Environmental Impact Assessment of Solid Waste to Energy Technologies and Their Perspectives in Australia
Round 1
Reviewer 1 Report
English language and style are minor spell check required.
Paper lacks an adequate explanation of results.
Author Response
English language and style are minor spell check required.
Response:
- Thank you for the comment. The manuscript has been revised and corrections have been applied.
Paper lacks an adequate explanation of results.
Response:
- Thank you for the comment. More explanations have been added to the result section as advised as follows (Page 9, Lines 355-358, Page 9, Lines 368-370, Page 11, Lines 396-400 in the Clean Copy of the Revised Manuscript):
“The absence of digestion in incineration compared to landfilling and AD technologies avoid methane emissions. Fugitive methane in landfills is one of the main sources of GHG emissions in landfilling treatment.”
“Translation of emissions into a limited number of endpoint scores utilising characterisation factors is useful to compare the technologies at a higher level.”
“Global warming has over 86.5% contribution to damage to ecosystem. Therefore, global warming is the most influential impact category in both ecosystem and human health endpoint impacts. Employing carbon capture technology and improving the pollution control system in incineration power plants can reduce GHG emissions and alleviate the ecosystem and human health impacts.”
Reviewer 2 Report
Title: Environmental impact assessment of solid waste to energy technologies and their perspectives in Australia
Summary: An excellent piece of an article. Authors constructed review an excellent approach. The growing share of renewable energy in the Australian power grid is expected to decrease the grid GHG emissions and the effect of avoided impacts of replaced electricity. The literature provided is up to date. This version of article can be acceptable for publication following are some suggestions for further improvements.
Review comments:
1. Graphical Abstract: Impressive.
2. Abstract: Acceptable.
3. Introduction: Very well constructed. For the line 35-37: “The world is currently facing global warming due to high level of greenhouse gas (GHG) emissions mainly originating from fossil fuel consumption, while the consequent 36 extreme climate change impacts threaten the life throughout the planet [1-2]”. Reference needs to be quoted. Following published articles might be helpful.
- [1] Advancements of fermentable sugar yield by pretreatment and steam explosion during enzymatic saccharification of Amorphophallus sp. starchy tuber for bioethanol production
- [2] Enhancement of biohydrogen production by employing a packed-filter bioreactor (PFBR) utilizing sulfite-rich organic effluent obtained from a washing process of beverage manufactures
4. Materials and methods: Well explanatory.
5. Results and discussion: Acceptable in present form.
6. Figures and Graphs: Acceptable.
7. Conclusion: Acceptable.
8. Line 666: Check space before NPI.
Author Response
Title: Environmental impact assessment of solid waste to energy technologies and their perspectives in Australia
Summary: An excellent piece of an article. Authors constructed review an excellent approach. The growing share of renewable energy in the Australian power grid is expected to decrease the grid GHG emissions and the effect of avoided impacts of replaced electricity. The literature provided is up to date. This version of article can be acceptable for publication following are some suggestions for further improvements.
Response:
- We would like to appreciate the comments of the respected reviewer. We modified the paper based on the comments. The details of modifications in the manuscript is presented in response to the comments below.
Review comments:
- Graphical Abstract: Impressive.
Response:
- Thank you for the comment.
- Abstract: Acceptable.
Response:
- Thank you for the comment.
- Introduction: Very well constructed. For the line 35-37: “The world is currently facing global warming due to high level of greenhouse gas (GHG) emissions mainly originating from fossil fuel consumption, while the consequent 36 extreme climate change impacts threaten the life throughout the planet [1-2]”. Reference needs to be quoted. Following published articles might be helpful.
- [1] Advancements of fermentable sugar yield by pretreatment and steam explosion during enzymatic saccharification of Amorphophallus sp. starchy tuber for bioethanol production
- [2] Enhancement of biohydrogen production by employing a packed-filter bioreactor (PFBR) utilising sulfite-rich organic effluent obtained from a washing process of beverage manufactures
Response:
- Thank you for the comment. 2 references have been added to the manuscript as advised as follows:
- Dastjerdi, B.H.; Strezov, V.; Kumar, R.; Behnia, M. Economic Feasibility and Sustainability Assessment of Residual Municipal Solid Waste Management Scenarios in NSW, Australia. Sustainability 2021, 13, 8972, doi:10.3390/su13168972.
- Chu, C.-Y.; Zheng, J.-L.; Bhuyar, P. Enhancement of Biohydrogen Production by Employing a Packed-Filter Bioreactor (PFBR) Utilising Sulfite-Rich Organic Effluent Obtained from a Washing Process of Beverage Manufactures. Biomass and Bioenergy 2022, 161, 106451, doi:10.1016/j.biombioe.2022.106451.
- Materials and methods: Well explanatory.
Response:
- Thank you for the comment.
- Results and discussion: Acceptable in present form.
Response:
- Thank you for the comment.
- Figures and Graphs: Acceptable.
Response:
- Thank you for the comment.
- Conclusion: Acceptable.
Response:
- Thank you for the comment.
- Line 666: Check space before NPI.
Response:
- Thank you for the comment. The typo mistake has been corrected as advised.
Reviewer 3 Report
The work aims to assess the environmental impact of waste to energy technologies and their perspective in Australia.
Overall, the manuscript is well-written and organized. But still, I have found some flaws in key features of the articles, which are mentioned below.
1. The abstract is clearly described. But, please shortened by highlighting the background, purpose, brief methodology and finding of the research
2. The introduction is nice, the purpose of the research has been written clearly
3. What kind of fuels used in Australian power grid?
4. Kindly give an overview on the energy mix in Australia? How many percentages of the use of fossil-based fuel such as coal, natural gas, and oil and renewable energy source including solar, wind, and other sources
5. Does Australia consider the use of biomass (wooden based, agricultural and forestry residues) as an energy source?
6. Table 1 would be more perfect and meaningful for environmental assessment if you could provide the national standard limit / threshold limit value each air pollutants
7. From the graphical abstract, it seems that in Australia the food waste and municipal solid waste is well separated before being disposed of. Please give your opinion and described them in the introduction
8. The properties of waste need to be presented including the moisture content, heating value, and proximate and ultimate analysis if possible. Those waste properties will be easily compared with the properties if black coal and brown coal.
9. Please consider to use the combination of color and pattern style for the figures you have drawn e.g., Fig.1 and Fig.2
Author Response
The work aims to assess the environmental impact of waste to energy technologies and their perspective in Australia.
Overall, the manuscript is well-written and organised. But still, I have found some flaws in key features of the articles, which are mentioned below.
Response:
- Thank you for the comment. We highly appreciate the reviewers for their efforts and time to review our manuscript.
- The abstract is clearly described. But, please shortened by highlighting the background, purpose, brief methodology and finding of the research
Response:
- Thank you for the comment. We have modified the abstract of the manuscript as advised as follows:
“The study assessed the environmental impacts of landfilling, anaerobic digestion and incineration technologies and investigated the effect of the replaced source of electricity on environmental impacts of these waste to energy (WtE) technologies. Data published in the national pollutant inventories and ReCiPe impact assessment method was employed in this study. The study showed that electricity generation through incineration had the highest impacts on human health and ecosystems followed by landfilling. Compared to the electricity of the Australian national grid, electricity generated from all the three WtE technologies have lower environmental impact. The results revealed that global warming and fine particulate matter formation with more than 97.6% contribution were the main impact factors for human health, while terrestrial acidification, global warming and ozone formation were contributing to more than 99% of the impacts to ecosystems. Global warming was the most impactful category on human health and ecosystems for incineration with over 85% contribution to both endpoint categories. Incineration revealed significantly higher avoided global warming impacts to human health and ecosystems than landfilling from treatment of one tonne of solid waste by replacing electricity from brown coal, black coal or the Australian power grid. The growing share of renewable energy in the Australian power grid is expected to decrease the grid GHG emissions and the effect of avoided impacts of replaced electricity. The results revealed that if the GHG emissions from the Australian power grid (757 kg CO2 eq/MWh) decreases to break-even point (621 kg CO2 eq/MWh), incineration loses the climate advantage over landfilling.”
- The introduction is nice, the purpose of the research has been written clearly
Response:
- Thank you for the comment.
- What kind of fuels used in Australian power grid?
Response:
- Thank you for the comment. Table 2 shows the type of fuel that power plant connected to grid consume.
- Kindly give an overview on the energy mix in Australia? How many percentages of the use of fossil-based fuel such as coal, natural gas, and oil and renewable energy source including solar, wind, and other sources
Response:
- Thank you for the comment. We have modified Table 2 by adding a percentage column to the table as advised as follows:
Table 2. Selected power plants connected to the power grid for each technology and annual electricity generation and GHG emissions per technology from July 2017 to June 2018 [31].
|
Primary Fuel |
Number of power plants connected to grid |
Electricity generation (MWh) |
Total Emissions |
Emission Intensity |
Percentages of total electricity generation |
|
Black coal |
17 |
1.26E+08 |
1.12E+08 |
8.83E-01 |
55% |
|
Brown coal |
3 |
3.61E+07 |
4.41E+07 |
1.22E+00 |
15.7% |
|
Gas |
76 |
3.10E+07 |
1.59E+07 |
5.12E-01 |
13.5% |
|
Hydro |
57 |
1.57E+07 |
4.05E+05 |
2.58E-02 |
6.83% |
|
Wind |
57 |
1.51E+07 |
2.48E+04 |
1.64E-03 |
6.57% |
|
Waste coal mine gas |
11 |
1.69E+06 |
9.55E+05 |
5.63E-01 |
0.73% |
|
Coal seam methane |
7 |
1.50E+06 |
8.27E+05 |
5.50E-01 |
0.65% |
|
Landfill gas |
49 |
9.04E+05 |
5.35E+04 |
5.91E-02 |
0.39% |
|
Solar |
15 |
7.87E+05 |
2.65E+03 |
3.37E-03 |
0.34% |
|
Bagasse |
3 |
5.26E+05 |
1.94E+04 |
3.69E-02 |
0.23% |
|
Sewage |
1 |
6.43E+04 |
4.25E+03 |
6.61E-02 |
0.03% |
|
Biofuel (refuse derived fuel) |
1 |
1.85E+04 |
3.69E+04 |
2.00E+00 |
8.04E-03% |
|
Diesel |
10 |
1.14E+04 |
1.28E+04 |
1.12E+00 |
4.97E-03% |
|
Kerosene |
1 |
9.74E+03 |
1.39E+04 |
1.42E+00 |
4.24E-03% |
|
Total |
308 |
2.30E+08 |
1.74E+08 |
7.57E-01 |
100% |
- Does Australia consider the use of biomass (wooden based, agricultural and forestry residues) as an energy source?
Response:
- Thank you for the comment. The data provided in Table 2 shows that Australia uses bagasse and biofuel (refuse derived fuel) as energy sources for electricity generation.
- Table 1 would be more perfect and meaningful for environmental assessment if you could provide the national standard limit / threshold limit value each air pollutants
Response:
- Thank you for the comment. To the best of our knowledge, there is no national standard limit/threshold value for emissions from landfill, AD and incineration in Australia. The jurisdiction level guideline in Northern Territory draw allowed limits for exhaust gas emission concentrations for incineration power plants. We have used data from the national pollution inventory which is based on annual emissions of facilities. While the standards are based on allowed limits of exhaust gas emission concentrations and adding the values to the table would make the table very confusing.
- From the graphical abstract, it seems that in Australia the food waste and municipal solid waste is well separated before being disposed of. Please give your opinion and described them in the introduction
Response:
- Thank you for the comment. We have added explanation to the manuscript as advised as follows (Page 4, Lines 140-144, in the Clean Copy of the Revised Manuscript):
“Data related to direct pollutant emissions of the AD power station operating in Australia (Earthpower facility) was adopted for AD technology from NPI [32]. The Earthpower facility accepts source separated food waste with no more than 5% contamination by weight [33].”
- The properties of waste need to be presented including the moisture content, heating value, and proximate and ultimate analysis if possible. Those waste properties will be easily compared with the properties if black coal and brown coal.
Response:
- Thank you for the comment. We have added explanation about the references of data related to the properties of Australian solid waste as advised as follows (Page 7, Lines 209-212, in the Clean Copy of the Revised Manuscript):
“Treatment of one tonne of solid waste generates a different amount of electricity through incineration (0.798 MWh/t) and landfilling (0.037 MWh/t) [35,45]. The characteristics of Australian solid waste including the moisture content, ash content and heating value was adopted from national reports and literature [46,47].”
- Please consider to use the combination of color and pattern style for the figures you have drawn e.g., Fig.1 and Fig.2
Response:
- Thank you for the comment. We have modified the colour in Fig.1 and Fig.2, as advised.
