Preparation and thermal conductivity enhancement of a paraffin wax-based composite phase change material doped with garlic stem biochar microparticles

Teng Xiong, Yong Sik Ok, Pavani Dulanja Dissanayake, Daniel C.W. Tsang, Sumin Kim, Harn Wei Kua, Kwok Wei Shah

Research output: Contribution to journalArticlepeer-review

27 Citations (Scopus)


The addition of thermally conductive nanomaterials is an effective strategy for increasing the thermal conductivity of phase change materials (PCMs). However, nanomaterials are expensive and may significantly reduce the latent heat capacity of PCMs. In this study, low-cost and eco-friendly biochar microparticles were prepared from garlic stems, a common food waste in Singapore. The thermal properties of paraffin wax (PW) doped with 1, 3, and 5 wt% garlic stem biochar (GSB) microparticles were investigated. The GSB microparticles prepared at 700 °C had three-dimensional porous and two-dimensional flake-like structures, which contributed to the formation of additional heat transfer pathways in the PW. The addition of 5 wt% GSB microparticles enhanced the thermal conductivity of PW by 27.3% and 7.2% in the solid and liquid phases, respectively. The T-history test revealed that the melting and solidification rates of PW improved by 90 and 115 s, respectively. The improved heat transfer performance was mainly ascribed to the high degree of graphitization and the interconnected porous carbon structure of the GSB microparticles. The phase change temperatures of PW were slightly changed upon the addition of GSB microparticles, and the latent heat capacity was only reduced by 6.1%. These results suggest that the GSB microparticles can be used as a potential alternative to other nanoadditives such as metal- and metal oxide-based nanoadditives.

Original languageEnglish
Article number154341
JournalScience of the Total Environment
Publication statusPublished - 2022 Jun 25

Bibliographical note

Funding Information:
This work was supported by the City Developments Limited (CDL) project R-296-000-174-720 and NUS-AGC Inc. project R-296-000-183-597 . The authors would also like to acknowledge the support provided by the Department of the Built Environment, National University of Singapore .

Publisher Copyright:
© 2022


  • Food waste management
  • Garlic stem biochar
  • Phase change material
  • Thermal conductivity
  • Thermal storage

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution


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