HBI is developing a novel approach for the transformation of WWTPs from end-of-pipe treatment facilities into Urban Circular Biorefineries, able to regenerate water, energy and critical raw materials while reducing the risks associated with sewage sludge. HBI approach combines established technologies in an innovative configuration. Hydrothermal carbonization and gasification are integrated with existing WWTP infrastructure and anaerobic digestion, creating valuable synergies. This enables the destruction of persistent pollutants while recovering energy, phosphorous, and up to 80% of the sludge water.
Following two pilot-scale installments that validated the technological performances and resource recovery potential, HBI inaugurated its first industrial-scale Circular Urban Biorefinery in September 2026. The plant demonstrates the engineering advancement achieved, particularly in process automation, and is employed to conduct real-case operations to further optimize efficiency and demonstrate the applicability of the process to different types of sewage sludge.
To further catalyze the transformation, HBI employs performance-based financial instruments that offset the techno-economical risks away from pubic entities. The combination of circular objectives for sludge management, aligned with the new EU directives, and an approach designed for straightforward implementation by public entities makes the HBI vision a replicable model for WWTPs across Europe.