Preparation of biochar as a coating material for biochar-coated urea

• Published in: The Science of the total environment Vol. 731; p. 139063
• Main Authors: Jia, Yiman, Hu, Zhengyi, Mu, Jing, Zhang, Wantong, Xie, Zijian, Wang, Guoxi
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 20.08.2020
• Subjects: Adhesion of biochar to urea surface; Biochar surface functional groups; Biomass feedstock; Biomass pyrolysis; Grey correlation analysis; Slow-release urea; PP; RS; Biochar surface functional groups; BV6; AD; GCA; BR6; BP6; CM; Biomass pyrolysis; SB; Adhesion of biochar to urea surface; VI; BCU; Biomass feedstock; Slow-release urea; Grey correlation analysis
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2020.139063

Biochar was used as a coating material for slow release urea. However, influence of biochar performance on preparing biochar-coated urea (BCU) and nitrogen release characteristics is rarely reported. In this study, total of 24 biochars were prepared and characterized from six biomass residues (rice straw, chicken manure, vinasse, Phyllostachys pubescens, Arundo donax and sugarcane bagasse) at four pyrolysis temperatures (400–700 °C). Grey correlation analysis (GCA) was used to select biochar as a coating material for BCU based on biochar performance indicators. The feasibility (BCU formability) for preparing BCU and characteristics of nitrogen release in BCU based on hydrostatic dissolution test and soil column leaching experiment were evaluated. Biochar prepared at low pyrolysis temperature was not suitable as a coating material for BCU due to low specific surface area. Biochars derived from pyrolysis of Phyllostachys pubescens (BP6), vinasse (BV6) and rice straw (BR6) at 600 °C were selected as coating materials for BCU based on grey correlation analysis (GCA). The adhesion of biochar to urea surface was related to biomass type that preparing biochar. BV6 was recommended for use as coating material for BCU because the feasibility of the biochars followed the order BR6 > BV6 > BP6, and the practicality of the biochars followed the order BP6 > BV6 > BR6. The findings suggest that biochar with a high specific surface area, hydrophilic oxygen-containing functional groups and low pH is a suitable material for BCU. [Display omitted] •Biochar prepared at low pyrolysis temperature is not suitable as a coating material for biochar-coated urea.•The adhesion of biochar to urea surface is related to feedstock for preparing biochar.•Biochar with high specific surface area, hydrophilic oxygen-containing functional groups and low pH is suitable coating material.•Biochar properties affect the nitrogen release in biochar-coated urea.•Grey correlation analysis could be used to select biochar as a coating material for biochar-coated urea.