Hydrochar derived from municipal sludge through hydrothermal processing: A critical review on its formation, characterization, and valorization

Liu, Huan; Başar, İbrahim Alper; Nzihou, Ange; Eskicioğlu, Çiğdem

doi:10.1016/j.watres.2021.117186

Cited by 117 publications

(42 citation statements)

References 306 publications

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“…These data are consistent with those reported in the literature for SS but contrast those of OFSMW, which have a lower solid yield. Liu et al [35] in their review reported an average solid yield of 60.2% for HTC from SS, varying from 22.6% and 84.9% for all studies considered. High variability in solid yield was attributed to different severities of the HTC reaction in terms of temperature and treatment time, which had a major impact on the performance of the HTC process [35].…”

Section: Yields Of the Htc Testsmentioning

confidence: 98%

“…Liu et al [35] in their review reported an average solid yield of 60.2% for HTC from SS, varying from 22.6% and 84.9% for all studies considered. High variability in solid yield was attributed to different severities of the HTC reaction in terms of temperature and treatment time, which had a major impact on the performance of the HTC process [35]. Recently, Lucian et al [14] reported that the yield of the hydrochar, the HTCL, and the gas for the HTC of OFMSW, performed at a reaction time of 1 h and with a temperature of 180 • C, were 67%, 32% and 1%, respectively.…”

Section: Yields Of the Htc Testsmentioning

confidence: 98%

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Investigating the Enhancement in Biogas Production by Hydrothermal Carbonization of Organic Solid Waste and Digestate in an Inter-Stage Treatment Configuration

et al. 2022

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In recent years, sewage sludge (SS) and bio-waste management have attracted increasing environmental attention. In this study, hydrothermal carbonization (HTC) technology is investigated in the framework of a co-treatment of sewage sludge digestate (SSD) and an organic fraction of municipal solid waste (OW). The proposed configuration integrates HTC with anaerobic digestion (AD) in an inter-stage configuration (AD1 + HTC + AD2). The effects of different percentages of OW added to SSD in the HTC treatment are evaluated in terms of characteristics and methane yield of the produced HTC liquor (HTCL) and HTC slurry (i.e., the mixture hydrochar-HTCL), as well as dewaterability of the HTC slurry. Results show that, with the increase in the percentage of OW in the OW-SSD mixture fed to the HTC process, production of biogas and biomethane of both HTC slurry and HTCL increases. The highest biogas production is achieved when a mixture consisting of half SSD and half OW is used, reaching 160 ± 10 and 240 ± 15 mL biogas g−1 CODadded, respectively, for HTCL and HTC slurry. Furthermore, sludge dewaterability is significantly improved by the combined AD1-HTC-AD2 process. Finally, an energy assessment allows estimating that the co-treatment of OW with SSD in HTC can cover up to 100% of the energy consumption of the system.

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Section: Yields Of the Htc Testsmentioning

confidence: 98%

Section: Yields Of the Htc Testsmentioning

confidence: 98%

Investigating the Enhancement in Biogas Production by Hydrothermal Carbonization of Organic Solid Waste and Digestate in an Inter-Stage Treatment Configuration

et al. 2022

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“…As lignin in lignocellulosic biomass is the most stable compound during HTC (Borrero-L opez et al, 2018;Wang et al, 2018), the residual C of the lignin after HTC leads to lower O/C and H/C ratios (see also section 3.1.3), creating a less developed porous structure. Conversely, hydrochars from non-lignocellulosic biomass such as sewage sludge are generally characterized by less stable C compounds (Liu et al, 2021;Wilk et al, 2019), resulting in larger O/C and H/C ratios after HTC, enhanced transfer of C to the liquid phase, and increased porosity.…”

Section: Influence Of Feedstockmentioning

confidence: 99%

Pore characteristics of hydrochars and their role as a vector for soil bacteria: A critical review of engineering options

Thunshirn

Wenzel

Pfeifer

2021

Critical Reviews in Environmental Science and Technology

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Hydrothermal carbonization (HTC) is the method of choice to convert wet waste biomass to hydrochars. Their porous structure can serve as a microenvironment to plantgrowth-promoting rhizobacteria (PGPR), supporting their growth, survival, and activities. As published work lacks the systematic compilation of pore characteristics of hydrochars related to bacterial colonization, we collect available data and elaborate on their dependence on the carbonization process conditions, feedstocks, and methodology of pore system characterization. Our analysis indicates a high abundance of pores sized between 1 and 20 lm relevant for the protection of PGPR from predators, and of nutrients and labile C in hydrochars supporting bacterial growth. In addition to the selection of optimized process parameters and feedstocks (240-260 C, low feedstock pH, nonlignocellulosic biomass), adding mineral amendments prior to HTC offers opportunities for engineering hydrochars with an even larger share of pore space suited for bacterial colonization. Using the comprehensive literature on biochars, we demonstrate that the interior pore space in chars determines the potential to serve as an inoculum carrier to PGPR, thereby enhancing nutrient acquisition and protecting plants from diseases and abiotic stresses. The pore characteristics of hydrochars are comparable to biochars, and hydrochars are generally superior in providing a labile C reservoir that PGPR can readily access. We argue that HTC provides a cost-effective conversion route to produce PGPR vectors/carriers from wet (waste) biomass serving various environmental management objectives (waste recycling, soil fertility, soil remediation technologies) and circular bioeconomy (sustainable agriculture, substituting non-renewable carrier materials and fertilizers). HIGHLIGHTSWe review the role of pore characteristics of hydrochars for bacterial colonization We identify opportunities for engineering hydrochars to provide favorable habitat conditions to PGPR 240-260 C, low pH, non-lignocellulosic feedstocks, and adding mineral amendments increase the habitable pore space Hydrochars offer suitable pore characteristics and high labile C amounts and are promising PGPR carriers/vectors CONTACT Walter W. Wenzel

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“…Among all possible strategies, hydrothermal carbonization (HTC) of municipal sewage sludge has been recently recognized as a promising technology for efficient waste volume reduction and recovery of bioenergy and nutrients [ 6 , 7 ], such as phosphorus and nitrogen. HTC is a thermochemical process in which moist biomass is carbonized at a temperature between 180 and 250 °C and a reaction time of 0.5–8 h at saturated vapor pressure, leaving the water in the liquid phase.…”

Section: Introductionmentioning

confidence: 99%

Sewage Sludge Management at District Level: Reduction and Nutrients Recovery via Hydrothermal Carbonization

Scrinzi

Ferrentino

Baù

et al. 2022

Waste Biomass Valor

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In this study, two scenarios of a municipal wastewater treatment plant (WWTP) are presented, which include the integration of the hydrothermal carbonization (HTC) process into the sludge line as a post-treatment of the anaerobic digestion (AD) process. The objective of the simulation is to investigate the performances of AD + HTC treatment to reduce sludge production and improve nutrient and energy recovery. For this purpose, the scheme of an under-construction WWTP was considered, named Trento 3 (Trento, Italy) and with a treatment capacity of 300,000 PE. In the first scenario, the HTC process was fed with thickened sludge from the Trento 3 WWTP, while in the second scenario, dewatered sludge from other local WWTPs was also used as feedstock for the HTC process. Both scenarios allowed to obtain a considerable sludge reduction ranging from 70 to 75% with a notably increase in the biogas production up to 47%, due to the recycling of HTC liquor (HTCL) to the anaerobic digester. Considering nutrients recovery, all the phosphorus and nitrogen present in the HTCL could be used for struvite precipitation with an average yearly gain of 1 million euros. Moreover, the introduction of HTC in the Trento 3 WWTP could allow a reduction in the sludge management costs of up to 2 M€/year. Graphical Abstract

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Hydrochar derived from municipal sludge through hydrothermal processing: A critical review on its formation, characterization, and valorization

Cited by 117 publications

References 306 publications

Investigating the Enhancement in Biogas Production by Hydrothermal Carbonization of Organic Solid Waste and Digestate in an Inter-Stage Treatment Configuration

Investigating the Enhancement in Biogas Production by Hydrothermal Carbonization of Organic Solid Waste and Digestate in an Inter-Stage Treatment Configuration

Pore characteristics of hydrochars and their role as a vector for soil bacteria: A critical review of engineering options

Sewage Sludge Management at District Level: Reduction and Nutrients Recovery via Hydrothermal Carbonization

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