• Energy Research

This study evaluated the use of an anaerobic packed-bed reactor for hydrogen production at different hydraulic retention times (HRT) (1–8 h). Two reactors filled with expanded clay and fed with glucose (3136–3875 mg L−1) were operated at different total upflow velocities: 0.30 cm s−1(R030) and 0.60 cm s−1(R060). The effluent pH of the reactors was maintained between 4 and 5 by adding NaHCO3and HCl solutions. It was observed a maximum hydrogen production rate of 0.92 L H2 h−1 L−1in R030 at HRT of 1 h. Furthermore, the highest hydrogen yield of 2.39 mol H2 mol−1glucose was obtained in R060. No clear trend was observed by doubling the upflow velocities at this experiment. High ethanol production was also observed, indicating that the ethanol-pathway prevailed throughout the experiment.

This study evaluated the use of an anaerobic packed-bed reactor for hydrogen production at different hydraulic retention times (HRT) (1–8 h). Two reactors filled with expanded clay and fed with glucose (3136–3875 mg L−1) were operated at different total upflow velocities: 0.30 cm s−1(R030) and 0.60 cm s−1(R060). The effluent pH of the reactors was maintained between 4 and 5 by adding NaHCO3and HCl solutions. It was observed a maximum hydrogen production rate of 0.92 L H2 h−1 L−1in R030 at HRT of 1 h. Furthermore, the highest hydrogen yield of 2.39 mol H2 mol−1glucose was obtained in R060. No clear trend was observed by doubling the upflow velocities at this experiment. High ethanol production was also observed, indicating that the ethanol-pathway prevailed throughout the experiment.

Abstract The substrate and yeast extract (YE) concentrations of a batch reactor were changed according to a central composite design in order to optimize the conversion of sugarcane bagasse (SCB) into hydrogen. The optimum hydrogen production (1.50 mmol/L) was obtained using 2.77 and 5.84 g/L of YE and SCB, respectively. Taxonomic analysis using the SEED database indicated that Clostridium (33% of total communities) and Methanothermobacter (40% of archaeal community) were the most abundant genera in the high hydrogen performance reactor. Key microorganisms and related pathways involved in all steps of the anaerobic digestion were further revealed and may help drive sugarcane bagasse bioconversion.

Abstract The substrate and yeast extract (YE) concentrations of a batch reactor were changed according to a central composite design in order to optimize the conversion of sugarcane bagasse (SCB) into hydrogen. The optimum hydrogen production (1.50 mmol/L) was obtained using 2.77 and 5.84 g/L of YE and SCB, respectively. Taxonomic analysis using the SEED database indicated that Clostridium (33% of total communities) and Methanothermobacter (40% of archaeal community) were the most abundant genera in the high hydrogen performance reactor. Key microorganisms and related pathways involved in all steps of the anaerobic digestion were further revealed and may help drive sugarcane bagasse bioconversion.

Abstract Two continuous anaerobic fluidized bed reactors (AFBRs) were operated under thermophilic (55 °C) temperature for 150 days to investigate the effect of dark H 2 fermentation of diluted and raw sugarcane vinasse on H 2 production using mixed seed sludge. Although effective H 2 production (52.8% of H 2 ; 0.80 L H 2 h −1 L −1 ; 0.79 mmol gCOD added −1 ) was observed using an elevated substrate concentration (30,000 mg COD L −1 ), the optimal operational conditions were found for the AFBR 1 (10,000 mg COD L −1 ) fed with diluted sugarcane vinasse (HRT 6 h; OLR 40 kg COD m −3 d −1 ), achieving a H 2 yield of 2.86 mmol H 2 g COD added −1 . H 2 production was inhibited by elevated volatile fatty acid (VFA) concentrations (butyric and acetic acids = 3.7 and 3.0 g L −1 , respectively) in the raw feedstock. Denaturing gradient gel electrophoresis (DGGE) analyses revealed changes in the bacterial population of the expanded clay biofilm as a function of the substrate concentration.

Abstract Two continuous anaerobic fluidized bed reactors (AFBRs) were operated under thermophilic (55 °C) temperature for 150 days to investigate the effect of dark H 2 fermentation of diluted and raw sugarcane vinasse on H 2 production using mixed seed sludge. Although effective H 2 production (52.8% of H 2 ; 0.80 L H 2 h −1 L −1 ; 0.79 mmol gCOD added −1 ) was observed using an elevated substrate concentration (30,000 mg COD L −1 ), the optimal operational conditions were found for the AFBR 1 (10,000 mg COD L −1 ) fed with diluted sugarcane vinasse (HRT 6 h; OLR 40 kg COD m −3 d −1 ), achieving a H 2 yield of 2.86 mmol H 2 g COD added −1 . H 2 production was inhibited by elevated volatile fatty acid (VFA) concentrations (butyric and acetic acids = 3.7 and 3.0 g L −1 , respectively) in the raw feedstock. Denaturing gradient gel electrophoresis (DGGE) analyses revealed changes in the bacterial population of the expanded clay biofilm as a function of the substrate concentration.

Abstract Solid waste (pulp and husk) and wastewater from post-harvest coffee processing contain high carbohydrate content, which can be used in biofuel production. However, the recalcitrance of lignocellulosic material in the pulp and husk, in addition to the polyphenols in wastewater limits its application. The objective of this research was to evaluate the coffee processing waste for H2 production. The experiments were carried out in batch reactors analyzing the co-digestion of: (1) wastewater with pulp and husk in natura or ground, (2) pulp and husk pretreated in the hydrothermal system and (3) liquid fraction from pretreatment of the pulp and husk in the hydrothermal system. The severity factor of the pulp and husk hydrothermal pretreatment was between 3.2 and 4.2, in addition to bioaugmentation of the autochthonous consortium (bacteria and fungi) from the waste. The highest H2 production potential of 8 mL was obtained by co-digestion of pretreated pulp and husk in severity 3.5 with coffee processing wastewater. Pulp and husk pretreatment with the hydrothermal system at 180 °C for 15 min favored in increased 20% cellulose, 14% hemicellulose, and 31% lignin. Hydrothermal pretreatment and waste co-digestion improved up to 7 times the H2 production when compared to in natura waste.

Abstract Solid waste (pulp and husk) and wastewater from post-harvest coffee processing contain high carbohydrate content, which can be used in biofuel production. However, the recalcitrance of lignocellulosic material in the pulp and husk, in addition to the polyphenols in wastewater limits its application. The objective of this research was to evaluate the coffee processing waste for H2 production. The experiments were carried out in batch reactors analyzing the co-digestion of: (1) wastewater with pulp and husk in natura or ground, (2) pulp and husk pretreated in the hydrothermal system and (3) liquid fraction from pretreatment of the pulp and husk in the hydrothermal system. The severity factor of the pulp and husk hydrothermal pretreatment was between 3.2 and 4.2, in addition to bioaugmentation of the autochthonous consortium (bacteria and fungi) from the waste. The highest H2 production potential of 8 mL was obtained by co-digestion of pretreated pulp and husk in severity 3.5 with coffee processing wastewater. Pulp and husk pretreatment with the hydrothermal system at 180 °C for 15 min favored in increased 20% cellulose, 14% hemicellulose, and 31% lignin. Hydrothermal pretreatment and waste co-digestion improved up to 7 times the H2 production when compared to in natura waste.

The efficiency of linear alkylbenzene sulfonate (LAS) removal from laundry wastewater and the related microbial community was investigated in an anaerobic fluidized bed reactor (AFBR). The AFBR was operated in three stages, in addition to the biomass adaptation stage without LAS (stage I). The stages were differentiated by their supplementary co-substrates: stage II had sucrose plus ethanol, stage III had only ethanol, and stage IV had no co-substrate. The replacement of sucrose plus ethanol with ethanol only for the substrate composition favored the efficiency of LAS removal, which remained high after the co-substrate was removed (stage II: 52 %; stage III: 73 %; stage IV: 77 %). A transition in the microbial community from Comamonadaceae to Rhodocyclaceae in conjunction with the co-substrate variation was observed using ion sequencing analysis. The microbial community that developed in response to an ethanol-only co-substrate improved LAS degradation more than the community that developed in response to a mixture of sucrose and ethanol, suggesting that ethanol is a better option for enriching an LAS-degrading microbial community.