Engineered hydrochar from polyester waste: Synthesis, optimization, and environmental impact

Polyester has been revalorized to generate new products. Among various alternatives, thermal treatments for producing carbon‐based materials are highlights. Within these methods, hydrothermal carbonization (HTC) stands out for its environmental advantages, as it yields a carbon‐based material known as hydrochar. However, limited studies have explored how HTC process changes textural, chemical, thermal, and surface properties of the hydrochar. Therefore, hydrochar production using polyester as feedstock under varying process conditions, including polyester ratios, FeSO 4 addition, carbonization temperature, and drying time, was performed. The results indicated that HTC modifies the properties of polyester. Hydrochars synthesized at 200°C with 120 g L −1 polyester and FeSO 4 exhibited superior mesoporous structures, enhancing thermal stability, and reduced mass loss during thermal decomposition, attributed to the presence of FeSO 4 . A life cycle assessment (LCA) using the Eco‐Indicator 99 method revealed that processes without FeSO 4 had lower environmental impacts, primarily due to the high energy demand associated with the iron salt. Nonetheless, processing conditions using 120 g L −1 of polyester at 200°C were identified as the most sustainable, offering minimal environmental trade‐offs despite a reduced yield. In contrast, the process using 120 g L −1 polyester and FeSO 4 at 190°C optimized yield with acceptable environmental compromises, making it more suitable for yield‐driven applications. The process using 60 g L −1 polyester, without FeSO 4 at 200°C, presented a balanced approach between sustainability and efficiency. These findings highlight the potential of polyester waste in hydrochar production and underscore the importance of optimizing process parameters to balance environmental impact and material performance.