Hydrothermal carbonization of kitchen waste: An analysis of solid and aqueous products and the application of hydrochar to paddy soil

Yongji Xu; Bingyu Wang; Shudong Ding; Mengying Zhao; Yang Ji; Wenping Xie; Zhaozhong Feng; Yanfang Feng

doi:10.1016/j.scitotenv.2022.157953

Hydrothermal carbonization of kitchen waste: An analysis of solid and aqueous products and the application of hydrochar to paddy soil

Sci Total Environ. 2022 Dec 1:850:157953. doi: 10.1016/j.scitotenv.2022.157953. Epub 2022 Aug 10.

Authors

Yongji Xu¹, Bingyu Wang², Shudong Ding³, Mengying Zhao⁴, Yang Ji⁵, Wenping Xie⁶, Zhaozhong Feng⁴, Yanfang Feng³

Affiliations

¹ Research Center for Global Changes and Ecosystem Carbon Sequestration & Mitigation, College of Applied Meteorology, Nanjing University of Information Science & Technology, Nanjing 210044, China; Key Laboratory of Agro-Environment in Downstream of Yangtze Plain, Ministry of Agriculture and Rural Affairs, Institute of Agricultural Resources and Environment, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China.
² Jiangsu Key Laboratory of Chemical Pollution Control and Resources Reuse, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, China.
³ Key Laboratory of Agro-Environment in Downstream of Yangtze Plain, Ministry of Agriculture and Rural Affairs, Institute of Agricultural Resources and Environment, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China; School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang 212001, China.
⁴ Research Center for Global Changes and Ecosystem Carbon Sequestration & Mitigation, College of Applied Meteorology, Nanjing University of Information Science & Technology, Nanjing 210044, China.
⁵ Research Center for Global Changes and Ecosystem Carbon Sequestration & Mitigation, College of Applied Meteorology, Nanjing University of Information Science & Technology, Nanjing 210044, China. Electronic address: jiyang@nuist.edu.cn.
⁶ State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences (CAS), Nanjing 210008, China.

PMID: 35963404
DOI: 10.1016/j.scitotenv.2022.157953

Abstract

Hydrothermal carbonization (HTC) technology can potentially be used to safely and sustainably utilize kitchen waste (KW). However, the characteristics of HTC solid products (hydrochar) and aqueous products (HAP) based on different types of KW have not yet been clarified. Here, four types of KW, cellulose-based (CL), skeleton-based (SK), protein-based (PT), and starch-based (ST) KW, were used for HTC at 180 °C, 220 °C, and 260 °C. The basic physicochemical properties and structures of hydrochars and HAP were analyzed, and the effects of different hydrochars on rice growth were characterized. HTC decreased the H/C and O/C of KW. All hydrochars were acidic (3.12 to 6.78) and the pH values increased with the HTC temperature, while high HTC temperature reduced the porosity of hydrochars. HTC promoted the enrichment of total carbon (up to 78.1 %), total nitrogen (up to 62.6 %), and total phosphorus (up to 171.6 %) in KW. More carbon (60.7-88.0 %) and nitrogen (up to 87.4 %) were present in the hydrochars than in the HAP. The relative content of C_1s increased and O_1s decreased in CL and ST hydrochars as the HTC temperature increased, while the opposite pattern was observed for SK and PT hydrochars. The dissolved organic matter (DOM) of different hydrochars and HAP were mainly humus-like substances. The biodegradability of the DOM in HAP was often higher than the corresponding hydrochar, and their DOM biodegradability increased with the HTC temperature. The content of heavy metals from different hydrochars did not exceed the relevant thresholds of fertilizer standards. Rice grain yield increased by 3.7-11.1 % in the hydrochar treatments without phosphate fertilizer addition compared with the control treatment. The results of this study provide new theoretical and empirical insights into the potential for HTC technology to be used for the recycling of KW and its products in the agricultural environment.

Keywords: 3D-EEM; Aqueous product characteristic; Hydrochar characteristic; Hydrothermal carbonization; Kitchen waste; Soil application.

MeSH terms

Carbon
Cellulose
Fertilizers*
Nitrogen
Phosphates
Phosphorus
Soil*
Starch
Temperature
Water

Substances

Fertilizers
Phosphates
Soil
Water
Phosphorus
Carbon
Cellulose
Starch
Nitrogen