Integration of Hydrothermal Carbonization and Anaerobic Digestion for Energy Recovery of Biomass Waste: An Overview

Abstract

Hydrothermal carbonization is emerging as a promising eco-friendly technology for the management of wet biomass wastes through energy recovery. It avoids drying of the feedstock and operates at a much lower temperature than conventional thermal conversion technologies, giving rise to a carbonaceous solid, hydrochar, of improved fuel quality with respect to the starting biomass. However, the aqueous fraction resulting from this process, the so-called process water, represents a troublesome secondary waste requiring effective treatment because of the high chemical oxygen demand and the presence of varying amounts of nutrients. Anaerobic digestion appears as a potential solution allowing significant reduction of the organic load while producing methane-rich biogas, thus contributing to energy recovery. Integrating hydrothermal carbonization and anaerobic digestion is gaining interest in the literature. This review compiles the reported studies on the application of hydrothermal carbonization coupled with anaerobic digestion for energy recovery of different biomass wastes, analyzing the energy balances. The main characteristics of the resulting HC and the methanogenic potential of the process waters are reviewed in connection with the operating conditions, as well as the possibility of nutrient recovery. Life cycle assessment and economic studies are included.

Activated Carbon and Carbon Quantum Dots/Titanium Dioxide Composite Based on Waste Rice Noodles: Simultaneous Synthesis and Application in Water Pollution Control

“…In recent years, hydrothermal carbonization has proved to be a new and effective method for cooking waste treatment [ 14 , 15 , 16 ], whose process is simple, environment friendly, requires mild conditions, results in near-zero emissions, and may provide functional carbon materials such as activated carbon (AC) [ 17 ] or fluorescent carbon quantum dots (CQDs) [ 18 ]. However, due to complicated compositions, the intermediate products of hydrothermal carbonization often display different physical chemical characters, which produce great difficulties for subsequent treatment.…”

Acid-Mediated Hydrothermal Treatment of Sewage Sludge for Nutrient Recovery

“…Recently, hydrothermal carbonization (HTC) has emerged as a thermal process that allows the treatment and stabilization of wet sewage sludge at mild temperatures (180-250 °C) and low residence times (5-240 min) under an autogenous pressure. During HTC, the oxygen and hydrogen contents of the feedstock decrease through hydrolysis, condensation, aromatization, dehydration, and decarboxylation reactions (He et al, 2022;Ipiales et al, 2021). The critical temperature for an effective HTC process primarily depends on the composition of the feedstock, particularly the content of lignin (Cao et al, 2021).…”

“…The physical and energetic properties of hydrochar make it suitable for use as a solid fuel (Marin-Batista et al, 2020;Ipiales et al, 2022), enhancer of anaerobic digestion (Kumar et al, 2021), CO 2 capture agent (Goel et al, 2021;Wang et al, 2021a), energy storage material in fuel cells, supercapacitors, and batteries (Arenas Esteban et al, 2020;Zhou et al, 2021;Arauzo et al, 2022), and as a precursor for adsorbents (Diaz et al, 2019;Román et al, 2020) and activated carbons (Belete et al, 2021;Kumar et al, 2020). The use of hydrochar as a solid biofuel is acquiring focus because 50-85 % of its energy is contained in the feedstock (Román et al, 2012;Ipiales et al, 2021). Further, hydrochar exhibits good combustion properties, such as a high "higher heating value" (HHV), high energy density (Ischia and Fiori, 2020), and low ash, nitrogen, and sulfur contents, thus producing less NO x and SO x during combustion than the feedstock (Marin-Batista et al, 2020).…”

2021 Pioneers in Energy Research: Javier Bilbao

“…The environmental and technical−economical aspects of integrated algae biorefinery are also discussed. Ipiales et al 32 have published a comprehensive coupling of hydrothermal conversion of wastes with the anaerobic digestion of process water, with a special emphasis on the nutrients to produce fertilizers. Energy balances and economical and environmental assessment are also included in this review.…”