Chiu-Yue Lin

Biohydrogen production using an up-flow anaerobic sludge blanket reactor

Abstract Sewage sludge was acclimated to establish H2-producing enrichment cultures for converting sucrose (20 g COD/l ) into H2 in an up-flow anaerobic sludge blanket (UASB) reactor. The operating hydraulic retention times (HRTs) were 24– 4 h . The experimental results indicated that this UASB system could be used for hydrogen production. The hydrogen productivity was HRT dependent and nearly constant at the HRT of 8– 20 h . However, it drastically decreased at an HRT of 4 or 24 h . The hydrogen production rate (HPR) and specific HPR peaked at the HRT of 8 h and drastically decreased at all other HRTs. At an HRT of 8 h , the average granular diameter peaked at 0.43 mm and each gram of biomass produced 53.5 mmol H 2 / day with a hydrogen gas content of 42.4% (v/v). Butyrate and acetate were the main fermentation volatile fatty acids. The anaerobic granule sludge kinetic constants were endogenous decay coefficient (K d ) 0.1 day −1 and yield coefficient (Y g ) 0.1 g VSS/g COD . The mean cell retention time was 22.2 h and the excess sludge discharge rate was 3.24 l/day .

Carbon/nitrogen-ratio effect on fermentative hydrogen production by mixed microflora

Abstract Anaerobic sewage sludge acclimated with sucrose was used as the seed in a batch experiment to investigate the carbon/nitrogen (C/N)-ratio effects on biological hydrogen production from sucrose. Experimental results indicated that the hydrogen production ability of the anaerobic microflora (dominated by Clostridium pasteurianum) in the sewage sludge was dependent on the influent C/N-ratio. At a C/N-ratio of 47, the hydrogen productivity and hydrogen production rate reached 4.8 mol-H 2 / mol-sucrose and 270 mmol-H 2 / L-day , respectively. This increased by 500% and 80%, respectively, compared with the blank. Proper C/N-ratio on hydrogen production enhancement was accomplished by shifting the metabolic pathway. Strategies for optimal hydrogen production are also proposed.

Hydrogen production during the anaerobic acidogenic conversion of glucose

Experiments on hydrogen production using chemostat-type anaerobic digesters were conducted. The results indicate that the anaerobic acidogenic conversion of glucose can produce hydrogen. The hydrogenic activity of acclimated anaerobic sewage sludge is high at a short solids retention time (SRT) and low pH. At pH 5.7, SRT 0.25 days and an organic loading rate of 416 mmol-glucose dm−3 day−1, each mole of glucose in the mesophilic acidogenic reactor can produce 1.7 mol of hydrogen; each gram of biomass produces 0.456 mole of hydrogen per day. Moreover, the hydrogen productivity of the sludge is comparable to that of an enrichment culture. © 1999 Society of Chemical Industry

Using sucrose as a substrate in an anaerobic hydrogen-producing reactor

This study investigated the performance of a Continuous Flow Stirred Tank Reactor (CSTR) reactor producing hydrogen using sucrose as a substrate. The hydraulic retention time (HRT) effect was also investigated. The hydrogen gas production increased from 4.9 to 26.9 L–H2/l per day with a HRT decrease from 13.3 to 3 h, but decreased to 20.8 L–H2/l per day with a HRT decrease to 2 h. The digestion gas contained 35∼47.2% hydrogen and the hydrogen percentage increased with a HRT decrease from 13.3 to 3 h, but decreased markedly at 2 h. Under steady state conditions, the hydrogen production rate (HPR) ranged from 1.42 to 4.52 mol-H2/mol sucrose and the specific hydrogen production rate ranged from 78 to 841 mmol H2/g VSS-day.

Biohydrogen production from lignocellulosic feedstock.

Due to the recent energy crisis and rising concern over climate change, the development of clean alternative energy sources is of significant interest. Biohydrogen produced from cellulosic feedstock, such as second generation feedstock (lignocellulosic biomass) and third generation feedstock (carbohydrate-rich microalgae), is a promising candidate as a clean, CO2-neutral, non-polluting and high efficiency energy carrier to meet the future needs. This article reviews state-of-the-art technology on lignocellulosic biohydrogen production in terms of feedstock pretreatment, saccharification strategy, and fermentation technology. Future developments of integrated biohydrogen processes leading to efficient waste reduction, low CO2 emission and high overall hydrogen yield is discussed.

Effect of heavy metals on acidogenesis in anaerobic digestion

The effects of chromium, cadmium, lead, copper, zinc and nickel on volatile fatty acid (VFA) production in anaerobic digestion were studied using serum bottle assays. Glucose acclimated seed sludge was used. The relative toxicity of heavy metals to production of acetic acid (HAc) and n-butyric acid (n-HBu) was Cu > Zn > Cr > Cd > Pb > Ni and Cu > Zn > Cr > Cd > Ni > Pb, respectively. Cu was the most and Pb was the least toxic heavy metals to VFA-producing organisms. An increase in HAc production was observed when the concentration of Ni was less than 300 mg l−1. The sensitivity of VFA production to metallic inhibition was n-HBu > HAc for the tested metals except Pb which had the same level of inhibition to the production of the two VFAs. Except Cu with Ni, mixtures of the other tested heavy metals caused synergistic inhibition on total VFA production. Some metal mixtures increased the production of HAc markedly.

Effect of heavy metals on volatile fatty acid degradation in anaerobic digestion

The effects of chromium, cadmium, lead, copper, zinc and nickel on volatile fatty acid (VFA) degradation in anaerobic digestion were studied by using serum bottle assays. Acetic acid acclimated seed sludge (AASS) and mixed acids acclimated seed sludge (MASS) were used. The relative toxicity of heavy metals to degradation of acetic acid (HAc), propionic acid (HPr), and n-butyric acid (n-HBu) was Cd > Cu > Cr > Zn > Pb > Ni. Cd > Cu > ≒ Zn ≒ Cr > Pb > Ni, and Cd > Cu > Cr > Zn > Pb > Ni, respectively. Cd and Cu were the most and Pb and Ni were the least toxic heavy metals to VFA-degrading organisms. To some heavy metals, VFA-degrading acetogens were more sensitive than HAc-utilizing methanogens. The sensitivity of the VFA degradation to the metallic inhibition was HPr > HAc ≒ HBu for Cr, HAc > HPr ≒ HBu for Cd and Pb, HPr > HAc > HBu for Zn, HAc ≒ HPc ≒ HBu for Cu, and HAc > HPR > HBu for Ni. Mixtures of the heavy metals caused synergistic inhibition on HAc degradation. The inhibition patterns for MASS of Pb and Zn dosages were kinetically uncompetitive and competitive, respectively.

An overview of food waste management in developing countries: Current status and future perspective

Food waste (FW) related issues in developing countries is currently considered to be a major threatening factor for sustainable development and FW management systems. Due to incomplete FW management systems, many developing countries are facing challenges, such as environmental and sanitary problems that are caused by FW. The difference in FW generation trends between developing countries and developed countries was reviewed in this work, which demonstrated that the effects of income level, population growth, and public participation in FW management are very important. Thus, this work aimed to provide an overview of recycling activities, related regulations, and current FW treatment technology in developing countries by following some case studies. Taiwan, has been suggested as being a successful case in terms of FW management, and is therefore a typical model for developing countries to follow. Finally, an integrative management system as a suitable model for FW management has been suggested for developing countries.

High-Efficiency Hydrogen Production by an Anaerobic, Thermophilic Enrichment Culture From an Icelandic Hot Spring

Dark fermentative hydrogen production from glucose by a thermophilic culture (33HL), enriched from an Icelandic hot spring sediment sample, was studied in two continuous‐flow, completely stirred tank reactors (CSTR1, CSTR2) and in one semi‐continuous, anaerobic sequencing batch reactor (ASBR) at 58°C. The 33HL produced H2 yield (HY) of up to 3.2 mol‐H2/mol‐glucose along with acetate in batch assay. In the CSTR1 with 33HL inoculum, H2 production was unstable. In the ASBR, maintained with 33HL, the H2 production enhanced after the addition of 6 mg/L of FeSO4 · 7H2O resulting in HY up to 2.51 mol‐H2/mol‐glucose (H2 production rate (HPR) of 7.85 mmol/h/L). The H2 production increase was associated with an increase in butyrate production. In the CSTR2, with ASBR inoculum and FeSO4 supplementation, stable, high‐rate H2 production was obtained with HPR up to 45.8 mmol/h/L (1.1 L/h/L) and HY of 1.54 mol‐H2/mol‐glucose. The 33HL batch enrichment was dominated by bacterial strains closely affiliated with Thermobrachium celere (99.8–100%). T. celere affiliated strains, however, did not thrive in the three open system bioreactors. Instead, Thermoanaerobacterium aotearoense (98.5–99.6%) affiliated strains, producing H2 along with butyrate and acetate, dominated the reactor cultures. This culture had higher H2 production efficiency (HY and specific HPR) than reported for mesophilic mixed cultures. Further, the thermophilic culture readily formed granules in CSTR and ASBR systems. In summary, the thermophilic culture as characterized by high H2 production efficiency and ready granulation is considered very promising for H2 fermentation from carbohydrates. Biotechnol. Bioeng. 2008;101: 665–678.

Batch fermentative hydrogen production by enriched mixed culture: Combination strategy and their microbial composition

The effect of individual and combined mixed culture on dark fermentative hydrogen production performance was investigated. Mixed cultures from cow dung (C1), sewage sludge (C2), and pig slurry (C3) were enriched under strict anaerobic conditions at 37°C with glucose as the sole carbon source. Biochemical hydrogen production test in peptone-yeast-glucose (PYG) and basal medium was performed for individual mixed cultures (C1, C2 and C3) and their combinations (C1-C2, C2-C3, C1-C3 and C1-C2-C3) at a glucose concentration of 10 g/L, 37°C and initial pH 7. Maximum hydrogen yields (HY) of 2.0 and 1.86 [Formula: see text] by C2, and 1.98 and 1.95 mol(H2)/mol(glucose) by C2-C3 were obtained in PYG and basal medium, respectively. Butyrate and acetate were the major soluble metabolites produced by all the cultures, and the ratio of butyrate to acetate was ∼2 fold higher in basal medium than PYG medium, indicating strong influence of media formulation on glucose catabolism. The major hydrogen-producing bacterial strains, observed in all mixed cultures, belonged to Clostridium butyricum, C. saccharobutylicum, C. tertium and C. perfringens. The hydrogen production performance of the combined mixed culture (C2-C3) was further evaluated on beverage wastewater (10 g/L) at pH 7 and 37°C. The results showed an HY of 1.92 mol(H2)/mol(glucose-equivalent). Experimental evidence suggests that hydrogen fermentation by mixed culture combination could be a novel strategy to improve the HY from industrial wastewater.