Suchergebnisse

Hydrothermal carbonization was evaluated as a food waste valorization strategy to obtain hydrochar and recover nutrients. In the hydrothermal treatment, the temperature (170–230 °C), reaction time (5–60 min), and addition of HCl (0.1–0.5 M) during the reaction were analyzed. Compared to the feedstock, hydrochar showed an increase in fixed carbon (greater than 45%) and a decrease in ash content (<7%), along with a higher heating value (18.6–26.2 MJ/kg), which would allow for its application as a biofuel for industry according to ISO/TS 17225–8. The hydrochar obtained using plain carbonization showed 75% P and 40% N of the feedstock content, whereas the HCl-mediated treatment (0.5 M) solubilized most of the P, K, and N in the process water (98% P as PO4-P, 98% K, and the total N content as NH4-N (16%) and organic-N) operating at 170 °C for 60 min. ; The authors greatly appreciate funding from Spanish MICINN (Project PID2019-108445RB-I00) and Madrid Regional Government (Project S2018/EMT-4344). A. Sarrion wishes to thank the Spanish MICINN and ESF for a research grant (BES-2017-081515). The authors thank Silvia Rodríguez for her valuable help

This work evaluates the potential of hydrothermal carbonization (HTC) to valorize the digestate derived from the anaerobic digestion of sewage sludge into useful materials for P and energy recovery. The hydrothermal treatment of digestate at 180–240 ºC did not lead to high-rank hydrochars. On the other hand, inorganic P concentration did not change with the temperature, while as the carbonization temperature increased, the organic P retention yield in hydrochar became lower, increasing the total P in the process water obtained at the highest temperature, up to 25.3%. P recovery from acid leaching of the hydrochar obtained at 180 ºC, via precipitation with CaO at pH up to 9, led to a brown solid precipitate with total P content close to 42 mg g-1 , in the range of low grade phosphorus ores. Moreover, acid leaching reduced by 50% the ash content, yielding lignite-like upgraded hydrochars with higher heating values in the range of 20.5–23.1 MJ kg-1 , fairly interesting as solid fuels. Anaerobic digestion of the process water enabled additional energy recovery in form of biogas (325 and 279 mL CH4 g-1 VS -at standard temperature and pressure; STP- from the process water resulting at 180 and 210 ºC, respectively) ; Authors greatly appreciate funding from Spanish Ministry of Economy and Competitiveness (Project CTM2016-76564-R; project RYC-2013-12549) and Madrid Regional Government (Project P2018/EMT-4344). Authors thank to Instituto Colombiano de Crédito Educativo y Estudios Técnicos en el Exterior (ICETEX) (Colombia) as part of the grant awarded to José Marin-Batista

Hydrothermal carbonization (HTC) is a suitable technology for managing wastes with a high moisture content, providing a carbon-rich and high energy density material called hydrochar and a process water (PW) with significant organic matter content. The aim of this work was to develop a new approach to sewage sludge management involving anaerobic digestion (AD) of the PW of dewatered waste activated sludge (DWAS) with primary sewage sludge (PSS). The process was optimized by performing semi-continuous experiments with different feed mixture compositions (10% PW/90% PSS and 5% PW/95% PSS, on a COD basis), organic loading rates (OLR; 1.5 and 2.5 g COD L−1 d−1), and temperature regimes (mesophilic and thermophilic). The combination of mesophilic conditions, a 10% PW/90% PSS feed mixture and OLR of 1.5 g COD L−1 d−1 provided concentrations of volatile fatty acids <400 mg COD L−1 in addition to a methane yield (172 ± 11 mL CH4 g−1 CODadded), 1.15 times the value for the control test (100% PSS). Therefore, the energy content of hydrochar from HTC of DWAS followed by AD of the process water with primary sewage sludge enhances the valorization of this renewable residue ; The authors greatly appreciate funding from Spain's MINECO (Project CTM2016-76564-R; project RYC-2013-12549), Madrid Regional Government (Project P2018/EMT-4344) and UAMSantander (Project 2017/EEUU/07)

This study analyzes the effects of COVID-19 confinement on the autonomous learning performance of students in higher education. Using a field experiment with 458 students from three different subjects at Universidad Autónoma de Madrid (Spain), we study the differences in assessments by dividing students into two groups. The first group (control) corresponds to academic years 2017/2018 and 2018/2019. The second group (experimental) corresponds to students from 2019/2020, which is the group of students that had their face-to-face activities interrupted because of the confinement. The results show that there is a significant positive effect of the COVID-19 confinement on students' performance. This effect is also significant in activities that did not change their format when performed after the confinement. We find that this effect is significant both in subjects that increased the number of assessment activities and subjects that did not change the student workload. Additionally, an analysis of students' learning strategies before confinement shows that students did not study on a continuous basis. Based on these results, we conclude that COVID-19 confinement changed students' learning strategies to a more continuous habit, improving their efficiency. For these reasons, better scores in students' assessment are expected due to COVID-19 confinement that can be explained by an improvement in their learning performance ; This research was funded by ADeAPTIVE (Advanced Design of e-Learning Applications Personalizing Teaching to Improve Virtual Education) project with the support of the Erasmus + programme of the European Union (grant number 2017-1-ES01-KA203-038266). This study was also funded by ACCIO´, Spain (Pla d'Actuacio´ de Centres Tecnològics 2019) under the project Augmented Workplace. This study was also funded by the Fondo Supera COVID-19 (Project: Development of tools for the assessment in higher education in the COVID-19 confinement