Integration of anaerobic digestion and hydrothermal carbonization towards low carbon disposal and utilization: a simulation study

Abstract

This study developed an integrated model for anaerobic digestion-hydrothermal carbonization (AD-HTC) and incorporated carbon emissions to create a comprehensive evaluation indicator for AD-HTC technology. The model was constructed based on the machine learning and Anaerobic Digestion Model NO.1. The parameters of the overall integrated ecology were predicted, and optimal benefits were assessed. The results indicated that the accuracy of the integrated model exceeds 87.5%. Carbon emissions were calculated based on fertilizer substitution, biomass energy conversion, and hydrochar carbon sequestration. The carbon emission reduction value was described with the anaerobic digestion batch reaction time. The overall carbon emissions of AD-HTC exhibit a rapid increased from days 0 to 13, followed by a gradual decline from days 13 to 21. The peak carbon reduction of 1.092 gCO₂eq occurred on day 13, which was 31.4–43.7% higher than that of AD/HTC alone. At present, the method proposed in this study was applicable for calculating the product end of AD-HTC reaction. The exploration of reaction equipment, suitability of feedstocks, and complex intermediate products will be further supplemented in the future. The findings of this study are expected to provide valuable insights for the scientific control and optimization of emerging AD-HTC technology.