figure 1).

Q9. Some percentage values in Table 1 are inconsistent (e.g., totals not summing to 100%). This must be verified and corrected.

Reply: It has been revised to make it correct.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Dear authors, I believe that all the observations I shared with you in the previous review have been satisfactorily addressed, which has substantially improved the quality of the article. Congratulations. Best regards.

Author Response

Q1. I believe that all the observations I shared with you in the previous review have been satisfactorily addressed, which has substantially improved the quality of the article.

Reply: Thank you for the reviewer’s positive comment on the revised manuscript.

Reviewer 3 Report

Comments and Suggestions for Authors

1) Research question / scientific objective
The paper still says it “updates Taiwan’s achievements” and “addresses challenges” (Abstract, Introduction) there is no research question, hypothesis, or analytical framing anywhere. It remains a policy overview.

2) Energy potential of biomass (MJ → GWh)

Reviewer demand: LHV × recoverable fraction × efficiency → GWh/year

What the paper does:
Section 4.1 lists tons of biomass (rice straw, manure, husks, etc.) but never converts them into energy or electricity potential.
No MJ/kg, no recoverable fraction, no efficiency, no GWh.

3) FIT vs deployment (causality)

It only states that FIT increased and capacity increased (Table 4 vs Table 2) and asserts causality without analysis.
There is no regression, no elasticity, no scenario modeling.

4) Capacity factor paradox (Table 2)
They notice the paradox (capacity ↓, generation ↑) and give a verbal explanation (CHP efficiency, phase-out) but they never compute capacity factors (GWh/MW/yr).
No numbers, no trends, no maturity metrics.

5) CO₂ accounting
It repeats that biomass “reduces GHG” but provides zero emission factors, zero kWh-based CO₂, zero comparisons.
No numbers anywhere.

6) Economics (FIT → profitability)
Only one sentence: biogas plants have 8–12 year payback (Section 3.1).
No CAPEX, no OPEX, no revenue per MW, no system cost to Taiwan.

7) International comparison
Mentions Japan once qualitatively (more gasification capacity) but provides no MW per capita, no waste-to-electricity ratios, no FIT efficiency.

8) Use of Tables 1–5 as analytical tools
Tables are reported but not exploited analytically.
No ratios (e.g., GWh/MW), no growth rates, no efficiencies.

9) Percentage inconsistencies in Table 1
Table 1 still contains typos and inconsistencies (e.g., “8..6%”, “18..5%”) and questionable percentage totals.
No correction or validation is provided.

Comments on the Quality of English Language

Substantial revisions to text or experimental methods needed

Author Response

Q1. question / scientific objective
The paper still says it “updates Taiwan’s achievements” and “addresses challenges” (Abstract, Introduction) there is no research question, hypothesis, or analytical framing anywhere. It remains a policy overview.

Reply: Thank you for your comment. In the Introduction, we addressed the imitations of biomass-to-power expansion in Taiwan based on insufficient domestic biomass feedstock and its high operation cost. In this regard, we briefly analyzed the trends of biomass-to-power in terms of installed capacity and electricity generation during the period of 2020-2024 (Sec. 2.1), and also summarized the challenges in the development of biomass-to-power and their possible solutions (Sec. 4). After all, the type of the paper is a perspective character.

Q2. Energy potential of biomass (MJ → GWh)

Reviewer demand: LHV × recoverable fraction × efficiency → GWh/year

Reply: Indeed, the energy potential of biomass in Taiwan can be estimated by its heating value (HV), recoverable fraction and combustion efficiency. As required, we briefly estimated the energy potential of main biomass resources (i.e., rice straw, rice husk and spent mushroom compost) by using the data on annual generation amount, HV, recoverable fraction and combustion efficiency, which was added to the first paragraph of Sec. 4.1. Herein, manure was not included the calculation because of its high contents of moisture and ash.

“In addition, a simple method was used to estimate the electricity potential of main biomass resources (i.e., rice straw, rice husk and spent mushroom compost) based on the annual generation amount, heating value (HV), recoverable fraction and combustion efficiency. Herein, manure was not included the calculation because of its high contents of moisture and ash. Adopting the following data, the electricity potential was thus estimated to be approximately 50.3 GWh/year in Taiwan without considering other energy consumption issues during operation (e.g., collection, transport, pretreatment).

Annual generation amount [26]: rice straw (1,542.9 × 10³ metric tons), rice husk (308.5 × 10³ metric tons), spent mushroom compost (141.7 × 10³ metric tons).

Values of HV [28, 29]: rice straw (15.4 MJ/kg), rice husk (15.2 MJ/kg), spent mushroom compost (21.3 MJ/kg).

Recoverable fraction (estimated values) [26]: 30%.

Combustion efficiency [30]: 20%.

Electricity potential = [(1,542.9 × 10⁶ kg/year× 15.4 MJ/kg× 10⁶ J/MJ × 30% × 20% ÷ (3.6 × 10¹² J/GWh)] + [(308.5 × 10⁶ × 15.2 × 10⁶ × 30% × 20% ÷ (3.6 × 10¹²)] + [(141.7 × 10⁶ × 20.6 × 10⁶ × 30% × 20% ÷ (3.6 × 10¹²)] = 396.0 + 78.2 + 48.7 = 522.6 GWh/year”

Q3. FIT vs deployment (causality)

It only states that FIT increased and capacity increased (Table 4 vs Table 2) and asserts causality without analysis.
There is no regression, no elasticity, no scenario modeling.

Reply: Thank you for your comment. In Sec. 4.2, we briefly included the analytical description about the regression between FIT and capacity growth in Taiwan based on the data in Table 2 and Table 4.

“…… As compared to the data in Table 2, this promotion incentive by increasing FIT rate from 5.1176 NT$/kWh in 2020 to 7.0192 NT$/kWh in 2023 (increased by 37.2%) positively facilitated the establishments of biogas-to-power plants in terms of installed capacity by increasing from 14.5 MW in 2021 to 21.4 MW IN 2024 (a 47.6% increase). ……”

Q4. Capacity factor paradox (Table 2)
They notice the paradox (capacity ↓, generation ↑) and give a verbal explanation (CHP efficiency, phase-out) but they never compute capacity factors (GWh/MW/yr).
No numbers, no trends, no maturity metrics.

Reply: Thank you for your comment. Regarding the paradox in Table 2 we briefly included the analytical description about the capacity factors using the data in Table 2.

Q5. CO₂ accounting
It repeats that biomass “reduces GHG” but provides zero emission factors, zero kWh-based CO₂, zero comparisons.
No numbers anywhere.

Reply: Thank you for your comment. We estimated the mitigation of equivalent CO₂ (CO_2eq) emissions resulting from the biomass-to-power based on an updated electricity carbon emission factor (0474 kg CO_2eq/kWh, announced by the Taiwan government in 2024), which has been added to the new (third) paragraph of Sec. 3.1.

“Using the official electricity carbon emission factor for 2024 (i.e., 0.474 kg CO₂-equivalent per kilowatt-hour, announced by the Taiwan government) and the data in Table 2, the mitigation of equivalent CO₂ (CO_2eq) emissions (metric ton, MT) resulting from the biomass-to-power can be thus estimated as follows:

CO_2eq (MT) = (173.8 + 63.9) GWh × 10⁶ kWh/GWh × 0.474 kg/kWh × 10^-3 MT/kg)

= 112,670 MT

It should be noted that the estimation of CO₂ accounting was only based on the actual biomass-to-power in 2024 without considering other carbon emission processes like feedstock collection, transport and pretreatment.”

Q6. Economics (FIT → profitability)
Only one sentence: biogas plants have 8–12 year payback (Section 3.1).
No CAPEX, no OPEX, no revenue per MW, no system cost to Taiwan.

Reply: Thank you for your comment. In Sec. 3.1, Regarding the costs of biogas-to-power systems, we accessed the website at the Energy Administration and also inquired with the owners of biomass-to-power systems, but received limited data. We briefly included the description about the payback periods and initial installation cost in the current state of biogas-to-power systems in Taiwan.

“……….. Based on the data in Table 2, the values of capacity factor for gas-type biomass-to-power systems were larger than those for solid-type biomass-to-power systems during the period of 2020-2024, which can be attributed to higher energy efficiencies in the former. According to the preliminary data on cost analysis by the owners of biomass-to-power systems, the payback periods of the existing biogas-to-power systems in Taiwan ranged from 8 to 12 years, which were attributed to high initial installation cost (NT$205,400/kW, equivalent to US$6,700/kW) and operation cost (NT$24,116/kW, equivalent to US$800/kW). On the other hand, the contradiction between the installed capacity decreased and electricity generation increased in the solid biomass-to-power systems could be attributed to the phase-out of some cogeneration plants (e.g., sugar refineries) and the significant increase in heat recovery efficiency in the existing cogeneration plants.”

Q7. International comparison
Mentions Japan once qualitatively (more gasification capacity) but provides no MW per capita, no waste-to-electricity ratios, no FIT efficiency.

Reply: Thank you for your comment. In the second (new) paragraph of Sec. 3.1, we briefly included the description about the Japan’s case in the installed capacity and feed-in-tariff (FIT) of biomass-to-power systems based on the new references [20-22].

“As compared to other countries, the installed capacity of biomass-to-power systems by mostly adopting the gasification of solid-type woody biomass (including unutilized wood, ordinary wood, recycled wood) in Japan was significantly larger than that in Taiwan [20]. This status should be related to the feed-in-tariff (FIT) policy. Currently, Japan’s FIT tariff rates for biomass-to-power were different by category and installed capacity. For example, ¥40 (US$0.38)/kWh for domestic unutilised wood with less than 2MW capacity and ¥39 ($0.37)/kWh for biogas-to-power, but ¥32 (US$0.30)/kWh for domestic unutilised wood with more than or equal to 2MW capacity. According to the report [21], Japan's biomass-to-power capacity has grown significantly, driven by its FIT system since 2012, with operational capacity reaching around 7.3 GW by March 2024, nearing its 8 GW target for 2030 (including about 0.2 GW target from biogas-to-power). This target will be about hundred times compared to that of Taiwan (Table 1). Regarding the FIT rates of biomass-to-power systems in Japan [22], it showed that the Japan government encouraged small-scale biomass-to-power plants and biogas plants due to the cost analysis.”

Q8. Use of Tables 1–5 as analytical tools
Tables are reported but not exploited analytically.
No ratios (e.g., GWh/MW), no growth rates, no efficiencies.

Reply: Thank you for your comment. We included the analytical description about the growth rates or ratios (Sec.2.2, Sec. 3.1 and Sec. 4.2, respectively) based on the data in Table 1, Table 2, and Table 4.

Q9. Percentage inconsistencies in Table 1
Table 1 still contains typos and inconsistencies (e.g., “8..6%”, “18..5%”) and questionable.

Reply: They have been revised to make them correct.

Author Response File: Author Response.pdf