Characterization of the pyrolytic solid derived from used disposable diapers

Abstract

This paper confirms through physical and chemical analyses the possibility to reuse the solid pyrolytic residue derived from used disposable diapers (UDD), heated at different temperatures ranging from 500, 700 and 900°C as a soil amendment. With an increasing pyrolytic temperature, the pH, electrical conductivity, available P₂O₅, exchangeable K⁺ and cation exchange capacity tended to increase; however, total-N and exchangeable Ca²⁺ and Mg²⁺ decreased. The pyrolytic diaper solid produced at 500°C had a high volatile matter (60.22%) and low ash content (19.10%), which can negatively affect crop growth and productivity when added to soil. Heavy metal concentrations were less than the maximum allowable limits according to Japan standards. The surface of the pyrolytic diaper solid was coarse, porous and heterogeneous with higher temperatures. Hydrogen-containing functional groups, such as OH, C‒H, N‒H and CH₂, decreased with increasing pyrolytic temperature. Based on these results, we concluded that the pyrolytic product derived from UDD at higher temperatures offers a potentially effective soil amendment option.

Keywords:

• used disposable diapers
• pyrolysis
• biochar
• characterization
• reuse

Acknowledgements

The authors cordially thank Prof. Jiro Chikushi for his invaluable guidance, comments and suggestions to improve this manuscript. They also appreciate Dr. Yuki Mori, Kyushu University for helping with the analysis and measurement of total phosphorus. This work was supported by the JSPS Institutional Program for Young Researcher Overseas Visits.