Papers by Keyword: Biohydrogen

Abstract: A complete set-up of obtaining bio-hydrogen from palm oil mill effluent (POME) was successfully demonstrated in this study. The proposed set-up is a combination of upflow anaerobic sludge blanket (UASB) bioreactor (POME is digested to obtain methane) and subsequent a dry reforming tubular reactor (conversion of methane into bio-hydrogen). The UASB reactor with 10 litres working volume was operated in continuous operation at mesophilic temperature (38 °C), pH was maintained between 6.5 and 7.2 by adding buffering solution containing of 5 gL^-1 of calcium oxide (CaO) and hydraulic retention time (HRT) was set at 1 day. Prior to feeding of POME, the UASB reactor was inoculated with sludge taken from anaerobic pond at Lepar Hilir Palm Oil Mill. Then, the reactor was continuously fed with the raw POME with COD concentration of 7,773 mgL^-1 and organic loading rate (OLR) of 7.61 g CODL^-1d^-1. Meanwhile the dry reforming fixed-bed tubular reactor was operated at 750 °C and 0.1 g catalyst type Ni/SBA-15. Biogas produced from the UASB reactor was fed into the tubular reactor and gas samples were collected at the inlet and outlet and analyzed using GC-TCD. On average, the UASB reactor produced about 32 Ld^-1 biogas containing of 80 % methane and removing 67 % of COD. This biogas was fed into the dry reforming rector and the reaction took place in the reactor produced about 32 % of H₂, 0.24 % of CH₄, 28 % of CO₂ and 39 % of CO. This result yielded a H₂/CO ratio close to 1, demonstrated an efficient route for producing bio-hydrogen gas. Meanwhile, CH₄ conversion was recorded at 99.7 %.

Abstract: The biological methods of hydrogen generation have attracted a significant interest recently. In this work the hybrid system applying both dark fermentation bacteria in co-culture was tested. Objective of this work was to investigate the optimization of different parameters on co-culture of Clostridium beijerinckii DSM-791 and Rhodobacter sphaeroides O.U.001. The effect of glucose concentration (1–5 g/L), temperature and initial pH (6,5–7,5) was analyzed. Moreover the influence of organic nitrogen sources were tested for their capacity to support hydrogen production (yeast extract, peptone, glutamic acid). Fermentations were conducted in batch tests with glucose as sole substrate. Hydrogen production in mixed culture was compared with pure cultures. The process was greatly affected by pH and light/dark bacteria ratio. Liquid metabolites, namely acetic and butyric acids, from the dark fermentation step were the source of organic carbon for photosynthetic bacteria. This increased the hydrogen yield in comparison to single-step dark fermentation to over 4 mol H₂/mol glucose. Obtained results showed that combination of photo and dark fermentation may increase hydrogen production and conversion efficiency of complex substrates or wastewaters.

Abstract: Four commonly-used temperatures (37°C, 30°C, 55°C, and 70°C) were examined on mixed-culture H₂-producing behavior with corn stover hydrolyzate as the substrate. Experimental results indicated that the optimum biogas (1505.7 mL/L) and H₂ (717.2 mL/L) production was achieved at 55°C. For soluble metabolites, the highest acetate/butyrate concentrations and the lowest ethanol production were also found at 55°C. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) was employed to analyze corresponding microbial community structure. At 55°C, most bacteria were identified as Clostridium spp., which might be responsible for higher H₂ yield in this case. Totally, fermentation temperation of 55°C was probably preferable for H₂ production from corn stover hydrolyzate.

Abstract: Oil palm (Elaeis guineensis) is the most important crop of Malaysia. Malaysia can be considered as the worlds largest producer and exporter of crude palm oil. The objectives of this work are to analyze and investigate the chemical compositions and the characterization of empty fruit bunches. The chemical compositions of EFB are analyzed using National Renewable Energy Laboratory method. Milled empty fruit bunches submitted to different treatments are characterized by FTIR spectroscopy, carbon-hydrogen-nitrogen analyzer (CHN), thermo gravimetric analysis (TGA), and surface morphology. Chemical compositions which are analyzed include glucan, xylan, arabinan, extractive, ash and lignin contents. The compositions of EFB are determined in two forms which are extractive free sample and native whole sample. The results obtained show that extractive free sample has higher glucan and xylan contents which are 37.8% and 20.5% as compared with whole native sample which are 34.3% and 19.7% respectively. However, the contents of arabinan and lignin of extractive free sample which are 1.5% and 21.8% are much lower than whole native sample which are 2% and 28.7% respectively. The ash content for both samples is 5.2%. The result for extractive analysis of extractive free sample is 15%. The basic functional groups and elements which present in EFB are obtained by FTIR and CHN analysis respectively. TGA analysis curve shows the decomposition of EFB peak value at 312.5oC. The morphology study of EFB carried out using Scanning Electron Microscopy (SEM) shows a roughness surface.

Abstract: Oily wastewater is a potential source for biohydrogen production due to its high organic content. Incorporation of surfactant could enhance the solubilization of oil in water, and thus increase its biodegradability. The first part of this work studied the influence of surfactant concentrations (0-240 CMC) and temperatures (28-70 °C) on oil solubilization in aqueous solution. Results from batch tests showed that the oil solubilization improved as the surfactant concentration increased up to 100 CMC. As high as 0.002 mg/L oil concentration could be solubilized at 1 CMC and 55 °C, which was 90 times higher than that obtained without surfactant application. Moreover, the time to reach oil-in-liquid equilibrium could be shortened by increasing the temperature. In the second part, the effect of surfactant addition on hydrogen production was investigated at pH 5.5 and 55 °C. In 148 h batch assays, the highest hydrogen production observed was 19.3 mL at 1 CMC while it was 8.7 mL at no surfactant. Further investigation at 1 CMC revealed that surfactant degradation to H₂ was 2.36 mL, thus the effect of surfactant to enhance oil degradability was 0.24 L H₂ per liter of aqueous solution under excess oil condition.

Abstract: The effect of SO2-4 concentration ranging from 0 to 10 g/L on fermentative hydrogen production by enriched anaerobic sludge was investigated using glucose as substrate at 35°C and initial pH 7.0. The experimental results showed that the hydrogen yield increased with increasing SO2-4 concentration from 0 to 0.05 g/L. The maximum maximum hydrogen yield of 272.2 mL/g glucose were obtained at the SO2-4 concentration of 0.05 g/L. The average hydrogen production rate increased with increasing SO2-4 concentration from 0 to 0.1 g/L and the maximum average hydrogen production rate of 8.4 mL/h was obtained at the SO2-4 concentration of 0.1 g/L. The Han-Levenspiel model could describe the effect of SO2-4 concentration on average hydrogen production rate successfully.

Abstract: Two continuously stirred tank reactors (CSTR) were used to investigate the effect of L-cysteine on continuous dark fermentative hydrogen production system. L-cysteine was added into one of the reactors at 0.1 g/L continuously, the other reactor was without L-cysteine addition. Liquid end products, oxidation-reduction potential (ORP), pH, biomass and hydrogen production rate (HPR) were examined during the operation. The lag time of ethanol generation in the L-cysteine added reactor was shortened to 21 days compared to 25 days in the blank. The HPR increased from 2.73 L/d in the reactor without L-cysteine addition to 2.82 L/d in the added one. The volatile suspended solids (VSS) in the reactor with L-cyateine was 10.1 g/L by the end of the operation compared to 9.2 g/L in the other. Addition of L-cysteine into the hydrogen production system accelerates the formation of ethanol-type fermentation and enhances the hydrogen production by creating an optimal low ORP environment, and by increasing the biomass growth simultaneously.

Abstract: Kinetics of mesophilic biohydrogen production from ozone-pretreated palm oil mill effluent (POME) using C. butyricum and C. acetobutylicum co-culture was investigated. All experiments were setup in 0.5-L batch reactors under mesophilic condition (37°C), pH 6, and POME concentration of 5,000-30,000 mg COD L^-1. At the concentration of 15,000 mg COD L^-1, maximum hydrogen production yield for non-ozone pretreated POME and ozone pretreated POME were 318 and 122 mL g^-1 COD_removed, respectively. Acetic and butyric acids were dominant fermentation products in liquid phase. Ozone-pretreatment of POME showed no significant improvement on the hydrogen production by the co-culture.

Abstract: A dark hydrogen fermentation process of food waste by Clostridium butyricum TISTR 1032 was examined under the condition of initial pH 6, 37oC and varied condition with oxygen scavenger in 5 L semi-batch reactors. Results showed that oxygen scavenger significantly elevated the maximum rate of hydrogen production (R_m) (203.5 mL h^-1) compared to that without oxygen scavenger (30.6 mL h^-1). However, it did not improve the maximum cumulative hydrogen production (Hmax). Carbon mass balance was used to explore the direction of fermentative process including toidentify type of fermentative process. Butyric acid fermentation was recognized as the fermentation type of this study under both conditions. Drop of pH and accumulation of total undissociated acid considerably reduced the hydrogen production.

Abstract: Anaerobic hydrogen production in a continuous two-stage fermentation system was studied. Two continuously stirred tank reactors (CSTR) were employed to evaluate performances of the system. The first stage was fed with molasses wastewater, and the effluent discharged from the first stage was subsequently fed into the second stage. The hydrogen production rate (HPR) in the second stage achieved a remarkable increase from 1.76 L/d to 6.45 L/d during the operation by re-utilizing the residual substrates from the first reactor effluent. The two stages showed a similar metabolic pathway for biohydrogen fermentation. The hydrogen production yield (HY) and acidification efficiency increased markedly by more than 70% and 50% respectively, which indicated the hydrogen recovery and anaerobic acidification of organic substrates can be improved by the combined continuous two-stage hydrogen production process.