Review Reports - National Mineral Waste Databases as an Information Source for Assessing Material Recovery Potential from Mine Waste, Tailings and Metallurgical Waste

Round 1

Reviewer 1 Report

This paper presents a review of national mine waste inventories from 7 European countries to evaluate the potential to use these inventories as an initial source of information to identify promising secondary source of strategic or valuable metals. This paper is of huge interest as several countries around the world are looking at the potential to recover strategic metals or critical metals from secondary sources including mine tailings to reduce their dependency towards China or Democratic Republic of Congo for their supplies of these crucial elements for industry development. However, I suggest to the author to add some information of the results and discussion to highlight the type of data that are missing and that should be included in the future to use these inventories to identify secondary source of elements of interest.

General comments:

Relevant information are sometimes presented without any reference. I suggest to the author to add reference when specific information or values are indicated in the manuscript to identify where they found this information.

Title: the title of the present paper reflects the content and contain relevant search terms for discoverability.

Abstract is very well-written and summarize the main objectives and results of the paper.

Introduction : This section is very interesting and the relevant literature is presented to highlight the research needs. An interesting paper has recently been published in Minerals on the challenges related to the processing of old mine waste in the Russian Federation. It might be of interest to present this work: “Environmental and Business Challenges Presented by Mining and Mineral Processing Waste in the Russian Federation”.

Page 2 Lines 49-52: Could you, please, add a reference.
Page 3 Lines 81: Replace “exergy costs” by “energy costs”.
Page 3 Lines 87-88: The authors are presenting the technologies used to recover metals of interest from mine waste. Mine waste reprocessing including the use of hydrometallurgical processes and agromining are also getting attention over the last years. It might be of interest to discuss these processes also, not only biohydrometallurgical processes.
Page 3 Lines 98-103: The link between this paragraph and the previous or the next one is not clear. This paragraph should be moved at the beginning of the introduction or additional sentences should be added to facilitate the reading between each paragraph.
Page 4 Lines 130-137: These sentences should be moved to the Materials and Methods as they present the methodological approach used in the present study.

Material and Methods: This section presents the methodological approach used to carried out the present study. This section is useful to better understand how the experiment was performed. Additional information are required:

Page 4 Lines 150-151: “This objective was achieved through a literature review,” Could you, please, present as Supplementary Materials the different papers used on this literature review?
Page 4 Lines 152-153: “refined by experts”. Could you, please, specify the number of experts and their field of expertise?
Page 4 Lines 154-156: “These parameters included those which define the extractability and accessibility of the secondary resources, the policy and legislative environment, as well as relevant chemical and physical properties.” Could you, please, be more specific about what you mean by “extractability”, “accessibility”, “relevant chemical and physical properties”?
Page 5 Lines 186-189 and Line 194: Could you, please, replace “physiochemical properties” by “physico-chemical properties”?

Results and Discussion:

For each country, it might be of interest to present the number of mine site registered and the number of site for which each parameter (B1, B2, etc.) is available or missing to get a better idea of how national inventories can be used as relevant basic tool for the identification of secondary source of strategic metals.
Did the authors consider if the mine sites have been restored or revegetalized? This could be a restriction to the potential recovery of strategic metals from mine tailings. Are these information available in the different national inventories?
Page 8 Lines 249-250: “classified as PTE”. Could you, please, specify the potential toxic elements registered in the national inventories. Are these PTE identic for the different countries?
Page 10 Lines 300-302: “have been used in in conjunction with information held by local authorities and to assess the risk from closed and abandoned mine” Please, remove a term “in”.
The authors made some recommendation to improve the presentation of the data in the national inventories. It might be of interest to prioritize the data that should be collected to identify the potential to recover strategic metals from mine tailings.

Comments for author File: Comments.doc

Author Response

Dear reviewer.

We would like to thank you for your time, a positive review and for all the valuable comments, which certainly helped to make improve the paper. We have considered each comment carefully and our response to each comment, point by point, can be found below.

All changes are shown using track changes, except those changes related to the references arrangement according to the instructions for authors. Other smaller changes in forms and tables can be corrected later during the publication process.

We hope that the paper is now acceptable for the publication.

Best regards,

authors

General comments:

Relevant information are sometimes presented without any reference. I suggest to the author to add reference when specific information or values are indicated in the manuscript to identify where they found this information.

>>> We tried to do that, we hope this is improved now.

Title: the title of the present paper reflects the content and contain relevant search terms for discoverability.

Abstract is very well-written and summarize the main objectives and results of the paper.

Page 2 Lines 49-52: Could you, please, add a reference.

>>> Added to line 50

Page 3 Lines 81: Replace “exergy costs” by “energy costs”.

>>> This paragraphs is now removed .

Page 3 Lines 87-88: The authors are presenting the technologies used to recover metals of interest from mine waste. Mine waste reprocessing including the use of hydrometallurgical processes and agromining are also getting attention over the last years. It might be of interest to discuss these processes also, not only biohydrometallurgical processes.

>>> These technologies have been included (line 94-95), however, much of this content has been removed.

Page 3 Lines 98-103: The link between this paragraph and the previous or the next one is not clear. This paragraph should be moved at the beginning of the introduction or additional sentences should be added to facilitate the reading between each paragraph.

>>> Thank you for the observation. Some of this paragraph has been deleted, but the majority has been transferred and incorporated in text to lines 135 to 137 where it fits better.

Page 4 Lines 130-137: These sentences should be moved to the Materials and Methods as they present the methodological approach used in the present study.

>>> Some of this content has been incorporated into the Materials and Methods (lines 215 to 221), with the rest being removed to avoid repetition.

Page 4 Lines 150-151: “This objective was achieved through a literature review,” Could you, please, present as Supplementary Materials the different papers used on this literature review?

>>> Thank you for your interest in the review. However, we feel providing this information would shift the focus from research paper to review paper. We have, therefore, decided to present four key papers from the topic instead, with the notation, that references mentioned in these papers were also included in this study (lines 184 to 189).

Page 4 Lines 152-153: “refined by experts”. Could you, please, specify the number of experts and their field of expertise?

>>> We can not identify exact number of experts in such short time, however, we have indicated their number and fields of expertise, and provided a list of the events that led to this paper (lines 193 to 202).

Page 4 Lines 154-156: “These parameters included those which define the extractability and accessibility of the secondary resources, the policy and legislative environment, as well as relevant chemical and physical properties.” Could you, please, be more specific about what you mean by “extractability”, “accessibility”, “relevant chemical and physical properties”?

>>> Done, we have added a sentence to lines 191 to 193: "By accessibility we mean if there are any environmental or societal obstacles for material recovery project, and by extractability we mean whether the material can be extracted without posing serious risk to workers and environment." We have also adjusted names of valorisation parameters, to be coherent with the text.

Page 5 Lines 186-189 and Line 194: Could you, please, replace “physiochemical properties” by “physico-chemical properties”?

>>> Done (L239, 245 and Tab. 2).

Results and Discussion:

For each country, it might be of interest to present the number of mine site registered and the number of site for which each parameter (B1, B2, etc.) is available or missing to get a better idea of how national inventories can be used as relevant basic tool for the identification of secondary source of strategic metals.

Did the authors consider if the mine sites have been restored or revegetalized? This could be a restriction to the potential recovery of strategic metals from mine tailings. Are these information available in the different national inventories?

Page 8 Lines 249-250: “classified as PTE”. Could you, please, specify the potential toxic elements registered in the national inventories. Are these PTE identic for the different countries?

>>> Thank you for these three comments, these are useful observations – there is so much variation between the inventories that such information cannot be easily extracted. However, we have provided additional information to the Table 1 regarding the total number of addressed sites, number of sites with more detailed assessment, and a list of harmful substances measured. Information whether the site is revegetated or not have been added as another valorisation parameter (Table 2).

Page 10 Lines 300-302: “have been used in in conjunction with information held by local authorities and to assess the risk from closed and abandoned mine” Please, remove a term “in”.

>>> Done (line 400).

The authors made some recommendation to improve the presentation of the data in the national inventories. It might be of interest to prioritize the data that should be collected to identify the potential to recover strategic metals from mine tailings.

>>> A new recommendation is inserted (line 427 to 429): "A shift of scope from environmental protection towards including consideration of material recovery from abandoned mine waste sites is needed in any possible future nation or EU-wide data collection”.

Reviewer 2 Report

Review of Minerals – 771122 : National mineral waste databases as an information source for assessing material recovery potential from mine waste, tailings and metallurgical waste

The manuscript presents a study on databases on mine waste sites from seven European countries to assess the potential use of the information stored in the databases for mine waste reprocessing or repurposing. The topic is important and relevant for the current trend in valorisation of industrial wastes. The authors express clearly the context of the research through an historical perspective on the European mining industry. The objective of the study is clear and relevant. The methodology to determine the key mine waste valorisation parameters was comprehensive and collaborative, which ensure acceptance (if not consensus) among stakeholders. The discussion and conclusion highlight the limitations of the national databases and the authors formulate interesting recommendations.

I recommend accepting the paper with very few minor edits expressed below.

Line 84: Explain what is meant by “direct” and “indirect” recovery. Does “direct” mean a single-step process that provides the end product?
Figure 2: Enlarge the entire figure to make the legends readable and easier to distinguish on the maps. In Fig 2a, there is pink in the legend, but it is not visible on the map.
Table 3: Identify the legend for the numbers in brackets (1 to 4)
Line 253: refer to Table 5.

Author Response

Dear reviewer.

We hope that the paper is now acceptable for the publication.

Best regards,

authors

Comments and Suggestions for Authors

Review of Minerals – 771122 : National mineral waste databases as an information source for assessing material recovery potential from mine waste, tailings and metallurgical waste

I recommend accepting the paper with very few minor edits expressed below.

Line 84: Explain what is meant by “direct” and “indirect” recovery. Does “direct” mean a single-step process that provides the end product?

>>> This section has been removed from the paper.

Figure 2: Enlarge the entire figure to make the legends readable and easier to distinguish on the maps. In Fig 2a, there is pink in the legend, but it is not visible on the map.

>>> Figure 2 has been enlarged.

Table 3: Identify the legend for the numbers in brackets (1 to 4)

>>> Thank you. Numbers must have been lost during conversion process.

Line 253: refer to Table 5.

>>> Done (line 323).

Reviewer 3 Report

see attached word doc

Comments for author File: Comments.pdf

Author Response

Dear reviewer.

We hope that the paper is now acceptable for the publication.

Best regards,

authors

Review Manuscript ID: minerals-771122

Type of manuscript: Article

Title: National mineral waste databases as an information source for assessing material recovery potential from mine waste, tailings and metallurgical waste

General: Abstract lines21 to 35 : Given the title : Assessing the Material Recovery Potential it is somewhat disturbing that not a single material ( i.e. metal or mineral ) is given in the in any of the tables. is given. The mine wastes appear to stem of historic mines Even in Wikipedia , I just picked Spain https://en.wikipedia.org/wiki/Category:Mines_in_Spain . I do not understand this and checked Poland https://en.wikipedia.org/wiki/List_of_mines_in_Poland , https://en.wikipedia.org/wiki/Category:Mines_in_France and I am sure I could go on. Either I missed something fundamental, or the National Mineral Waste Database used in for this objective is just not the correct source.

Below just some comments so you know this reviewer really tried to go through the manuscript in detail.

IN line 23 in the abstract it is stated but on line 29 it is stated “…..…’for their resource recovery”. I am puzzled and the conclusion in line 33 -34 “This misses an opportunity to see theses sites as a resource “. Well if one takes the wrong database this conclusion is correct !!!. The Raw Minerals Initiative ( COM(2008) seems not to contain any minerals – strange !

>>> Thank you for the comments, but we feel that the reviewer has misunderstood the objectives of this research. Our research aimed to assess material recovery potential from old and abandoned mine waste sites on the territory of EU; so, it is high level assessment. We have examined national mine waste inventories as a potential source of the this information, given that each EU member state is obliged to prepare and make public these inventories we felt that they made provide a comparable source of the necessary data. Unfortunately, there are, to our knowledge no other comparable datasets held at the national level across the EU. However, we found that such inventories are not suitable for this use as they do not contain the necessary information, and we feel that this is a valuable finding as EU member states are potentially missing an opportunity to incorporate this information into these inventories, increasing their usefulness to experts and policy makers with this manuscript. Of course, one will certainly collect much more information if a project has a potential from a numerous other publication, reports, and site investigations etc. But this is not the topic of this paper; this paper focuses solely on national mine waste databases according to the EC "mine waste" directive.

>>> However, to reduce such misunderstanding also by other readers we have reformulated the penultimate section of introduction, and we hope it is much clearer now what is the relation between COM paper, directive, inventories, and minerals (lines 133 to 154).

Line 53 correct at the end of the line mineral processing and leave plant out – as you do not process the mineral plant –

>>> Done (line 53).

Line 74 Figure 1 is useful – but in none of the tables we find the amounts, or an estimate of the amount based on mineralogy / geology. However what is also essential to is the periodic table of endangered elements – this is also essential for Sustainability https://www.acs.org/content/acs/en/greenchemistry/research-innovation/endangered-elements.html

>>> Thank you, we have now referred to this list in the paper (Lines 73 to 77).

Line 110 …..in the past and could act as a potential … it is very few mineral mining wastes which do not lead to pollution due to natural weathering.

>>> Yes, this has been corrected (line 119).

Line 115 /RIS-RECOVER ,01 January 2018 – 31 March 2021 :Objective :Due to their quantity and composition, mining tailings and metallurgical heaps can pose a substantial risk to the environment, while on the other hand representing valuable sources of secondary raw materials, including critical raw materials. The amount of funding is impressive – so I would assume that there are also some data re resources in wastes.

>>> Yes, there are, but assessing information provided by such projects are not within the scope of this paper, as they are not available at a national or EU level, which is the focus of this paper. So, we only mentioned them.

Line 132 -133 How can major data gaps ( which are data which do not exists ) be evaluated – they can be identified – and recommendations are not enabled – this needs to be rephrased

>>> This sentence, which was moved to section 2.2 following the suggestion of Rewiewer#1 , has been reformulated (lines 220 to 222): " Major data gaps on critical information for deposit ranking were identified, and according to the findings recommendations made, to assist a collection of initial information, needed for mine wastes resource recovery project in the future."

Line 145 What is COSI

>>> It is European Cooperation in Science and Technology; an explanation has been added to the text (line 174).

Line 146 “Resource potential in residues from extractive industries” This would need to be evaluated for the mining industry as for example in the attachment of the Canadian Mineral Sector

>>> This is the official title of the working group, so we cannot change it. We have, however, put this in quotation marks which hopefully makes this clear (line 175).

Lines 159 to 168 what do all these other non-European countries have in common in the mining industry ?.

>>> These are mine waste recycling projects, where we have much more detailed information to work on in terms of the parameters needed to evaluate the resource potential from the waste – we felt that the experience of other countries was useful to develop the parameters that would be required in the EU inventories..

Lines 171 to 197 : the question arises are these parameters , which are not quantified useful to a mining company ? Please explain ?

>>> Yes, during the whole process we found out that also qualitative (descriptive) parameters are needed, because not all parameters can be quantified, i.e. legislative or land-use barriers, for example, but are of crucial importance for mining company.

Table 1 page 6- of 18 needs at least a title Table 1 “continued on page 7-18 in the Table is no mention of subsidence of underground working or in coal mines a major problem

>>> Thank you for the comment, we assume this will be corrected during the publication process when the paper will get its final form.

Line 201 I could not find a Table 2 so I suspect it might be Figure 2

>>> Table 2 is above (a previous page). I am sure this will also be corrected during final production.

Line 213 The national mine waste inventory is not considered useful . but then one questions why other sources are not used.

>>> Because this was not the scope of this paper. Of course, one can look into other sources, but in this study, we assessed only national mine waste registries, as they are required in each member state and we feel present an opportunity to provide a common source of information.

Line 259 to 260j Figure 2: how can language be a problem there are companies which could translate the material- with this the barrier would be removed.

>>> Yes, this is true, but we feel that, when making decisions across member states, it is beneficial if data are available in one of the "world" languages. Added an explanation (lines 363 to 371): " Another potential barrier is language, where the information and reports are, with the only exception of Hungary, provided only in the national language. UK, France or Spain are, of course, a special case here, because their languages can be regarded as world languages. But it is not the case for smaller countries such as, for example, Slovenia or Portugal. This barrier can be overcome by hiring translation services or local experts, but initial identification of potential future mine waste recycling projects by international companies can be much easier if data are available in a commonly spoken language."

Line 316 to 318 these are conclusions and do not belong into this section as you have a section of conclusions

>>> These are recommendations, and we feel they are best placed in the Discussion. However, they have also been summarized in the Conclusions (line 460).

Line 327 to 328 Should this manuscript serve as a beginning of an EU wide assessment – this is the question?

>>> We certainly hope this will be the case.

Line 349 to 351 This was said many times before

>>> Yes, but we think this should also be included in the Conclusions, for those who do not read the whole paper.

Line 367 to 368 what are the XXX to mean ?

>>> These was generated by some sort of automatic system. We have corrected that (lines 470 to 477). Thank you.

Round 2

Reviewer 1 Report

The authors adequately addressed all the comments made in the previous review. Additional minor revision have been suggested to the authors to clarify some points. Please, refer to the attached file for precision.

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

We thank you again for your time for an additional screening through manuscript, and we are glad that we adequately addressed all of your comments. We have also inspected your suggestions for further improvements, which have been taken into account when preparing a revised version.

Abstract: Please, add some information or definition about what is considered by ‘basic’, the ‘metal-centric’ and the ‘material-centric’ group.

>>> Two explanatory sentences were added in the abstract.

Introduction:

Figure 1: Please, specify if metals identified as strategic in 2012 were strategic for the United States, Europe, North America?

>>> This was for the EU, added description in the Fig. 1 caption.

Line 137: “Aznalcollar tailing dam collapse [17,18] and the Baia Mare cyanide spill [19]” Please, indicate the country and the year of the cited events.

>>> Added.

Material and Methods:

Lines 171-172: “different experts in public and private institutions”. Please, specify the number of experts consulted in the present study.

>>> Numbers have been stated already in the revised version: “The initial list of parameters was further evaluated and refined by between 40 and 50 experts from the fields of mining, geosciences, material processing and others, who participated in a series of w…”

Line 180: “through a literature review”. Please, specify the number of papers consulted.

>>> This have been described in more details in lines 184-187 (revised version) or lines 173-175 in this revision. However, we have added several more key references, but we are sorry that can not specify exact number of papers reviewed, because we didn't keep the record. And even if we could do that we do not see any significant added value of such information. Authors hope that that issue is addressed adequately now.

One Figure presenting the methodological approach and the different steps followed should be included.

>>> A figure has been included.

Results and Discussion:

Line 276: “Zn have neem tested.” Should be replace by “Zn have been tested.”

>>> Thank you, corrected.

Line 300: “(i.e. state, county, municipality, private entity etc.),”. Please replace “county” by “country”

>>> county = a territorial division of some countries, forming the chief unit of local administration. State (country) is listed first.

Lines 427-429: “A shift of scope from environmental protection towards including consideration of material recovery from abandoned mine waste sites is needed in any possible future nation or EU-wide data collection.” It will be of interest to recommend and prioritize the type of information that owners of mine sites should collect to fulfill a relevant inventory of mine waste.

>>> Done. Some recommendations for data prioritisation have been inserted.

Reviewer 3 Report

Hello Authors, thank you now the text is much improved . I have made some miner comments in the pdf attached. What may be missing and should potentially be mentioned in the conclusion is that in the mean time also the methodologies or the hydrometalurgical measures have improved with respect to tailing re-processing eg. check out Harris or Neomet

Comments for author File: Comments.pdf

Author Response

Dear reviewer,

Thank you again for your time and comments and suggestions. We are glad that the text is more clear now. We have mentioned electronic translator and improved conclusions as recommended. We will add notes “Table 2 continued” etc. as suggested after we will have final version of the manuscript.

Many thanks again for your time, and we hope that you will also benefit a bit from reading this paper, at least maybe you are better informed what is happening in the EU regarding mine wastes.

Best regards, authors.