Co-digestion and metal ion addition strategies to improve the biogas production potential of Jatr... more Co-digestion and metal ion addition strategies to improve the biogas production potential of Jatropha seed cake (JSC) by anaerobic digestion were evaluated in the present study. Initially, batch experiments were carried out to obtain the maximum JSC concentration for optimum biogas yield, followed by co-digestion with bagasse, and addition of Fe2+. The optimum JSC concentration of 15% (w/v) gave biogas production rate (BPR) of 66.4 mL/d, specific BPR of 9.7 mL/d/gVS and biogas yield of 0.064 m3/kgVS. The co-digestion strategy increased the carbon/nitrogen of feed (10% JSC+5% Bagasse, w/v) to 26.5 from 14 (JSC alone), resulting in biogas yield of 0.136 m3/kgVS of JSC, a 2.1-fold increase. Addition of Fe2+ to JSC and bagasse mixture led to biogas yield of 0.203 m3/kgVS, with methane content of 66% and methane production of 8.8 L/L reactor. With short digestion time of 15 days, co-digestion of JSC with bagasse and addition of Fe2+ showed 3.2-fold higher biogas yield than JSC alone.
The molecular structure of humic acid (HA) extracted was investigated by FT-IR and 13C CP/MAS NMR... more The molecular structure of humic acid (HA) extracted was investigated by FT-IR and 13C CP/MAS NMR spectroscopy during the vermicomposting of sugar industry wastes, viz. pressmud, trash and bagasse for 60 days. A rapid decrease in C/N and lignocellulosic (lignin, cellulose, hemicellulose) content was observed in vermicompost during early phase of the process. The FT-IR and 13C CP/MAS NMR spectra of HA indicated a high rate of change in structure with increase in the alkyl C/O-alkyl C ratio during the process. Aromatic structures and carboxyl groups showed an initial increase but decreased after ∼40 days indicating extensive mineralization during final stages of vermicomposting.
Two laboratory-scale systems were set up (i) composting (without earthworms) and (ii) vermicompos... more Two laboratory-scale systems were set up (i) composting (without earthworms) and (ii) vermicomposting (with earthworms) and were monitored for 60 days after pre-composting. The physico-chemical parameters (pH, C/N, organic matter, NH4+-N and ash content) showed similar evolution in both systems except a higher NH4+-N in the initial vermicomposts. However, principle component analysis (PCA) of enzymatic activities and community level physiological profiles revealed differences in the functional response of microbial communities in compost and vermicompost during maturation. Dehydrogenase activity and bacterial counts indicated a steady decrease in biological activity and population during composting, whereas vermicomposting exhibited higher activity on day 30 and a reduction in bacterial counts on day 10. PCA of denatured gradient gel electrophoresis (DGGE) profiles showed divergent dynamics of bacterial communities in two processes. These results indicated differences in the functional response and genetic structure of microbial community in composts and vermicomposts despite similar changes in their physico-chemical parameters.
The present study deals with the biohydrogen production from starch-containing wastewater collect... more The present study deals with the biohydrogen production from starch-containing wastewater collected from the textile industry in Taiwan. The effects of inoculums collected from different sources (sewage sludge, soil and cow dung), substrate concentrations (5–25 g COD/L) and pH (4.0–8.0) on hydrogen production from wastewater were investigated.The cow dung seed had the highest hydrogen production of 101 mL with hydrogen content in biogas of 32.2%. It corresponds to a hydrogen yield (HY) of 1.56 mol H2/mol hexose and hydrogen production rate (HPR) of 0.93 L/L/d. Response surface methodology was used to evaluate the effects of initial cultivation pH (4.0–8.0) and substrate concentration (5–25 g COD/L) on the hydrogen production at 35 °C. At pH 7.0 with a wastewater concentration of 20 g COD/L, a maximum hydrogen production of 66 mL with 31.9% H2 and corresponding to an HY of 0.97 mol H2/mol hexose and an HPR of 1.14 L/L/d were obtained. According to the response surface analysis, the optimal conditions for high HPR were a wastewater concentration of 13 g COD/L at an initial cultivation pH of 7.0. The main soluble metabolic products were acetate and butyrate for hydrogen fermentation from textile wastewater.► The textile wastewater containing starch is a potential energy resource for anaerobic hydrogen fermentation. ► The optimum initial cultivation pH for H2production was 7.0. ► The optimum wastewater concentration for H2 production was 13 g COD/L. ► The main soluble metabolic products were acetate and butyrate.
The effects of substrate concentration and temperature on fermentative hydrogen production from E... more The effects of substrate concentration and temperature on fermentative hydrogen production from Eichhornia crassipes using pig slurry microflora were studied, and the optimal values for maximum biohydrogen production were determined in batch experiments. Hydrogen and methane yield (HY and MY) and production rate (HPR and MPR) were evaluated at various E. crassipes concentrations (10–80 g/L) and incubation temperatures (25, 35, 45, 55, and 65 °C). Hydrogen and methane production were observed during the E. crassipes fermentation without any nutrients addition, and were dependent on E. crassipes concentrations. Maximum HPR (38.2 mmol H2/L/d) and MPR (29.0 mmol CH4/L/d) were obtained at E. crassipes concentration of 40 g/L and 80 g/L, respectively. Monod model and modified Andrew model were used to fit the hydrogen production rate data. Modified Andrew model could describe better the effects of substrate concentration on hydrogen production rate (greater R2 value). Maximum HPR (221.3 mmol H2/L/d) and MPR (24.4 mmol CH4/L/d) were obtained at 45 and 55 °C, respectively. These values were ca. 1105 and 18 folds higher than the HPR (0.2 mmol H2/L/d) and MPR (7.3 mmol CH4/L/d) at 25 °C, probably due to increased hydrolysis of E. crassipes at higher temperatures. Ratkowsky model could best describe the progress of hydrogen and methane production potential and rate (R2 > 0.9). The optimum E. crassipes concentration and incubation temperature were determined as 47.8 g/L and 62.5 °C, respectively for maximum hydrogen and methane production. Biohydrogen and biomethane yields from E. crassipes were 31.3 GJ/ha/y and 853.9 GJ/ha/y, respectively, with a total CO2 emission reduction from 15.2 to 23.7 tons.► Temperature and water hyacinth concentration could affect anaerobic biogas production. ► The optimum temperature for H2 and CH4 production were 48 and 63 °C, respectively. ► The optimum water hyacinth concentration for biogas production was 40 g/L ► H2 and CH4 yields from water hyacinth were 31 GJ/ha-y and 854 GJ/ha/y, respectively. ► Total CO2 emission reduction from this biogas production process was 15–24 ton/y.
Phase holdups play an important role in high-rate hydrogen production in an anaerobic fermentativ... more Phase holdups play an important role in high-rate hydrogen production in an anaerobic fermentative reactor, especially in understanding biomass content, biogas flow and distribution that significantly affect the flow regimes change in the reactor. In the present study three-phase hydrogen producing reactor with different configurations were tested to investigate the phase holdups phenomenon and microbial community. It was found that the major fatty acids produced from the reactors were acetate and butyrate (HBu), accounting for 74.4–93.5% of total soluble microbial products (SMP). When the HRT was shortened from 8 to 1 h, the HBu was the dominant acid product among the soluble metabolites and the ratio of Ethanol/SMP was lower than 15.1. Moreover, the gas holdup (ɛg) and solid holdup (ɛs) increased but liquid holdup (ɛl) decreased when the HRT was shortened. When the HRT was down to 1 h an increase in gas and solid holdups were noted. The gas holdups (ɛg) increased in the range of 0.30–0.34, and the solid holdups (ɛs) increased in the range of 0.32–0.34, which mean that the values of liquid holdups in high-rate fermentative hydrogen bioreactors could be decreased in the range of 0.38–0.32. Moreover, the empirical correlations of this study were satisfactory to predict the phase holdups in a dark-fermentation biohydrogen system. PCR-DGGE analysis revealed that bioreactor hydrodynamics under different HRTs significantly affects the occurrence of Streptococcus sp. and Bacillus sp. which mainly promotes granulation and retains high yielding hydrogen producing Clostridium sp. through their exopolysaccharides production. SEM results showed three dominant bacterial species namely Clostridium pasteurianum, Streptococcus sp. and Propionibacterium sp. in the bioreactors.
Aims: To evaluate bacterial community structure and dynamics in triplicate vermicomposts made fro... more Aims: To evaluate bacterial community structure and dynamics in triplicate vermicomposts made from the same start-up material, along with certain physico-chemical changes. Methods and Results: The physico-chemical parameters (pH, temperature, carbon, nitrogen, soluble substances and cellulose) evolved similarly in the triplicate vermicomposts, indicating a steady function. The 16S bacterial gene abundance remained constant over time. To monitor changes in the bacterial community structure, fingerprinting based on capillary electrophoresis singlestrand conformation polymorphism was employed. A rise in bacterial diversity occurred after precomposting and it remained stable during the maturation phase. However, a rapid shift in the structure of the bacterial community in the vermicompost replicates was noted at the beginning that stabilized with the process maturation. Multivariate analyses showed different patterns of bacterial community evolution in each vermicompost that did not correlate with the physico-chemical changes. Conclusions: The broad-scale functions remained similar in the triplicates, with stable bacterial abundance and diversity despite fluctuation in the community structure. Significance and Impact of the Study: This study has demonstrated that microbial fingerprinting with multivariate analysis can provide significant understanding of community structure and also clearly suggests that an ecosystem's efficacy could be the outcome of functional redundancy whereby a number of species carry out the same function.
Biohydrogen is a promising candidate which can replace a part of our fossil fuels need in day-to-... more Biohydrogen is a promising candidate which can replace a part of our fossil fuels need in day-to-day life due its perceived environmental benefits and availability through dark fermentation of organic substrates. Moreover, advances in biohydrogen production technologies based on organic wastewater conversion could solve the issues related to food security, climate change, energy security and clean development in the future. An evaluation of studies reported on biohydrogen production from different wastewaters will be of immense importance in economizing production technologies. Here we have reviewed biohydrogen production yields and rates from different wastewaters using sludges and microbial consortiums and evaluated the feasibility of biohydrogen production from unexplored wastewaters and development of integrated bioenergy process. Biohydrogen production has been observed in the range of substrate concentration 0.25e160 g COD/L, pH 4e8, temperature 23e60 C, HRT 0.5e72 h with various types of reactor configuration.
Two laboratory-scale systems were set up (i) composting (without earthworms) and (ii) vermicompos... more Two laboratory-scale systems were set up (i) composting (without earthworms) and (ii) vermicomposting (with earthworms) and were monitored for 60 days after pre-composting. The physico-chemical parameters (pH, C/N, organic matter, NH þ 4 À N and ash content) showed similar evolution in both systems except a higher NH þ 4 À N in the initial vermicomposts. However, principle component analysis (PCA) of enzymatic activities and community level physiological profiles revealed differences in the functional response of microbial communities in compost and vermicompost during maturation. Dehydrogenase activity and bacterial counts indicated a steady decrease in biological activity and population during composting, whereas vermicomposting exhibited higher activity on day 30 and a reduction in bacterial counts on day 10. PCA of denatured gradient gel electrophoresis (DGGE) profiles showed divergent dynamics of bacterial communities in two processes. These results indicated differences in the functional response and genetic structure of microbial community in composts and vermicomposts despite similar changes in their physico-chemical parameters.
The conversion efficiency of tofu-processing wastewater (TPW) into hydrogen and ethanol for energ... more The conversion efficiency of tofu-processing wastewater (TPW) into hydrogen and ethanol for energy source in a tofu-making factory was evaluated by testing various sludge types, initial cultivation pH values, temperatures and substrate concentrations. Experimental results indicated that a peak H 2 production yield (HY) of 107.5 mL-H 2 /g COD and ethanol concentration of 2181 mg-COD/L were at 35 C, TPW concentration 20 g-COD/L and pH 5.5e6.0 in batch tests. Peak H 2 production rate of 1.73 L H 2 /Ld was obtained at HRT 8 h in a CSTR. Main soluble metabolic products were acetate and butyrate during TPW fermentation. The peak total energy (H 2 and ethanol) production efficiency of 485 J/g COD (160 J/g COD from H 2 and 325 J/g COD from ethanol) and rate of 43.3 kJ/L-d (19.6 kJ/L-d from H 2 and 23.7 kJ/Ld from ethanol) were obtained at HRT 12 and 8 h, respectively. This could support up to 3.5% of the annual energy consumption in a tofu-making factory and also reduce the carbon dioxide emission up to 6.65 ton CO 2 equivalents/y.
Mesophilic Wastewater Net energy a b s t r a c t Biohydrogen (bioH 2 ) production from starch-con... more Mesophilic Wastewater Net energy a b s t r a c t Biohydrogen (bioH 2 ) production from starch-containing wastewater is an energy intensive process as it involves thermophilic temperatures for hydrolysis prior to dark fermentation.
h i g h l i g h t s " Sweet potato has hydrogen and ethanol production potential using dark ferme... more h i g h l i g h t s " Sweet potato has hydrogen and ethanol production potential using dark fermentation. " At pH 6.5 and 150 g/L sweet potato, cow dung gave peak hydrogen production rate. " At pH 8.5 and 150 g/L sweet potato cow dung gave peak ethanol concentration. " Main organic acids were acetate and butyrate at all pH values.
Co-digestion and metal ion addition strategies to improve the biogas production potential of Jatr... more Co-digestion and metal ion addition strategies to improve the biogas production potential of Jatropha seed cake (JSC) by anaerobic digestion were evaluated in the present study. Initially, batch experiments were carried out to obtain the maximum JSC concentration for optimum biogas yield, followed by co-digestion with bagasse, and addition of Fe2+. The optimum JSC concentration of 15% (w/v) gave biogas production rate (BPR) of 66.4 mL/d, specific BPR of 9.7 mL/d/gVS and biogas yield of 0.064 m3/kgVS. The co-digestion strategy increased the carbon/nitrogen of feed (10% JSC+5% Bagasse, w/v) to 26.5 from 14 (JSC alone), resulting in biogas yield of 0.136 m3/kgVS of JSC, a 2.1-fold increase. Addition of Fe2+ to JSC and bagasse mixture led to biogas yield of 0.203 m3/kgVS, with methane content of 66% and methane production of 8.8 L/L reactor. With short digestion time of 15 days, co-digestion of JSC with bagasse and addition of Fe2+ showed 3.2-fold higher biogas yield than JSC alone.
The molecular structure of humic acid (HA) extracted was investigated by FT-IR and 13C CP/MAS NMR... more The molecular structure of humic acid (HA) extracted was investigated by FT-IR and 13C CP/MAS NMR spectroscopy during the vermicomposting of sugar industry wastes, viz. pressmud, trash and bagasse for 60 days. A rapid decrease in C/N and lignocellulosic (lignin, cellulose, hemicellulose) content was observed in vermicompost during early phase of the process. The FT-IR and 13C CP/MAS NMR spectra of HA indicated a high rate of change in structure with increase in the alkyl C/O-alkyl C ratio during the process. Aromatic structures and carboxyl groups showed an initial increase but decreased after ∼40 days indicating extensive mineralization during final stages of vermicomposting.
Two laboratory-scale systems were set up (i) composting (without earthworms) and (ii) vermicompos... more Two laboratory-scale systems were set up (i) composting (without earthworms) and (ii) vermicomposting (with earthworms) and were monitored for 60 days after pre-composting. The physico-chemical parameters (pH, C/N, organic matter, NH4+-N and ash content) showed similar evolution in both systems except a higher NH4+-N in the initial vermicomposts. However, principle component analysis (PCA) of enzymatic activities and community level physiological profiles revealed differences in the functional response of microbial communities in compost and vermicompost during maturation. Dehydrogenase activity and bacterial counts indicated a steady decrease in biological activity and population during composting, whereas vermicomposting exhibited higher activity on day 30 and a reduction in bacterial counts on day 10. PCA of denatured gradient gel electrophoresis (DGGE) profiles showed divergent dynamics of bacterial communities in two processes. These results indicated differences in the functional response and genetic structure of microbial community in composts and vermicomposts despite similar changes in their physico-chemical parameters.
The present study deals with the biohydrogen production from starch-containing wastewater collect... more The present study deals with the biohydrogen production from starch-containing wastewater collected from the textile industry in Taiwan. The effects of inoculums collected from different sources (sewage sludge, soil and cow dung), substrate concentrations (5–25 g COD/L) and pH (4.0–8.0) on hydrogen production from wastewater were investigated.The cow dung seed had the highest hydrogen production of 101 mL with hydrogen content in biogas of 32.2%. It corresponds to a hydrogen yield (HY) of 1.56 mol H2/mol hexose and hydrogen production rate (HPR) of 0.93 L/L/d. Response surface methodology was used to evaluate the effects of initial cultivation pH (4.0–8.0) and substrate concentration (5–25 g COD/L) on the hydrogen production at 35 °C. At pH 7.0 with a wastewater concentration of 20 g COD/L, a maximum hydrogen production of 66 mL with 31.9% H2 and corresponding to an HY of 0.97 mol H2/mol hexose and an HPR of 1.14 L/L/d were obtained. According to the response surface analysis, the optimal conditions for high HPR were a wastewater concentration of 13 g COD/L at an initial cultivation pH of 7.0. The main soluble metabolic products were acetate and butyrate for hydrogen fermentation from textile wastewater.► The textile wastewater containing starch is a potential energy resource for anaerobic hydrogen fermentation. ► The optimum initial cultivation pH for H2production was 7.0. ► The optimum wastewater concentration for H2 production was 13 g COD/L. ► The main soluble metabolic products were acetate and butyrate.
The effects of substrate concentration and temperature on fermentative hydrogen production from E... more The effects of substrate concentration and temperature on fermentative hydrogen production from Eichhornia crassipes using pig slurry microflora were studied, and the optimal values for maximum biohydrogen production were determined in batch experiments. Hydrogen and methane yield (HY and MY) and production rate (HPR and MPR) were evaluated at various E. crassipes concentrations (10–80 g/L) and incubation temperatures (25, 35, 45, 55, and 65 °C). Hydrogen and methane production were observed during the E. crassipes fermentation without any nutrients addition, and were dependent on E. crassipes concentrations. Maximum HPR (38.2 mmol H2/L/d) and MPR (29.0 mmol CH4/L/d) were obtained at E. crassipes concentration of 40 g/L and 80 g/L, respectively. Monod model and modified Andrew model were used to fit the hydrogen production rate data. Modified Andrew model could describe better the effects of substrate concentration on hydrogen production rate (greater R2 value). Maximum HPR (221.3 mmol H2/L/d) and MPR (24.4 mmol CH4/L/d) were obtained at 45 and 55 °C, respectively. These values were ca. 1105 and 18 folds higher than the HPR (0.2 mmol H2/L/d) and MPR (7.3 mmol CH4/L/d) at 25 °C, probably due to increased hydrolysis of E. crassipes at higher temperatures. Ratkowsky model could best describe the progress of hydrogen and methane production potential and rate (R2 > 0.9). The optimum E. crassipes concentration and incubation temperature were determined as 47.8 g/L and 62.5 °C, respectively for maximum hydrogen and methane production. Biohydrogen and biomethane yields from E. crassipes were 31.3 GJ/ha/y and 853.9 GJ/ha/y, respectively, with a total CO2 emission reduction from 15.2 to 23.7 tons.► Temperature and water hyacinth concentration could affect anaerobic biogas production. ► The optimum temperature for H2 and CH4 production were 48 and 63 °C, respectively. ► The optimum water hyacinth concentration for biogas production was 40 g/L ► H2 and CH4 yields from water hyacinth were 31 GJ/ha-y and 854 GJ/ha/y, respectively. ► Total CO2 emission reduction from this biogas production process was 15–24 ton/y.
Phase holdups play an important role in high-rate hydrogen production in an anaerobic fermentativ... more Phase holdups play an important role in high-rate hydrogen production in an anaerobic fermentative reactor, especially in understanding biomass content, biogas flow and distribution that significantly affect the flow regimes change in the reactor. In the present study three-phase hydrogen producing reactor with different configurations were tested to investigate the phase holdups phenomenon and microbial community. It was found that the major fatty acids produced from the reactors were acetate and butyrate (HBu), accounting for 74.4–93.5% of total soluble microbial products (SMP). When the HRT was shortened from 8 to 1 h, the HBu was the dominant acid product among the soluble metabolites and the ratio of Ethanol/SMP was lower than 15.1. Moreover, the gas holdup (ɛg) and solid holdup (ɛs) increased but liquid holdup (ɛl) decreased when the HRT was shortened. When the HRT was down to 1 h an increase in gas and solid holdups were noted. The gas holdups (ɛg) increased in the range of 0.30–0.34, and the solid holdups (ɛs) increased in the range of 0.32–0.34, which mean that the values of liquid holdups in high-rate fermentative hydrogen bioreactors could be decreased in the range of 0.38–0.32. Moreover, the empirical correlations of this study were satisfactory to predict the phase holdups in a dark-fermentation biohydrogen system. PCR-DGGE analysis revealed that bioreactor hydrodynamics under different HRTs significantly affects the occurrence of Streptococcus sp. and Bacillus sp. which mainly promotes granulation and retains high yielding hydrogen producing Clostridium sp. through their exopolysaccharides production. SEM results showed three dominant bacterial species namely Clostridium pasteurianum, Streptococcus sp. and Propionibacterium sp. in the bioreactors.
Aims: To evaluate bacterial community structure and dynamics in triplicate vermicomposts made fro... more Aims: To evaluate bacterial community structure and dynamics in triplicate vermicomposts made from the same start-up material, along with certain physico-chemical changes. Methods and Results: The physico-chemical parameters (pH, temperature, carbon, nitrogen, soluble substances and cellulose) evolved similarly in the triplicate vermicomposts, indicating a steady function. The 16S bacterial gene abundance remained constant over time. To monitor changes in the bacterial community structure, fingerprinting based on capillary electrophoresis singlestrand conformation polymorphism was employed. A rise in bacterial diversity occurred after precomposting and it remained stable during the maturation phase. However, a rapid shift in the structure of the bacterial community in the vermicompost replicates was noted at the beginning that stabilized with the process maturation. Multivariate analyses showed different patterns of bacterial community evolution in each vermicompost that did not correlate with the physico-chemical changes. Conclusions: The broad-scale functions remained similar in the triplicates, with stable bacterial abundance and diversity despite fluctuation in the community structure. Significance and Impact of the Study: This study has demonstrated that microbial fingerprinting with multivariate analysis can provide significant understanding of community structure and also clearly suggests that an ecosystem's efficacy could be the outcome of functional redundancy whereby a number of species carry out the same function.
Biohydrogen is a promising candidate which can replace a part of our fossil fuels need in day-to-... more Biohydrogen is a promising candidate which can replace a part of our fossil fuels need in day-to-day life due its perceived environmental benefits and availability through dark fermentation of organic substrates. Moreover, advances in biohydrogen production technologies based on organic wastewater conversion could solve the issues related to food security, climate change, energy security and clean development in the future. An evaluation of studies reported on biohydrogen production from different wastewaters will be of immense importance in economizing production technologies. Here we have reviewed biohydrogen production yields and rates from different wastewaters using sludges and microbial consortiums and evaluated the feasibility of biohydrogen production from unexplored wastewaters and development of integrated bioenergy process. Biohydrogen production has been observed in the range of substrate concentration 0.25e160 g COD/L, pH 4e8, temperature 23e60 C, HRT 0.5e72 h with various types of reactor configuration.
Two laboratory-scale systems were set up (i) composting (without earthworms) and (ii) vermicompos... more Two laboratory-scale systems were set up (i) composting (without earthworms) and (ii) vermicomposting (with earthworms) and were monitored for 60 days after pre-composting. The physico-chemical parameters (pH, C/N, organic matter, NH þ 4 À N and ash content) showed similar evolution in both systems except a higher NH þ 4 À N in the initial vermicomposts. However, principle component analysis (PCA) of enzymatic activities and community level physiological profiles revealed differences in the functional response of microbial communities in compost and vermicompost during maturation. Dehydrogenase activity and bacterial counts indicated a steady decrease in biological activity and population during composting, whereas vermicomposting exhibited higher activity on day 30 and a reduction in bacterial counts on day 10. PCA of denatured gradient gel electrophoresis (DGGE) profiles showed divergent dynamics of bacterial communities in two processes. These results indicated differences in the functional response and genetic structure of microbial community in composts and vermicomposts despite similar changes in their physico-chemical parameters.
The conversion efficiency of tofu-processing wastewater (TPW) into hydrogen and ethanol for energ... more The conversion efficiency of tofu-processing wastewater (TPW) into hydrogen and ethanol for energy source in a tofu-making factory was evaluated by testing various sludge types, initial cultivation pH values, temperatures and substrate concentrations. Experimental results indicated that a peak H 2 production yield (HY) of 107.5 mL-H 2 /g COD and ethanol concentration of 2181 mg-COD/L were at 35 C, TPW concentration 20 g-COD/L and pH 5.5e6.0 in batch tests. Peak H 2 production rate of 1.73 L H 2 /Ld was obtained at HRT 8 h in a CSTR. Main soluble metabolic products were acetate and butyrate during TPW fermentation. The peak total energy (H 2 and ethanol) production efficiency of 485 J/g COD (160 J/g COD from H 2 and 325 J/g COD from ethanol) and rate of 43.3 kJ/L-d (19.6 kJ/L-d from H 2 and 23.7 kJ/Ld from ethanol) were obtained at HRT 12 and 8 h, respectively. This could support up to 3.5% of the annual energy consumption in a tofu-making factory and also reduce the carbon dioxide emission up to 6.65 ton CO 2 equivalents/y.
Mesophilic Wastewater Net energy a b s t r a c t Biohydrogen (bioH 2 ) production from starch-con... more Mesophilic Wastewater Net energy a b s t r a c t Biohydrogen (bioH 2 ) production from starch-containing wastewater is an energy intensive process as it involves thermophilic temperatures for hydrolysis prior to dark fermentation.
h i g h l i g h t s " Sweet potato has hydrogen and ethanol production potential using dark ferme... more h i g h l i g h t s " Sweet potato has hydrogen and ethanol production potential using dark fermentation. " At pH 6.5 and 150 g/L sweet potato, cow dung gave peak hydrogen production rate. " At pH 8.5 and 150 g/L sweet potato cow dung gave peak ethanol concentration. " Main organic acids were acetate and butyrate at all pH values.
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Papers by Biswarup Sen