Biofuel Production Process Research Articles

Microbial Beta Glucosidase Enzymes: Recent Advances in Biomass Conversation for Biofuels Application.

The biomass to biofuels production process is green, sustainable, and an advanced technique to resolve the current environmental issues generated from fossil fuels. The production of biofuels from biomass is an enzyme mediated process, wherein β-glucosidase (BGL) enzymes play a key role in biomass hydrolysis by producing monomeric sugars from cellulose-based oligosaccharides. However, the production and availability of these enzymes realize their major role to increase the overall production cost of biomass to biofuels production technology. Therefore, the present review is focused on evaluating the production and efficiency of β-glucosidase enzymes in the bioconversion of cellulosic biomass for biofuel production at an industrial scale, providing its mechanism and classification. The application of BGL enzymes in the biomass conversion process has been discussed along with the recent developments and existing issues. Moreover, the production and development of microbial BGL enzymes have been explained in detail, along with the recent advancements made in the field. Finally, current hurdles and future suggestions have been provided for the future developments. This review is likely to set a benchmark in the area of cost effective BGL enzyme production, specifically in the biorefinery area.

Green energy from brown seaweed: Sustainable polygeneration industrial process via fast pyrolysis of S. Japonica combined with the Brayton cycle

Carbohydrate-rich and fast-growing seaweeds such as the S. japonica species are increasingly becoming the 3rd generation biomass of choice. Environmentally friendly as well as economically sound processes for biofuel production are essential if the benefits of these novel marine feedstocks are to be harnessed. This study features an experiment-based process design that combines a fluidized bed fast pyrolysis reactor system, non-intensive pretreatment, and a Bryton power cycle in an, energy-wise, nearly self-sustainable system, considerably reducing the utilization of fossil fuel-derived utilities. Complex liquid products of pyrolysis and catalytic upgrading were modeled using a specialized software ensuring strict adherence to experimental data, hence retaining a highly realistic simulation. Results of comprehensive techno-economic and market uncertainty assessments have shown a capital investment of 170 mil. USD, and a minimum selling price range of 1.534–1.852 USD/L. When compared to traditional oil and gas extraction and refining processes, the designed process yielded a 12.8-fold reduction of the total CO2 emitted, indicating a superior process in terms of environmental sustainability.

Performance of Bimetallic Fe and Co Catalyst Supported on HZSM-5 for Fischer-Tropsch Synthesis

Fischer-Tropsch synthesis is a polymerization reaction which produces various products such as paraffin, olefins, alcohols, and aldehydes. The purpose of this study was to determine the performance of Fe and Co bimetallic catalysts with the support of HZSM-5 for Fischer-Tropsch synthesis. This study consists of two stages. The first stage was started by making a mesopore sized HZSM-5 catalyst through desilication, then impregnated with bimetallic Fe and Co which acted as a promoter. The impregnation method used was the incipient wetness impregnation. In the impregnation, process variations were made in the ratio of Fe to Co 1:9 and 2:8 metal loading was 10%. The Fe-Co catalyst / HZSM-5 was analyzed for characterization and activity tests. The characteristic tests were BET, XRD, FTIR, and EDX. The second stage was activity test of Fe-Co / HZSM-5 catalyst in the biofuel production process from syngas through Fischer-Tropsch reaction: The best performance catalyst was used for the biofuel production process. Fischer-Tropsch process was carried out in a fixed bed reactor, with an operating temperature of 200, 225, 250 °C carried out for 100 hours in one run, then analysis of product composition by GC-MS.

Numerical Validation of a Pressurized Batch Reactor for In-Situ Transesterification

Subcritical in-situ transesterification is one of the more recently developed processes that consumes less energy and is more environmental friendly than conventional methods. Diving deeper into this process, the fluid dynamics of the liquid mixture is an area of interest not studied before due to the solid, thick metal enclosure of the reactor vessel. Previous studies observed that the mixing characteristics of the agitator being used influences biodiesel yield. As commercialization of this biofuel production process is of importance in order to contribute to biofuel demand in a nation-wide scale, this study considers a reactor vessel working volume of around 1.5L, which is relatively larger than typical laboratory batch-type sizes. A numerical validation study, through mesh analyses, was performed to produce a numerically accurate model for the study. Factoring in computational time and accuracy of the solution, a steady state, multiphase model running the standard k-∈ turbulence model was chosen. The Multiple Reference Frames approach was used for the steady state condition to be met. The validation model is of a 6.3L-volume cylinder with baffles. Glass beads served as the solids and water as the liquid in the system. The first mesh analysis was performed by comparing 11 unique mesh models. The model with a relevance of fine 30 was seen to have the closest data fit with the experimental data. It was seen that only when using the size function ‘proximity’ showed a slightly different velocity profile among the models. The second mesh analysis was conducted to check if the chosen mesh setting would affect this study’s smaller reactor geometry before the main study’s simulations are to be conducted. The model with baffle’s percent error at the specified point was at an acceptable 8.2%, and its resultant velocity profile’s is at 23.5% which is around the same range as that of the 1st mesh analysis’ models. With this, the numerical model developed was deemed to be applicable for the main study.

Experimental analysis and preliminary assessment of an integrated thermochemical process for production of low-molecular weight biofuels from municipal solid waste (MSW)

This work explores the use of advanced thermal technologies for the conversion of refuse derived fuel prepared from MSW into clean syngas suitable for catalytic transformation into light hydrocarbon products. In particular, the possibilities for the specific production of C1–C4 hydrocarbons utilising a good quality syngas produced by two-stage plasma assisted gasification method are investigated. A number of catalytic tests were prepared with modified chemistry to evaluate the preliminary component activities on real waste-derived syngas. C1–C4 paraffins formed in all cases as a main products, with different product distribution for different conditions examined (up to 95% bioSNG on hydrocarbon product for supported nickel, 40% bioLPG for Cu–Zn/ZSM-5 catalysts mix). CO2 was the main byproduct with outlet concentrations ranging from 10 to 50% in volume. When increasing H2:CO in the syngas by external addition of hydrogen, CO conversion increases, as well as paraffin selectivity and hydrocarbons yield. Projections on a 65 MW thermal input bioSNG plant show that if 40 MW of electrical output from renewable sources are used to power a PEM stack during high power availability, the production of bioSNG could be increased by more than 33%, with a simultaneous reduction in CO2 emissions of more than 43%.

Prognostication of lignocellulosic biomass pyrolysis behavior using ANFIS model tuned by PSO algorithm

In-depth knowledge on pyrolysis behavior of lignocellulosic biomass is pivotal for efficient design, optimization, and control of thermochemical biofuel production processes. Experimental thermogravimetric analysis (TGA) is usually employed to peruse the pyrolysis kinetics of biomass samples. In addition to that, the main constituents of biomass (i.e., cellulose, hemicellulose, lignin) as well as the process heating rate can excellently reflect its pyrolysis characteristics through modeling techniques. However, the application of statistical and phenomenological models for extremely complex and highly nonlinear phenomena like lignocellulose pyrolysis is challenging. To address this challenge, adaptive network-based fuzzy inference system (ANFIS) was consolidated with particle swarm optimization (PSO) algorithm to prognosticate the kinetic constants of lignocellulose pyrolysis. More specifically, the PSO algorithm was applied to tune membership function parameters of the ANFIS model. Three ANFIS−PSO topologies were designed and trained to estimate the kinetic constants of lignocellulose pyrolysis, i.e., energy of activation, pre-exponential coefficient, and order of reaction. The input variables of the developed models were biomass main constituents and the process heating rate. The developed models could predict the kinetic constants of lignocellulosic biomass pyrolysis with an R2 > 0.970, an MAPE < 3.270%, and an RMSE < 5.006. The pyrolysis behaviors of three different biomass feedstocks (unseen data to the developed models) were adequately prognosticated with an R2 > 0.91 using the developed models, further confirming their fidelity. Overall, the lignocellulose pyrolysis behavior could be reliably and accurately estimated using the trained ANFIS–PSO approaches as an alternative to the TGA measurements. In order to make practical use of the trained models, a handy freely-accessible software platform was designed using the selected ANFIS−PSO models for approximating biomass pyrolysis kinetics.

Improvement of the properties of 1-ethyl-3-methylimidazolium acetate using organic solvents for biofuel process

Imidazolium-based ionic liquids (ILs) are widely used in bio-chemical processes for biofuel production. Ionic liquids always possess high viscosity that would impede the dissolution process of biomass and decrease the transfer rate. In this work, four organic solvents of N,N-dimethylacetamide (DMA), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and pyridine (PYR) are chosen as the diluent to improve the properties of IL, namely, 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]) that shows promise for biofuel process in recent studies. The experimental density and viscosity of the binary mixtures are determined to quantitatively evaluate the effects of organic solvents on IL. The thermal expansion coefficient is derived from the experimental data. The excess properties are calculated to study the molecular interaction.

Design of a highly thermostable hemicellulose-degrading blend from Thermotoga neapolitana for the treatment of lignocellulosic biomass

The biological conversion of lignocellulose into fermentable sugars is a key process for the sustainable production of biofuels from plant biomass. Polysaccharides in plant feedstock can be valorized using thermostable mixtures of enzymes that degrade the cell walls, thus avoiding harmful and expensive pre-treatments. (Hyper)thermophilic bacteria of the phylum Thermotogae provide a rich source of enzymes for such industrial applications. Here we selected T. neapolitana as a source of hyperthermophilic hemicellulases for the degradation of lignocellulosic biomass. Two genes encoding putative hemicellulases were cloned from T. neapolitana genomic DNA and expressed in Escherichia coli. Further characterization revealed that the genes encoded an endo-1,4-β-galactanase and an α-l-arabinofuranosidase with optimal temperatures of ˜90 °C and high turnover numbers during catalysis (kcat values of ˜177 and ˜133 s−1, respectively, on soluble substrates). These enzymes were combined with three additional T. neapolitana hyperthermophilic hemicellulases – endo-1,4-β-xylanase (XynA), endo-1,4-β-mannanase (ManB/Man5A) and β-glucosidase (GghA) – to form a highly thermostable hemicellulolytic blend. The treatment of barley straw and corn bran with this enzymatic cocktail resulted in the solubilization of multiple hemicelluloses and boosted the yield of fermentable sugars by up to 65% when the complex substrates were further degraded by cellulases.

Platforms planning and process optimization for biofuels supply chain

Sustainable biofuel supply chain is a key to sustainable manufacturing and the future of production. Greener production is now becoming an order qualifier for the global competition. Modeling biofuel supply chains that achieve economic, social, and environmental feasibility is a challenge. This article develops biofuel platform planning and optimization that unifies biofuel product, production process and networks design into an umbrella of sustainable supply chain planning. A design of biofuel supply chain networks under various production paths is considered. The modeling results show that an optimum region of composition ratio between rice straws and waste cooking oils can be set within the range from 0% to 50%. Bio-diesel is favored over ethanol by occupying over 40% of the total biofuel outputs. However, ethanol yield is 99.1% and therefore it is sufficient to be directly mixed with gasoline at final depots. In terms of social contribution, it is estimated that the supply chain contribution to the case country GDP is about 0.17%. Looking at the above statistics, future research on global economic impacts and competitiveness of biofuel production is suggested.

Jan J. Lyczakowski.

Jan J. Lyczakowski.

The potential of pervaporation for biofuel recovery from fermentation: An energy consumption point of view

Abstract Recovering alcohols from dilute fermentation broth is an emergent task in bio-fuel production process. Since they are primary planned for fuels, energy required to separate these alcohols should be considered in evaluating the potential of a separation technology. A membrane-based process, pervaporation, is of special interest because of its environmental friendliness and easy integrating character. This review probes into the fundamentals of pervaporation especially in terms of the heat required for evaporation. Meanwhile, the separation data of the most representative alcohol-selective pervaporation membranes reported in the literatures are collected and compared with the vapor–liquid equilibrium curve, which represents the distillation selectivity. They include: inorganic membranes, silicon rubber based membranes, Mixed Matrix Membranes and some other special materials. By doing so, the status of alcohol recovery via pervaporation would be more clear for researchers. For ethanol recovery, it is selectivity rather than flux that is in urgent need of solution. While for butanol recovery, membranes with satisfactory selectivity have been developed, increasing the separation capacity would be more pressing.

Microalgae-bacteria symbiosis in microalgal growth and biofuel production: a review.

Photosynthetic microalgae can capture solar energy and convert it to bioenergy and biochemical products. In nature or industrial processes, microalgae live together with bacterial communities and may maintain symbiotic relationships. In general interactions, microalgae exude dissolved organic carbon that becomes available to bacteria. In return, the bacteria remineralize sulphur, nitrogen and phosphorous to support the further growth of microalgae. In specific interactions, heterotrophic bacteria supply B vitamins as organic cofactors or produce siderophores to bind iron, which could be utilized by microalgae, while the algae supply fixed carbon to the bacteria in return. In this review, we focus on mutualistic relationship between microalgae and bacteria, summarizing recent studies on the mechanisms involved in microalgae-bacteria symbiosis. Symbiotic bacteria on promoting microalgal growth are described and the relevance of microalgae-bacteria interactions for biofuel production processes is discussed. Symbiotic microalgae-bacteria consortia could be utilized to improve microalgal biomass production and to enrich the biomass with valuable chemical and energy compounds. The suitable control of such biological interactions between microalgae and bacteria will help to improve the microalgae-based biomass and biofuel production in the future.

Exergetic Analysis of the Biodiesel Production Process in a Biofuel Plant

This paper deals with the exergy analysis of the biodiesel production process from the binary mixture of soybean oil and beef tallow. The biodiesel is produced by transesterification of the methyl group and through basic catalysis. Thus, it was investigated the biofuel production process of a specific plant in the State of Minas Gerais, Brazil, characterizing the parameters of the main equipment and analyzing the raw material and by-products of the process and quantifying the mass and energy. The exergy analysis methodology followed the mass balance of each step, calculating irreversibility and exergetic balance and efficiency of the plant. The calculation of chemical exergy of the compounds of biomass from soybean oil and beef tallow, biodiesel, glycerol and free fatty acids was accomplished by raising the calorific value of the compounds by their chemical composition and mass percentage. Moreover, they were also calculated the specific irreversibility of methanol and process inputs, the irreversibility concerning electricity, mechanical work and steam. It was found that the useful exergy was 63.4%, however, considering that the glycerin can be sold as a final product and that some raw materials can be reused, the useful exergy of the system could be equal to 94.2%. The exergy efficiency of the plant is 71.7%, due to the irreversibility of the system. The exergy destroyed was 5.8% and could be minimized by changing variables such as temperature, reaction time and type of catalyst.

Mixing alkali pretreated and acid pretreated biomass for cellulosic ethanol production featuring reduced chemical use and decreased inhibitory effect

Alkali and acid pretreatment based processes for lignocellulosic biofuel production typically consume substantial amount of alkali and acid. In addition, alkali pretreatment generates compounds with high toxicity rendering washing/detoxification inevitable. In this work, alkali (AL) and dilute acid (DA) pretreatment based processes were compared side by side for ethanol production from corn stover (CS) using commercial enzymes and Zymomonas mobilis 8b strain. Next, AL and DA pretreated CS slurries (without removing liquid stream) were mixed to neutralize for enzymatic hydrolysis and ethanol fermentation. The digestibility and fermentability of the mixed pretreated biomass were systematically studied and compared to unmixed pretreated biomass. Results showed that mixed biomass process saved 40–50% alkali/acid use and enhanced fermentability compared to AL-CS. This work suggests that it could be beneficial to have both alkali and acid pretreatments operating in a biorefinery, which could accommodate various feedstocks.

Preparation and Application of Biochar-Based Catalysts for Biofuel Production

Firstly, this paper reviews two main methods for biochar synthesis, namely conventional pyrolysis and hydrothermal carbonization (HTC). The related processes are described, and the influences of biomass nature and reaction conditions, especially temperature, are discussed. Compared to pyrolysis, HTC has advantages for processing high-moisture biomass and producing spherical biochar particles. Secondly, typical features of biochar in comparison with other carbonaceous materials are summarized. They refer to the presence of inorganics, surface functional groups, and local crystalline structures made up of highly conjugated aromatic sheets. Thirdly, various strategies for biochar modification are illustrated. They include activation, surface functionalization, in situ heteroatom doping, and the formation of composites with other materials. An appropriate modification is necessary for biochar used as a catalyst. Fourthly, the applications of biochar-based catalysts in three important processes of biofuel production are reviewed. Sulfonated biochar shows good catalytic performance for biomass hydrolysis and biodiesel production. Biodiesel production can also be catalyzed by biochar-derived or -supported solid-alkali catalysts. Biochar alone and biochar-supported metals are potential catalysts for tar reduction during or after biomass gasification. Lastly, the merits of biochar-based catalysts are summarized. Biochar-based catalysts have great developmental prospects. Future work needs to focus on the study of mechanism and process design.

Hedging Against Uncertainty in Biomass Processing Network Design Using a Data-Driven Approach

Sustainability has become a key concern in process systems engineering. Renewable energy, such as biofuels, and renewable materials, such as bioproducts, could replace their non-renewable, petroleum-based counterparts. However, there remain many challenges in producing biofuels and bioproducts economically and efficiently. There are many different biomass feedstocks, processes to convert them, and many different possible biofuels and bioproducts to produce. Furthermore, prices and demands of biofuels and bioproducts are uncertain. The variation of price or demand of one bioproduct could influence price or demand of another, further complicating the problem. An approach that can identify economical, efficient, and sustainable biofuel and bioproduct production processes from the myriad possible options while also considering correlated and uncorrelated price and demand uncertainties of the final bioproducts is required. In this work, a data-driven decision-making framework is proposed for biomass processing network design that directly integrates machine learning with robust optimization. Principal component analysis (PCA) is used to identify latent uncertainties behind observed uncertainty data. A kernel density estimation approach captures probability distributions of the projected uncertainty data extracted from PCA. This uncertainty data analysis approach is applied to a bioconversion product and process network to identify cost-effective and environmentally-friendly biofuels and bioproducts production pathways. Our approach identifies a total annualized cost of $ 18.3M/y, 6 % lower than the cost found with conventional adaptive robust optimization.

Thermo-catalytic reforming of pulper rejects from a secondary fibre mill

This paper investigates thermal conversion of pre-treated pulper reject waste using a Thermo-Catalytic Reforming process (TCR®) for production of biofuels. Approximately 40% of the original feedstock energy was transferred to the solid and liquid energy vectors. The bio-oil organic fraction accounts for approximately 35% of total liquid yield with a HHV of 40.17 MJ/kg. The two most abundant compounds were oleic acid methyl ester (18.90%; C18:1 FAME) and naphthalene (16.23%). The bio-oil exhibits characteristics well suited for blending with fossil fuels. The other products formed was a synthesis gas with hydrogen content of 29.33 vol% which is attractive for hydrogen separation for hydrogen fuel cell vehicles, process heating and other high value applications. The gasification of char is also a promising valorisation opportunity. TCR technology was able to tolerate high plastic content in the feedstock and produced a liquid fuel analogue to the fossil fuels, therefore, this paper highlighted the advantages of the TCR technology as a promising route for pulper rejects valorisation to produce energy vectors.

Quantifying the exergetic performance of bio-fuel production process including fast pyrolysis and bio-oil hydrodeoxygenation

Fast pyrolysis of biomass in a dual fluidized bed and bio-oil hydrodeoxygenation are simulated by Aspen plus. The process includes the following unit operations: drying, pyrolysis, char combustion, bio-oil vapor condensation, mild hydrodeoxygenation, and depth hydrodeoxygenation. Based on the simulative results, exergetic analysis of the whole process is performed to optimize the overall exergetic efficiency. The overall exergetic efficiency of the process is 57%. The exergetic efficiencies of the fast pyrolysis process and the bio-oil hydrodeoxygenation process are 68% and 78%, respectively. The results indicate that the exergetic efficiency is improved slightly with a decrement in the system pressure drop. Moreover, the exergetic efficiency of pyrolysis is improved from 69% to 76% when the percentage of the pyrolysis char combusted is reduced from 100% to 65%. Compared to other conversion technologies, biomass to liquid fuel conversion via fast pyrolysis and subsequent hydrodeoxygenation has higher exergetic efficiency.

Nutrients recycling and energy evaluation in a closed microalgal biofuel production system

A closed process for microalgal biofuel production involving in lipid extraction, anaerobic digestion, and microalgal cultivation was proposed. Nutrients recycling and energy in the system were evaluated. During the anaerobic digestion process, 69.37% of nitrogen and 60.22% of phosphorus resided in the lipid-extracted microalgae (LEM) were released into the digested liquid (DL). Microalgae (Chlorella pyrenoidosa) could grow normally in mixed 10% DL and Selenite Enrichment (SE) medium (without nitrogen and phosphorus additives). The maximum biomass concentration was 1.25 g/L (dry biomass), which was higher than that obtained with the standard SE medium (1.18 g/L dry biomass). This indicates that the abundant nutrients in the DL can be recycled for more sustainable microalgae growth. Economic analysis evaluated that recycling of nutrients in the DL could potentially reduce nutrient cost by 41.77%. Additionally, 28.38% more energy was recovered as methane in LEM during the anaerobic digestion process. This would compensate for the cost of microalgae biofuel production.

Gasification process integration with existing combined heat and power plants for polygeneration of dimethyl ether or methanol: A detailed profitability analysis

Combustion of waste for cogeneration of heat and power is the most convenient and practical choice to carry out through combined heat and power (CHP) plants. But, seasonal variation in heat demand throughout the year affects the operation of CHP plants. This fluctuation in the CHP operation cause less annual operating hours for the plant equipment and is also not profitable for stakeholders. This study aims to assess the technical potential of integrated gasification process with existing CHP plants for either dimethyl ether (DME) or methanol production through refuse-derived fuel (RDF). Process integration considers that the CHP plant provides the necessary heat for biofuel synthesis during off-peak hours. Mass and heat integration methods are used to develop and simulate the polygeneration processes for heat, power, and biofuel production. Both technical and economic indicators are reported and compared to assess the potential for both biofuels through process integration. Annual operation data of a real CHP plant has been extracted to evaluate the integrated processes. A flexible gasification configuration is selected for the integrated approach i.e. CHP runs at full load to provide the heat demand and only the excess heat of CHP plant is utilized for biofuel production. The energetic efficiencies of the polygeneration systems are compared with the standalone systems. Technical analysis of process integration shows the enhancement of the operational capacity of CHP during off-peak hours and it can produce biofuels without compromising the annual heat demand. Production of methanol through process integration shows ∼67% energetic efficiency while methanol production gives ∼65%. The efficiencies are higher than standalone DME and methanol processes (51% and 53%, respectively) but lower than standalone CHP plant i.e. 81%, however the process integration increases the operating time of the CHP plant with more economic benefits. Economic analysis coupled with uncertainty analysis through Monte Carlo simulations shows that by integrating CHP with gasifier to produce biofuels is significantly profitable as compared with only heat and electricity production. But, DME as a potential product shows more economic benefits than methanol. The uncertainty analysis through Monte Carlo simulations shows that the profitable probability of DME as a product in future is also greater than methanol due to higher DME selling price. The uncertainty analysis further shows that prices of DME and methanol with waste biomass prices in future will have a greater impact on the economic performance of the proposed polygeneration process.