Raman spectra of amino acids and their aqueous solutions.

Hydrothermal carbonization is an important thermochemical conversion process that can be used as an energy-efficient alternative to enhance the dewaterability of sewage sludge and meanwhile to convert sewage sludge into high value-added products, such as clean biofuel, organic fertilizer and precursors of functional materials. This paper presents an overview of the latest development of hydrothermal carbonization in the field of sewage sludge treatment, with a particular focus on critical hydrothermal parameters, physicochemical characteristics of products streams, current understanding on hydrochar formation mechanisms, sewage sludge dewaterability improvement and techno-economic advantages. Recent advances have shown that hydrothermal carbonization of sewage sludge is an exothermal process, which is governed by temperature to a large extent. Both polymerizations of highly reactive intermediates derived from degradation of biopolymers in sewage sludge and solid-solid conversion of their undissolved fractions are regarded as the major mechanisms of hydrochar formation. The high ash content of hydrochar is probably the limiting factor for its potential applications in energy and functional materials. The chemistry in hydrothermal carbonization of sewage sludge, closely related to the process parameters and the chemical composition of sewage sludge, offers huge potential to influence the products distribution and characteristics and the process energetics as desired, which provides a promising opportunity to construct a high-efficiency industrial chain for energy and resources recovery from sewage sludge by a controlled hydrothermal process. This review identifies the current challenges and knowledge gaps, and provides new perspectives for future research efforts targeting at sustainable treatment of sewage sludge by hydrothermal carbonization.

Hydrothermal carbonization for energy-efficient processing of sewage sludge: A review

Valorisation of citrus processing waste: A review

Potential of chicken by-products as sources of useful biological resources.

A review of wet air oxidation and Thermal Hydrolysis technologies in sludge treatment.

Hydrolysis technology and kinetics of poultry waste to produce amino acids in subcritical water.

Production of reducing sugars from bean dregs waste by hydrolysis in subcritical water

The recovery of waste substances is important not only for the prevention of environmental issues, but also for the rational utilization of natural resources. Hydrolysis reaction in sub-critical water is a promising method for the treatment of organic wastes and has been attracting worldwide attention. In this paper, sub-critical water hydrolysis was employed as a method for producing amino acids, reducing sugars, bio-oil and gas fuels from biomass wastes. The current statuses of these useful chemicals production from biomass wastes by hydrolysis in sub-critical water were reviewed. The review indicates that sub-critical water hydrolysis can be an efficient process for recovering useful chemicals from biomass wastes. This method is renewable, sustainable, efficient, and safe for the environment.

Recovery of biomass wastes by hydrolysis in sub-critical water.

Amino acids play an important physiological role in all life-forms and can be recovered from bean dregs waste using sub-critical water hydrolysis. This work deals with the hydrolysis kinetics of bean dregs. Kinetics was conducted in a temperature range of 200–240°C using a 300-ml stainless steel batch reactor. Since the reaction kinetics in sub-critical water is very complicated, a simplified kinetic model to describe the hydrolysis of bean dregs is proposed: a single consecutive reaction. The differential equations resulting from the model were fit to experimental data to obtain kinetic rate constants. By means of the Arrhenius plot, the activation energy as well as the pre-exponential factor was determined. A good agreement between the simplified model and the experimental data was obtained. The kinetic parameters provided useful information for understanding the hydrolysis reaction of bean dregs. The experimental results show that the best hydrolysis technology is: reaction temperature 200°C, reaction time 20 min. Under this condition, the total amino acid yield reaches 52.9%. Based on the results, this method could become an efficient method for bean dregs liquefaction, producing valuable amino acid.

Xueliang Wan

Papers

Raman spectra of amino acids and their aqueous solutions.

Hydrolysis technology and kinetics of poultry waste to produce amino acids in subcritical water.

Production of reducing sugars from bean dregs waste by hydrolysis in subcritical water

Recovery of biomass wastes by hydrolysis in sub-critical water.

Kinetics of amino acid production from bean dregs by hydrolysis in sub-critical water