Ethanol Production Technology Research Articles

Impact of exogenous acetate on ethanol formation and gene transcription for key enzymes in Clostridium autoethanogenum grown on CO

Gas fermentation using C1 substrate (CO or CO2) is a novel and attractive technology for ethanol production. Clostridium autoethanogenum, a promising gas fermentation strain, can grow on 100 % CO and produce acetate and ethanol through the Wood-Ljungdahl pathway. Like other autotrophic acetogens, C. autoethanogenum produces ethanol primarily via the reduction of acetyl-CoA. In this study, we demonstrated that ethanol was also formed via acetate reduction. 13C-labeled acetate was employed to investigate the conversion of acetate in C. autoethanogenum during its autotrophic growth on CO. The addition of exogenous acetate can improve ethanol production in C. autoethanogenum, 13C abundance in ethanol increased significantly with the increase of exogenous 13C-labeled acetate, confirming that acetate can be transformed to ethanol. Moreover, transcriptional analysis of genes encoding phosphotransacetylase(pta), aldehyde:ferredoxin oxidoreductase(aor), carbon monoxide dehydrogenase(codh) and alcohol dehydrogenase(adh) in C. autoethanogenum revealed their differential expression under varied exogenous acetate levels. Among these genes, pta gene was down-regulated due to its involvement in acetate formation, whereas aor gene CAETHG_0102, codh gene CAETHG_3005, adh genes CAETHG_1841 and CAETHG_1813 were found to be highly up-regulated at higher levels of exogenous acetate, suggesting that they may play important roles in the conversion of acetate to ethanol.

Ascertaining the Trajectory of Wood-Based Bioenergy Development in the United States Based on Current Economic, Social, and Environmental Constructs

Wood-based bioenergy development could play a vital role in attaining energy independence, reducing carbon emissions, and ensuring rural prosperity in the United States. An understanding of policies supporting wood-based bioenergy development coupled with the current status of production of various wood-based bioenergy products would better the prospects of wood-based bioenergy development in the United States. An understanding of the economic feasibility, social acceptability, and environmental externalities would contribute to effective policy prescriptions for establishing the US bioeconomy. Based on a comprehensive review of existing studies, we show that the heat and electricity derived from woody feedstocks that would prevail in the future as a commercial-level conversion technology for wood-based ethanol production are still under development. Society in general is positive about the use of woody feedstocks for bioenergy development. The production cost of wood-based ethanol and electricity generation has not reduced over time, indicating a need for targeted policy support focusing on sharing the production cost of wood-based bioenergy products. Wood-based bioenergy development could meet the need for sustainable energy production without affecting existing roundwood markets with the advent of advanced silvicultural treatments and efficient biotechnologies.

Evaluation of endoglucanase and β-glucosidase production by bacteria and yeasts isolated from an eucalyptus plantation in the cerrado of Minas Gerais

The current global environmental and economic scenario is intrinsically related to the increase in fossil fuel consumption caused by technological development and world population growth. Thus, it is necessary to search for renewable sources of biofuel in an attempt to mitigate the effects of fossil fuels on the environment and the lack of these non-renewable fuels. The use of lignocellulosic biomass, an abundant and renewable resource in Brazilian regions, has contributed successfully to new research and technologies for second-generation ethanol production. The conversion of lignocellulosic biomass into fermentable sugars requires the use of cellulolytic enzymes produced by microorganisms found in the microbiota. This work evaluated the production of endoglucanase and β-glucosidase in a liquid medium containing carboxymethylcellulose by five microorganisms (bacteria and yeasts) from the bank of 348 isolates from eucalyptus soils in the Cerrado Mineiro. Microorganisms with the following enzymatic activity indexes were selected: IM1-74 (22), IM25-9 (5.33), IM32-90 (7.33), IM1-5 (10.33) and IM32-91 (5.44). The microorganisms with the highest enzymatic activity in the liquid medium were IM32-90 (endoglucanase = 0.214 U mL-1) and IM32-91 (β-glucosidase = 0.067 U mL-1).

Comparative analysis of key technologies for cellulosic ethanol production from Brazilian sugarcane bagasse at a commercial scale

AbstractBiorefineries can upgrade waste lignocellulosic biomass (LB) into soluble (C5 and C6) sugars that can be fermented into second‐generation (2G) ethanol‐based biofuels and a range of valuable byproducts derived from lignin. Research advances made in various laboratories worldwide have not been easy to translate into large‐scale operations. Here, we performed a simple economic analysis of cellulosic ethanol production from a stand‐alone 100ton dry sugarcane bagasse per day process, from a Brazilian market perspective, based on current state‐of‐the‐art biorefinery process technologies. Economic analysis reveals that the cost of manufacturing (COM) of 2G ethanol in an annexed Brazilian facility is close to USD 1.33 L−1. Fixed and variable costs contributed 57% and 24% in COM of 2G ethanol with a high payback period of ~31 years and a negative net present value (NPV). Further cost reduction can be realized by continuous R&D efforts aiming for innovation in new processing paradigms for cellulosic biorefineries. The key market players (Poet‐DSM, DuPont, Abengoa, Beta Renewables, Raizen, Granbio, Praj, etc.) and other new emerging players (Global Yeast, Taurus Energy, Leaf, Mascoma‐Lallemand) working on ethanologen development, and cellulase producers (Novozyme, Metgen), should also develop partnerships / joint ventures to establish a sustainable business model to develop cost‐competitive 2G ethanol production from bagasse in Brazil. This paper presents additional commentary and analysis with pertinent information about the commercialization of integrated 2G ethanol biorefineries processing sugarcane bagasse, from a Brazilian perspective. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd

Waste paper to bioethanol: Current and future prospective

AbstractBioethanol is considered to be a possible substitute for non‐renewable fossil fuels. Biofuels, including bioethanol, are gradually replacing coal and oil for energy production. It is expected that, by 2040, fossil fuels’ contribution to the world's energy demands will only be 25% with the remaining contribution made up by biofuels. One of the major factors affecting ethanol production is the cost of raw materials, which can be substantially reduced by utilizing industrial or agricultural lignocellulosic wastes. Using waste paper as a feedstock for bioethanol production would reduce the production cost and may eliminate problems in managing this waste material in the environment. The cellulose, hemicellulose, and lignin in waste paper are less complicated and so only mild pretreatment is needed before enzymatic hydrolysis and fermentation. This review covers topics such as bioethanol as a promising alternative to petroleum fuels, feedstocks for bioethanol production, lignocellulosic technology and challenges for ethanol production, advantages and disadvantages of pretreatments methods, waste paper as feedstock for ethanol production, processing of waste paper to ethanol, and the different integration methods of hydrolysis and fermentation. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd.

Energy Integration of Biogas Production in an Integrated 1G2G Sugarcane Biorefinery: Modeling and Simulation

The integration of the first and second generation (1G2G) ethanol production promotes the increase of biofuel productivity per hectare of planted sugarcane, as well as the main liquid waste stream: vinasse, derived from ethanol distillation. As a sustainable way for it disposal, biogas production from anaerobic digestion (AD) promotes environmental suitability while enabling bioenergy generation. This work evaluated the potential energy generated from AD applied to vinasse within the context of an integrated 1G2G sugarcane biorefinery. Data from a literature survey based the scenario modeling and assessment, including economic and environmental indicators to compare the studied alternatives. AD allowed at least 68% increase of released bagasse for 2G ethanol production compared to 2G base scenario, being able to even double 2G ethanol productivity to 30 L t−1 cane. Organic matter removal efficiency of vinasse AD played an important role in 2G ethanol production so that higher the efficiency, larger the fraction of bagasse released for ethanol production. Economic indicators showed the unviability of 1G2G sugarcane mill including AD unit when considering the current technologies for 2G ethanol production in view of their high operational costs; however, with the envisaged technologies for 2025, the internal rate of return (IRR) of 14.3 and 17% was achieved, when considering conservative and optimistic data for vinasse AD efficiency, respectively. The results evidenced the importance of investment in R&D especially in 2G ethanol production but also in the AD of vinasse to reach the viability of this business.

Development of rapid bioconversion with integrated recycle technology for ethanol production from extractive ammonia pretreated corn stover.

High enzyme loading and low productivity are two major issues impeding low cost ethanol production from lignocellulosic biomass. This work applied rapid bioconversion with integrated recycle technology (RaBIT) and extractive ammonia (EA) pretreatment for conversion of corn stover (CS) to ethanol at high solids loading. Enzymes were recycled via recycling unhydrolyzed solids. Enzymatic hydrolysis with recycled enzymes and fermentation with recycled yeast cells were studied. Both enzymatic hydrolysis time and fermentation time were shortened to 24 h. Ethanol productivity was enhanced by two times and enzyme loading was reduced by 30%. Glucan and xylan conversions reached as high as 98% with an enzyme loading of as low as 8.4 mg protein per g glucan. The overall ethanol yield was 227 g ethanol/kg EA-CS (191 g ethanol/kg untreated CS). Biotechnol. Bioeng. 2017;114: 1713-1720. © 2017 Wiley Periodicals, Inc.

O205 エタノール生産のための木質バイオマスの前処理・酵素糖化技術の開発(セッション2:技術～生物化学～,口頭発表)

O205 エタノール生産のための木質バイオマスの前処理・酵素糖化技術の開発(セッション2:技術～生物化学～,口頭発表)

P-122 バイオエタノール生産を目的としたスギの前処理技術の開発(ポスター1,ポスター発表)

P-122 バイオエタノール生産を目的としたスギの前処理技術の開発(ポスター1,ポスター発表)

Effect of enzyme preparations on the main parameters of products in the development of processing technology of concentrated wort on ethanol

Among the priority directions of the development of the alcohol industry, the development of energy and resource-saving technologies for ethanol production from grain is currently in the forefront. To obtain and fermented sugared grain must, starch and other components of the raw material must be transferred to a dissolved state. The choice of modes and technological parameters for obtaining sugared wort during the development of new technologies for ethanol production is based on economic and instrumental-technological aspects of production and is largely determined by the properties of the processed raw materials. In this regard, the need to develop new technologies that take into account the composition of protein substances and non-starch compounds of various types of grain raw materials, with the purpose of efficient bioconversion of all constituents of grain, which not only intensify the process of alcoholic fermentation and increase the yield of alcohol, but also obtain fodder protein Products is timely and relevant. To study the effect of enzymatic preparations containing xylanase, ?-glucanase and cellulase, as well as the thinning, saccharifying and proteolytic effects on the characteristics and viscosity of the wort, the aim was to obtain a highly concentrated wort from an aqueous-powdery wheat suspension. Application as a thinning preparation Termoferm 3500 L allows to obtain wort with the maximum concentration of solids, fermented carbohydrates and reducing sugars. At the same time, the indicator of apparent goodness of the wort when using Thermoferm 3500 L was 85.8%. The dependence of the flowability of starch wort on the duration of hydrodynamic and enzymatic treatment at the stage of mechano-enzymatic treatment was studied. As a result of studying the rheological characteristics during the preparation of starch wort, an effective, simple technological method for reducing the viscosity of media, namely, raising the temperature of water during batching from 50 to 70 ° C, could be propose.

Global warming potential and energy analysis of second generation ethanol production from rice straw in India

The environmental sustainability of cellulosic ethanol production from rice straw in India is conducted using life cycle assessment (LCA). Greenhouse gas (GHG) emissions, net energy ratio (NER) and net energy balance (NEB) are studied for ethanol production system using two diverse pretreatment technologies, i.e. dilute acid (DA) and steam explosion (SE) followed by separate hydrolysis and fermentation. 1ton of rice straw is the reference flow of study and 1MJ transportation fuel is the functional unit while comparing the results with gasoline. The inventory data is collected based on several experiments conducted at our pilot plant and is a novel contribution to country specific LCA. Using DA and SE, the ethanol yields from the processing of 1ton straw are 239 and 253L and life cycle GHG emissions are 292 and 288kgCO2eq./ton straw respectively. The results indicated that production of enzyme used in hydrolysis is the major contributor to GHG emissions in both DA (54%) and SE (57%) methods of ethanol production. The net energy input during the life cycle of ethanol is 1736 and 1377MJ/ton straw in DA and SE respectively. The major GHG emissions and energy benefits are obtained using lignin produced in the plant to generate electricity resulting in displacement of the coal based electricity. With a higher xylose recovery in the SE, it gives larger amount of ethanol and also generates more surplus electricity. Enzyme production and its use are identified as GHG emission and energy consumption hotspot in the ethanol production process. While comparing the results with gasoline, DA and SE resulted in a reduction of 77 and 89% GHG emissions and NER of 2.3 and 2.7 respectively. The E5 blending would reduce GHG emissions by 4.3% (DA) and 4.8% (SE) whereas; E20 blend would lead to a reduction of 17.4% (DA) and 18.8% (SE) respectively. Sensitivity analysis indicates that with every 12.5% increase in the price of rice straw from the base case, there is a 2.3% increase in GHG emissions and vice versa. 1FPU/g WIS increase during hydrolysis gives 2.9% increase in ethanol production, but at the same time there is an increase of 5% emissions from enzyme production. The results of the study conclude that cellulosic ethanol production technology in India is sustainable from GHG reduction and energy efficiency perspective.

Viable Feedstock Options and Technological Challenges for Ethanol Production in India

Though improvements in processing and technology are important, the fluctuating price of inputs such as molasses, corn, sugar beet, sugarcane, sweet sorghum, starch, etc. and their seasonal availability play an important role in ethanol industry. As a matter of fact, the ethanol industry based on conventional resources has reached its saturation point. Technologies for ethanol production from lignocellulosics are being developed by scientists world over with the objective of exploiting the potential of a resource, which is otherwise considered a waste, to generate energy. The focus has been to produce ethanol in a cost-effective manner, besides aiming to find use of its by-products as food supplements for cattles, etc. Recent developments like adoption of technologies such as dry grind fractionation, which is now commercially viable, would reduce the cost of milling; wet milling being cost-intensive and dry milling requiring smaller plants.

Synthesis of South Africa’s Biomass to Bioethanol Supply Network

South Africa produces synthetic ethanol and to date there are no commercial bioethanol production plants in operation in the country. Sugarcane, as well as residues from sugarcane, maize, sorghum, wheat and barley are among the acceptable bioethanol feedstocks in South Africa. As the feedstock cultivation areas are scattered over a wide geographical land area, and the potential bioethanol feedstocks have low energy density, there is a need to locate the processing facilities in strategic positions such that production and logistic costs and greenhouse gas (GHG) emissions due to transportation are minimized. To address the above mentioned challenges associated with bioethanol production in South Africa, a mathematical programming approach for the synthesis of optimal bioethanol supply network is developed. It accounts for sugar demands, production of bioenergy (ethanol, electricity and heat) and other byproducts, various feedstocks and their geographical distributions, etc. Various processing technologies for ethanol production are considered and two data sources for availabilities of feedstocks are used. Synthesis is performed by maximizing the economic objective, measured by annual profit. Evaluation of greenhouse gas (GHG) emissions is also performed. Based on the results obtained, it would be possible, in terms of economics, to meet and surpass the 2 % target penetration of biofuel into the South African national liquid fuel supply stipulated by the government.

Ethanol production technology by fermentation form fiber residues.

We studied the effects of various factors on the yield of ethanol from enzymatic hydrolysate of Tara fiber residues by the single factor experiment,and then optimized ethanol production technology by orthogonal experiments. The optimum conditions were the ratio of sodium alginate-yeast of 1 ∶ 2 g · g~(- 1),substrate sugar concentration of 30%,the amount of yeast of 1. 5 g,and fermentation time of 120 h,with the yield of ethanol of 83. 68%.

Social life cycle assessment of first and second-generation ethanol production technologies in Brazil

The main goal of this study is to suggest quantitative social metrics to evaluate different sugarcane biorefinery systems in Brazil by exploring a novel hybrid approach integrating social life cycle assessment and input-output analysis. Social life cycle assessment is the main methodology for evaluating social aspects based on a life-cycle approach. Using this framework, a hybrid model integrating social life cycle assessment and input-output analysis was introduced to evaluate different social effects of biorefinery scenarios considering workers as the stakeholder category. Job creation, occupational accidents, wage profile, education profile, and gender profile were selected as the main inventory indicators. A case study of three scenarios considering variations in agricultural and industrial technologies (including sugarcane straw recovery and second-generation ethanol production, for instance) was carried out for evaluating present first-generation (1G-basic, 1G-optimized) and future first- and second-generation ethanol production (1G2G). The 1G-basic scenario leads to higher job creation levels over the supply chain mainly because of the influence of agricultural stage whose workers are mostly employed in sugarcane manual operations. On the other hand, 1G-optimized and 1G2G present supply chains are more reliant on the manufacturing, trade, and services sectors whose workers are associated with a lower level of occupational accidents, higher average wages, higher education level, and more participation of women in the work force. The use of a novel hybrid approach integrating social life cycle assessment (SLCA) and input-output analysis (IOA) was useful to quantitatively distinguish the social effects over different present and future sugarcane biorefinery supply chains. As a consequence, this approach is very useful to support decision-making processes aiming to improve the sustainability of sugarcane biorefineries taking social aspects into account.

Two-Step Hot-Compressed Water Treatment of Douglas Fir for Efficient Total Sugar Recovery by Enzymatic Hydrolysis

The non-catalytic hydrothermal pretreatment of softwood is generally less effective for subsequent enzymatic hydrolysis. In this study, the efficacy of hot-compressed water (HCW) treatment of Douglas fir was investigated between 180 °C and 260 °C, allowing solubilization of the cellulose components. The enzymatic digestibility of cellulosic residues increased significantly under HCW conditions > 250 °C, and the enhanced glucan digestibility was closely related to the decomposition of the cellulose component. Combination of the first-stage HCW treatment (220 °C, 5 min) to recover hemicellulosic sugars with the second-stage HCW treatment (260 °C, 5 min) to improve cellulose digestibility gave a total sugar recovery of 56.2% based on the dried raw materials. This yield was 1.4 times higher than that from the one-step HCW-treated sample (260 °C, 5 min). Additionally, an enzymatic hydrolysate from the two-step HCW-treated sample exceeded 90% of the ethanol fermentation yield based on the total sugars present in the hydrolysates. These results suggest the potential of the two-step HCW treatment of softwood as a pretreatment technology for efficient total sugar recovery and ethanol production.

Ethanol production by Pichia stipitis immobilized on sugarcane bagasse

AbstractThe search for new ethanol production technologies is due to this biofuel being a renewable and environmentally friendly option. Immobilized cell systems for ethanol production have been studied; however, the phenomenon involved in cell sorption on raw materials has been poorly explored. Therefore, this work evaluates P. stipitis immobilization on sugarcane bagasse pretreated with sulphuric acid, as well as ethanol production in batch culture. The results obtained showed that the Guggenheim-Anderson-de Boer (GAB) model explained the sorption phenomenon. The selected inoculum size for immobilization was the same as the monolayer sorption capability (1.17 gl-1). Using 1:100 g ml- 1 solid-liquid ratio, at 250 rpm, ethanol yield and productivity of 0.404 gg-1 glucose and 0.41 gl-1h-1 were obtained, respectively. The immobilized systems were stable for up to twenty-five repeated batches (36 h each). Ethanol production was increased from the first to the twenty-fifth batch (18.1 and 24.7 gl-1 ethanol). The use of complex media, such as molasses “B” or sugarcane hydrolyzates, caused an increase in process efficiency 2.4 and 1.8-fold respectively, compared with free cells systems. Biotechnological ethanol production from lignocellulosic hydrolyzates could be improved by the use of the immobilization cell sorption on pre-treated raw materials.

Co-Utilization of Glucose and Xylose for Enhanced Lignocellulosic Ethanol Production with Reverse Membrane Bioreactors.

Integrated permeate channel (IPC) flat sheet membranes were examined for use as a reverse membrane bioreactor (rMBR) for lignocellulosic ethanol production. The fermenting organism, Saccharomyces cerevisiae (T0936), a genetically-modified strain with the ability to ferment xylose, was used inside the rMBR. The rMBR was evaluated for simultaneous glucose and xylose utilization as well as in situ detoxification of furfural and hydroxylmethyl furfural (HMF). The synthetic medium was investigated, after which the pretreated wheat straw was used as a xylose-rich lignocellulosic substrate. The IPC membrane panels were successfully used as the rMBR during the batch fermentations, which lasted for up to eight days without fouling. With the rMBR, complete glucose and xylose utilization, resulting in 86% of the theoretical ethanol yield, was observed with the synthetic medium. Its application with the pretreated wheat straw resulted in complete glucose consumption and 87% xylose utilization; a final ethanol concentration of 30.3 g/L was obtained, which corresponds to 83% of the theoretical yield. Moreover, complete in situ detoxification of furfural and HMF was obtained within 36 h and 60 h, respectively, with the rMBR. The use of the rMBR is a promising technology for large-scale lignocellulosic ethanol production, since it facilitates the co-utilization of glucose and xylose; moreover, the technology would also allow the reuse of the yeast for several batches.

Hybrid Input‐Output Life Cycle Assessment of First‐ and Second‐Generation Ethanol Production Technologies in Brazil

SummaryA hybrid approach combining life cycle assessment and input‐output analysis was used to demonstrate the economic and environmental benefits of current and future improvements in agricultural and industrial technologies for ethanol production in Brazilian biorefineries. In this article, three main scenarios were evaluated: first‐generation ethanol production with the average current technology; the improved current technology; and the integration of improved first‐ and second‐generation ethanol production. For the improved first‐generation scenario, a US$1 million increase in ethanol demand can give rise to US$2.5 million of total economic activity in the Brazilian economy when direct and indirect purchases of inputs are considered. This value is slightly higher than the economic activity (US$1.8 million) for an energy equivalent amount of gasoline. The integration of first‐ and second‐generation technologies significantly reduces the total greenhouse gas emissions of ethanol production: 14.6 versus 86.4 grams of carbon dioxide equivalent per megajoule (g CO2‐eq/MJ) for gasoline. Moreover, emissions of ethanol can be negative (–10.5 g CO2‐eq/MJ) when the system boundary is expanded to account for surplus bioelectricity by displacement of natural gas thermal electricity generation considering electricity produced in first‐generation optimized biorefineries.

An economic analysis of bioethanol production from the marine macroalga Ulva (Chlorophyta)

We performed a cost-benefit analysis for bioethanol production using biomass of Ulva rigida, a marine macroalga (seaweed), co-cultured with fish in an intensive offshore aquaculture unit. This is the first report for such analysis that takes into consideration offshore seaweed cultivation and uses a recently developed, novel and simplified ethanol production technology that is devoid of costly pre-treatments imposed to the seaweed biomass. By simultaneously producing ethanol with valuable Dried Distillers Grains with Solubles (DDGS) by-products such as animal feed, the economic viability of this system is plausible over a production range of 77–240 dry tons of seaweed per day. As such, applying the model to suggested future scenarios for the Israeli Mediterranean shorelines, which limits aquaculture to ca. 600 ha, results in unprofitability. Further, sensitivity analyses place profitability as mainly dependent on DDGS prices and on the daily growth rate (biomass yield) of the macroalga. These two are key factors to achieve profitability at the 600-ha scenario.