Anaerobic Digestion of Organic Solid Waste: Challenges Derived from Changes in the Feedstock

Over the years, research on the anaerobic digestion of solid waste has mainly focused on single feedstocks with a fixed composition. Nevertheless, the impact assessment that drastic changes in the type and composition of feedstock might have on AD process stability has not been investigated in depth. The existence of a wide variety of organic solid waste whose generation and composition are highly dependent on seasonality, just as the possibility of using treatment plant facilities already in operation for treating new waste, makes it necessary to improve our knowledge of transitory states in AD. This chapter aims to provide insight into research on transitory states during the AD process when the type or composition of the feedstock has suffered a change to assess whether the AD process was finally able to adapt to system disturbances. Information about process stability control and microbial population adaptation, among others, derived from the transition states will be addressed

Anaerobic conversion of Chromolaena odorata (Siam weed) to biogas

This study evaluated the anaerobic mono-digestion of two different samples of Chromolaena odorata. Combinations of mechanical and thermo-alkaline pretreatments were applied to one of the two samples and labeled as ‘‘X’’ while the second had no thermo-alkaline treatment and was labeled as ‘‘Y’’. The Central Composite Design was used to design the pre treatments. The physicochemical characteristics of the substrates were carried out using standard methods after appropriate pretreatments. From the experimental set-ups, the most probable actual biogas yields in experiments ‘‘X’’ and ’’Y’’ were 0.3554 m3/kg Total Solid (TS)fed and 0.1803 m3/kg TSfed with the desirability of 99 and 100%, respectively. Further shown in the result is a 49.2% higher experimental (actual) biogas yield in experiment ‘‘X’’ over ‘‘Y’’. Gas chromatographic analysis revealed the CH4 and CO2 content of both experiments to be 65±1.5%; 21±3% and 53.5±2.5%; 26±3%, respectively. Combination of different pretreatment methods enhanced enormous biogas yield from the digested substrates. Optimization of the generated biogas data was carried out using the Response Surface Methodology (RSM) and the Artificial Neural Networks (ANNs). The coefficient of determination (R2) for RSM was lower compared to that of ANN. This shows that ANN

Biochemical conversion of fruit rind of Telfairia occidentalis (fluted pumpkin) and poultry manure

Environmental pollution by solid wastes and inadequate energy supply are some of the major challenges facing the developing world. This study evaluated the potentials of Fluted pumpkin fruit rind and poultry manure for biogas generation. Mechanical and thermo-alkaline pre-treatments were applied to two samples labeled ‘O’ and ‘P’ while the third sample (Q) had no thermo-alkaline treatment. The physicochemical characteristics of the substrates revealed richness in nutrients and mineral elements. The results showed that use of a combination of pre-treatment methods enhanced the biogas yield in the pre-treated substrates. Analysis of the gas composition showed 66.5 ± 2.5% Methane, 25 ± 1% Carbon dioxide; 58.5 ± 2.5% Methane, 26 ± 1% Carbon dioxide; 54.5 ± 1.5% Methane, 28 ± 2% Carbon dioxide for the three experiments, respectively. All the obtained values show the models had a high predictive ability. The substrates should be further used for energy generatio

Rapid biological reduction of graphene oxide: Impact on methane production and micropollutant transformation

10 Páginas.-- 8 Figuras- 1 TablaThis study investigates the impact of graphene oxide (GO) addition to anaerobic sludge and the formation of biologically reduced GO (bioRGO) on both the anaerobic transformation of organic contaminants and the corresponding biogas production. A hydrogel-like material of anaerobic digestate and bioRGO was formed on the first day after GO addition. Raman spectroscopy showed an increase in the ID/IGratio from 0.74 to 1.01, confirming the reduction of GO due to anaerobic respiration. The anaerobic removal of model antibiotics sulfamethoxazole and trimethoprim was unaffected by the GO addition. Yet formation of bioRGO inhibited the formation of the identified transformation products (TPs) of sulfamethoxazole, TP253 and TP257. Furthermore, the formation of TP253 and TP257 biotransformation products of sulfamethoxazole in sterilized sludge confirmed that their removal was likely achieved via intracellular enzymes that had enough thermal stability to remain active after the sterilization. For trimethoprim, no transformation products could be detected using the employed analytical method. The production of methane was generally inhibited up to 18% due to the presence of high GO levels (>100 mg/L) (288 vs. 353 mL CH4/g VS).This work was supported by the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement – MSCA-ITN-2018 (EJD Nowelties, grant number 812880). J.R. is grateful for the financial support provided by the Spanish State Research Agency of the Spanish Ministry of Science, Innovation, and Universities (PID2019-110346RB-C22), ANTARES Project.Peer reviewe

Improvement of anaerobic digestion of sewage mixed sludge using free nitrous acid and Fenton pre-treatment

Abstract Background Recently, it has been indicated that free nitrous acid (FNA) and Fenton pre-treatment of waste activated sludge can enhance methane production in anaerobic digestion of waste activated sludge. In addition, it has been revealed that the substances used in these pre-treatments are both eco-friendly and economically attractive because not only are they produced in anaerobic digestion, but they are also low priced. Since primary sludge and waste activated sludge are mixed prior to anaerobic digestion in the majority of wastewater treatment plants, this study aims to assess the influence of combined FNA and Fenton on the anaerobic digestion of mixed sludge. Results According to this study’s results, methane generation from anaerobic digestion of mixed sludge was enhanced when using FNA and Fenton pre-treatment, affirming the effectiveness of the individual and combined pre-treatments in anaerobic digestion of mixed sludge. The enhanced methane production was significant in combined pre-treatments (up to 72%), compared with FNA and Fenton pre-treatment alone (25% and 27%, respectively). This corroborates the positive synergistic effect of the combined pre-treatments on methane production. The enhanced methane can be attributed to augmented soluble fractions of organic matter in addition to increased readily biodegradable organic matter, caused by the pre-treatments. Additionally, the amount of chemical oxygen demand (COD) was assessed during anaerobic digestion, and it was revealed that COD decreased considerably when the pre-treatment strategies were combined. Conclusions This study reveals that the pre-treatments are potentially applicable to full-scale wastewater treatment plants because a mixture of primary sludge and waste activated sludge was used for the pre-treatments. Additionally, combined FNA and Fenton pre-treatments prove more effective in enhancing methane production and organic removal than these pre-treatments alone. The enhanced methane production is important for two reasons: a higher amount of renewable energy could be generated from the enhanced methane production and the COD of digested sludge reduces in such a way that facilitates application of the sludge to agricultural lands and reduces sludge transport costs

Graphene oxide addition to anaerobic digestion of waste activated sludge: Impact on methane production and removal of emerging contaminants

8 Páginas.-- 4 Figuras.-- 3 TablasThe effect of graphene oxide on the anaerobic digestion of waste activated sludge was investigated at two graphene oxide concentrations (0.025 and 0.075 g graphene oxide per g volatile solids) using biochemical methane potential tests. The occurrence of 36 pharmaceuticals was monitored in the solid and liquid phases before and after the anaerobic treatment. The addition of graphene oxide improved the removal of most pharmaceuticals detected, even those that are considered persistent to biological degradation, such as azithromycin, carbamazepine, and diclofenac. No significant differences were observed in the final specific methane production without graphene oxide and with the lowest graphene oxide concentration, yet the highest graphene oxide concentration partially inhibited methane production. The relative abundance of antibiotic resistance genes was not affected by the graphene oxide addition. Finally, significant changes in the microbial community including bacteria and archaea were detected with graphene oxide addition.This research is funded by AEI (Agencia Estatal de Investigación, Spanish Government) through project ANTARES (PID 2019-110346RB-C22). O. Casabella acknowledges funding from the Secretariat of Universities and Research from Generalitat de Catalunya and the European Social Fund for his FI fellowship (2022 FI_B1 00122). M. Gros acknowledges her Ramon y Cajal contract (RYC 2020-030324-I) funded by the MCIN/AEI 10.13039/501100011033 and by “ESF Investing in your future”. The authors acknowledge the support from the Economy and Knowledge Department of the Catalan Government through a Consolidated Research Group (ICRA-TECH - 2021 SGR 01283) and (SGR ICRA-ENV 2021 01282).Peer reviewe

Biochemical conversion of fruit rind of Telfairia occidentalis (fluted pumpkin) and poultry manure

Environmental pollution by solid wastes and inadequate energy supply are some of the major challenges facing the developing world. This study evaluated the potentials of Fluted pumpkin fruit rind and poultry manure for biogas generation. Mechanical and thermo-alkaline pre-treatments were applied to two samples labeled ‘O’ and ‘P’ while the third sample (Q) had no thermo-alkaline treatment. The physicochemical characteristics of the substrates revealed richness in nutrients and mineral elements. The results showed that use of a combination of pre-treatment methods enhanced the biogas yield in the pre-treated substrates. Analysis of the gas composition showed 66.5 ± 2.5% Methane, 25 ± 1% Carbon dioxide; 58.5 ± 2.5% Methane, 26 ± 1% Carbon dioxide; 54.5 ± 1.5% Methane, 28 ± 2% Carbon dioxide for the three experiments, respectively. All the obtained values show the models had a high predictive ability. The substrates should be further used for energy generation