Energy recovery from garden and park waste by hydrothermal carbonisation and anaerobic digestion

Hydrothermal carbonisation (HTC) can transform wet lignocellulosic biomass, which is not considered an effective biofuel for energy production at the industrial level, into a carbonaceous product called hydrochar (HC) that is suitable for combustion and a process water (PW). PW is an interesting by-product that can be valorised for biogas production via anaerobic digestion (AD). This study presents a new approach for the valorisation of garden and park wastes (GPW) by integrating HTC to generate HC for energy production, while PW is subjected to AD for biogas production. The hydrothermal treatment was performed at 180, 210, and 230 °C, yielding HC with improved physicochemical properties, such as an elevated higher heating value (21–25 MJ kg−1); low ash (<5 wt.%), nitrogen (1.3 wt.%), and sulphur (0.2 wt.%) contents; better fuel ratio (0.4–0.6); and a broad comprehensive combustibility index (8.0×10−7 to 9.6×10−7 min−2 °C−3). AD of the generated PW was conducted under mesophilic conditions (35 °C), resulting in a methane production in the range of 253–326 mL g−1 CODadded and COD removal of up to 65%. The combination of HTC and AD allowed the recovery of 91% and 94% of the energy content feedstock, as calculated from the combustion of HC and methane, respectivelyThe authors gratefully acknowledge funding from Spain’s MINECO (PID2019-108445RB-I00; PDC2021-120755-I00) and the Comunidad de Madrid (Project S2018/EMT-4344). R. P. Ipiales acknowledges financial support from the Comunidad de Madrid (IND2019/AMB-17092) and the Arquimea-Agrotech Compan

Effect of inoculum source and initial concentration on the anaerobic digestion of the liquid fraction from hydrothermal carbonisation of sewage sludge

Hydrothermal carbonisation (HTC) is a relatively new alternative for the management of sewage sludge that allows obtaining a HTC char (hydrochar) with a high heating value (≈22 MJ/kg). The aim of this work has been to study the anaerobic digestion of the liquid fraction generated as by-product during HTC (LFHTC) of dewatered sewage sludge, to get more value to the overall process. For this purpose, three different inocula: granular biomass from industrial reactors treating brewery and sugar beet wastewaters and a flocculent biomass from a full-scale digester of municipal sewage sludge, at two initial inoculum concentrations (IC) (10 and 25 g COD/L) were tested. ANOVA test was applied to evaluate the ultimate methane yield for each IC. The effect was different for each inoculum studied: an increase from 10 to 25 g COD/L increased the methane yield by 23% for brewery waste, achieving the highest value obtained (177 ± 5 mL STP CH4/g CODadded), while declining to 99 ± 2 mL STP CH4/g CODadded for sugar beet; it is not affected by the municipal sludge, yielding around 135 mL STP CH4/g CODadded. Therefore, among the inocula tested, brewery waste was the most appropriate for the anaerobic digestion of the LFHTC of dewatered sewage sludge at high ICThe authors wish to express their gratitude to the Spanish MINECO (CTM2016-76564-R) for providing financial support. M.A. de la Rubia acknowledges financial support from the Spanish Ministry of Economy and Competitiveness (RYC-2013-12549

Using plant-based preparations to protect common bean against halo blight disease: the potential of nettle to trigger the immune system

Halo blight disease of beans (Phaseolus vulgaris L.), caused by the bacterium Pseudomonas syringae pv. phaseolicola (Pph), is responsible for severe losses in crop production worldwide. As the current agronomic techniques used are not effective, it is necessary to search for new ones which may prevent disease in common bean. In this study, we challenged four plant-based preparations (PBPs), with no other agronomic uses, as they come from industrial waste (grapevine pomace (R-G) and hop residue (R-H)) or wild plants (Urtica dioica (U) and Equisetum sp. (E)), to be used as immune defense elicitors against Pph in common bean. After studying their inhibitory effect against Pph growth by bioassays, the two most effective PBPs (R-G and U) were applied in common bean plants. By measuring the total H2O2, lipid peroxidation, and antioxidant enzymatic activities, as well as the expression of six defense-related genes-PR1, WRKY33, MAPKK, RIN4, and PAL1-, it was observed that U-PBP application involved a signaling redox process and the overexpression of all genes, mostly PR1. First infection trials in vitro suggested that the application of U-PBP involved protection against Pph. The elicitation of bean defense with U-PBP involved a decrease in some yield parameters, but without affecting the final production. All these findings suggest a future use of U-PBP to diminish halo blight disease

Anaerobic co-digestion of the aqueous phase from hydrothermally treated waste activated sludge with primary sewage sludge. A kinetic study

The mesophilic anaerobic co-digestion of the liquid fraction from hydrothermal carbonization (LFHTC) of dewatered waste activated sludge with primary sewage sludge (PSS) has been studied. Mixtures of different composition (25, 50 and 75% of LFHTC on a chemical oxygen demand (COD) basis), as well as the individual substrates, have been tested using two inocula (flocculent (FS) and granular (GS) sludges). Methane production decreased as the LFHTC/PSS ratio increased, which can be related to the presence of recalcitrant compounds in the LFHTC, such as alkenes, phenolics, and other oxygen- and nitrogen-bearing aromatics hard-to-degrade through anaerobic digestion. Methane yield reached 248 ± 11 mL CH4 STP/g CODadded with the GS inoculum and 25% LFHTC. A 74 and a 30% increase of methane production was achieved in the 25% LFHTC runs respect to the obtained in the similar experiments with 100% LFHTC, using the FS and GS inocula, respectively. In those late runs, the COD was reduced more than 86%, with a negligible concentration of total volatile fatty acids. With both inocula, total Kjeldahl nitrogen hydrolysis increased as the LFHTC to PSS mixture ratio decreased, reaching values higher than 79% at the end of the experiments. Methane yield values fitted well the first-order, Cone and Weibull kinetic models for both inocula. Significant differences in the kinetic constant values, ranging from 0.100 to 0.168 d−1 and 0.059–0.068 d−1, were found with the FS and GS inocula, respectively. The results obtained support the potential integration of HTC of dewatered waste activated sludge in wastewater treatment plantsThe authors greatly appreciate financial support from the SpanishMINECO (Project CTM2016-76564-R) and the Community of Madrid(Project P2013/MAE-2716). M.A. de la Rubia acknowledges financialsupport from the Spanish MINECO (RYC-2013-12549). The valuablecontribution of

Structure and electrical behavior relationship of a magnesium–tellurite glass using Raman and impedance spectroscopy

In this paperwe present the study of the glassy systems of formula: xMgO(1−x)(0.5V2O5·0.5MoO3)2TeO2,with (0 b x b 1). The aim of the work is to understand the relationship between in the induced changes in the glassy matrix by the incorporation of MgO in a vanadium–tellurite glass and the electrical response of the material. It has been found that the incorporation of MgO in the glassy matrix raises the glass transition temperature. The whole system's electrical behavior is explained by the small polaron hopping, in good agreement with the variable range polaron hopping model. In this matrix, an ionic transport by Mg2+ is not allowed. The study gives an opportunity to understand how to tune in the middle-range glassy structural order and, as a direct implication, how to control the electrical conduction process.Instituto de Física La Plat

The effect of electronic energy loss on the dynamics of thermal spikes in Cu

We present results of a molecular dynamics simulation study of the effect of electron-ion interactions on the dynamics of the thermal spike in Cu. Interatomic forces are described with a modified embedded atom method potential. We show that the electron-ion interaction acts to reduce the lifetime of the thermal spike and therefore the amount of atomic rearrangement that takes place in energetic displacement cascades in Cu. The results point toward the important effect that inelastic energy losses might have on the dynamics of displacement cascades in the subcascade energy regime where the lifetime of the thermal spike is expected to exceed the electron-phonon coupling tim

Valorisation of the liquid fraction from hydrothermal carbonisation of sewage sludge by anaerobic digestion

This is the peer reviewed version of the following article: Journal of Chemical Technology and Biotechnology 93.2 (2018): 450-456, which has been published in final form at https://doi.org/10.1002/jctb.5375. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived VersionsBACKGROUND: The mesophilic anaerobic digestion of the liquid fraction from hydrothermal carbonisation (208°C, 1 h) of dehydrated sewage sludge has been studied. Two initial inoculum concentrations (IC) (10 and 25 g COD L-1) and four inoculum to substrate ratios (ISR) (2, 1, 0.5 and 0.4 on a COD basis) have been selected to analyse their influence on the evolution of the anaerobic digestion process. RESULTS: The substrate is characterised by a high COD (95.5 g L-1) and TKN (8.7 g N L-1) values. High inoculum concentration (25 g COD L-1) and/or low ISR (≤ 0.5) inhibited methanogenesis due to the high ammonia nitrogen (1.4 g TAN L-1) and VFA (&gt;4 g COD L-1) released. For the inhibited samples final COD removals lower than 15% and IA/TA ratios higher than 0.3 were found. The greatest methane yield (177±5 mL CH4 STP g-1 CODadded) was achieved at 25 g COD L-1 of IC and at an ISR of 2. CONCLUSION: During anaerobic digestion of the liquid fraction from the hydrothermal carbonisation of sewage sludge, the IC and ISR must be adequately selected for proper operation of the process and successful valorisation. According to the results, working at an ISR ≥ 1 is recommendedThe authors wish to express their gratitude to the UAM-Santander (Project CEAL-AL/2015-29) and Spanish MINECO (CTM2016-76564-R) for providing financial support. MA de la Rubia acknowledges financial support from the Spanish Ministry of Economy and Competitiveness (RYC-2013-12549

Mesophilic anaerobic co-digestion of the organic fraction of municipal solid waste with the liquid fraction from hydrothermal carbonization of sewage sludge

In the present study, the influence of substrate pre-treatment (grinding and sieving) on batch anaerobic digestion of the organic fraction of municipal solid waste (OFMSW) was first assessed, then followed by co-digestion experiments with the liquid fraction from hydrothermal carbonization (LFHTC) of dewatered sewage sludge (DSS). The methane yield of batch anaerobic digestion after grinding and sieving (20 mm diameter) the OFMSW was considerably higher (453 mL CH4 STP g−1 VSadded) than that of untreated OFMSW (285 mL CH4 STP g−1 VSadded). The modified Gompertz model adequately predicted process performance. The maximum methane production rate, Rm, for ground and sieved OFMSW was 2.4 times higher than that of untreated OFMSW. The anaerobic co-digestion of different mixtures of OFMSW and LFHTC of DSS did not increase the methane yield above that of the anaerobic digestion of OFMSW alone, and no synergistic effects were observed. However, the co-digestion of both wastes at a ratio of 75% OFMSW-25% LFHTC provides a practical waste management option. The experimental results were adequately fitted to a first-order kinetic model showing a kinetic constant virtually independent of the percentage of LFHTC (0.52–0.56 d−1) and decreasing slightly for 100% LFHTC (0.44 d−1)The authors wish to express their gratitude to the Spanish MINECO (CTM2016-76564-R) for providing financial support. M. A. de la Rubia received financial support from the Spanish Ministry of Economy and Competitiveness (RYC-2013-12549

Integration of hydrothermal carbonization and anaerobic digestion for energy recovery of biomass waste: an overview

Hydrothermal carbonization is emerging as a promising eco-friendly technology for the management of wet biomass wastes through energy recovery. It avoids drying of the feedstock and operates at a much lower temperature than conventional thermal conversion technologies, giving rise to a carbonaceous solid, hydrochar, of improved fuel quality with respect to the starting biomass. However, the aqueous fraction resulting from this process, the so-called process water, represents a troublesome secondary waste requiring effective treatment because of the high chemical oxygen demand and the presence of varying amounts of nutrients. Anaerobic digestion appears as a potential solution allowing significant reduction of the organic load while producing methane-rich biogas, thus contributing to energy recovery. Integrating hydrothermal carbonization and anaerobic digestion is gaining interest in the literature. This review compiles the reported studies on the application of hydrothermal carbonization coupled with anaerobic digestion for energy recovery of different biomass wastes, analyzing the energy balances. The main characteristics of the resulting HC and the methanogenic potential of the process waters are reviewed in connection with the operating conditions, as well as the possibility of nutrient recovery. Life cycle assessment and economic studies are includedThe authors gratefully acknowledge funding from Spain’s MINECO (PID2019-108445RB-I00) and the Comunidad de Madrid (Project S2018/EMT-4344). R. P. Ipiales acknowledges financial support from the Comunidad de Madrid (IND2019/AMB-17092) and the Arquimea Biotech Compan