Phosphorus recovered from digestate by hydrothermal processes with struvite crystallization and its potential as a fertilizer

Tao Zhang; Xinyue He; Yaxin Deng; Daniel C W Tsang; Rongfeng Jiang; Gero C Becker; Andrea Kruse

doi:10.1016/j.scitotenv.2019.134240

Phosphorus recovered from digestate by hydrothermal processes with struvite crystallization and its potential as a fertilizer

Sci Total Environ. 2020 Jan 1:698:134240. doi: 10.1016/j.scitotenv.2019.134240. Epub 2019 Sep 2.

Authors

Tao Zhang¹, Xinyue He², Yaxin Deng³, Daniel C W Tsang⁴, Rongfeng Jiang⁵, Gero C Becker⁶, Andrea Kruse⁶

Affiliations

¹ Biomass Engineering Center, Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation, Key Laboratory of Plant-Soil Interactions of Ministry of Education, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China; Institute for Agricultural Engineering, Conversion Technologies of Biobased Resources, University of Hohenheim, Garbenstrasse 9, 70599 Stuttgart, Germany. Electronic address: taozhang@cau.edu.cn.
² Biomass Engineering Center, Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation, Key Laboratory of Plant-Soil Interactions of Ministry of Education, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China; Institute for Agricultural Engineering, Conversion Technologies of Biobased Resources, University of Hohenheim, Garbenstrasse 9, 70599 Stuttgart, Germany.
³ Biomass Engineering Center, Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation, Key Laboratory of Plant-Soil Interactions of Ministry of Education, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China; Illinois Sustainable Technology Center, University of Illinois Urbana-Champaign, IL 61801, USA.
⁴ Department of Civil and Environmental Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
⁵ Biomass Engineering Center, Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation, Key Laboratory of Plant-Soil Interactions of Ministry of Education, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China.
⁶ Institute for Agricultural Engineering, Conversion Technologies of Biobased Resources, University of Hohenheim, Garbenstrasse 9, 70599 Stuttgart, Germany.

PMID: 31499343
DOI: 10.1016/j.scitotenv.2019.134240

Abstract

Phosphorus (P) recovery from digestate has attracted considerable interest. In this study, hydrothermal processes in combination with struvite crystallization were performed to promote P solubilization and capture from digestate; its potential as a phosphate-based fertilizer was also investigated. Hydrothermal treatment with HCl and H₂O₂ showed good results for the solubilization of organic and slightly soluble P, and achieved the lowest input energy need (768 kWhkg^-1_P). Struvite crystallization reached 99.3% (Mg²⁺:PO₄^3-1.84:1, pH 9.98). X-ray diffractometry and energy dispersive X-ray spectrometer mapping demonstrated the main precipitate component was struvite. For the fertilization of maize, P utilization from struvite was 19.0%. Light microscope analysis revealed that appropriate amounts of struvite may have an influence on the growth of the primary root. Overall, 16.6% of total P was recovered after P was solubilized, captured and made available.

Keywords: Digestate; Fertilizer; Hydrothermal; Phosphorus; Struvite.