Abstract
The disposal of macroalgal waste presents environmental and economic challenges, but its valorization offers interesting opportunities. Hydrothermal carbonization (HTC) is a promising technology for transforming this waste into hydrochar, a carbon-rich material with energy and industrial applications. This study aims to optimize HTC process parameters, including temperature (180–260 °C), residence time (0–240 min), and solid/water ratio (S/W), to improve hydrochar yield, higher heating value (HHV), and energy efficiency, using response surface methodology (Box-Behnken design). The results revealed that temperature and residence time were the most influential factors on hydrochar production. The maximum higher heating value (HHV) of 18.71 MJ/kg was observed at 260 °C, 240 min, and a 0.1875 S/W ratio, indicating efficient energy conversion. On the other hand, the highest hydrochar yield and energy yield were obtained at 180 °C, 0 min, and a 0.1875 S/W ratio, suggesting that more moderate conditions favor better material retention. Analysis of the samples showed an increase in porosity and an improvement in the physico-chemical characteristics of hydrochar compared with raw waste, reinforcing its potential as a biofuel or adsorbent material. These results confirm that the valorization of macroalgal waste by HTC represents a promising solution for the production of renewable energy, thus contributing to the sustainable management of resources in Morocco.