Recovery of Value-Added Products from Hydrothermal Carbonization of Sewage Sludge

Abstract

This paper is about the conversion of wet waste stream into valuable products via thermal processing. Hydrothermal carbonization of sewage sludge was carried out at 200°C and 2.1 MPa in a closed reactor for 1–6 h. Main products were in solid and liquid phases. The resulting hydrochar was shown to have H/C and O/C ratios moving towards natural lignite, improved energetic content, and adsorption property in terms of iodine number. The aqueous solution was found to contain high concentration of plant food nutrients, especially nitrogen and potassium. They may be desirable for subsequent fuel and chemical production as well as applications in agriculture. The study shows that valuable products can be generated successfully from sewage sludge using hydrothermal carbonization.