Thermophilic Hydrogen Fermentation Research Articles

Performance and energy recovery of single and two stage biogas production from paper sludge: Clostridium thermocellum augmentation and microbial community analysis

A two-stage thermophilic hydrogen fermentation and mesophilic methane production from paper sludge was successfully explored. The maximum hydrogen and methane potential were 0.165 L/g VS and 0.376 L/g CODeffluent, respectively with Clostridium thermocellum augmentation. 63 L of hydrogen and 122 L of methane were recovered from 1 kg Paper sludge (PS, dry weight) with an energy yield of 4.5 MJ/kg PS, 50% higher compared to the single-stage anaerobic digestion (94 L CH4, 3.0 MJ/kg PS). The bacterial community of second-stage process was dominated by genus Propionispira, Mesotoga and Aminobecterium with stability, whereas the bacterial structure in single-stage process presented dynamic changes where genus Acetivibrio and Fibrobacter played an indispensable role. However, Genus Methanosaeta, Methanosarcina, Methanobacterium and Methanospirillum existed stably and predominantly in the archaeal community of single-stage and second-stage processes. The present study suggests the potential application of the established two-stage process in valorization of low-value waste biomass.

The performance and kinetic characterization of the three metabolic reactions in the thermophilic hydrogen and acidic fermentation of cassava residue

The long-term performance of the thermophilic hydrogen fermentation of cassava residue was studied in a continuous stirred tank reactor by mixed culture. The effect of different hydraulic retention times (30 days, 6 days and 3 days) on the three metabolic steps of hydrolysis, acidogenesis and hydrogen production was investigated. The highest hydrogen yield, 2.38 mmol H2/g dry cassava residue, was achieved at an HRT of 30 days, while acetic acid (2.14 g/L) and butyric acid (2.85 g/L) were the majority of liquid by-products. It was confirmed that the addition of a nitrogen supplement ensured the stable operation of the thermophilic dark fermentation of hydrogen. The energy recovery calculations indicated that it is possible to stably operate the hydrogen fermentation of cassava residue with positive energy recovery efficiency and the highest net energy was 540.5 MJ/ton at an HRT of 30 days.

Enhancement of hydrogen and methane production from co-digestion of palm oil decanter cake and crude glycerol using two stage thermophilic and mesophilic fermentation

Two-stage thermophilic hydrogen fermentation and mesophilic methanogenic process for methane production with hydrogenic effluent from co-digestion of decanter cake (DC) and crude glycerol (GLC) was investigated. For the single stage, hydrogen reactor with 2% wv−1 total solid (TS) of DC and crude glycerol was operated at 4 days hydraulic retention time (HRT) with varying glycerol loading of 0.75–1.5% GLC while methane reactor with 2% wv−1 total solid (TS) of DC was operated at 13 days HRT. The maximum hydrogen production rate and hydrogen yield in the single stage obtained from the 1.5% GLC co-digestion condition were 461 mL H2 L−1 d−1 and 23 L H2 kg−1 TSadded, respectively. Crude glycerol was found to be an alternative pH-adjust substance in hydrogen reactor. At the condition of 0.75% GLC co-digestion, the pH was maintained in the range higher than 5.3 throughout the fermentation process. Semi-continuous methane production with 0.75% GLC hydrogenic effluent achieved the maximum methane production rate and methane yield about 736 mL CH4 L−1 d−1 and 44 L CH4 kg−1 TSadded compared with the single stage with 2% TSDC and the second stage with 1% GLC hydrogenic effluent. Total energy recovery from two-stage fermentation about 0.056 kWh kg−1 TSadded was achieved from the condition of 0.75% GLC hydrogenic effluent condition. It was improved by 6.2 and 1.6 times compared to the single stage in both hydrogen and methane reactor, respectively. This work demonstrated the practical enhancement of energy recovery and the efficiency of waste utilization by two-stage fermentation for hydrogen and methane production from decanter cake and crude glycerol.

Batch and continuous thermophilic hydrogen fermentation of sucrose using anaerobic sludge from palm oil mill effluent via immobilisation technique

This study aimed to investigate the feasibility to use immobilised cells on granular activated carbon (GAC) operated in fifteen cycles of repeated batch mode for enhancement of biohydrogen production under thermophilic conditions. The effects of the initial pH (5.0–6.5), sucrose concentration (13–43mM) and repeated batch cultivation on biohydrogen production from sucrose were investigated using anaerobic sludge from a palm oil mill effluent treatment plant. The cumulative hydrogen production results were fitted into a modified Gompertz equation in order to find the optimum operational conditions. The optimal hydrogen yield (2.8molH2/molhexose) was obtained at an initial pH of 5.5 and sucrose concentration of 13mM after fifteen cycles of repeated batch. Enriched granular activated carbon (GAC)-immobilised cells from the repeated batch cultivation were used as the immobilised seed culture for anaerobic fermentation of sucrose into hydrogen in continuous operation using a fluidised-bed column reactor (FBCR). The maximum hydrogen production rate (HPR) was found to be 2.7mmolH2/L/h and the hydrogen yield peaked at 2.8molH2/molhexose_consumed after a hydraulic retention time of 12h. The main soluble metabolites were identified as acetic acid, butyric acid and ethanol. The hydrogen content ranged from 48 to 50% of the total biogas.

Biohythane Production from Co-Digestion of Palm Oil Mill Effluent with Solid Residues by Two-Stage Solid State Anaerobic Digestion Process

Biohythane production from co-digestion of palm oil mill effluent (POME) with empty fruit bunches (EFB) and decanter cake (DC) by two-stage solid state anaerobic digestion process was investigated. The first stage, thermophilic hydrogen fermentation of co-digestion of POME with DC at 10, 30, 50 and 70% of DC in POME has hydrogen yield of 16, 14, 3 and 1ml H2/gVS, respectively. Co-digestion of POME with 10% DC gave the best hydrogen yield of 16ml H2/gVS with hydrogen production of 1.4 m3/ton mixed waste. Co-digestion of POME with 10% EFB gave the best hydrogen yield of 16ml H2/gVS with hydrogen production of 1.4 m3/ton mixed waste. The effluent from the hydrogen production was further converted to methane in the second stage. The methane yield from POME mixed withn10% DC was 391 mlCH4/gVS and from POME mixed with 10% EFB was 240 mlCH4/gVS. The hydrogen and methane content in biogas was 25.33% and 65.21% respectively. The two-stage solid stage anaerobic digestion process can be removal efficiently of cellulose 57-59%, hemicelluloses 35-40% and lignin 16-27%. Result obtained make practical use for the development of two-stage anaerobic digestion process providing hydrogen and methane co-production from palm oil waste residues.

Improved cellulose conversion to bio-hydrogen with thermophilic bacteria and characterization of microbial community in continuous bioreactor

Thermophilic hydrogen fermentation of cellulose was evaluated by a long term continuous experiment and batch experiments. The continuous experiment was conducted under 55 °C using a continuously stirred tank reactor (CSTR) at a hydraulic retention time (HRT) of 10 day. A stable hydrogen yield of 15.4 ± 0.23 mol kg−1 of cellulose consumed was maintained for 190 days with acetate and butyrate as the main soluble byproducts. An analysis of the 16S rRNA sequences showed that the hydrogen-producing thermophilic cellulolytic microorganisms (HPTCM) were close to Thermoanaerobacterium thermosaccharolyticum, Clostridium sp. and Enterobacter cloacae. Batch experiment demonstrated that the highest H2 producing activity was obtained at 55 °C and the ultimate hydrogen yield and the metabolic by-products were influenced greatly by temperatures. The effect of temperature variation showed that the activation energy for cellulose and glucose were estimated at 103 and 98.8 kJ mol−1, respectively.

Buffering and nutrient effects of white mud from ammonia–soda process on thermophilic hydrogen fermentation from food waste

Hydrogen production via anaerobic fermentation may suffer from instability or inhibition due to volatile fatty acids concentrations and inorganic elements deviations from optimality. A slight addition of white mud from ammonia–soda process (WMA) to the fermentation may show a feasible implement approach to use as buffer and inorganic nutrient. Batch tests were conducted to study the effect of the WMA addition on the hydrogen fermentation of food waste (FW) for the purpose of the maximum hydrogen yield (MHY) while achieving process stability and microbial germination through the endogenous alkalinity and inorganic elements of WMA. This was attributed to the existence of calcium, sodium, magnesium, potassium and alkali-rich materials, like calcium carbonate. 3 g of WMA addition to 200 g FW and fermentation time of 36 h resulted in obtaining the MHY of 145.4 mL H2/g VS, with a corresponding lag-phase time of 3.0 h. Under these operating conditions, the fermentation process demonstrated one of the highest measured stability with final pH 5.3.

Enhanced coproduction of hydrogen and methane from cornstalks by a three-stage anaerobic fermentation process integrated with alkaline hydrolysis

A three-stage anaerobic fermentation process including H2 fermentation I, H2 fermentation II, methane fermentation was developed for the coproduction of hydrogen and methane from cornstalks. Hydrogen production from cornstalks using direct microbial conversion by Clostridium thermocellum 7072 was markedly enhanced in the two-stage thermophilic hydrogen fermentation process integrated with alkaline treatment. The highest total hydrogen yield from cornstalks in the two-stage fermentation process reached 74.4mL/g-cornstalk. The hydrogen fermentation effluents and alkaline hydrolyzate were further used for methane fermentation by anaerobic granular sludge, and the total methane yield reached 205.8mL/g-cornstalk. The total energy recovery in the three-stage anaerobic fermentation process integrated with alkaline hydrolysis reached 70.0%.

Fungal pretreatment enhances hydrogen production via thermophilic fermentation of cornstalk

A promising fungal pretreatment method was developed for enhancing hydrogen production via thermophilic fermentation of raw cornstalk mixed with the pretreated cornstalk by Trichoderma reesei Rut C-30. In comparison with mesophilic hydrogen fermentation at 35 °C, thermophilic hydrogen fermentation at 55 °C gave higher hydrogen production from the mixed cornstalk because higher cellulase activity under thermophilic condition was favorable to lignocellulose hydrolysis. When the pretreated cornstalk was mixed with the raw cornstalk at an optimal blending ratio of 1:5, the cumulative hydrogen volume reached the maximum level of 194.9 mL, which was 209% of that obtained in direct fermentation of raw cornstalk. The present results indicated that the fungal pretreatment had a great potential to enhance the bioconversion efficiency of lignocellulosic waste to renewable hydrogen energy.

Thermophilic hydrogen fermentation from Korean rice straw by Thermotoga neapolitana

Rice straw, a low-cost lignocellulosic biomass was used as feedstock for thermophilic hydrogen fermentation by Thermotoga neapolitana. Hydrogen production, the growth and cellulose digestibility of the hyperthermophile in batch mode from untreated as well as chemically pretreated (ammonia and dilute sulfuric acid) Korean rice straws were investigated. Pretreatment method using combination of 10% ammonia and 1.0% dilute sulfuric acid was developed to increase the digestibility of rice straw for the hyperthermophilic H 2 fermentation and to decrease the time consumption. In a typical fermentation using raw rice straw, 29% of the substrate was digested and 2.3 mmol H 2/g straw of hydrogen yield was consistently obtained. Compared with the pretreatments using only ammonia or dilute sulfuric acid, the combined pretreatment method using both chemical agents significantly increases the digestibility of rice straw with 85.4% of substrate consumption. H 2 production on rice straw from this combined pretreatment showed the highest yield (2.7 mmol H 2/g straw) and the highest sugar conversions (72.9% of glucose and 95.7% of xylose).

Effects of seed sludge on fermentative characteristics and microbial community structures in thermophilic hydrogen fermentation of starch

In this work, effects of seed sludge on thermophilic hydrogen fermentation were investigated. Five different kinds of sludge were separately inoculated in completely stirred tank reactors (CSTRs), without any pretreatment. The reactors were operated in parallel with starch as substrate under thermophilic condition (55 °C) at a hydraulic retention time (HRT) of 24 h for 50 days. Stable hydrogen production was achieved in all reactors. The highest hydrogen yield (2.32 mol H 2/mol glucose) was obtained from the reactor seeded with thermophilically digested activated sludge. The stoichiometric equation of hydrogen fermentation calculated using the data obtained in this study was expressed as follows: starch ([C 6H 10O 5]n) → 2.32 n H 2 + 2.14 n CO 2 + 0.50 n acetate + 0.63 n butyrate + 0.11 n cell (C 5H 7NO 2). Microbial community structure was analyzed by polymerase chain reaction–denaturing gel gradient electrophoresis (PCR–DGGE) and 16S rRNA gene cloning. Close relatives of the Thermoanaerobacterium were found to be the most predominated one in all reactors.

Operation of a Two-Stage Fermentation Process Producing Hydrogen and Methane from Organic Waste

A pilot-scale experimental plant for the production of hydrogen and methane by a two-stage fermentation process was constructed and operated using a mixture of pulverized garbage and shredded paper wastes. Thermophilic hydrogen fermentation was established at 60 degrees C in the first bioreactor by inoculating with seed microflora. Following the hydrogenogenic process, methanogenesis in the second bioreactor was conducted at 55 degrees C using an internal recirculation packed-bed reactor (IRPR). After conducting steady-state operations under a few selected conditions, the overall hydraulic retention time was optimized at 8 d (hydrogenogenesis, 1.2 d; methanogenesis, 6.8 d), producing 5.4 m3/m3/d of hydrogen and 6.1 m3/m3/d of methane with chemical oxygen demand and volatile suspended solid removal efficiencies of 79.3% and 87.8%, respectively. Maximum hydrogen production yield was calculated to be 2.4 mol/mol hexose and 56 L/kg COD loaded. The methanogenic performance of the IRPR was stable, although the organic loading rate and the composition of the effluent from the hydrogenogenic process fluctuated substantially. A clone library analysis of the microflora in the hydrogenogenic reactor indicated that hydrogen-producing Thermoanaerobacterium-related organisms in the inoculum were active in the hydrogen fermentation of garbage and paper wastes, although no aseptic operations were applied. We speculate that the operation at high temperature and the inoculation of thermophiles enabled the selective growth of the introduced microorganisms and gave hydrogen fermentation efficiencies comparable to laboratory experiments. This is the first report on fermentative production of hydrogen and methane from organic waste at an actual level.

混合微生物群によるでんぷんの高温水素発酵特性

The effects of inoculum on the characteristics of thermophilic hydrogen fermentation were investigated by performing a long-term continuous experiment lasting more 50 days. Continuous hydrogen fermentation of starch was conducted under thermophilic condition (55°C) by using five types of inoculum, including thermophilically digested sludge of activated sludge, cattle manure and sewage sludge, compost, and thermophilic acidogenic sludge. Five chemostat-type reactors were operated at an HRT (hydraulic retention time) of 24h. Stable hydrogen production was achieved in each culture without any methane production during the long-term continuous experiment. The highest hydrogen yield (2.32 mol H2/mol hexose converted) was obtained by thermophilically digested sludge of activated sludge. The thermophilic hydrogen fermentation of starch by thermophilically digested sludge of activated sludge was expressed using the following stoichiometric equation : starch → 2.32n H2 + 2.14n CO2 + 0.5n acetate + 0.63n butyrate + 0.11n biomass (C5H9O3N).