Hydrocarbon Biofuel Production Research Articles

Production of Renewable Hydrocarbon Biofuels with Lignocellulose and Its Derivatives over Heterogeneous Catalysts.

In recent years, the issues of global warming and CO2 emission reduction have garnered increasing global attention. In the 21st Conference of the Parties (convened in Paris in 2015), 179 nations and the European Union signed a pivotal agreement to limit the global temperature increase of this century to well below 2 K above preindustrial levels. To fulfill this objective, extensive research has been conducted to use renewable energy sources as potential replacements for traditional fossil fuels. Among them, the production of hydrocarbon transportation fuels from CO2-neutral and renewable biomass has proven to be a particularly promising solution due to its compatibility with existing infrastructure. This review systematically summarizes research progress in the synthesis of liquid hydrocarbon biofuels from lignocellulose during the past two decades. Based on the chemical structure (including n-paraffins, iso-paraffins, aromatics, and cycloalkanes) of hydrocarbon transportation fuels, the synthesis pathways of these biofuels are discussed in four separate sections. Furthermore, this review proposes three guiding principles for the design of practical hydrocarbon biofuels, providing insights into future directions for the development of viable biomass-derived liquid fuels.

Hydrocracking process of coconut oil using Ni-Zn/HZSM-5 catalyst for hydrocarbon biofuel production

Renewable hydrocarbon biofuel was produced by hydrocracking of coconut oil using a bifunctional catalyst. Hydrocarbon biofuel is promising for production of future fuels from vegetable oil. The advantage of the hydrocracking is the formation of hydrocarbon biofuel products at the conventional fuel range. The purpose of this work is to produce hydrocarbon biofuel by hydrocracking of coconut oil using the catalyst of Ni-Zn/HZSM-5. The processes of hydrocracking processes were performed in a vessel reactor by stirring with magnetically at 350 °C and the reaction pressure of 15 bar for 2 h under flowing H2 with Ni-Zn/HZSM-5 catalyst. The effect of Ni-Zn/HZSM-5 catalyst was evaluated by determining the composition of products (hydrocarbon biofuel). The hydrocarbon biofuel was determined by Gas Chromatography-Mass Spectrometry (GC-MS). The GC-MS results of hydrocarbon biofuel show the aliphatic compounds in the range C12-C22. The presence of C17-C18 in the hydrocarbon biofuel was relatively low. Hydrocarbon biofuel composition consists of 0.11 cycloparaffins, 5.33 normal paraffins, 7.85 olefin, and 0.08 aromatics based on area%. The total amount of detected oxygenated compounds was 86.63 area% carboxylic acid. These compounds are responsible for the low quality of the hydrocarbon biofuel. However, the reaction must be carried out at above 350 °C to eliminate the oxygenated compounds in the hydrocarbon biofuel, as an important step to replace non-renewable fossil fuels.

(Invited) Increasing Biogas to Liquid Fuel Yield By Solid Oxide Co-Electrolysis of Biogas CO2 Fraction

OxEon Energy, LLC (OxEon) plans to demonstrate production of liquid hydrocarbon fuels using both the methane and CO2 generated in a food waste digester operated by the Environmental Products & Technologies Corporation (EPT). The EPT food waste digester in Burley Idaho sells produced biogas into a natural gas pipeline after separating and venting the bio-CO2. This project will convert the bio-methane to synthesis gas (syngas, as CO & H2) using a non-thermal plasma catalyzed autothermal reformer. To achieve high bio-carbon utilization, an OxEon high temperature solid oxide co-electrolysis (HTCE) system will electrochemically generate additional syngas from the bio-CO2 combined with steam raised by cooling the Fischer Tropsch (FT) reactor. Syngas from the reformed methane and co-electrolyzed CO2, will be converted to liquid fuels using an OxEon developed FT reactor. Each of the technology components have been field tested independently and will be combined for the first time in this project. The project outcome will be an engineering scale demonstration of liquid hydrocarbon bio-fuel production achieving > 50% conversion to liquids of the biogenic carbon in both CH4 & CO2 produced by an anaerobic digester.Each of the three technology elements of the integrated engineering test incorporates numerous innovations. The plasma reactor is designed to be fuel flexible, sulfur tolerant, and economically scalable to small, distributed bio-gas resources. It is also very efficient using a low power non- thermal plasma. High temperature solid oxide electrolysis has demonstrated efficiency at the thermodynamic limit as shown by analysis and testing at DOE and NASA laboratories, and is unique in its ability to co-electrolyze steam and CO2 directly to syngas. The HTCE stacks use innovations proven for the NASA Mars 2020 project which required exceptional ruggedness and effective high temperature seals. The FT reactor enables economical fabrication of smaller size synthetic fuel plants designed to match the scale of distributed renewable biomass resources. This is achieved with large diameter standard piping combined with a novel internal thermal management structure.The status of the technology elements and the planned engineering demonstration will be presented.This work is supported by the Bioenergy Technologies Office of the US Department of Energy.

(Invited) Production of Liquid Hydrocarbons from Anaerobic Digester Gas

OxEon Energy, LLC (OxEon) plans to demonstrate production liquid hydrocarbon fuels using both the methane and CO2 generated in the food waste digester operated by the Environmental Products & Technologies Corporation (EPT). The EPT food waste digester in Burley Idaho sells produced biogas into a natural gas pipeline after separating and venting the bio-CO2. This project will convert the bio-methane to synthesis gas (syngas, as CO & H2) using a non-thermal plasma catalyzed autothermal reformer. To achieve high bio-carbon utilization, high temperature solid oxide co-electrolysis (HTCE) system will electrochemically generate additional syngas from the bio-CO2 combined with steam raised by cooling the Fischer Tropsch (FT) reactor. Syngas from the reformed methane and co-electrolyzed CO2, will be converted to liquid fuels using the FT reactor. Each of the technology components have been field tested independently and will be combined for the first time in this project. The project outcome will be an engineering scale demonstration of liquid hydrocarbon bio-fuel production achieving > 50% conversion to liquids of the biogenic carbon in both CH4 & CO2 produced by an anaerobic digester.Each of the three technology elements of the integrated engineering test incorporates numerous innovations. The plasma reactor is designed to be fuel flexible, sulfur tolerant, and economically scalable to small, distributed bio-gas resources. It is also very efficient using a low power non- thermal plasma. High temperature electrolysis has demonstrated efficiency at the thermodynamic limit as shown by analysis and testing at DOE and NASA laboratories, and is unique in its ability to co-electrolyze steam and CO2 directly to syngas. The HTCE stacks use innovations proven for the NASA Mars 2020 project which required exceptional ruggedness and effective high temperature seals. The FT reactor enables economical fabrication of smaller size synthetic fuel plants designed to match the scale of distributed renewable biomass resources. This is achieved with large diameter standard piping combined with a novel internal thermal management structure.The status of the technology elements and the planned engineering demonstration will be presented.This work is supported by the Bioenergy Technologies Office of the US Department of Energy.

Facile biphasic catalytic process for conversion of monoterpenoids to tricyclic hydrocarbon biofuels

Terpenoids have drawn much attention to scientists in synthesizing high-performance bio- jet fuels due to their ring structures, which feature potential high densities. Here, a facile biphasic catalytic process has been developed for the production of high-density tricyclic hydrocarbon biofuels from a monoterpenoid, 1,8-cineole, using sulfuric acid (H2SO4) as the homogeneous catalyst. A ~100% conversion of 1,8-cineole and a > 40% carbon yield of cyclic dimers were achieved at 100 °C within two hours. The mechanism for the acid-catalyzed conversion of 1,8-cineole to cyclic hydrocarbon dimers were explored. In particular, the formation of the diene intermediates and the following dimerization of dienes was essential to synthesize tricyclic terpene dimers. The biphasic catalytic process accelerated the deoxygenation rate and enabled the dimerization with the aid of organic solvent while controlling the reaction rates to avoid the formation of solid residues. Moreover, this process also facilitated the product separation by organic solvent extraction while enabling easy recycle of the homogenous catalysts.

Hydrocarbon Biofuel Production by Hydrocracking Process with Nickel-Iron Supported on HZSM-5 Catalyst

The production of hydrocarbon biofuel from coconut oil can substitute for fossil fuels to reduce the environmental issues. Hydrocracking is an effective method that can convert vegetable oil into biofuel using catalyst. In this experiment, nickel-iron was combined with HZSM-5 catalyst to produce biofuel. Hydrocracking of coconut oil was carried out in a batch reactor over Ni-Fe/HZSM-5 catalyst at a temperature of 350 and 400 °C for 2 h. Liquid hydrocarbon biofuel product was analyzed by gas chromatography-mass spectrometry (GC-MS). Based on GC-MS analysis, processing at the temperature of 350 °C produced sample containing 72.56% carboxylic acids. When the temperature increased to 400 °C, the carboxylic acids decreased rapidly from 72.56% to 24.83%. Analysis results suggested that increase of temperature promoted to the increase of desirable content, hydrocarbon compounds. At the same like, it also suppressed formation of undesirable compounds: acids, ketones, phenols, alcohols, and esters. Overall, synthesized catalyst in this study improved production of n-paraffin compounds such as (tridecane (n-C13), tetradecane (n-C14) and pentadecane (n-C15)) as high 71.85%.

Catalytic conversion of waste cooking oils for the production of liquid hydrocarbon biofuels using in-situ coating metal oxide on SBA-15 as heterogeneous catalyst

Liquid hydrocarbon biofuels obtained from the catalytic cracking of animal fats and plant oils have become attractive because of their possible environmental benefits, and the current concerns over the depletion of fossil-fuel sources. In this work, five different metal-oxide (ZnO, La2O3, CeO2, NiO and MgO) modified SBA-15 (MeO-SBA-15) samples were prepared by a simple one-pot synthesis method and were used in the catalytic cracking of waste cooking oils. The synthesized catalysts were characterized using X-ray diffraction, N2 physisorption, transmission electron microscopy and Fourier-transform infrared techniques, and their catalytic performances were investigated in detail in the cracking of waste cooking oils. To obtain high-quality biofuel, all the pyrolysis products were separated into two compounds by distillation: (a) liquid hydrocarbon biofuels including gasoline and diesel fractions (distillation temperature ≤ 350 °C); (b) heavy oils (distillation temperature >350 °C). The results indicated that the mesostructure of the SBA-15 was well preserved after metal oxide modification, and the MeO-SBA-15 catalysts improved the hydrocarbon biofuels yield and decreased the heavy oil yield. Among the catalysts, the ZnO-SBA-15 showed an excellent catalytic performance and produced the highest biofuel yield (37.3%) and the lowest yield of heavy oils (39.9%). The liquid hydrocarbon biofuels obtained using the ZnO-SBA-15 catalyst had a similar chemical composition to the diesel-based fuels and showed a lower density, lower viscosity and higher heating values than raw waste cooking oils. These results indicated that ZnO-SBA-15 can promote the chemical reactions, such as deoxygenation and decarbonylation.

Selective production of the acyclic monoterpene β-myrcene by microplantlet suspension cultures of the macrophytic marine red alga Ochtodes secundiramea under nutrient perfusion cultivation with bromide-free medium

This study demonstrated the selective production of a single acyclic monoterpene, β-myrcene, by photosynthetic, clonal microplantlet suspension cultures of the macrophytic red alga Ochtodes secundiramea (Cryptonemiales, Rhizophyllidaceae). Microplantlets were cultivated within an airlift photobioreactor under continuous medium perfusion with enhanced nutrients (nitrate, phosphate) and 3500 ppm CO2 in the aeration gas to provide nutrient-replete conditions. The removal of bromide (Br-) and vanadate (VO43−) from the medium shut down bromoperoxidase-catalyzed halogenation, so that only the common precursor to halogenated monoterpenes, β-myrcene, accumulated within the biomass. Nutrient-replete cultivation enabled near-exponential biomass production to density of 6 g DW/L, with specific growth rate of 4.4 ± 0.1% per day over the 36 day cultivation period at near-saturation light intensity. Myrcene was produced during biomass production, and the specific rate of β-myrcene production within the biomass exceeded the specific rate of biomass production, so that β-myrcene accumulated within the biomass. Increasing the mean light intensity from approximately 60 to 95% of light saturation linearly increased the growth rate, but did not increase the specific rate of β-myrcene production. At near saturation light intensity, the specific rate of β-myrcene production was 6.8 ± 0.7% per day (1.0 S.E.) with yield of 40 μmol/g DW after 36 days. Although the yields of β-myrcene were low (0.6 wt% in biomass), the potential for high biomass density, ease of microplantlet separation, and high selectivity of hydrocarbon biosynthesis suggest that microplantlets of terpenoid-producing red macroalgae have promise as a new platform for advanced hydrocarbon biofuel production from CO2, provided new strategies can be developed to enhance monoterpene yield.

Direct conversion of simulated propene-rich bio-syngas to liquid iso-hydrocarbons via FT-oligomerization integrated catalytic process

The bio-syngas formed from the catalytic cracking of bio-oil include two types of useful components which are light olefin and H2, CO. The integration of FTS and olefinic polymerization seems potential way for the production of hydrocarbon bio-fuels while fully utilizing the olefin-rich bio-syngas. This work aimed to develop an integrated process for the production of liquid hydrocarbons directly from the olefin-rich bio-syngas through a one-stage process, which included the synthesis of liquid hydrocarbons via the oligomerization of light olefin over HZSM-5 along with the FT (Fischer-Tropsch) synthesis of H2, CO over FeMn catalyst. A series of integration configuration composed of Fe-based catalyst (FeMn) and acidic zeolite (HZSM-5) were investigated, it was found that the undesired hydrogenation of lower olefin on the nearby metal active site seems greatly affected the yield of C5+ . More significantly, the proximity of the two active components plays a crucial role in suppressing the undesired hydrogenation reaction and contributing to the high selectivity of liquid hydrocarbons. The optimal catalytic performance yields a high selectivity to gasoline-range hydrocarbons (87.3%) with excellent low olefin hydrogenation selectivity (7.4%). Meanwhile, the obtained gasoline-range hydrocarbon showed high degree of isomerization. The integrated transformation process potentially provides an alternative way for the production of gasoline range isomerized hydrocarbon fuels using olefin-rich bio-syngas.

Modified mesoporous HMS supported Ni for deoxygenation of triolein into hydrocarbon-biofuel production

A series of modified hexagonal mesoporous silica (HMS) supported by various Ni loading (5 wt% Ni, 10 wt% Ni, 40 wt% Ni and 100 wt% Ni) have been synthesized and systematically characterized. The resultant Ni catalysts improved the performance of the deoxygenation (DO) of triolein at a reaction temperature of 380 °C in a simple glass batch reactor under a solvent-free condition and are hydrogen-free. The incorporation of Ni loading into the HMS framework casued the catalytic activity to increase when compared to that of HMS. Surprisingly, 10 wt% Ni/HMS catalyst exhibited the highest conversion. It was observed that 10 wt% Ni loading was highly dispersed on the HMS which is capable of achieving 92.5% and 95.2% of conversion and selectivity, respectively. This is due to the synergistic effect of Si-O-Ni bonding and high dispersion of NiO on HMS. In this respect, the nature of catalyst support such as pore size and the high surface areas of HMS play an important role in enhancing the catalytic performance of DO reaction. This study has revealed that Ni/HMS catalyst is a promising catalyst that can be applied to the development of sustainable biofuel from non-edible oil.

Effects of Coproduct Uses on Environmental and Economic Sustainability of Hydrocarbon Biofuel from One- and Two-Step Pyrolysis of Poplar

This study investigated the environmental and economic sustainability of liquid hydrocarbon biofuel production via fast pyrolysis of poplar biomass through two pathways: a one-step pathway that converted poplar via fast pyrolysis only, and a two-step pathway that includes a torrefaction step prior to fast pyrolysis. Optimization of these fast pyrolysis-based biofuel processes were investigated through heat integration and alternative uses of the coproduct biochar, which can be sold as an energy source to displace coal, soil amendment or processed into activated carbon. The impacts of optimization on the cost of hydrocarbon biofuel production as well as the environmental impacts were investigated through a technoeconomic analysis (TEA) and life cycle assessment (LCA), respectively, with two-step and one-step processing compared to fossil fuels. The TEA indicates that a one-step heat integrated pathway with the production of activated carbon has a minimum selling price of $3.23/gallon compared to $5.16/gallon for a two-step heat integrated process with burning of the coproduct biochar to displace coal. The LCA indicates that using the displacement analysis approach, a two-step heat integrated pathway had a global warming potential of −102 g CO2 equivalent/MJ biofuel compared to 16 CO2 equivalent/MJ biofuel for the heat integrated one-step pathway.

Catalytic cracking of Swida wilsoniana oil for hydrocarbon biofuel over Cu-modified ZSM-5 zeolite

Catalytic cracking of Swida wilsoniana oil over non-catalyst and various Cu-modified ZSM-5 catalysts doped with different concentration of Cu (0, 5, 10, 20 and 30 wt%) was studied. The physicochemical properties of the prepared catalysts were investigated by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) model, Transmission electron microscopy (TEM) and temperature-programmed desorption of ammonia (NH3-TPD) analysis. Results showed that the introduction of Cu did not change the crystalline structure of ZSM-5 and CuO might deposit on the surface or inside the pores. The numbers of ZSM-5 total acidic sites were increased after it was loaded with 5 wt% and 10 wt% concentration of Cu. The overall hydrocarbon biofuels yields obtained from Cu-modified ZSM-5 catalysts were improved relative to parent ZSM-5. Determination of composition of the hydrocarbon biofuels showed that the hydrocarbon fractions were the main components produced. The optimum Cu concentration used for ZSM-5 modification was 10 wt%, which obtained the highest hydrocarbon biofuels yield (68.20 wt%) and percentage of hydrocarbon fractions content (89.07 wt%). The reuse of Cu-modified ZSM-5 catalysts results showed acceptable levels of reusability after three times regeneration. In addition, the physical properties of the Cu-modified ZSM-5 catalysts produced hydrocarbon biofuels were improved compared to non-catalytic cracking of S. wilsoniana oil. This work showed that the newly developed 10 wt% concentration Cu-modified ZSM-5 was an efficient catalyst for cracking of S. wilsoniana oil for the production of hydrocarbon biofuels.

Alternative Hydrocarbon Biofuel Production via Hydrotreating under a Synthesis Gas Atmosphere

Direct use of syngas, a cheaper hydrogen-rich gas, instead of pure hydrogen, as a deoxygenating agent for biohydrogenated diesel (BHD) production is presented in this study. Low-cost palm fatty acid distillate (PFAD), an inedible byproduct from refining palm oil, is used as a feedstock in the presence of a Pd/C catalyst. The results indicate that syngas can be effectively used in BHD production, while the achieved BHD yield is slightly lower than that obtained from pure hydrogen. The liquid products contain mostly n-C15 and n-C17, which fall into a diesel range. Decarbonylation is a prominent pathway under both hydrogen and syngas atmospheres. It was found that CO in syngas can act as a reducing agent, which can remove an oxygen atom from fatty acid molecules to form alkenol that could be further reduced to alkene and then cyclized to cycloparaffins. After reactivation, the activity of the catalyst could be fully recovered for at least 4 reused cycles. Reaction pathways for the catalytic deoxygenation und...

Directional liquefaction of biomass for phenolic compounds and in situ hydrodeoxygenation upgrading of phenolics using bifunctional catalysts

Phenolic compounds derived from biomass are important feedstocks for the sustainable production of hydrocarbon biofuels. Hydrodeoxygenation is an effective process to remove oxygen-containing functionalities in phenolic compounds. This paper reported a simple method for producing hydrocarbons by liquefying biomass and upgrading liquefied products. Three phenolic compounds fractions (1#, 2#, and 3#) were separated from liquefied biomass with stepwise precipitation and extraction. Based on HSQC NMR analysis, three phenolic compounds fractions were mainly comprised of aromatic and phenolic derivatives. Three phenolic compounds fractions were hydrogenated and deoxygenated to cyclohexanes using bifunctional catalysts via in situ hydrodeoxygenation. During the in situ hydrodeoxygenation, we introduced bifunctional catalysts combined of Raney Ni with HZSM-5. The bifunctional catalysts showed high selectivity for removing oxygen-containing groups in biomass-derived phenolic compounds. And the hydrogen was supplied by aqueous phase reforming of methanol without external H2. Additionally, the mechanism based on our investigation of in situ hydrodeoxygenation of phenolic compounds was proposed. During the in situ hydrodeoxygenation, the metal-catalyzed hydrogenation and acid-catalyzed hydrolysis/dehydration were supposed to couple together. Current results demonstrated that in situ hydrodeoxygenation using bifunctional catalysts is a promising and efficient route for converting biomass-derived phenolic compounds into fuel additives and liquid hydrocarbon biofuels.

Production of Hydrocarbon Fuel Using Two-Step Torrefaction and Fast Pyrolysis of Pine. Part 1: Techno-economic Analysis

As part I of two companion papers, the present paper evaluates the economic feasibility of hydrocarbon biofuel production via two pathways: a one-step production pathway through fast pyrolysis of biomass followed by the catalytic upgrade of bio-oil to a liquid hydrocarbon biofuel and a novel two-step pathway that includes a torrefaction pretreatment step prior to fast pyrolysis and then the catalytic upgrade. These two pathways were modeled using Aspen Plus to process 1000 dry metric tons/day of feed through the fast pyrolysis unit operating at 530 °C whereas torrefaction for the two-step pathway was investigated at three different torrefaction temperatures of 290, 310, and 330 °C. Three scenarios of producing process heat from natural gas, internal byproducts biochar supplemented with natural gas, and torrefaction condensate were investigated, with additional heat integration considered. Minimum selling price ranged from $4.01/gal to $4.78/gal for the heat-integrated processes whereas the price ranged fr...

Production of Hydrocarbon Fuel Using Two-Step Torrefaction and Fast Pyrolysis of Pine. Part 2: Life-Cycle Carbon Footprint

This study, as part II of two companion papers, investigated the environmental performance of liquid hydrocarbon biofuel production via fast pyrolysis of pine through two pathways: a one-step pathway via fast pyrolysis only, and a two-step pathway that includes a torrefaction step prior to fast pyrolysis. Fast pyrolysis in all cases took place at a temperature of 530 °C whereas for the two-step pathways, torrefaction was investigated at temperatures of 290, 310, and 330 °C. Bio-oil produced was then catalytically upgraded to hydrocarbon biofuel. Different scenarios for providing the required process heat either by using fossil energy or renewable energy, as well as the effect of heat integration, were also investigated. Our life cycle analysis indicated that using the energy allocation approach, a two-step heat integrated pathway with torrefaction taking place at 330 °C had the lowest global warming potential among all scenarios of about 29.0 g CO2 equiv/MJ biofuel. Using the system expansion approach, significantly higher reductions in GHG emissions of about 56 to 265% relative to conventional gasoline were observed for the heat integrated processes. More modest percentage reduction in emissions of about 34 to 67% was observed across all scenarios using the energy allocation approach.

Catalytic hydrocracking of Kapuk seed oil (Ceiba pentandra) to produce biofuel using Zn-Mo supported HZSM-5 catalyst

In the present paper Kapuk seed oil (KSO) was considered as a potential biofuel for alternative fuel from inedible oil. Catalytic hydrocracking of Kapuk seed oil using Zn-Mo supported on the HZSM-5 catalyst in a slurry pressure batch reactor at various temperature with reactor pressure in range 10-15 bar. The Zn-Mo/HZSM-5 catalyst was prepared by incipient wetness impregnation. The physicochemical properties of the catalyst were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) method. The best catalyst performance on catalytic hydrocracking of KSO using Zn-Mo/HZSM-5 (Si/Al = 25) with loading 2.92%wt for Zn and 7.55%wt for Mo. It displayed the highest hydrocarbon content decarboxylation and/or decarbonylation were 35.51 area% of n-paraffins and the highest content for gasoil-range alkanes was 17.24 area% at 4000C. The liquid product predominant is n-C15, and the second component is n-C17. The catalyst Zn-Mo/HZSM-5 was helpful for the catalytic hydrocracking of KSO for hydrocarbon biofuel production.

Application, Deactivation, and Regeneration of Heterogeneous Catalysts in Bio-Oil Upgrading

The massive consumption of fossil fuels and associated environmental issues are leading to an increased interest in alternative resources such as biofuels. The renewable biofuels can be upgraded from bio-oils that are derived from biomass pyrolysis. Catalytic cracking and hydrodeoxygenation (HDO) are two of the most promising bio-oil upgrading processes for biofuel production. Heterogeneous catalysts are essential for upgrading bio-oil into hydrocarbon biofuel. Although advances have been achieved, the deactivation and regeneration of catalysts still remains a challenge. This review focuses on the current progress and challenges of heterogeneous catalyst application, deactivation, and regeneration. The technologies of catalysts deactivation, reduction, and regeneration for improving catalyst activity and stability are discussed. Some suggestions for future research including catalyst mechanism, catalyst development, process integration, and biomass modification for the production of hydrocarbon biofuels are provided.

Direct bioconversion of sorghum extract sugars to free fatty acids using metabolically engineered Escherichia coli strains: Value addition to the sorghum bioenergy crop

The unprecedented challenge of meeting the energy demand of growing economies has increased the need to produce hydrocarbon fuels using renewable sources. Among different platforms being researched these days, hydrocarbon biofuel and chemical production from free fatty acids (FFAs) have gained a lot of attention. The current study reports on value addition to sorghum energy crop through utilization of sorghum extract as a renewable carbon source for FFA production using genetically engineered Escherichia coli. In order to reduce the production cost of FFAs, direct sucrose utilizing E. coli strains were developed. The E. coli strain MG1655 with fadD mutant (named as ML103) either carrying the plasmid bearing the gene for acyl-ACP thioesterase (TE) from Ricinus communis (pXZ18) or a plasmid bearing a combination of the TE and the native (3R)-hydroxyacyl-ACP dehydrase gene (fabZ) (pXZ18Z) was modified to utilize sucrose by incorporating the pUR400 plasmid. The newly created strains utilized a mixture of pure sugars and sorghum extract efficiently. The 24 h pH adjusted culture of ML103 pXZ18Z pUR400 produced a maximum of 6.18 ± 0.52 g l−1 from 30 g l−1 of pure sugar mixture and 2.95 ± 0.04 g l−1 with sorghum extract (15 g l−1 equivalent sugar concentration). These data suggest that modified E. coli strains were capable of directly utilizing sucrose and produce FFAs from it. Successful demonstration of direct bioconversion of sorghum extract to FFA was validated as a possible value addition of the sorghum bioenergy crop.

Economic implications of incorporating emission controls to mitigate air pollutants emitted from a modeled hydrocarbon‐fuel biorefinery in the United States

AbstractThe implementation of the US Renewable Fuel Standard is expected to increase the construction and operation of new biofuel facilities. Allowing this industry to grow without adversely affecting air quality is an important sustainability goal sought by multiple stakeholders. However, little is known about how the emission controls potentially required to comply with air quality regulations might impact biorefinery cost and deployment strategies such as siting and sizing. In this study, we use a baseline design for a lignocellulosic hydrocarbon biofuel production process to assess how the integration of emission controls impacts the minimum fuel selling price (MFSP) of the biofuel produced. We evaluate the change in MFSP for two cases as compared to the baseline design by incorporating (i) emission controls that ensure compliance with applicable federal air regulations and (ii) advanced control options that could be used to achieve potential best available control technology (BACT) emission limits. Our results indicate that compliance with federal air regulations can be achieved with minimal impact on biofuel cost (~$0.02 per gasoline gallon equivalent (GGE) higher than the baseline price of $5.10 GGE−1). However, if air emissions must be further reduced to meet potential BACT emission limits, the cost could increase nontrivially. For example, the MFSP could increase to $5.50 GGE−1 by adopting advanced emission controls to meet potential boiler BACT limits. Given tradeoffs among emission control costs, permitting requirements, and economies of scale, these results could help inform decisions about biorefinery siting and sizing and mitigate risks associated with air permitting. Published 2016. This article is a U.S. Government work and is in the public domain in the USA. Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley & Sons Ltd.