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5 pages, 206 KiB

Open AccessEditorial

Special Issue on “Bioethanol Production Processes”

by Antonio D. Moreno and Paloma Manzanares

Processes 2023, 11(5), 1368; https://doi.org/10.3390/pr11051368 - 30 Apr 2023

Cited by 1 | Viewed by 1315

Abstract

The transportation sector is facing a profound challenge to utilize a greater proportion of sustainable substitutes in relation to oil-derived products [...] Full article

(This article belongs to the Special Issue Bioethanol Production Processes)

Research

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28 pages, 3010 KiB

Open AccessArticle

Design and Control Applied to an Extractive Distillation Column with Salt for the Production of Bioethanol

by Carlos Alberto Torres Cantero, Ricardo Pérez Zúñiga, Mario Martínez García, Silvia Ramos Cabral, Manuela Calixto-Rodriguez, Jorge Salvador Valdez Martínez, Mayra Guadalupe Mena Enriquez, Abraham Jashiel Pérez Estrada, Gerardo Ortiz Torres, Felipe de J. Sorcia Vázquez, Azael García Rebolledo and Jesse Yoe Rumbo Morales

Processes 2022, 10(9), 1792; https://doi.org/10.3390/pr10091792 - 5 Sep 2022

Cited by 17 | Viewed by 3607

Abstract

Extractive distillation with salts, unlike other dehydration technologies, is better due to the null toxicity that exists in the distillate, since salt cannot be evaporated. With this distillation technology, it is possible to obtain a high concentration of ethanol, however, there are still [...] Read more.

Extractive distillation with salts, unlike other dehydration technologies, is better due to the null toxicity that exists in the distillate, since salt cannot be evaporated. With this distillation technology, it is possible to obtain a high concentration of ethanol, however, there are still problems in the control of the distillation columns in the presence of disturbances. The present work deals with the simulation and control of an extractive distillation column using CaCl

_{2}

as a separating agent, for which the Aspen Dynamics^® simulator is used. The measurement and control of the ethanol composition are carried out by means of temperature, in addition, four control structures are evaluated and compared. These structures are L, D, LV, and DV, which are the most common in conventional distillation, and their performance is measured by means of deterministic indicators applying changes (disturbances) of composition and the flow rate in the main feed of the column. The most relevant results of this work lead to the fact that by applying a controller, it is possible to maintain the desired purity above the international purity standards (99% ethanol) that govern biofuels. Full article

(This article belongs to the Special Issue Bioethanol Production Processes)

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14 pages, 3911 KiB

Open AccessCommunication

Introducing a Marine Biorefinery System for the Integrated Production of Biofuels, High-Value-Chemicals, and Co-Products: A Path Forward to a Sustainable Future

by Abdelrahman Saleh Zaky

Processes 2021, 9(10), 1841; https://doi.org/10.3390/pr9101841 - 17 Oct 2021

Cited by 17 | Viewed by 4999

Abstract

Biofuels have many environmental and practical benefits as a transportation fuel. They are among the best alternatives to fossil fuels- thanks to their capacity for negative carbon emissions, which is vital for archiving the global ambition of a net-zero economy. However, conventional biofuel [...] Read more.

Biofuels have many environmental and practical benefits as a transportation fuel. They are among the best alternatives to fossil fuels- thanks to their capacity for negative carbon emissions, which is vital for archiving the global ambition of a net-zero economy. However, conventional biofuel production takes place on inland sites and relies on freshwater and edible crops (or land suitable for edible crop production), which has led to the food versus fuel debate. It also suffers technical and economical barriers owing to the energy balance and the cost of production compared with fossil fuels. Establishing a coastal integrated marine biorefinery (CIMB) system for the simultaneous production of biofuels, high-value chemicals, and other co-products could be the ultimate solution. The proposed system is based on coastal sites and relies entirely on marine resources including seawater, marine biomass (seaweed), and marine microorganisms (marine yeasts and marine microalgae). The system does not require the use of arable land and freshwater in any part of the production chain and should be linked to offshore renewable energy sources to increase its economic feasibility and environmental value. This article aims to introduce the CIMB system as a potential vehicle for addressing the global warming issue and speeding the global effort on climate change mitigation as well as supporting the world’s water, food and energy security. I hope these perspectives serve to draw attention into research funding for this approach. Full article

(This article belongs to the Special Issue Bioethanol Production Processes)

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18 pages, 2711 KiB

Open AccessFeature PaperArticle

A Preliminary Life Cycle Analysis of Bioethanol Production Using Seawater in a Coastal Biorefinery Setting

by Abdelrahman S. Zaky, Claudia E. Carter, Fanran Meng and Christopher E. French

Processes 2021, 9(8), 1399; https://doi.org/10.3390/pr9081399 - 13 Aug 2021

Cited by 18 | Viewed by 4254

Abstract

Bioethanol has many environmental and practical benefits as a transportation fuel. It is one of the best alternatives to replace fossil fuels due to its liquid nature, which is similar to the gasoline and diesel fuels traditionally used in transportation. In addition, bioethanol [...] Read more.

Bioethanol has many environmental and practical benefits as a transportation fuel. It is one of the best alternatives to replace fossil fuels due to its liquid nature, which is similar to the gasoline and diesel fuels traditionally used in transportation. In addition, bioethanol production technology has the capacity for negative carbon emissions, which is vital for solving the current global warming dilemma. However, conventional bioethanol production takes place based on an inland site and relies on freshwater and edible crops (or land suitable for edible crop production) for production, which has led to the food vs. fuel debate. Establishing a coastal marine biorefinery (CMB) system for bioethanol production that is based on coastal sites and relies on marine resources (seawater, marine biomass and marine yeast) could be the ultimate solution. In this paper, we aim to evaluate the environmental impact of using seawater for bioethanol production at coastal locations as a step toward the evaluation of a CMB system. Hence, a life cycle assessment for bioethanol production was conducted using the proposed scenario, named Coastal Seawater, and compared to the conventional scenario, named Inland Freshwater (IF). The impact of each scenario in relation to climate change, water depletion, land use and fossil depletion was studied for comparison. The Coastal Seawater scenario demonstrated an improvement upon the conventional scenario in all the selected impact categories. In particular, the use of seawater in the process had a significant effect on water depletion, showing an impact reduction of 31.2%. Furthermore, reductions were demonstrated in natural land transformation, climate change and fossil depletion of 5.5%, 3.5% and 4.2%, respectively. This indicates the positive impact of using seawater and coastal locations for bioethanol production and encourages research to investigate the CMB system. Full article

(This article belongs to the Special Issue Bioethanol Production Processes)

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14 pages, 1329 KiB

Open AccessArticle

Enzymatic Process for Cystoseira barbata Valorization: Ethanol Production and Additional By-Products

by Doinita-Roxana Cioroiu Tirpan, Ancaelena Eliza Sterpu, Claudia Irina Koncsag, Alina Georgiana Ciufu and Tănase Dobre

Processes 2021, 9(5), 741; https://doi.org/10.3390/pr9050741 - 22 Apr 2021

Cited by 1 | Viewed by 2144

Abstract

The aim of this study is to evaluate the potential of dried Cystoseira barbata alga for ethanol production through alcoholic fermentation. The influence of the main factors affecting the fermentation are studied in the frame of a 2³ factorial experimental plan. The [...] Read more.

The aim of this study is to evaluate the potential of dried Cystoseira barbata alga for ethanol production through alcoholic fermentation. The influence of the main factors affecting the fermentation are studied in the frame of a 2³ factorial experimental plan. The main factors influencing the process are the fermentation temperature (t from 25 °C to 35 °C), the solid to liquid ratio (S/L from 0.040 g/g to 0.080 g/g), and the cellulase ratio (R from 8 U/g d.m to 16 U/g d.m.). The maximum volatile compounds yield of 0.2808 g/g d.m and ethanol yield of 0.0158 g/g d.m were favored by the following experimental conditions: process temperature of 35 °C, solid to liquid ratio of 0.0415, and enzyme ratio of 16 U/g d.m. A statistical model was used to correlate the product yield with the process factors. Additionally, 19 interesting bioactive compounds were found in the enzymatic hydrolysis and alcoholic fermentation broths which seem likely to maintain natural defence mechanisms against diseases and physical disorders. Full article

(This article belongs to the Special Issue Bioethanol Production Processes)

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18 pages, 922 KiB

Open AccessArticle

Stability and Performance Analysis of Bioethanol Production with Delay and Growth Inhibition in a Continuous Bioreactor with Recycle

by Rubayyi T. Alqahtani, Samir Kumar Bhowmik, Abdelhamid Ajbar and Mourad Boumaza

Processes 2021, 9(3), 461; https://doi.org/10.3390/pr9030461 - 4 Mar 2021

Cited by 1 | Viewed by 2273

Abstract

This paper proposes and analyzes a mathematical model for the production of bioethanol in a continuous bioreactor with recycling. The kinetics correspond to the use of Saccharomyces bayanus for the fermentation of sugars found in wastewater from soft drinks. The proposed model considers [...] Read more.

This paper proposes and analyzes a mathematical model for the production of bioethanol in a continuous bioreactor with recycling. The kinetics correspond to the use of Saccharomyces bayanus for the fermentation of sugars found in wastewater from soft drinks. The proposed model considers product growth latency, which was experimentally found in batch studies of ethanol production. Furthermore, the inhibition effect of ethanol is expressed by a modified version of the classical Andrew’s model for substrate inhibition. The proposed model consists of only three ordinary differential equations containing a minimal number of operating parameters, which include the bioreactor residence time, glucose feed concentration, recycle ratio and the fraction of biomass removed from the reactor by the flow. The positivity and the boundedness of solutions of the model were confirmed under reasonable restrictions of parameters. The stability analysis showed that there is a value of residence time at which an exchange of stability occurs between the trivial washout and non-washout solutions. This critical value depends only on the substrate feed concentration, biomass death rate, recycle ratio and purge fraction. Dynamic simulations of the model were carried out for substrate concentration in the range of 100–250 g/L, commonly used for the production of ethanol. An inverse response due to the inhibition effects of ethanol was observed in the time evolution of substrate and biomass concentrations. Parametric studies showed that ethanol concentration increases with the recycle ratio, with the inverse of residence time and with the inverse of purge fraction. The effect of ethanol latency has, on the other hand, a substantial effect on ethanol concentration. Despite its unstructured nature and the fact that some parameters such as temperature and acidity were not taken into consideration, the proposed model managed to provide useful results on the bioreactor-settler stability and the effect of key parameters on its dynamic behavior, which could pave the way for future optimization studies. Full article

(This article belongs to the Special Issue Bioethanol Production Processes)

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18 pages, 2203 KiB

Open AccessArticle

Optimised Fractionation of Brewer’s Spent Grain for a Biorefinery Producing Sugars, Oligosaccharides, and Bioethanol

by Soma Bedő, Margaréta Rozbach, Leonóra Nagy, Anikó Fehér and Csaba Fehér

Processes 2021, 9(2), 366; https://doi.org/10.3390/pr9020366 - 16 Feb 2021

Cited by 13 | Viewed by 3362

Abstract

Brewer’s spent grain (BSG) is the main by-product of the beer brewing process. It has a huge potential as a feedstock for bio-based manufacturing processes to produce high-value bio-products, biofuels, and platform chemicals. For the valorisation of BSG in a biorefinery process, efficient [...] Read more.

Brewer’s spent grain (BSG) is the main by-product of the beer brewing process. It has a huge potential as a feedstock for bio-based manufacturing processes to produce high-value bio-products, biofuels, and platform chemicals. For the valorisation of BSG in a biorefinery process, efficient fractionation and bio-conversion processes are required. The aim of our study was to develop a novel fractionation of BSG for the production of arabinose, arabino-xylooligomers, xylose, and bioethanol. A fractionation process including two-step acidic and enzymatic hydrolysis steps was investigated and optimised by a response surface methodology and a desirability function approach to fractionate the carbohydrate content of BSG. In the first acidic hydrolysis, high arabinose yield (76%) was achieved under the optimised conditions (90 °C, 1.85 w/w% sulphuric acid, 19.5 min) and an arabinose- and arabino-xylooligomer-rich supernatant was obtained. In the second acidic hydrolysis, the remaining xylan was solubilised (90% xylose yield) resulting in a xylose-rich hydrolysate. The last, enzymatic hydrolysis step resulted in a glucose-rich supernatant (46 g/L) under optimised conditions (15 w/w% solids loading, 0.04 g/g enzyme dosage). The glucose-rich fraction was successfully used for bioethanol production (72% ethanol yield by commercial baker’s yeast). The developed and optimised process offers an efficient way for the value-added utilisation of BSG. Based on the validated models, the amounts of the produced sugars, the composition of the sugar streams and solubilised oligo-saccharides are predictable and variable by changing the reaction conditions of the process. Full article

(This article belongs to the Special Issue Bioethanol Production Processes)

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15 pages, 1364 KiB

Open AccessArticle

Agro-Food Residues and Bioethanol Potential: A Study for a Specific Area

by Marina Basaglia, Massimiliano D’Ambra, Giuseppe Piubello, Veronica Zanconato, Lorenzo Favaro and Sergio Casella

Processes 2021, 9(2), 344; https://doi.org/10.3390/pr9020344 - 13 Feb 2021

Cited by 14 | Viewed by 3235

Abstract

Bioethanol obtained from agro-food wastes could contribute to decrease the dependency on fossil resources, reduce the impact of fossil fuels on the environment, and mitigate the food versus fuel debate. This study is aimed to investigate the availability of residual inexpensive agro-food biomasses [...] Read more.

Bioethanol obtained from agro-food wastes could contribute to decrease the dependency on fossil resources, reduce the impact of fossil fuels on the environment, and mitigate the food versus fuel debate. This study is aimed to investigate the availability of residual inexpensive agro-food biomasses that could feed a second-generation bioethanol plant located in a specific area of North Eastern Italy. After the identification of all crops in the area, more than 40 agro-food residues were analyzed for their availability and compositions in terms of water, polysaccharides, and sugars potentially convertible into bioethanol. 574,166 Mg of residual wet lignocellulosic biomass corresponding to 297,325 Mg of dry material were found available for bioethanol conversion. The most promising substrates were wheat straw and vine shoots. Based on the chemical composition of residues, the potential attainable ethanol was determined. Theoretical potential ethanol production was estimated at nearly 72,000 Mg per year. This quantity extensively exceeds the minimum yearly capacity of a sustainable bioethanol plant previously identified as around 50,000 Mg of ethanol. Taken together, these results demonstrate that, in the analyzed area, agro-food residues are available in an amount that could sustain bioethanol production in a specific and restricted district. Techno-economical evaluations are in progress to assess the actual feasibility of installing a second generation bioethanol production plant in the area of interest. Full article

(This article belongs to the Special Issue Bioethanol Production Processes)

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11 pages, 1226 KiB

Open AccessArticle

Novel Methods Using an Arthrobacter sp. to Create Anaerobic Conditions for Biobutanol Production from Sweet Sorghum Juice by Clostridium beijerinckii

by Chalida Daengbussadee, Lakkana Laopaiboon, Anuphon Kaewmaneewat, Likit Sirisantimethakom and Pattana Laopaiboon

Processes 2021, 9(1), 178; https://doi.org/10.3390/pr9010178 - 19 Jan 2021

Cited by 16 | Viewed by 2820

Abstract

Biobutanol can be produced by Clostridia via an acetone–butanol–ethanol (ABE) fermentation under strictly anaerobic conditions. Oxygen-free nitrogen (OFN) gas is typically used to create anaerobic conditions for ABE fermentations. However, this method is not appropriate for large-scale fermentations as it is quite costly. [...] Read more.

Biobutanol can be produced by Clostridia via an acetone–butanol–ethanol (ABE) fermentation under strictly anaerobic conditions. Oxygen-free nitrogen (OFN) gas is typically used to create anaerobic conditions for ABE fermentations. However, this method is not appropriate for large-scale fermentations as it is quite costly. The aim of this work was to study the feasibility of butanol production from sweet sorghum juice (SSJ) by Clostridium beijerinckii TISTR 1461 using various methods to create anaerobic conditions, i.e., growth of a strictly aerobic bacterium, an Arthrobacter sp., under different conditions and a chemical method using sodium dithionite (SDTN) to consume residual oxygen. SSJ containing 60 g/L of total sugar supplemented with 1.27 g/L of (NH₄)₂SO₄ was used as a substrate for butanol production. The results showed that 0.25 mM SDTN could create anaerobic conditions, but in this case, C.beijerinckii TISTR 1461 could produce butanol at a concentration (P_B) of only 8.51 g/L with a butanol productivity (Q_B) of 0.10 g/L·h. Arthrobacter sp. BCC 72131 could also be used to create anaerobic conditions. Mixed cultures of C.beijerinckii TISTR 1461 and Arthrobacter sp. BCC 72131 created anaerobic conditions by inoculating the C.beijerinckii 4 h after Arthrobacter. This gave a P_B of 10.39 g/L with a Q_B of 0.20 g/L·h. Comparing butanol production with the control treatment (using OFN gas to create anaerobic conditions, yielding a P_B of 9.88 g/L and Q_B of 0.21 g/L·h) indicated that using Arthrobacter sp. BCC 72131 was an appropriate procedure for creating anaerobic conditions for high levels of butanol production by C. beijerinckii TISTR 1461 from a SSJ medium. Full article

(This article belongs to the Special Issue Bioethanol Production Processes)

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15 pages, 909 KiB

Open AccessFeature PaperArticle

Hemicellulosic Bioethanol Production from Fast-Growing Paulownia Biomass

by Elena Domínguez, Pablo G. del Río, Aloia Romaní, Gil Garrote and Lucília Domingues

Processes 2021, 9(1), 173; https://doi.org/10.3390/pr9010173 - 19 Jan 2021

Cited by 17 | Viewed by 4005

Abstract

In order to exploit a fast-growing Paulownia hardwood as an energy crop, a xylose-enriched hydrolysate was obtained in this work to increase the ethanol concentration using the hemicellulosic fraction, besides the already widely studied cellulosic fraction. For that, Paulownia elongata x fortunei was [...] Read more.

In order to exploit a fast-growing Paulownia hardwood as an energy crop, a xylose-enriched hydrolysate was obtained in this work to increase the ethanol concentration using the hemicellulosic fraction, besides the already widely studied cellulosic fraction. For that, Paulownia elongata x fortunei was submitted to autohydrolysis treatment (210 °C or S₀ of 4.08) for the xylan solubilization, mainly as xylooligosaccharides. Afterwards, sequential stages of acid hydrolysis, concentration, and detoxification were evaluated to obtain fermentable sugars. Thus, detoxified and non-detoxified hydrolysates (diluted or not) were fermented for ethanol production using a natural xylose-consuming yeast, Scheffersomyces stipitis CECT 1922, and an industrial Saccharomyces cerevisiae MEC1133 strain, metabolic engineered strain with the xylose reductase/xylitol dehydrogenase pathway. Results from fermentation assays showed that the engineered S. cerevisiae strain produced up to 14.2 g/L of ethanol (corresponding to 0.33 g/g of ethanol yield) using the non-detoxified hydrolysate. Nevertheless, the yeast S. stipitis reached similar values of ethanol, but only in the detoxified hydrolysate. Hence, the fermentation data prove the suitability and robustness of the engineered strain to ferment non-detoxified liquor, and the appropriateness of detoxification of liquor for the use of less robust yeast. In addition, the success of hemicellulose-to-ethanol production obtained in this work shows the Paulownia biomass as a suitable renewable source for ethanol production following a suitable fractionation process within a biorefinery approach. Full article

(This article belongs to the Special Issue Bioethanol Production Processes)

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12 pages, 659 KiB

Open AccessArticle

Insights on Monosaccharides and Bioethanol Production from Sweet Sorghum Stalks Using Dilute Acid Pretreatment

by Cristian-Teodor Buruiană, Luminița Georgescu, Simona-Florina Isticioaia, Oana Emilia Constantin, Camelia Vizireanu, Rodica Mihaela Dinică and Bianca Furdui

Processes 2020, 8(11), 1486; https://doi.org/10.3390/pr8111486 - 18 Nov 2020

Cited by 6 | Viewed by 2120

Abstract

Sweet sorghum is a unique bioenergy crop that produces stalks with fermentable free sugars. The purpose of this study was to evaluate how the production of hemicellulosic saccharides and bioethanol from sweet sorghum stalks (SSS) can be influenced by a dilute sulfuric acid [...] Read more.

Sweet sorghum is a unique bioenergy crop that produces stalks with fermentable free sugars. The purpose of this study was to evaluate how the production of hemicellulosic saccharides and bioethanol from sweet sorghum stalks (SSS) can be influenced by a dilute sulfuric acid (H₂SO₄) pretreatment under different isothermal conditions. The bioethanol production from untreated SSS and pretreated solid phases was achieved through the Simultaneous Saccharification and Fermentation (SSF) process. A good SSS fractionation and an extensive hemicellulose hydrolysis into soluble saccharides were obtained, the most abundant hemicellulose-derived compounds present in the pretreated liquid phase being monosaccharides, with up to 17.22 g/L of glucose and 16.64 g/L of xylose in the pretreatments performed with 3% and 1% H₂SO₄ for 30 min at 134 °C, respectively. The SSF process of untreated SSS allowed a maximum bioethanol concentration of 9.78 g/L, corresponding to a maximum glucan conversion into ethanol of 49.8%. Bioethanol production from untreated SSS led to a higher bioethanol concentration and conversion than in the case of using acid pretreated solid phases obtained under the most severe conditions (with 3% H₂SO₄ for 30, 60 and 120 min at 134 °C), suggesting that, in the case of this biomass naturally rich in soluble sugars, the acidic pretreatment could negatively influence the fermentative process. Full article

(This article belongs to the Special Issue Bioethanol Production Processes)

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13 pages, 481 KiB

Open AccessArticle

Cellulosic Ethanol: Improving Cost Efficiency by Coupling Semi-Continuous Fermentation and Simultaneous Saccharification Strategies

by Patricia Portero Barahona, Bernardo Bastidas Mayorga, Jesús Martín-Gil, Pablo Martín-Ramos and Enrique Javier Carvajal Barriga

Processes 2020, 8(11), 1459; https://doi.org/10.3390/pr8111459 - 15 Nov 2020

Cited by 21 | Viewed by 3158

Abstract

A novel approach to improve ethanol production from sugarcane bagasse is proposed. Biomass was pretreated with sodium hydroxide, sulfuric, oxalic, and maleic acids (1% w/v) at different temperatures (130–170 °C) and times (10–30 min). The pretreatment with NaOH at 160 °C for [...] Read more.

A novel approach to improve ethanol production from sugarcane bagasse is proposed. Biomass was pretreated with sodium hydroxide, sulfuric, oxalic, and maleic acids (1% w/v) at different temperatures (130–170 °C) and times (10–30 min). The pretreatment with NaOH at 160 °C for 20 min was found to be the most efficient for further enzymatic saccharification. A semi-continuous fermentation system coupled with a simultaneous saccharification and fermentation strategy was used, attaining fermented liquor every 24 h. The amount of enzymes needed for saccharification was optimized, as well as the production time and ethanol concentration. The process occurred with near to complete depletion of glucose, obtaining ethanol concentrations ranging from 8.36 to 10.79% (v/v). The whole system, at bench scale, showed stability over 30 days, and ease of management and control. This strategy may improve cost efficiency in the production of cellulosic ethanol at industrial scale. Full article

(This article belongs to the Special Issue Bioethanol Production Processes)

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13 pages, 1176 KiB

Open AccessArticle

Techno-Economic Evaluation of Biorefineries Based on Low-Value Feedstocks Using the BioSTEAM Software: A Case Study for Animal Bedding

by Miguel Sanchis-Sebastiá, Joaquín Gomis-Fons, Mats Galbe and Ola Wallberg

Processes 2020, 8(8), 904; https://doi.org/10.3390/pr8080904 - 31 Jul 2020

Cited by 9 | Viewed by 4918

Abstract

Biofuels are still too costly to compete in the energy market and it has been suggested that low-value feedstocks could provide an opportunity for the production of low-cost biofuels; however, the lower quality of these feedstocks requires the introduction of a conditioning step [...] Read more.

Biofuels are still too costly to compete in the energy market and it has been suggested that low-value feedstocks could provide an opportunity for the production of low-cost biofuels; however, the lower quality of these feedstocks requires the introduction of a conditioning step in the biorefinery process. The aim of this study was to evaluate whether feedstock savings cover the cost of conditioning in the case of animal bedding. The BioSTEAM software was used to simulate a wheat straw biorefinery and an animal bedding biorefinery, whose economic performance was compared. The wheat straw biorefinery could deliver ethanol at a minimum selling price of USD 0.61 per liter, which is similar to prices in the literature. The cost of producing ethanol in the animal bedding biorefinery without water recycling was almost 40% higher, increasing the minimum selling price to USD 1.1 per liter of ethanol. After introducing water recycling in the conditioning step, the animal bedding biorefinery could deliver ethanol at a minimum selling price of USD 0.38 per liter, which is 40% lower than in the case of the wheat straw biorefinery. This demonstrates that low-value feedstocks can be used to reduce the biofuel price, as feedstock savings easily cover the additional conditioning cost. Full article

(This article belongs to the Special Issue Bioethanol Production Processes)

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10 pages, 598 KiB

Open AccessFeature PaperArticle

Production of Ethanol from Hemicellulosic Sugars of Exhausted Olive Pomace by Escherichia coli

by Juan Carlos López-Linares, Irene Gómez-Cruz, Encarnación Ruiz, Inmaculada Romero and Eulogio Castro

Processes 2020, 8(5), 533; https://doi.org/10.3390/pr8050533 - 1 May 2020

Cited by 20 | Viewed by 3981

Abstract

Exhausted olive pomace (EOP) is the main residue generated in olive oil industries, after the extraction of the residual oil from olive pomace with hexane. This work studies the ethanol production from hemicellulosic sugars of EOP. The fermentability of the sugar solution, resulting [...] Read more.

Exhausted olive pomace (EOP) is the main residue generated in olive oil industries, after the extraction of the residual oil from olive pomace with hexane. This work studies the ethanol production from hemicellulosic sugars of EOP. The fermentability of the sugar solution, resulting from the acid pretreatment of EOP, was evaluated using Escherichia coli SL100, although a detoxification step was required before fermentation. Overliming and activated charcoal detoxification were tested to minimize the presence of inhibitory compounds in the hydrolysate and to achieve a fermentable medium. E. coli assimilated all sugars in both detoxified hydrolysates and achieved ethanol yields of about 90% of the theoretical one. However, the fermentation time was much shorter when the hydrolysate had been detoxified with activated charcoal (20 h versus 120 h). Full article

(This article belongs to the Special Issue Bioethanol Production Processes)

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13 pages, 1219 KiB

Open AccessFeature PaperArticle

Biorefining Oat Husks into High-Quality Lignin and Enzymatically Digestible Cellulose with Acid-Catalyzed Ethanol Organosolv Pretreatment

by Rushab Chopda, Jorge A. Ferreira and Mohammad J. Taherzadeh

Processes 2020, 8(4), 435; https://doi.org/10.3390/pr8040435 - 7 Apr 2020

Cited by 16 | Viewed by 5185

Abstract

Oat husks are low-value lignocellulosic residues of oat processing that carry an environmental impact. Their polymers (cellulose, hemicellulose, and lignin) can be converted into a wide variety of value-added products; however, efficient pretreatment methods are needed that allow their fine separation for further [...] Read more.

Oat husks are low-value lignocellulosic residues of oat processing that carry an environmental impact. Their polymers (cellulose, hemicellulose, and lignin) can be converted into a wide variety of value-added products; however, efficient pretreatment methods are needed that allow their fine separation for further tailored valorization. This study pioneered the use of milling-free and low acid-catalyzed ethanol organosolv for the delignification of oat husks, allowing their conversion into three high-quality streams, namely, glucan-rich, lignin-rich, and hemicellulosic compound-rich streams. Temperature, retention time, and solid-to-liquid ratio were found to impact the delignification of oat husks when using a one-factor-at-a-time strategy. The ideal conditions that were found (210 °C, 90 min, and solid-to-liquid ratio of 1:2) culminated into glucan and lignin fractions containing 74.5% ± 11.4% glucan and 74.9% ± 7.6% lignin, respectively. These high-purity lignin fractions open the possibility for higher value applications by lignin, potentially impacting the feasibility of second generation biorefineries. The glucan fraction showed 90% digestibility after 48 h of hydrolysis with 10 filter paper units of enzyme cocktail per gram of glucan. Considering the absence of size reduction and high solid loading, together with the quality of the obtained streams, organosolv pretreatment could be a potential strategy for the valorization of oat lignocellulosic residues. Full article

(This article belongs to the Special Issue Bioethanol Production Processes)

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36 pages, 60001 KiB

Open AccessArticle

Adsorption and Separation of the H²O/H²SO₄ and H²O/C²H₅OH Mixtures: A Simulated and Experimental Study

by Jesse Y. Rumbo Morales, Alan F. Perez Vidal, Gerardo Ortiz Torres, Alexis U. Salas Villalobo, Felipe de J. Sorcia Vázquez, Jorge A. Brizuela Mendoza, Miguel De-la-Torre and Jorge S. Valdez Martínez

Processes 2020, 8(3), 290; https://doi.org/10.3390/pr8030290 - 4 Mar 2020

Cited by 17 | Viewed by 6126

Abstract

Adsorption processes are characterized by their kinetics and equilibrium isotherms described by mathematical models. Nowadays, adsorption with molecular sieves is a method used to separate certain elements or molecules from a mixture and produce hydrogen, nitrogen, oxygen, ethanol, or water treatment. This study [...] Read more.

Adsorption processes are characterized by their kinetics and equilibrium isotherms described by mathematical models. Nowadays, adsorption with molecular sieves is a method used to separate certain elements or molecules from a mixture and produce hydrogen, nitrogen, oxygen, ethanol, or water treatment. This study had two main objectives. The first one was focused on the use of different natural (Clinoptilolite-S.L. Potosi, Clinoptilolite-Puebla, and Heulandite-Sonora) and synthetic (Zeolite Type 3A) adsorbents to separate the mixtures

H_{2} O / H_{2} S O_{4}

and

H_{2} O / C_{2} H_{5} O H

. It was determined that both Zeolite Type-3A and Heulandite-Sonora have greater adsorption capacity in a shorter time compared with the Clinoptilolites at different temperatures. The second objective was the simulation of a pressure swing adsorption process to dehydrate ethanol using the parameters obtained from Zeolite Type 3A (with maximum adsorption capacity). Several configurations were considered to calculate the appropriate nominal values for the optimal process. The results illustrate that the purity of ethanol is increased when the following parameters are considered in the adsorption process: a high pressure, a constant temperature between 100 and 120

^{°}

C, a feed composition near the azeotropic point with lower water content, and a purge pressure near the vacuum. Finally, the results show that it is possible to take advantage of the length of the absorber bed in order to reduce the energy costs by increasing the ethanol production as well as complying with the international purity standards. Full article

(This article belongs to the Special Issue Bioethanol Production Processes)

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Open AccessReview

Biorefinery Gets Hot: Thermophilic Enzymes and Microorganisms for Second-Generation Bioethanol Production

by Luca Zuliani, Annabel Serpico, Mario De Simone, Nicola Frison and Salvatore Fusco

Processes 2021, 9(9), 1583; https://doi.org/10.3390/pr9091583 - 3 Sep 2021

Cited by 20 | Viewed by 4910

Abstract

To mitigate the current global energy and the environmental crisis, biofuels such as bioethanol have progressively gained attention from both scientific and industrial perspectives. However, at present, commercialized bioethanol is mainly derived from edible crops, thus raising serious concerns given its competition with [...] Read more.

To mitigate the current global energy and the environmental crisis, biofuels such as bioethanol have progressively gained attention from both scientific and industrial perspectives. However, at present, commercialized bioethanol is mainly derived from edible crops, thus raising serious concerns given its competition with feed production. For this reason, lignocellulosic biomasses (LCBs) have been recognized as important alternatives for bioethanol production. Because LCBs supply is sustainable, abundant, widespread, and cheap, LCBs-derived bioethanol currently represents one of the most viable solutions to meet the global demand for liquid fuel. However, the cost-effective conversion of LCBs into ethanol remains a challenge and its implementation has been hampered by several bottlenecks that must still be tackled. Among other factors related to the challenging and variable nature of LCBs, we highlight: (i) energy-demanding pretreatments, (ii) expensive hydrolytic enzyme blends, and (iii) the need for microorganisms that can ferment mixed sugars. In this regard, thermophiles represent valuable tools to overcome some of these limitations. Thus, the aim of this review is to provide an overview of the state-of-the-art technologies involved, such as the use of thermophilic enzymes and microorganisms in industrial-relevant conditions, and to propose possible means to implement thermophiles into second-generation ethanol biorefineries that are already in operation. Full article

(This article belongs to the Special Issue Bioethanol Production Processes)

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30 pages, 1220 KiB

Open AccessFeature PaperReview

Advanced Bioethanol Production: From Novel Raw Materials to Integrated Biorefineries

by Aleta Duque, Cristina Álvarez, Pablo Doménech, Paloma Manzanares and Antonio D. Moreno

Processes 2021, 9(2), 206; https://doi.org/10.3390/pr9020206 - 22 Jan 2021

Cited by 103 | Viewed by 12143

Abstract

The production of so-called advanced bioethanol offers several advantages compared to traditional bioethanol production processes in terms of sustainability criteria. This includes, for instance, the use of nonfood crops or residual biomass as raw material and a higher potential for reducing greenhouse gas [...] Read more.

The production of so-called advanced bioethanol offers several advantages compared to traditional bioethanol production processes in terms of sustainability criteria. This includes, for instance, the use of nonfood crops or residual biomass as raw material and a higher potential for reducing greenhouse gas emissions. The present review focuses on the recent progress related to the production of advanced bioethanol, (i) highlighting current results from using novel biomass sources such as the organic fraction of municipal solid waste and certain industrial residues (e.g., residues from the paper, food, and beverage industries); (ii) describing new developments in pretreatment technologies for the fractionation and conversion of lignocellulosic biomass, such as the bioextrusion process or the use of novel ionic liquids; (iii) listing the use of new enzyme catalysts and microbial strains during saccharification and fermentation processes. Furthermore, the most promising biorefinery approaches that will contribute to the cost-competitiveness of advanced bioethanol production processes are also discussed, focusing on innovative technologies and applications that can contribute to achieve a more sustainable and effective utilization of all biomass fractions. Special attention is given to integrated strategies such as lignocellulose-based biorefineries for the simultaneous production of bioethanol and other high added value bioproducts. Full article

(This article belongs to the Special Issue Bioethanol Production Processes)

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45 pages, 2320 KiB

Open AccessFeature PaperReview

Process Strategies for the Transition of 1G to Advanced Bioethanol Production

by Ana Susmozas, Raquel Martín-Sampedro, David Ibarra, María E. Eugenio, Raquel Iglesias, Paloma Manzanares and Antonio D. Moreno

Processes 2020, 8(10), 1310; https://doi.org/10.3390/pr8101310 - 19 Oct 2020

Cited by 73 | Viewed by 11681

Abstract

Nowadays, the transport sector is one of the main sources of greenhouse gas (GHG) emissions and air pollution in cities. The use of renewable energies is therefore imperative to improve the environmental sustainability of this sector. In this regard, biofuels play an important [...] Read more.

Nowadays, the transport sector is one of the main sources of greenhouse gas (GHG) emissions and air pollution in cities. The use of renewable energies is therefore imperative to improve the environmental sustainability of this sector. In this regard, biofuels play an important role as they can be blended directly with fossil fuels and used in traditional vehicles’ engines. Bioethanol is the most used biofuel worldwide and can replace gasoline or form different gasoline-ethanol blends. Additionally, it is an important building block to obtain different high added-value compounds (e.g., acetaldehyde, ethylene, 1,3-butadiene, ethyl acetate). Today, bioethanol is mainly produced from food crops (first-generation (1G) biofuels), and a transition to the production of the so-called advanced ethanol (obtained from lignocellulosic feedstocks, non-food crops, or industrial waste and residue streams) is needed to meet sustainability criteria and to have a better GHG balance. This work gives an overview of the current production, use, and regulation rules of bioethanol as a fuel, as well as the advanced processes and the co-products that can be produced together with bioethanol in a biorefinery context. Special attention is given to the opportunities for making a sustainable transition from bioethanol 1G to advanced bioethanol. Full article

(This article belongs to the Special Issue Bioethanol Production Processes)

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