Improving nutrients removal and energy recovery from wastes using hydrochar

Hydrothermal carbonization (HTC) is an eco-friendly, flexible and efficient way to valorise wet solid wastes, producing a carbon-rich material named as hydrochar. Considerable efforts have been devoted to studying the feasibility of using hydrochar in waste management to achieve the goal of circular economy. However, a comprehensive evaluation of the impacts of hydrochar on energy recovery from anaerobic digestion (AD), nutrient reclamation, and wastewater treatment is currently lacking. To understand the influence of hydrochar type on its application, this review will firstly introduce the mechanisms and biomass treatment for hydrochar preparation. Most recent studies regarding the improvement of methane (CH4) and volatile fatty acids (VFAs) production after dosing hydrochar in anaerobic digesters are quantitatively summarized and deeply discussed. The potential of using various hydrochar as slow-fertilizer to support the growth of plants are analysed by providing quantitative data. The usage of hydrochar in remediating pollutants from wastewater as effective adsorbent is also evaluated. Based on the review, we also address the challenges and demonstrate the opportunities for the future application of hydrochar in waste management. Conclusively, this review will not only provide a systematic understanding of the up-to-date developments of improving the nutrients removal and energy recovery from wastes by using hydrochar but also several new directions for the application of hydrochar in the future. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Hydrothermal carbonization (HTC) is an eco-friendly, flexible, and efficient method to valorize wet solid wastes, producing carbon-rich hydrochar. Research has focused on the impacts of hydrochar on energy recovery, nutrient reclamation, and wastewater treatment, while also analyzing the influence of hydrochar type on its application. Studies have quantitatively summarized the benefits of using hydrochar in anaerobic digestion and as a slow-fertilizer for plant growth, as well as evaluating its effectiveness as an adsorbent for remediating pollutants from wastewater. Challenges and opportunities for future applications of hydrochar in waste management are also discussed.