Process water recirculation for catalytic hydrothermal carbonization of anaerobic digestate: Water-Energy-Nutrient Nexus. (October 2022)

• Record Type: Journal Article
• Authors: He, Mingjing; Cao, Yang; Xu, Zibo; You, Siming; Ruan, Roger; Gao, Bin; Wong, Ka-Hing; Tsang, Daniel C.W.
• Is Part Of: Bioresource technology. Volume 361(2022)
• Publication Date: 2022-10
• Subjects: Anaerobic digestate -- Food waste hydrochar -- Sustainable bioenergy -- Waste valorization -- Wastewater reuse; Biomass -- Periodicals; Biomass energy -- Periodicals; Bioremediation -- Periodicals; Agricultural wastes -- Periodicals; Factory and trade waste -- Periodicals; Organic wastes -- Periodicals; Bioénergie -- Périodiques; Déchets agricoles -- Périodiques; Déchets industriels -- Périodiques; Déchets organiques -- Périodiques; Déchets (Combustible) -- Périodiques; 662.88
• DOI: 10.1016/j.biortech.2022.127694
• Languages: English
• ISSNs: 0960-8524

Abstract

Graphical abstract: Highlights: Recirculating HTC PW could valorize digestate into multifunctional hydrochar. HCl played a dual role in enhancing energy recovery and nutrient solubilization. Inherent Ca from FWD could recover P into Ca-P deposit as a slow-release fertilizer. HCl addition during PW recirculation had a marginal impact on hydrochar properties. Intermediates accumulation led to the formation of a hydrophilic shell on hydrochar. 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.