Microbial Risk Assessment of Mature Compost from Human Excreta, Cattle Manure, Organic Waste, and Biochar

Katharina A. Werner, Daniela Castro-Herrera, Fantaw Yimer, Menfese Tadesse, Dong-Gill Kim, Katharina Prost, Nicolas Brüggemann and Elisabeth Grohmann ()
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Katharina A. Werner: Faculty of Life Sciences and Technology, Department of Microbiology, Berliner Hochschule für Technik, 13347 Berlin, Germany
Daniela Castro-Herrera: Institute of Bio- and Geosciences—Agrosphere (IBG-3), Forschungszentrum Jülich, 52425 Jülich, Germany
Fantaw Yimer: Wondo Genet College of Forestry and Natural Resources, Hawassa University, Shashemene P.O. Box 128, Ethiopia
Menfese Tadesse: Wondo Genet College of Forestry and Natural Resources, Hawassa University, Shashemene P.O. Box 128, Ethiopia
Dong-Gill Kim: Wondo Genet College of Forestry and Natural Resources, Hawassa University, Shashemene P.O. Box 128, Ethiopia
Katharina Prost: Institute of Bio- and Geosciences—Agrosphere (IBG-3), Forschungszentrum Jülich, 52425 Jülich, Germany
Nicolas Brüggemann: Institute of Bio- and Geosciences—Agrosphere (IBG-3), Forschungszentrum Jülich, 52425 Jülich, Germany
Elisabeth Grohmann: Faculty of Life Sciences and Technology, Department of Microbiology, Berliner Hochschule für Technik, 13347 Berlin, Germany

Sustainability, 2023, vol. 15, issue 5, 1-11

Abstract: Lack of sanitation is the underlying cause of many diarrheal infections and associated deaths. Improving sanitation through the set-up of ecological sanitation dry toilets, followed by the thermophilic composting of human excreta, could offer a solution. In addition, treating the excreta via thermophilic composting allows us to recycle the nutrients to be used as fertilizer for agriculture. However, for this purpose, the compost should be free of pathogens. We conducted a thermophilic composting trial over 204 to 256 days with human excreta, along with vegetable scraps and teff straw, with and without biochar. A sawdust–cattle manure mixture with the same supplements served as a control treatment. To evaluate the hygienic quality of the mature compost, the bacterial indicators Escherichia coli and Salmonella were assessed using the cultivation-based most probable number method. In addition, Ascaris lumbricoides eggs were quantified through light microscopy. The amount of detected E. coli was below the thresholds of German and European regulations for organic fertilizer. Salmonella and Ascaris eggs were not detected. No significant differences between the treatments were observed. Thus, the composting process was efficient in decreasing the number of potential human pathogens. The mature compost fulfilled the legal regulations on organic fertilizer regarding potential human pathogens.

Keywords: thermophilic composting; ecological sanitation; dry toilets; pathogens; E. coli; Salmonella; MPN; Ascaris lumbricoides eggs; Mini-FLOTAC; biochar (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2023
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