Biofuels Production and Processing Technology 2.0

A special issue of Fermentation (ISSN 2311-5637). This special issue belongs to the section "Industrial Fermentation".

Deadline for manuscript submissions: closed (20 August 2023) | Viewed by 18559

Special Issue Editor

Special Issue Information

Dear Colleagues,

The negative global warming impact and global environmental pollution due to fossil fuels mean that the main challenge of modern society is finding alternatives to conventional fuels. In this scenario, biofuels derived from renewable biomass represent the most promising renewable energy sources. Depending on the biomass used by the fermentation technologies, it is possible to obtain first-generation biofuels produced from food crops, second-generation biofuels produced from non-food feedstocks (mainly originating from renewable lignocellulosic biomasses), and third-generation biofuels (represented by algae or food waste biomass).

Although biofuels appear to be the closest alternative to fossil fuels, it is necessary for them to be produced in competitive quantities and costs, requiring both improvements to production technologies and diversification of feedstock.

This topic is representing an interesting challenge for both the scientific and industrial world, and many efforts are still required in this field in order to reduce the negative global warming impact and global environmental pollution due to fossil fuels, in accordance with the environmentally sustainable development.

This Special Issue will focus on the development of new technologies and the implementation of new feedstock suitable for biofuels production, as well as different biomass pretreatments, fermentation strategies, different applied microorganisms used as monoculture or coculture, and different setups for biofuel fermentation processes. Moreover research on economic feasibility is also encouraged.

Therefore, I would like to invite authors to submit original innovative research articles and review papers related to the potential topics of the “Biofuels Production and Processing Technology 2.0” Special Issue.

Dr. Alessia Tropea
Guest Editor

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • biofuel production technologies
  • downstream processing
  • upstream processing
  • biorefinery
  • energy
  • bioethanol production
  • agroforest and industrial waste feedstock valorization
  • microorganisms for biofuel
  • sustainability

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Published Papers (10 papers)

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Research

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22 pages, 4596 KiB  
Article
Rapid Dilute Sulfuric Acid Hydrolysis of Soy Flour to Amino Acids for Microbial Processes and Biorefining
Fermentation 2023, 9(12), 1028; https://doi.org/10.3390/fermentation9121028 - 16 Dec 2023
Viewed by 973
Abstract
Amino acids have relevance in biorefining as fermentation nutrients but also as valued coproducts obtainable from plant biomass. Soy flour was studied as a representative low-cost protein source requiring hydrolysis to free primary amino acids for utilization. Within the context of biorefining, process [...] Read more.
Amino acids have relevance in biorefining as fermentation nutrients but also as valued coproducts obtainable from plant biomass. Soy flour was studied as a representative low-cost protein source requiring hydrolysis to free primary amino acids for utilization. Within the context of biorefining, process schemes, reactant concentrations, times, and temperatures were varied to explore the efficiency of dilute sulfuric acid hydrolysis of soy flour to release amino acids. Two process strategies were optimized. Either soy flour was co-processed with switchgrass biomass using a dilute-acid pretreatment, or it was hydrolyzed alone with dilute acid. Significant improvement to hydrolysate fermentability was accomplished by adding 2.5–10 g/L soy flour to switchgrass pretreatment with dilute sulfuric acid (0.936% v/v) for 15 min at 160 °C. This practice optimized accumulation of neutral sugars and resulted in a 25% reduction in furfural while boosting xylose 7% and up to doubling primary amino nitrogen (PAN), as compared to no soy flour addition to switchgrass pretreatment. When soy flour was hydrolyzed alone, PAN titers were optimized to 1588 mg N/L (9.9 g amino acids/L) and yield to 0.0529 g PAN/g flour (61% of theoretical) using a 10% (v/v) (1.8 M) sulfuric acid hydrolysis 30 min at 160 °C. Full article
(This article belongs to the Special Issue Biofuels Production and Processing Technology 2.0)
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16 pages, 3596 KiB  
Article
Batch Simultaneous Saccharification and Fermentation of Primary Sludge at Very High Solid Concentrations for Bioethanol Production
Fermentation 2023, 9(10), 888; https://doi.org/10.3390/fermentation9100888 - 30 Sep 2023
Viewed by 798
Abstract
A sustainable industrial future involves the exploitation of renewable resources to obtain a wide diversity of products and energy and the decrease of waste generation. Primary sludge (PS) from pulp and paper mills is a lignocellulosic residue mainly consisting of cellulose and hemicelluloses [...] Read more.
A sustainable industrial future involves the exploitation of renewable resources to obtain a wide diversity of products and energy and the decrease of waste generation. Primary sludge (PS) from pulp and paper mills is a lignocellulosic residue mainly consisting of cellulose and hemicelluloses that can be converted to bioethanol. In the present work, bioethanol was produced from untreated PS by simultaneous saccharification and fermentation (SSF). Studies were carried out on initial solid concentration, yeast inoculum percentage, cellulolytic enzyme dosage, and co-application of two enzyme complexes (cellulolytic NS 22192 and xylanolytic Cellic® HTec2, Bagsværd, Denmark). Increasing solid content up to 22% improved ethanol concentration (59.1 g L−1), productivity (1.97 g L−1 h−1), and yield (86.3%); however, at the maximum solid concentration (28%), both yield and productivity decreased. At the highest solid concentration, a decrease of 33% in the cellulolytic enzyme dosage was observed (compared to reference enzyme loadings). The co-application of the two enzyme complexes had a positive effect on PS conversion efficiency. When a preliminary scale-up strategy was implemented from 50 mL to 2.5 L at 22% solids concentration, similar results were obtained despite the initial mixing difficulties of the heterogeneous system. Full article
(This article belongs to the Special Issue Biofuels Production and Processing Technology 2.0)
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23 pages, 3036 KiB  
Article
Influence of Different Angles in the Photobioreactor on Algal Biomass Growth with Optimized Poultry Excreta Leachate: A Batch-Scale Study
Fermentation 2023, 9(3), 265; https://doi.org/10.3390/fermentation9030265 - 07 Mar 2023
Cited by 2 | Viewed by 1284
Abstract
In this study, the influence of solar inclination angles on biomass growth and the biomolecule profile of Chlorella pyrenoidosa (C. pyrenoidosa) were analyzed in the vertical flat–panel photobioreactor (FPPBR). The growth of C. pyrenoidosa was analyzed at three different solar inclination [...] Read more.
In this study, the influence of solar inclination angles on biomass growth and the biomolecule profile of Chlorella pyrenoidosa (C. pyrenoidosa) were analyzed in the vertical flat–panel photobioreactor (FPPBR). The growth of C. pyrenoidosa was analyzed at three different solar inclination angles (32.9°, 47.9°, and 90°) in a natural open environment with BG-11 medium and poultry excreta leachate (PEL). The maximum yield of biomass was obtained at 2.40 g/L with PEL and 1.45 g/L with BG-11 medium at a solar inclination angle of 47.9°. The biomass yield with PEL and BG-11 was 5.09–10.26%, 3.94–5.72%, respectively, while biomass productivity with PEL and BG-11 was 5.27–10.63%, 4.06–5.90% higher at a solar inclination angle of 47.9° as compared to 32.9°. The average temperature and radiation of FPPBR were recorded ≈3.90 ± 0.40% and ≈17.28 ± 2.23% higher at a solar inclination angle of 47.9° as compared to a solar inclination angle of 32.9°. The inclined radiation was acquired the maximum area of FPPBR. Results indicated that solar inclination angles enhanced the productivity of algae in FPPBR. Full article
(This article belongs to the Special Issue Biofuels Production and Processing Technology 2.0)
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14 pages, 2073 KiB  
Article
Effect of Laccase Detoxification on Bioethanol Production from Liquid Fraction of Steam-Pretreated Olive Tree Pruning
Fermentation 2023, 9(3), 214; https://doi.org/10.3390/fermentation9030214 - 23 Feb 2023
Cited by 4 | Viewed by 1426
Abstract
During lignocellulosic bioethanol production, the whole slurry obtained by steam explosion is filtered, generating a water-insoluble fraction rich in cellulose which is used for saccharification and ethanol fermentation, as well as a liquid fraction containing solubilised glucose and xylose but also some inhibitory [...] Read more.
During lignocellulosic bioethanol production, the whole slurry obtained by steam explosion is filtered, generating a water-insoluble fraction rich in cellulose which is used for saccharification and ethanol fermentation, as well as a liquid fraction containing solubilised glucose and xylose but also some inhibitory by-products (furan derivatives, weak acids and phenols), which limits its use for this purpose. Since utilization of this liquid fraction to ethanol is essential for an economically feasible cellulosic ethanol process, this work studied a laccase from Myceliophthora thermophila to detoxify the liquid fraction obtained from steam-pretreated olive tree pruning (OTP) and to overcome the effects of these inhibitors. Then, the fermentation of laccase-treated liquid fraction was evaluated on ethanol production by different Saccharomyces cerevisiae strains, including the Ethanol Red, with the capacity to ferment glucose but not xylose, and the xylose-fermenting recombinant strain F12. Laccase treatment reduced total phenols content by 87% from OTP liquid fraction, not affecting furan derivatives and weak acids concentration. Consequently, the fermentative behavior of both Ethanol Red and F12 strains was improved, and ethanol production and yields were increased. Moreover, F12 strain was capable of utilizing some xylose, which increased ethanol production (10.1 g/L) compared to Ethanol Red strain (8.6 g/L). Full article
(This article belongs to the Special Issue Biofuels Production and Processing Technology 2.0)
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10 pages, 2482 KiB  
Article
Effect of Corn Straw on Hydrogen Production from Lignite
Fermentation 2023, 9(2), 106; https://doi.org/10.3390/fermentation9020106 - 23 Jan 2023
Cited by 1 | Viewed by 1284
Abstract
The conversion of lignite to clean energy has won considerable attention and plays an important role in achieving the goal of carbon reduction. The effects of corn straw on hydrogen production from lignite was explored by using lignite as the substrate and corn [...] Read more.
The conversion of lignite to clean energy has won considerable attention and plays an important role in achieving the goal of carbon reduction. The effects of corn straw on hydrogen production from lignite was explored by using lignite as the substrate and corn straw as an exogenous substance. The fermentation mechanism was elucidated through the analysis of total and daily hydrogen production; the concentration of humic acid, benzoic acid, pyruvate, and glucose, as well as pH value. In addition, total solid (TS), and volatile solid (VS) from activated sludge before and after fermentation are examined. The results showed that corn straw could accelerate hydrogen production from lignite with an optimal content of corn straw of 40%. The fermentative hydrogen production with 40% corn straw was up to 186.20 mL, 3.40 times higher than that of the control group. Corn straw effectively improved the concentration of humic acid and benzoic acid, accelerating the anaerobic fermentation of lignite to produce hydrogen. The concentration of pyruvic acid, glucose, pH, and the changes in TS and VS before and after fermentation showed that the group of 40% corn straw had a better promotion effect than other systems for hydrogen production. This provides a new idea for improving hydrogen production through lignite anaerobic fermentation. Full article
(This article belongs to the Special Issue Biofuels Production and Processing Technology 2.0)
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15 pages, 1776 KiB  
Article
Evaluation of Laminaria Digitata Hydrolysate for the Production of Bioethanol and Butanol by Fermentation
Fermentation 2023, 9(1), 59; https://doi.org/10.3390/fermentation9010059 - 11 Jan 2023
Cited by 2 | Viewed by 1727
Abstract
Seaweeds (macroalgae) are gaining attention as potential sustainable feedstock for the production of fuels and chemicals. This comparative study focuses on the characterization of the microbial production of alcohols from fermentable carbohydrates in the hydrolysate of the macroalgae Laminaria digitata as raw material. [...] Read more.
Seaweeds (macroalgae) are gaining attention as potential sustainable feedstock for the production of fuels and chemicals. This comparative study focuses on the characterization of the microbial production of alcohols from fermentable carbohydrates in the hydrolysate of the macroalgae Laminaria digitata as raw material. The potential of a hydrolysate as a carbon source for the production of selected alcohols was tested, using three physiologically different fermentative microbes, in two main types of processes. For the production of ethanol, Saccharomyces cerevisiae was used as a benchmark microorganism and compared with the strictly anaerobic thermophile Thermoanaerobacterium strain AK17. For mixed production of acetone/isopropanol, butanol, and ethanol (A/IBE), three strictly anaerobic Clostridium strains were compared. All strains grew well on the hydrolysate, and toxicity constraints were not observed, but fermentation performance and product profiles were shown to be both condition- and strain-specific. S. cerevisiae utilized only glucose for ethanol formation, while strain AK17 utilized glucose, mannitol, and parts of the glucan oligosaccharides. The clostridia strains tested showed different nutrient requirements, and were able to utilize glucan, mannitol, and organic acids in the hydrolysate. The novelty of this study embodies the application of different inoculates for fermenting a common brown seaweed found in the northern Atlantic Ocean. It provides important information on the fermentation properties of different microorganisms and pinpoints the value of carbon source utilization when selecting microbes for efficient bioconversion into biofuel and chemical products of interest. Full article
(This article belongs to the Special Issue Biofuels Production and Processing Technology 2.0)
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16 pages, 1661 KiB  
Article
Integration of Dark Fermentation with Microbial Electrolysis Cells for Biohydrogen and Methane Production from Distillery Wastewater and Glycerol Waste Co-Digestion
Fermentation 2022, 8(10), 537; https://doi.org/10.3390/fermentation8100537 - 13 Oct 2022
Cited by 3 | Viewed by 2285
Abstract
This study aimed to enhance dark fermentative hydrogen production from co-digestion of distillery wastewater (DW) and glycerol waste (GW) through integration with microbial electrolysis cells. First, the optimal proportion of DW and GW in hydrogen production was investigated in batch mode. The results [...] Read more.
This study aimed to enhance dark fermentative hydrogen production from co-digestion of distillery wastewater (DW) and glycerol waste (GW) through integration with microbial electrolysis cells. First, the optimal proportion of DW and GW in hydrogen production was investigated in batch mode. The results show that DW and GW co-digestion at a ratio of 99:1 (% v/v) gave the highest hydrogen yield of 149.5 mL-H2/g − VSadded. Continuous hydrogen production using the optimal proportion was conducted in a continuously stirred tank reactor. As a result, a maximal hydrogen yield of 99.7 mL-H2/g − VSadded was achieved, and the dominant hydrogen-producing bacterium was Clostridium sensu stricto 7. The dark fermentation effluent from the continuously stirred tank reactor was later used to produce methane using batch MECs. The maximum methane yield of 115.1 mL-CH4/g − VSadded was obtained under an applied voltage of 1 V and continuous stirring at 120–140 rpm. Microbial community analysis revealed that Metahnobacterium, Methanomethylovorans, Methanoculleus, and Methanosarcina were the methanogenic archaea in the microbial electrolysis cell reactor. Full article
(This article belongs to the Special Issue Biofuels Production and Processing Technology 2.0)
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21 pages, 4148 KiB  
Article
Increasing Biomethane Production in MSW Anaerobic Digestion Process by Chemical and Thermal Pretreatment and Process Commercialization Evaluation
Fermentation 2022, 8(9), 463; https://doi.org/10.3390/fermentation8090463 - 16 Sep 2022
Cited by 1 | Viewed by 1749
Abstract
One of the methods of municipal waste disposal and energy production is anaerobic digestion. This study investigates the effect of thermal and chemical pretreatment on the anaerobic digester’s biomethane production. The optimal condition was evaluated using RSM in two modes: maximum and minimum [...] Read more.
One of the methods of municipal waste disposal and energy production is anaerobic digestion. This study investigates the effect of thermal and chemical pretreatment on the anaerobic digester’s biomethane production. The optimal condition was evaluated using RSM in two modes: maximum and minimum use of H2O2. The optimal state was obtained in the first case under 110.8 °C, 4.63% NaOH, 8% H2O2, and 111.9 °C, 4.47% NaOH, 2% H2O2 in the second case. Experimental results obtained 77%, 76.6% VS (volatile solid) reduction, and 89.1%, 88.7% SCOD (soluble chemical oxygen demand) reduction in the two optimum conditions, respectively. Experiment results were extrapolated to dry industrial digesters using a factor of 0.89% and durations including 30 days and 25 days. Then, the processes of biogas improvement were simulated. After biogas improvement, the economic analysis of the process was conducted with the definition of various scenarios. It was determined that, at current prices, pretreatment is not economically viable and that, with an increase in electricity prices to 0.09 $/kWh and 0.145 $/kWh, the digestion process with a NaOH 4.47% 112 °C pretreatment, chemical scrubbing, and digestion with NaOH 4.47% 112 °C, 2% H2O2 are sequentially economically viable. Full article
(This article belongs to the Special Issue Biofuels Production and Processing Technology 2.0)
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Review

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15 pages, 635 KiB  
Review
Characteristics of Substrates Used for Biogas Production in Terms of Water Content
Fermentation 2023, 9(5), 449; https://doi.org/10.3390/fermentation9050449 - 09 May 2023
Cited by 5 | Viewed by 3274
Abstract
New technologies based on the anaerobic digestion process make it possible to manage problematic waste. Methane efficiency depends largely on the level of the hydration of the substrates used for biogas production and their ability to decompose easily. The aim of this study [...] Read more.
New technologies based on the anaerobic digestion process make it possible to manage problematic waste. Methane efficiency depends largely on the level of the hydration of the substrates used for biogas production and their ability to decompose easily. The aim of this study was to present the current state of knowledge and practices in substrate hydration characteristics, focusing on pretreatment methods as the preferred method for improving efficiency. The paper discusses issues related to the degree of hydration of substrates in the context of their use in biogas plants. Reference was also made to topics related to the transportation and logistics of raw material supply regarding environmental impact. Biogas plant projects should be expanded to include an element related to assessing the impact of raw material deliveries on the immediate environment. Previous papers have not sufficiently analyzed the aspect related to the hydration of substrates used in anaerobic digestion processes. The presented and discussed research results can be implemented to optimize biogas plant water management processes. By replacing standard feedstock transportation methods with a pipeline, the environmental impact can be reduced by nearly ten times. Full article
(This article belongs to the Special Issue Biofuels Production and Processing Technology 2.0)
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29 pages, 1918 KiB  
Review
Microbial Behavior and Influencing Factors in the Anaerobic Digestion of Distiller: A Comprehensive Review
Fermentation 2023, 9(3), 199; https://doi.org/10.3390/fermentation9030199 - 21 Feb 2023
Cited by 6 | Viewed by 2293
Abstract
Anaerobic digestion technology is regarded as the most ideal technology for the treatment of a distiller in terms of environmental protection, resource utilization, and cost. However, there are some limitations to this process, the most prominent of which is microbial activity. The purpose [...] Read more.
Anaerobic digestion technology is regarded as the most ideal technology for the treatment of a distiller in terms of environmental protection, resource utilization, and cost. However, there are some limitations to this process, the most prominent of which is microbial activity. The purpose of this paper is to provide a critical review of the microorganisms involved in the anaerobic digestion process of a distiller, with emphasis on the archaea community. The effects of operating parameters on microbial activity and process, such as pH, temperature, TAN, etc., are discussed. By understanding the activity of microorganisms, the anaerobic treatment technology of a distiller can be more mature. Aiming at the problem that anaerobic treatment of a distiller alone is not effective, the synergistic effect of different substrates is briefly discussed. In addition, the recent literature on the use of microorganisms to purify a distiller was collected in order to better purify the distiller and reduce harm. In the future, more studies are needed to elucidate the interactions between microorganisms and establish the mechanisms of microbial interactions in different environments. Full article
(This article belongs to the Special Issue Biofuels Production and Processing Technology 2.0)
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