## 4 Conclusions  
The composts produced from 100% MGW (C1) and those from 75% MGW and 25% discarded green peppers (C2) in a composting facility of a regional nonhazardous waste landfill (RNHWL) differed in terms of analyzed physicochemical parameters and the content of heavy metals. C2 demonstrated higher values of EC, P, K, Mg, Cu, Cr and Ni, and lower values of Pb compared to C1 (_p_ \(<\) 0.05-0.001). In both composts, the Cd and Hg values and the _E. coli_ counts were very low. The presence of _Salmonella_ was detected in neither of the two composts.  
The fertilizing index (FI) values determined C2 as a better organic soil fertilizer (FI = 4.33) compared to C1 (FI = 3.40), while the clean index (CI) values (CI > 4.0) characterized both composts as clean with low potential for heavy metal pollution. The complex assessment of the produced composts by FI and CI values categorized C1 as Class B compost with very good quality with medium fertilizing potential and low heavy metal content, and C2 as Class A compost of the best quality with high soil fertility potential and low heavy metal content. Based on this assessment, both composts were comparable to--and in some cases even better than--composts produced from other organic wastes.  
The produced composts meet the requirements of Bulgarian legislation (BGL) regarding soil fertilizers and environmental protection for pH, EC, heavy metals (Zn, Cu, Pb, Cr, Ni, Cd and Hg) values, _E. coli_ and _Salmonella_ spp. counts and those of EU legislation for the levels of the same heavy metals, and deviate from the standard only as far as moisture content (BGL) and Cd content (EU) are concerned.  
The municipal GW composting in the industrial composting facility of a RNHWL was an effective method for environmentally friendly management of municipal GW, resulting in the production of good-quality compost for soil application.  
**Author Contributions:** Conceptualization, G.S.P., G.S.K. and D.V.B.; methodology, G.S.P., G.G.B. and D.M.D.; software, G.G.B. and D.M.D.; validation, G.G.B., G.S.K. and D.V.B.; formal analysis, G.S.P., G.G.B. and G.S.K.; investigation, D.V.B. and D.M.D.; resources, D.V.B. and G.G.B.; data curation, G.S.P., D.M.D. and D.V.B.; writing--original draft preparation, G.S.P. and G.G.B.; writing--review and editing, D.V.B., G.S.K., G.S.P., D.M.D. and G.G.B.; visualization, G.S.P., G.G.B. and D.V.B.; supervision, G.S.P. and G.G.B.; project administration, G.S.K. and D.V.B.; funding acquisition, D.V.B. and G.G.B. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the Bulgarian Ministry of Education and Science under the National Research Programme \"Healthy Foods for a Strong Bio-Economy and Quality of Life\" approved by DCM #577/17.08.2018.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Not applicable.  
**Acknowledgments:** The authors are grateful to Harmanli City Council and the management team of Ecoresource Harmanli Ltd.--Regional nonhazardous waste landfill and the National Program for Research \"Young Scientists and Postdoctoral Students\" for the help during the performance of this experiment.  
**Conflicts of Interest:** The authors declare no conflict of interest.