Cane molasses fermentation for continuous ethanol production in an immobilized cells reactor by Saccharomyces cerevisiae

Sodium-alginate immobilized yeast was employed to produce ethanol continuously using cane molasses as a carbon source in an immobilized cell reactor (ICR). The immobilization of Saccharomyces cerevisiae was performed by entrapment of the cell cultured media harvested at exponential growth phase (16 h) with 3% sodium alginate. During the initial stage of operation, the ICR was loaded with fresh beads of mean diameter of 5.01 mm. The ethanol production was affected by the concentration of the cane molasses (50, 100 and 150 g/l), dilution rates (0.064, 0.096, 0.144 and 0.192 h^?1) and hydraulic retention time (5.21, 6.94, 10.42 and 15.63 h) of the media. The pH of the feed medium was set at 4.5 and the fermentation was carried out at an ambient temperature. The maximum ethanol production, theoretical yield (Y_E/S), volumetric ethanol productivity (Q_P) and total sugar consumption was 19.15 g/l, 46.23%, 2.39 g l^?1 h^?1 and 96%, respectively.     

A techno-economic comparison between two technologies for bioethanol production from lignocellulose

The conversion of biomass into biofuels can reduce the strategic vulnerability of petroleum-based transportation systems. Bioethanol has received considerable attention over the last years as a fuel extender or even as a neat liquid fuel. Lignocellulosic materials are very attractive substrates for the production of bioethanol because of their low cost and their great potential availability. Two different process alternatives (i.e. the enzymatic hydrolysis and fermentation process and the gasification and fermentation process) for the production of fuel ethanol from lignocellulosic feedstock are considered and analysed. After a rigorous mass and energy balance, design optimisation is carried out. Both processes are assessed in terms of ethanol yield and power generation as well as from a financial point of view. A sensitivity analysis on critical parameters of the processes' productivity and profitability is performed.     

木质纤维素生物质生产乙醇的预处理技术

木质纤维素生物质经过预处理后，原料的内孔面积增大，纤维素的结晶性降低，并且半纤维素和木质素被去除．预处理后的生物质容易进行酶水解生产燃料乙醇。总结了近些年来的预处理技术，如物理法、化学法和生物法。     

Kinetic modelling of continuous production of ethanol from cheese whey

A kinetic model for continuous fermentation of ethanol from cheese whey was developed. The model accounts for substrate limitation, substrate inhibition, ethanol inhibition and cell death. Three bioreactors of 5 L volume each were operated at different hydraulic retention times (HRT) ranging from 18 to 42 h and initial lactose concentrations ranging from 50 to 150 g/L. The experimental data were used to validate the model. The model predicted the cell, lactose and ethanol concentrations with high accuracy (R² = 0.96–0.99). The cell concentration, lactose utilization and ethanol production were significantly affected by hydraulic retention time and initial substrate concentration. Lactose utilizations of 98, 91 and 83% were obtained with 50, 100 and 150 g/L initial lactose concentrations at 42 h HRT. The highest cell concentration (5.5 g/L), highest ethanol concentration (58.0 g/L) and maximum ethanol yield (99.6% of theoretical) were achieved at 42 h HRT and 150 g/L initial lactose concentration.     

Feasibility evaluation of fermentative biomass-derived gas production from condensed molasses in a continuous two-stage system for commercialization

The excessive burning of fossil fuels is one of the main sources of emissions of carbon dioxide (CO₂) which causes the greenhouse effect. The effect could be resulted in climate changes and disorder of our ecosystem. Thus, bioenergy developments will play important roles to help decreasing CO₂ emission for better global environment in the future. In the domain of biohydrogen production, biomass including: cellulose, wastewater and agricultural waste are the main resources to maintain feedstock demand. Developing sustainable energy with sustainable feedstock sources like sugary wastewater by using two-stage biomass-derived gas production system might bring great economic profits to business. In this study, the system will be chosen to testify its sustainability when producing the sugary wastewater to renewable source energy. The commercial potential analysis is derived from the internal rate of return (IRR). The novelty finding of this study, as the result showed, found out that the energy recovery is 1.12 times higher than single stage. According to the IRR analysis with the calculated years of 15 years, the IRR is 32.47% that means the system can payback within 3.19 years. Therefore, the feasibility of commercialization potential of biomass-derived gas production system can be verified.     

Dark fermentative hydrogen production from sucrose and molasses

There are many factors affecting the dark fermentative hydrogen production. The interaction of these factors, that is, their combined effects, should be investigated for better design of the systems with stable and higher hydrogen yields. This study aimed to investigate the combined effects of initial substrate, pH, and biomass (or initial substrate to biomass) values on hydrogen production from sucrose and sugar‐beet molasses. Therefore, optimum initial chemical oxygen demand (COD), pH, and volatile suspended solids (VSS) or initial substrate to biomass (VSS) ratio (S/X_o) values leading to the highest dark fermentative hydrogen production were investigated in batch reactors. An experimental design approach (response surface methodology) was used. Results revealed that when sucrose was the substrate, maximum hydrogen production yield (HY) of 2.3 mol H₂/mol sucrose_added was obtained at initial pH of 7 and COD of 10 g/L. Initial S/X_o values studied (4–20 g COD/g VSS) had no effect on HY, while the initial pH was found as the parameter mostly affecting both HY and hydrogen production rate (HPR). When substrate was molasses, initial COD concentration was the only variable affecting HY and HPR. Maximum of both was achieved at 10 g/L initial COD. Initial VSS values studied (2.5–7.5 g/L) had no effect on HPR and HY. This study also indicated that molasses leads to homoacetogenesis for potentially containing intrinsic microorganism and/or natural constituents; thus, sucrose is more advantageous for hydrogen production via fermentation. Homoacetogenesis should be prevented for effective optimization via response surface methodology, if substrate is a natural carbon source potential to have intrinsic microorganisms. Copyright © 2017 John Wiley & Sons, Ltd.     

Emerging technologies for hydrogen production from wastewater

Wastewater treatment is essential to shield the environment. The production of H₂ is substantial for prospering its applications in diversified sectors; hence the study of wastewater treatment for H₂ production is accomplished. Various technologies have been developed and studied considering the potential of wastewater to generate hydrogen-rich gas. These technologies have different mechanisms, diversified setups, and processes. Perhaps these technologies are proven to be exceptional exposures for hydrogen production. Fortunately, a valuable contribution to the environment and the H₂ economy is that some technological processes have been promoted to synthesize H₂ from lab scale to pilot scale. Contemplating such comprehensive exposure to H₂ synthesis from wastewater, the critical information of eight emerging technologies, including their mechanism and reaction parameters influencing the process, pros, cons, and future developmental scopes, are described in this review by classifying them into three different classes, namely light-dependent technologies, light-independent technologies, and other technologies.     

Full chain energy analysis of fuel ethanol from cane molasses in Thailand

An analysis of energy performance and supply potential was performed to evaluate molasses utilization for fuel ethanol in Thailand. The Thai government recently has set up a production target of 1.925 million litres a day of sugar-based ethanol. The molasses-based ethanol (MoE) system involves three main segments: sugar cane cultivation, molasses generation, and ethanol conversion. Negative net energy value found for MoE is a consequence of not utilizing system co-products (e.g. stillage and cane trash) for energy. Taking into account only fossil fuel or petroleum inputs in the production cycle, the energy analysis provides results in favour of ethanol. A positive net energy of 5.95 MJ/L which corresponds to 39% energy gain shows that MoE is efficient as far as its potential to replace fossil fuels is concerned. Another encouraging result is that each MJ of petroleum inputs can produce 6.12 MJ of ethanol fuel. Regarding supply potential, if only the surplus molasses is utilized for ethanol, a shift of 8–10% sugar cane produce to fuel ethanol from its current use in sugar industry could be a probable solution.     

Fuel ethanol from cane molasses in Thailand: Environmental and cost performance

In the context of the world's energy crisis and environmental concerns, crop-based ethanol has emerged as an energy alternative, the use of which can help reduce oil imports as well as emissions of CO₂ and other air pollutants. However, a clear disadvantage of ethanol is its high cost over gasoline under the current pricing scheme that does not include externalities. The intent of this study is to perform a life cycle analysis comparing environmental and cost performance of molasses-based E10 with those of CG. The results show that although E10 provides reduction in fossil energy use, petroleum use, CO₂ and NO_x emissions, its total social costs are higher than those of gasoline due to higher direct production costs and external costs for other air emissions, e.g. CH₄, N₂O, CO, SO₂, VOC and PM₁₀. An analysis of projection scenarios shows that technological innovations towards cleaner production help maximize ethanol's benefits whilst minimizing its limitations.     

Performance comparison among different multifunctional reactors operated under energy self-sufficiency for sustainable hydrogen production from ethanol

Four ethanol-derived hydrogen production processes including conventional ethanol steam reforming (ESR), sorption enhanced steam reforming (SESR), chemical looping reforming (CLR) and sorption enhanced chemical looping reforming (SECLR) were simulated on the basis of energy self-sufficiency, i.e. process energy requirement supplied by burning some of the produced hydrogen. The process performances in terms of hydrogen productivity, hydrogen purity, ethanol conversion, CO₂ capture ability and thermal efficiency were compared at their maximized net hydrogen. The simulation results showed that the sorption enhanced processes yield better performances than the conventional ESR and CLR because their in situ CO₂ sorption increases hydrogen production and provides heat from the sorption reaction. SECLR is the most promising process as it offers the highest net hydrogen with high-purity hydrogen at low energy requirement. Only 12.5% of the produced hydrogen was diverted into combustion to fulfill the process's energy requirement. The thermal efficiency of SECLR was evaluated at 86% at its optimal condition.     

Biohydrogen production from beet molasses by sequential dark and photofermentation

Biological hydrogen production using renewable resources is a promising possibility to generate hydrogen in a sustainable way. In this study, a sequential dark and photofermentation has been employed for biohydrogen production using sugar beet molasses as a feedstock. An extreme thermophile Caldicellulosiruptor saccharolyticus was used for the dark fermentation, and several photosynthetic bacteria (Rhodobacter capsulatus wild type, R. capsulatus hup⁻ mutant, and Rhodopseudomonas palustris) were used for the photofermentation. C. saccharolyticus was grown in a pH-controlled bioreactor, in batch mode, on molasses with an initial sucrose concentration of 15 g/L. The influence of additions of NH₄⁺ and yeast extract on sucrose consumption and hydrogen production was determined. The highest hydrogen yield (4.2 mol of H₂/mol sucrose) and maximum volumetric productivity (7.1 mmol H₂/L_c.h) were obtained in the absence of NH₄⁺. The effluent of the dark fermentation containing no NH₄⁺ was fed to a photobioreactor, and hydrogen production was monitored under continuous illumination, in batch mode. Productivity and yield were improved by dilution of the dark fermentor effluent (DFE) and the additions of buffer, iron-citrate and sodium molybdate. The highest hydrogen yield (58% of the theoretical hydrogen yield of the consumed organic acids) and productivity (1.37 mmol H₂/L_c.h) were attained using the hup⁻ mutant of R. capsulatus. The overall hydrogen yield from sucrose increased from the maximum of 4.2 mol H₂/mol sucrose in dark fermentation to 13.7 mol H₂/mol sucrose (corresponding to 57% of the theoretical yield of 24 mol of H₂/mole of sucrose) by sequential dark and photofermentation.     

System expansion for handling co-products in LCA of sugar cane bio-energy systems: GHG consequences of using molasses for ethanol production

This study aims to establish a procedure for handling co-products in life cycle assessment (LCA) of a typical sugar cane system. The procedure is essential for environmental assessment of ethanol from molasses, a co-product of sugar which has long been used mainly for feed. We compare system expansion and two allocation procedures for estimating greenhouse gas (GHG) emissions of molasses ethanol. As seen from our results, system expansion yields the highest estimate among the three. However, no matter which procedure is used, a significant reduction of emissions from the fuel stage in the abatement scenario, which assumes implementation of substituting bioenergy for fossil-based energy to reduce GHG emissions, combined with a negligible level of emissions from the use stage, keeps the estimate of ethanol life cycle GHG emissions below that of gasoline. Pointing out that indirect land use change (ILUC) is a consequence of diverting molasses from feed to fuel, system expansion is the most adequate method when the purpose of the LCA is to support decision makers in weighing the options and consequences. As shown in the sensitivity analysis, an addition of carbon emissions from ILUC worsens the GHG balance of ethanol, with deforestation being a worst-case scenario where the fuel is no longer a net carbon saver but carbon emitter.     

Pilot-scale outdoor photofermentative hydrogen production from molasses using pH control

The duration of photofermentative hydrogen production from sugar-based nutrients is limited by gradual acidification caused by the production of organic acids, leading to suboptimal pH. To address this issue, a custom pH control system was built and installed on a 20 L tubular photobioreactor, and operated under outdoor conditions. Long-term, single-stage hydrogen production from molasses was achieved using the purple non-sulfur bacterium, Rhodobacter capsulatus. The run lasted for 48 days, the longest duration achieved in a tubular photobioreactor on molasses as the only feed. pH was maintained close to its optimum value. High-purity hydrogen (above 90% by mole, on average) and near-complete conversion of sucrose was observed. The highest hydrogen productivity was 0.69 molH₂/(m³.h). On the other hand, hydrogen production was observed to cease after periods of activity. Production resumed after dilution followed by artificial illumination, indicating that the production activity could be recovered during prolonged runs.     

Biohydrogen production from soluble condensed molasses fermentation using anaerobic fermentation

Using anaerobic micro-organisms to convert organic waste to produce hydrogen gas gives the benefits of energy recovery and environmental protection. The objective of this study was to develop a biohydrogen production technology from food wastewater focusing on hydrogen production efficiency and micro-flora community at different hydraulic retention times. Soluble condensed molasses fermentation (CMS) was used as the substrate because it is sacchariferous and ideal for hydrogen production. CMS contains nutrient components that are necessary for bacterial growth: microbial protein, amino acids, organic acids, vitamins and coenzymes. The seed sludge was obtained from the waste activated sludge from a municipal sewage treatment plant in Central Taiwan. This seed sludge was rich in Clostridium sp.A CSTR (continuously stirred tank reactor) lab-scale hydrogen fermentor (working volume, 4.0 L) was operated at a hydraulic retention time (HRT) of 3–24 h with an influent CMS concentration of 40 g COD/L. The results showed that the peak hydrogen production rate of 390 mmol H₂/L-d occurred at an organic loading rate (OLR) of 320 g COD/L-d at a HRT of 3 h. The peak hydrogen yield was obtained at an OLR of 80 g COD/L-d at a HRT of 12 h. At HRT 8 h, all hydrogenase mRNA detected were from Clostridium acetobutylicum-like and Clostridium pasteurianum-like hydrogen-producing bacteria by RT-PCR analysis. RNA based hydrogenase gene and 16S rRNA gene analysis suggests that Clostridium exists in the fermentative hydrogen-producing system and might be the dominant hydrogen-producing bacteria at tested HRTs (except 3 h). The hydrogen production feedstock from CMS is lower than that of sucrose and starch because CMS is a waste and has zero cost, requiring no added nutrients. Therefore, producing hydrogen from food wastewater is a more commercially feasible bioprocess.     

A processing scheme for industrial ethanol production from straw

We describe a model for the industrial production of ethanol, using wheat straw as a raw material, for use in automobiles as a fuel mixed with gasoline. In particular for Greece, we have in mind that wheat straw production of the Thessalia Plain.The energy requirements of the factory are covered totally by burning the produced lignin. Particularly, the electric energy needs are covered by an electric generator which consumes part of the thermal energy produced by the combustion of lignin.The fermentable sugars are obtained from cellulose by hydrolysis, using an enzymatic system of cellulases which are produced from a cultivation of Trichoderma viride.The cellulose is separated from the lignin by heating the straw at 100°C, in water solution of NaOH 1%.We propose a fast fermentation method in order to reduce the cost, and the rejected/24 hr yeast from the Laval separators is processed for the production of a protein-containing animal food (8 kg of pressed yeast per 1001 of alcohol).We give the mass and energy balance and the cost, in current prices, of the produced ethanol, which is estimated to be 7.9 Dr ($0.19 U.S.) per liter. We also estimate that the plant cost will be about 20 million dollars for a production capacity of 100 thousand litres of ethanol per day.     

Biological fermentative hydrogen and ethanol production using continuous stirred tank reactor

Hydrogen and ethanol are promising biofuels and have great potential to become alternatives to fossil fuels. The influence of organic loading rates (OLRs) on the production of fermentative hydrogen and ethanol were investigated in a continuous stirred tank reactor (CSTR) from fermentation using molasses as substrate. Four OLRs were examined, ranging from 8 to 32 kg/m³·d. The H₂ and ethanol production rate in CSTR initially increased with increasing OLR (from 8 to 24 kg/m³ d). The highest H₂ production rate (12.4 mmol/h l) and ethanol production rate (20.27 mmol/h l) were obtained in CSTR both operated at OLR = 24 kg/m³ d. However, the H₂ and ethanol production rate tended to decrease with an increase of OLR to 32 kg/m³ d. The liquid fermentation products were dominated by ethanol, accounting for 31-59% of total soluble metabolities. Linear regression results show that ethanol production rate (y) and H₂ production rate (x) were proportionately correlated which can be expressed as y = 0.5431x + 1.6816 (r² = 0.7617). The total energy conversion rate based on the heat values of H₂ and ethanol was calculated to assess the overall efficiency of energy conversion rate. The best energy conversion rate was 31.23 kJ/h l, occurred at OLR = 24 kg/m³ d.     

Clostridium strain co-cultures for biohydrogen production enhancement from condensed molasses fermentation solubles

An anaerobic continuous-flow hydrogen fermentor was operated at a hydraulic retention time of 8 h using condensed molasses fermentation solubles (CMS) substrate of 40 g-COD/L. Serum bottles were used for seed micro-flora cultivation and batch hydrogen fermentation tests (CMS substrate concentrations of 10–160 g-COD/L). Three hydrogen-producing bacterial strains Clostridium sporosphaeroides F52, Clostridium tyrobutyricum F4 and Clostridium pasteurianum F40 were isolated from the seed fermentor and used as the seeding microbes in single and mixed-culture cultivations for determining their hydrogen productivity. These strains possessed specific hydrogenase genes that could be detected from CMS-fed hydrogen fermentors and were major hydrogen producers. C. pasteurianum F40 was the dominant strain with a high hydrogen production rate while C. sporosphaeroides F52 may play a main role in degrading carbohydrate and glutamate. These strains could be co-cultivated as a symbiotic mixed-culture process to enhance hydrogen productivity. C. pasteurianum F40 or C. tyrobutyricum F4 co-culture with the glutamate-utilizing strain C. sporosphaeroides F52 efficiently enhanced hydrogen production by 12–220% depending on the substrate CMS concentrations.     

Efficiency comparison of tri-generating HTFC to conventional hydrogen production technologies

This study compares the production of hydrogen with high temperature fuel cells (HTFCs) that tri-generate power, heat and hydrogen to distributed and centralized steam methane reformation (SMR) supply chains. The defined supply chain steps of hydrogen production include: production, treatment, distribution, storage, dispensing and use. Different technologies for each step in the supply chain have been analyzed from an energy standpoint, resulting in ten different supply chain scenarios.     

木质纤维素制取燃料乙醇菌种的研究

目前,随着石油资源的日益枯竭,寻求一种廉价的、清洁的、可再生的新型能源成为各国能源领域科研人员的一项重要任务.乙醇作为一种工业燃料,具有许多优点,利用生物质制取燃料乙醇技术,越来越受到人们的广泛关注.文章报道了国内外近年来利用木质纤维素稀酸水解液制取燃料乙醇的菌种的研究现状,主要包括木质纤维素稀酸水解液乙醇发酵的酵母菌、细菌及基因重组菌的菌种构建等.     

Dark fermentative hydrogen gas production from molasses using hot spring microflora

This study reports hydrogen gas (H₂) production from molasses by hot spring microflora in three stages. During the first two stages most convenient temperature, inoculation percentage (INP) ensuring the highest H₂ yield and rate were determined using suspended culture. Then, H₂ was produced by the same culture immobilized on porous ceramic rings at three different hydraulic retention times. For the suspended culture experiments, the most effective H₂ production resulting 202.32 mL H₂/g COD was obtained at 37 °C with 10 INP. The highest H₂ formation of 534.35 mLH₂/d was realized for the biofilm culture at 0.53-day hydraulic retention time and H₂ production using hot spring microflora in biofilm form was found to be promising. The pH of the experiments remained stable around 5.5–6.5 without a requirement for pH adjustment during the fermentation.