Process water recirculation for catalytic hydrothermal carbonization of anaerobic digestate: Water-Energy-Nutrient Nexus

Mingjing He, Yang Cao, Zibo Xu, Siming You, Roger Ruan, Bin Gao, Ka Hing Wong, Daniel C.W. Tsang

Research output: Journal article publicationJournal articleAcademic researchpeer-review

Abstract

The process water (PW) from acid-catalyzed hydrothermal carbonization (HTC) is still an environmental burden due to the enriched organics, nutrients, and salts. This study proposed a novel strategy to valorize food waste digestate into multifunctional hydrochar by recirculating the PW in the HCl-catalyzed HTC process. The produced multifunctional hydrochar could be utilized as a high-quality solid fuel with HHV of 27.9 MJ kg−1 (hydrochar without PW recirculation) and a slow-release fertilizer by converting the complex Ca and P compounds from the food waste digestate into a Ca-P deposit (hydroxyapatite) with more than a 93 % P recovery rate (hydrochar with PW recirculation). Adding fresh HCl in the HTC PW recirculation system only displayed a marginal catalytic impact on the hydrochar properties after two cycles of recirculation. This study demonstrated the importance of inherent Ca in the feedstocks and the dual role of HCl in the HTC with PW recirculation.

Original languageEnglish
Article number127694
JournalBioresource Technology
Volume361
DOIs
Publication statusPublished - Oct 2022

Keywords

  • Anaerobic digestate
  • Food waste hydrochar
  • Sustainable bioenergy
  • Waste valorization
  • Wastewater reuse

ASJC Scopus subject areas

  • Bioengineering
  • Environmental Engineering
  • Renewable Energy, Sustainability and the Environment
  • Waste Management and Disposal

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