Optimized hydrothermal carbonization of chicken manure and anaerobic digestion of its process water for better energy management.

Modern poultry production is faced with the challenge of properly managing its associated wastes, in particular chicken manure (CM). There is a need to improve the management of CM through conversion processes that allow the production of value-added products, particularly for energy purposes, such as hydrothermal carbonization (HTC) and anaerobic digestion (AD). The objectives of this study were: i) to optimize the CM-HTC, using response surface methodology with simultaneous optimization of mass yield and higher heating value (HHV), and ii) to evaluate the biomethane potential of the process water generated from hydrochar production under the optimized condition. An analysis of the overall energy potential was also performed. The optimal condition for HTC was 234 °C for 30 min, resulting in hydrochar with an HHV of 14.88 ± 0.22 MJ/kg and a mass yield of 50.00 ± 3.13 wt%. The cumulative methane yield was 179.2 ± 13.1 NmL CH₄/g VS and 255.5 ± 14.5 NmL CH₄/g VS for process water at 180 °C and 234 °C, respectively. The addition of hydrochar improved the methane yield by 49.6 ± 10.8%, indicating that this is a valuable option for energy recovery from CM. Overall, the HTC-AD integration approach achieved an energy recovery potential of more than 79%, offering an efficient strategy for CM valorization.