Hydrothermal carbonization of organic wastes to carbonaceous solid fuel – A review of mechanisms and process parameters

Pauline, A. Leena; Joseph, Kurian

doi:10.1016/j.fuel.2020.118472

Cited by 204 publications

(72 citation statements)

References 129 publications

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“…Identifying these compounds in the aqueous phase (Table S1, Supplementary Data) evokes the dehydration mechanism demonstrated in Figure 3. These results are consistent with those obtained previously by Pauline and Joseph (2020).…”

Section: Aqueous-phase Compositionsupporting

confidence: 94%

Coupling hydrothermal carbonization with anaerobic digestion: an evaluation based on energy recovery and hydrochar utilization

2021

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This work evaluates the effect of hydrothermal carbonization (HTC) as a pretreatment and post-treatment technique to anaerobic digestion (AD) of dairy sludge. HTC's effect on AD was evaluated based on energy recovery, nutrient transformation, and hydrochar utilization. The first approach was executed by performing HTC under a range of temperatures before mesophilic AD. HTC optimal pretreatment temperature was 210 °C for 30 min residence time. HTC pretreatment significantly increased the methane yield potential by 192%, the chemical oxygen demand removal by 18%, and the sludge biodegradability during AD by 30%. On the other hand, the application of HTC after AD (post-treatment) increased the total energy production, i.e., in addition to methane, a hydrochar with a caloric value of 10.2 MJ/kg was also obtained. Moreover, HTC post-treatment improved the steam gasification performance of the AD digestate. From the fertilizer quality point of view, HTC implementation generally boosted the concentrations of macro, micro, and secondary nutrients, suggesting its suitability for use as a liquid fertilizer. Overall, the findings of the present study indicate that if bioenergy production were the main target, HTC post-treatment following AD would lead to the most promising outcomes.

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Section: Aqueous-phase Compositionsupporting

confidence: 94%

Coupling hydrothermal carbonization with anaerobic digestion: an evaluation based on energy recovery and hydrochar utilization

2021

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“…During HTC treatment, water has the crucial role of solvent and catalyst. At high temperatures and pressures, water promotes chemical bond breaking to produce high water soluble volatile organic acids (i.e., acetic, formic, and levulinic acid) leaving more stable solid aromatic compounds in character [35,36]. Under HTC reaction conditions, dehydration and decarboxylation reactions lead to a substantial reduction of oxygen content, which is one overall objective of producing fuels from biomass [37].…”

Section: Introductionmentioning

confidence: 99%

Process Water Recirculation during Hydrothermal Carbonization of Waste Biomass: Current Knowledge and Challenges

2021

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Hydrothermal carbonization (HTC) is considered as an efficient and constantly expanding eco-friendly methodology for thermochemical processing of high moisture waste biomass into solid biofuels and valuable carbonaceous materials. However, during HTC, a considerable amount of organics, initially present in the feedstock, are found in the process water (PW). PW recirculation is attracting an increasing interest in the hydrothermal process field as it offers the potential to increase the carbon recovery yield while increasing hydrochar energy density. PW recirculation can be considered as a viable method for the valorization and reuse of the HTC aqueous phase, both by reducing the amount of additional water used for the process and maximizing energy recovery from the HTC liquid residual fraction. In this work, the effects of PW recirculation, for different starting waste biomasses, on the properties of hydrochars and liquid phase products are reviewed. The mechanism of production and evolution of hydrochar during recirculation steps are discussed, highlighting the possible pathways which could enhance energy and carbon recovery. Challenges of PW recirculation are presented and research opportunities proposed, showing how PW recirculation could increase the economic viability of the process while contributing in mitigating environmental impacts.

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“…Decreased amount of carboxyl and carbonyl groups, due to decarboxylation, also slightly decreases solid products' O/C ratio [44,46,47]. Intermediates become substrates of polymerisation, condensation and aromatisation [43,47,48], which are also instrumental in an aggregation of carbonaceous microspheres [43]. Microspheres precipitate, thus forming secondary hydrochar [43,49].…”

Section: Introductionmentioning

confidence: 99%

Cascade Membrane System for Separation of Water and Organics from Liquid By-Products of HTC of the Agricultural Digestate—Evaluation of Performance

et al. 2021

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New regulations aimed at curbing the problem of eutrophication introduce limitations for traditional ways to use the by-product of anaerobic digestion—the digestate. Hydrothermal carbonisation (HTC) can be a viable way to valorise the digestate in an energy-efficient manner and at the same time maximise the synergy in terms of recovery of water, nutrients, followed by more efficient use of the remaining carbon. Additionally, hydrothermal treatment is a feasible way to recirculate recalcitrant process residues. Recirculation to anaerobic digestion enables recovery of a significant part of chemical energy lost in HTC by organics dissolved in the liquid effluent. Recirculating back to the HTC process can enhance nutrient recovery by making process water more acidic. However, such an effect of synergy can be exploited to its full extent only when viable separation techniques are applied to separate organic by-products of HTC and water. The results presented in this study show that using cascade membrane systems (microfiltration (MF) → ultrafiltration (UF) → nanofiltration (NF)), using polymeric membranes, can facilitate such separation. The best results were obtained by conducting sequential treatment of the liquid by-product of HTC in the following membrane sequence: MF 0.2 µm → UF PES 10 → NF NPO30P, which allowed reaching COD removal efficiency of almost 60%.

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Hydrothermal carbonization of organic wastes to carbonaceous solid fuel – A review of mechanisms and process parameters

Cited by 204 publications

References 129 publications

Coupling hydrothermal carbonization with anaerobic digestion: an evaluation based on energy recovery and hydrochar utilization

Coupling hydrothermal carbonization with anaerobic digestion: an evaluation based on energy recovery and hydrochar utilization

Process Water Recirculation during Hydrothermal Carbonization of Waste Biomass: Current Knowledge and Challenges

Cascade Membrane System for Separation of Water and Organics from Liquid By-Products of HTC of the Agricultural Digestate—Evaluation of Performance

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