This manuscript presents experimental results on the separation of copper and zinc from spent catalyst material using pyrometallurgical and hydrometallurgical methods. The work is of interest, and appears to have been performed well. The manuscript is hard to read in some parts, so can use improvement in language. In addition, some information is missing, more discussion of the results in needed, and better organization of the section is required. The following are the main revisions I suggest: 1) Title: What does “Low-waste recycling” mean? Do you mean low-grade waste, low-value waste? But catalysts are not cheap. So I am confused. Please revise. 2) Abstract: Unclear what the environmental benefit is. You are still having a waste residue after either pyro or hydro processes, so are those residues less harmful (or perhaps more harmful), or is it simply because the mass of waste is smaller that you say there is an environmental benefit. Please make sure to have a strong reason to claim environmental benefit, other you can just explain the economic benefits of waste reuse. 3) Line 13: is that ZnO in the dust? 4) Introduction: Add one or more sentences at the end to say how you propose to overcome the pyrometallurgical challenge, and how is this novel compared to what has been previously reported. 5) Section 2: there are sections 2.1 and 2.3, but where is section 2.2? 6) Where is the heading for Section 3, which should be the results and discussion? 7) Lines 38-40: revise, not well written and contains grammar issue. 8) Section 2.1: you said in the introduction that there are many catalysts with copper and zinc, but you did not say here where you got your catalyst from, who made it, what are its applications, is it new or used, etc. Readers must understand what material you are working with. 9) Line 43: what criteria you use to select a single catalyst sample? Explain in the text. 10) Line 43: how what chemical analysis done? Write the method and equipment used. Same for all other characterization methods used. 11) Fig 2: indicate with an arrow, circle, square, etc. where in this picture the spectrum from Fig. 3 comes from. 12) Methodology and results should be presented in separate sections. So move the results and discussion of results to a new section 3. 13) Line 80: what is the % in reference to? Weight %? % of the catalyst weight? Better to use g/g values (i.e. grams of carbon per grams of catalyst). 14) Line 93: does separation come before cooling? 15) Line 94: do not abbreviate Table. 16) Table 1: can you add lines that show losses of mass to the dust phase? 17) Pyro results: unclear if you optimized the recovery of copper to the alloy phase, or the recovery of zinc in the dust phase (is that where you want the zinc to go?). More discussion and analysis of the results is needed. 18) Line 137: how are they produced? Can you explain that for the readers? 19) Line 150: so what did you do to overcome the fine grain issue? Could you centrifuge instead? 20) Lines 150-153: not well written, confusing. Is this all you have to say about the leaching results? How were leachate solutions analyzed for metals? Did you measure pH? Did you measure ORP? 21) Lines 160-162: again, unclear, confusing. How do you recycle the leaching agents? How do you recover Zn and Cu from the leachates? 22) Line 164: explain the “burning” process conditions. 23) Lines 17-19: you did not actually test the reduction of the residue, or its use to make catalyst, so you can say this in the conclusions section, but seems less appropriate for the abstract. 24) Conclusions: you did not say anything about the environmental or economic benefits of the proposed processes. 25) Conclusions: any recommendation for future work?