From scraps to purification: innovative use of food waste-derived hydrochar in eradicating pharmaceutical pollutants.

Chemical products (CPs) such as carbamazepine and naproxen, present in aquatic environments, pose significant risks to both aquatic life and human health. This study investigated the use of hydrothermally carbonized food waste-derived hydrochar (AC-HTC) at three distinct temperatures (200, 250, and 300 °C) as an adsorbent to remove these CPs from water. Our research focused on the impact of hydrothermal carbonization temperature on hydrochar properties and the effects of chemical activation with phosphoric acid on adsorption capacity. Hydrothermal carbonization increased the hydrochar's surface area from 1.47 to 7.52 m2/g, which was further enhanced to 32.81 m2/g after activation with phosphoric acid. Batch adsorption experiments revealed that hydrochar produced at 250 °C (AC-HTC-250) demonstrated high adsorption capacities of 49.10 mg/g for carbamazepine and 14.35 mg/g for naproxen, outperforming several conventional adsorbents. Optimal adsorption occurred at pH 4, aligning well with the Langmuir and pseudo-first-order models. The hydrochar showed potential for regeneration and multiple uses, suggesting its applicability in sustainable wastewater treatment. Future research will explore scalability and effectiveness against a broader range of pollutants.

Process water recirculation for catalytic hydrothermal carbonization of anaerobic digestate: Water-Energy-Nutrient Nexus.

The process water (PW) from acid-catalyzed hydrothermal carbonization (HTC) is still an environmental burden due to the enriched organics, nutrients, and salts. This study proposed a novel strategy to valorize food waste digestate into multifunctional hydrochar by recirculating the PW in the HCl-catalyzed HTC process. The produced multifunctional hydrochar could be utilized as a high-quality solid fuel with HHV of 27.9 MJ kg-1 (hydrochar without PW recirculation) and a slow-release fertilizer by converting the complex Ca and P compounds from the food waste digestate into a Ca-P deposit (hydroxyapatite) with more than a 93 % P recovery rate (hydrochar with PW recirculation). Adding fresh HCl in the HTC PW recirculation system only displayed a marginal catalytic impact on the hydrochar properties after two cycles of recirculation. This study demonstrated the importance of inherent Ca in the feedstocks and the dual role of HCl in the HTC with PW recirculation.

Catalytic co-hydrothermal carbonization of food waste digestate and yard waste for energy application and nutrient recovery.

Hydrothermal carbonization (HTC) provides a promising alternative to valorize food waste digestate (FWD) and avoid disposal issues. Although hydrochar derived from FWD alone had a low calorific content (HHV of 13.9 MJ kg-1), catalytic co-HTC of FWD with wet lignocellulosic biomass (e.g., wet yard waste; YW) and 0.5 M HCl exhibited overall superior attributes in terms of energy recovery (22.7 MJ kg-1), stable and comprehensive combustion behaviour, potential nutrient recovery from process water (2-fold higher N retention and 129-fold higher P extraction), and a high C utilization efficiency (only 2.4% C loss). In contrast, co-HTC with citric acid provided âˆ¼3-fold higher autogenous pressure, resulting in a superior energy content of 25.0 MJ kg-1, but the high C loss (∼74%) compromised the overall environmental benefits. The results of this study established a foundation to fully utilize FWD and YW hydrochar for bioenergy application and resource recovery from the process water.