Aviation Biofuels Research Articles

Production Cost and Carbon Footprint of Biomass-Derived Dimethylcyclooctane as a High-Performance Jet Fuel Blendstock

Near-term decarbonization of aviation requires energy-dense, renewable liquid fuels. Biomass-derived 1,4-dimethylcyclooctane (DMCO), a cyclic alkane with a volumetric net heat of combustion up to 9.2% higher than Jet A, has the potential to serve as a low-carbon, high-performance jet fuel blendstock that may enable paraffinic bio-jet fuels to operate without aromatic compounds. DMCO can be produced from bio-derived isoprenol (3-methyl-3-buten-1-ol) through a multistep upgrading process. This study presents detailed process configurations for DMCO production to estimate the minimum selling price and life-cycle greenhouse gas (GHG) footprint considering three different hydrogenation catalysts and two bioconversion pathways. The platinum-based catalyst offers the lowest production cost and GHG footprint of $9.0/L-Jet-Aeq and 61.4 gCO2e/MJ, given the current state of technology. However, when the supply chain and process are optimized, hydrogenation with a Raney nickel catalyst is preferable, resulting in a $1.5/L-Jet-Aeq cost and 18.3 gCO2e/MJ GHG footprint if biomass sorghum is the feedstock. This price point requires dramatic improvements, including 28 metric-ton/ha sorghum yield and 95–98% of the theoretical maximum conversion of biomass-to-sugars, sugars-to-isoprenol, isoprenol-to-isoprene, and isoprene-to-DMCO. Because increased gravimetric energy density of jet fuels translates to reduced aircraft weight, DMCO also has the potential to improve aircraft efficiency, particularly on long-haul flights.

Measurement and simulation of sooting characteristics by an ATJ-SKA biojet fuel and blends with Jet A-1 fuel in laminar non-premixed flames

We investigate the sooting propensity of an Alcohol-to-Jet-Synthetic Kerosene with Aromatics (ATJ-SKA) biojet fuel. The soot volume fraction and primary particle size in the pre-vaporised diffusion flames using ATJ-SKA biojet and blends with Jet A-1 at atmospheric conditions were measured experimentally and compared to numerical simulations. The measurements were conducted using extinction calibrated laser induced incandescence (LII). The soot volume fractions measured using the ATJ-SKA fuel do not show significant differences relative to measurements with Jet A-1. A comparison of the chemical composition of the fuels suggests that the Degree of Unsaturation (DoU) may not determine the sooting propensity of biojet fuels. The SEM analysis shows that diffusion flames using neat Jet A-1 produce finer soot particles and larger number density compared to the biojet and biojet surrogate. The soot model employs a semi-detailed chemical kinetic mechanism and a physical model which integrates the population balance equation governing the soot particle size distribution with an in-house reactive flow solver for multicomponent ideal gases. The model predicts the maximum soot volume fraction (SVFm) in the neat biojet case and the blended cases with Jet A-1 fuels within an error margin of 13% of the measured values. However, the predicted soot volume fraction distribution patterns differ from the measured one and the possible causes are discussed.

Isolated Metal Sites in Cu–Zn–Y/Beta for Direct and Selective Butene-Rich C3+ Olefin Formation from Ethanol

Direct and selective production of C3+ olefins from bioethanol remains a critical challenge and important for the production of renewable transportation fuels such as aviation biofuels. Here, we report a Cu–Zn–Y/Beta catalyst for selective ethanol conversion to butene-rich C3+ olefins (88% selectivity at 100% ethanol conversion, 623 K), where the Cu, Zn, and Y sites are all highly dispersed. The ethanol-to-butene reaction network includes ethanol dehydrogenation, aldol condensation to crotonaldehyde, and hydrogenation to butyraldehyde, followed by further hydrogenation and dehydration reactions to form butenes. Cu sites play a critical role in promoting hydrogenation of the crotonaldehyde C═C bond to form butyraldehyde in the presence of hydrogen, making this a distinctive pathway from crotyl alcohol-based ethanol-to-butadiene reaction. Reaction rate measurements in the presence of ethanol and acetaldehyde (543 K, 12 kPa ethanol, 1.2 kPa acetaldehyde, 101.9 kPa H2) over monometallic Zn/Beta and Y/Beta catalysts indicate that Y sites have higher C–C coupling rates than over Zn sites (initial C–C coupling rate, 6.1 × 10–3 mol molY–1 s–1 vs 1.2 × 10–3 mol molZn–1 s–1). Further, Lewis-acidic Y-site densities over Cu–Zn–Y/Beta with varied Y loadings are linearly correlated with the initial C–C coupling rates, suggesting that Lewis-acidic Y sites are the predominant sites that catalyze C–C coupling in Cu–Zn–Y/Beta catalysts. Control experiments show that the dealuminated Beta support is important to form higher density of Lewis-acidic Y sites in comparison with other supports such as silica, or deboronated MWW despite similar atomic dispersion of Y sites and Y–O coordination numbers over these supports, leading to more than 9 times higher C–C coupling rate per mole Y over dealuminated Beta relative to other supports. This study highlights the significance of unique combination of metal sites in contributing to the selective valorization of ethanol to C3+ olefins, motivating for exploring multifunctional zeolite catalysts, where the presence of multiple sites with varying reactivities and functions allows for controlling the predominant molecular fluxes toward the desired products in complex reactions.

Drop‐in ready jet biofuel from carinata: A real options analysis of processing plant investments

AbstractA promising feedstock for large‐scale production of sustainable jet biofuel is the inedible oilseed Brassica carinata (referred to simply as “carinata”), but transitioning to large‐scale fuel production entails significant economic uncertainty and requires substantial up‐front capital requirements for biorefinery construction. Furthermore, for carinata and other feedstocks attempting to compete within the established fossil jet fuel market, historically volatile aviation fuel prices affect the economic feasibility and return of biorefinery investments. In this study, we assess the impact of jet fuel price volatility on the return on investment in a carinata biorefinery employing a real options analysis (ROA). The key advantage of ROA over traditional net present value (NPV) analysis is that it simultaneously assesses the optimal timing for investments and the impact of jet fuel price dynamics on the likelihood of positive economic returns from investments in processing plants. Given the nonstationary nature of jet fuel prices and the presence of structural breaks, the price series are modeled as a geometric Brownian motion. Taking into account the volatility of jet fuel price, the ROA price threshold for a profitable investment is 45% greater than the NPV threshold. The ROA model identifies the necessary market conditions for a profitable investment and highlights the importance of considering market price dynamics before making substantial capital investments in a carinata biorefinery.

Effect of Hydrogen Donor Addition on Thermal Decomposition of Bio-jet Fuel

Effect of Hydrogen Donor Addition on Thermal Decomposition of Bio-jet Fuel

Defective UiO-66(Zr) as an efficient catalyst for the synthesis of bio jet-fuel precursors via aldol condensation of furfural and MIBK

The production of jet-fuel precursors from furfural (FUR) via aldol-condensation with methyl-isobutyl ketone (MIBK) over a defective UiO-66(Zr) catalyst is presented. The resultant C11 adduct (FuMe) would allow the selective production of branched alkanes in the range of jet fuel via a subsequent hydrogenation/hydrodeoxygenation process. The catalyst is prepared using formic acid as modulator, leading to the incorporation of defects on the microcrystalline structure of the metalorganic framework (MOF) material, which dramatically boosts the catalytic performance in this transformation. Thus, the benchmarking with different commercial solid acid catalysts and Zr-based heterogeneous catalysts has identified the defective MOF, UiO-66(Zr)-FA, as clearly superior. An extensive characterization of the modified catalyst by means of X-ray diffraction (XRD), argon adsorption isotherm, thermogravimetry (TGA), acid titration, X-ray photoelectron spectroscopy (XPS), and diffuse reflectance infrared Fourier transform (DRIFT) of adsorbed deuterated acetonitrile, has confirmed the incorporation of missing-linker and missing-node defects within the structure, enabling to explain the enhancement in the catalytic process. The analysis of the reaction kinetics, together with the optimization of the reaction conditions by means of a response surface methodology (allowing predicting the behaviour of the catalytic system under very different conditions) have identified the temperature as the most relevant parameter affecting the selectivity to FuMe. Thus, under the optimized reaction conditions (130 °C; 4 h; FUR/Cat = 2; MIBK/FUR = 4), outstanding total FUR conversion and FuMe selectivity (~100%) can be achieved. However, the catalyst gets progressively deactivated in successive catalytic runs under the studied reaction conditions, which is attributed to the formation of organic deposits coming from furfural side reactions.

The case for camelina-derived aviation biofuel: Sustainability underpinnings from a holistic assessment approach

This study performed a holistic assessment of a novel cracking alternative (olefin metathesis or OMT) that converts plant oil to aviation biofuel using lipids from Camelina sativa L. (camelina). A high-resolution spatially explicit life cycle assessment and technoeconomic analysis (HR + LCA + TEA) was employed to elucidate camelina’s sustainability case. The potential camelina land was determined via the wheat-fallow Integrated Rotational Cycle (IRC) at county level for the 48 lower states in the U.S. Results revealed these lands were aggregated on the top wheat producing states of Montana, Kansas, and North Dakota at 19.5 × 106 ha, 18.2 × 106 ha, and 19.2 × 106 ha, for 2009, 2012, and 2015, respectively. If the high producing wheat lands (counties with >60,000–80,000 ha) in those states were grown with camelina at U.S. average yield of 1.2 Mg/ha, around 6.35 million m3 (1.68 billion gal) of advanced biofuel will be produced, equivalent to 11.18 % of the expanded Renewable Fuel Standard (RFS2) volume mandate for advanced biofuel (15 billion gal). LCA results using 1 MJ functional unit and “well-to-air” (WTA) system boundary showed that the operations cumulative energy demand (CED) for the OMT case producing simultaneous biojet, avgas, and diesel was 0.75 MJ/MJ, lower than for hydroprocessed renewable jet (HRJ) fuel (0.77 MJ/MJ) but 6.8 times higher than for petroleum jet (PTJ) fuel (0.11 MJ/MJ). The entire OMT energy demand was offset by the bioelectricity produced (0.57 MJ/MJ) from burning the meal. OMT’s net GHG reduction relative to PTJ was 23.34 % but increasing camelina yield from 1.2 to 1.8 Mg/ha increased reduction to 75.71 %. TEA results adapting 100,000 m3/yr biofuel throughput showed that OMT and HRJ had profits of $21.94 M and $24.13 M, respectively, using mass product allocation. The limiting metric for OMT and HRJ was net present value (NPV), and the minimum camelina yield to ensure profit was 1.18 Mg/ha. OMT can achieve maximum profit by selling biojet fuel at a price not lower than $2.75/gal and selling camelina meal feed pellets at a minimum price of $330/Mg. No tax incentive was needed for biojet and avgas because even at their base median values (biojet = $2.19/gal, avgas = $2.59/gal), NPV is still positive.

Polar Aromatic Compounds in Soot from Premixed Flames of Kerosene, Synthetic Paraffinic Kerosene, and Kerosene–Synthetic Biofuels

Polar Aromatic Compounds (PAC) adsorbed on soot produced in laboratory premixed flames of fossil kerosene (Jet A-1), Synthetic Paraffinic Kerosene (SPK), and Jet A-1 - synthetic biofuels (2,5-dimethylfuran, methyloctanoate, diethylcarbonate and 1-butanol) were characterized for the first time in the aim of shedding light on the combustion mechanisms and evaluating the environmental impact of these synthetic biofuels. The following families of compounds were fractioned from the soot extracts and further their relative abundances estimated: (a) oxa-AHs (xanthenes, benzoxanthene, alcoxy-AHs, furan…); (b) aldehydes-AHs, (c) ketones-AHs; (d) quinones-AHs; (e) aromatic monocarboxylic acids; (f) aromatic hydroxy-acids; (g) aromatic dicarboxylic acids; (h) nitrated-AHs (including amines, acridines, cinnoline derivatives, carbazoles…); (i) nitro-AHs. The results obtained point out that overall, soot from Jet A-1 - biofuels premixed flames are richer in PAC than soot from pure Jet A-1 and SPK. Out of the fuels studied, Jet A-1 - 1-butanol produces the highest concentrations of nitro-AHs (namely nitro-benzaldehydes), of aldehydes-AH and hydroxy-AHs (including two isomers of hydroxy-benzaldehyde); whereas Jet A-1 - diethylcarbonate produces the highest concentrations of quinone-AHs (especially phenanthrene-quinones) and large concentrations of nitrated-AHs. On the other hand, soot from Jet A-1 - methyloctanoate is the richest one in mono aromatic and dicarboxylic acids, aromatic hydroxyacids, nitrated-AHs, and esters. Combustion of the Jet A-1 - 2,5-dimethylfuran mixture emits the highest concentrations of ketone-AHs, and oxa-AHs (namely, furan derivatives). We should remark that although the soot samples were obtained from pre-mixed flames, the lab conditions being far from the industrial conditions, particularly in terms of pressure; the chemistry going on should not be so different that our findings could not be extrapolated to industrial conditions.

Experimental Investigation of Emission Characteristics on Can-Combustor Using Jatropha Based Bio-derived Synthetic Paraffinic Kerosene

ABSTRACT Emissions emanating from gas turbine are important and critical in terms of environmental impact. In general, oxides of nitrogen, total unburned hydrocarbon, carbon monoxide, carbon dioxide, and soot particles are the most significant emissions from gas-turbine combustion systems. In order to reduce these emissions, fuels derived from bio-origin are being increasingly used for gas-turbine combustion. Since aviation accounts for more than 5% of anthropogenic emissions, and also due to increasing pressure from governments across the globe for emission reduction, it is important to investigate pathways to reduce aviation-generated emissions. We, therefore, propose the use of Jatropha-based bio-derived synthetic paraffinic kerosene (SPK) blended with aviation turbine fuel (ATF)-Jet A1, and experimentally investigate the emission characteristics within a laboratory-scale gas-turbine combustor from proposed fuel blends. The investigation is done for two different operating conditions: operating condition 1 (OC1) and operating condition 2 (OC2). The influence of emission characteristics of the two biofuel blends, namely BF-II and BF-IV, are analyzed and compared with that of neat ATF-Jet A1. A substantial reduction of 33.5% in THC, 20% in CO, 42% in soot and increase of 40% in NO x and 28.7% in CO2 emissions are evident for BF-II fuel in comparison to ATF with OC1. However, at OC2, these emission reductions are less with increased NO x emissions of 50.2% in comparison to that of ATF. In addition, for the fuel BF-IV, there have been reductions of 57.2% THC, 33.3% CO, 67.1% soot and increase of 49.4% NO x and 43.9% CO2 emissions as compared with ATF at OC1. Also THC, CO, soot, and CO2 emissions are reduced considerably with increased NO x emissions for BF-IV fuel at OC2.

Energy, exergy, exergoeconomic, and environmental assessment of different technologies in the production of bio-jet fuel by palm oil biorefineries

This work explores palm oil and the residual biomass from oil palm extraction to obtain valuable products via sustainable routes in integrated biorefineries, which were separated into three scenarios: Baseline Scenario is the current Brazilian application of palm in the energy sector using a biodiesel plant with a cogeneration system; Scenario 1 integrates a Hydrotreatment of Esters and Fatty Acids unit to produce bio-jet fuel into the previous case; and Scenario 2, integrates a second-generation ethanol plant and an Alcohol-to-Jet process in order to obtain bio-jet fuel from the second generation. Taking into account that the selection and integration of processes carried out in a biorefinery would impact the overall efficiency of the system, the production costs and the impacts on the environment of the plant make it is necessary to carry out a comprehensive evaluation of the system that allows characterizing and quantify the energy, economic and environmental aspects related to the biomass energy conversion. A methodology of analysis was proposed to address all of these aspects and to provide results that allow for a decision-making guide in technology selection. It was identified that the main need for improvement in the biorefineries relies on cogeneration, which exergy destruction rate ranged from 167.99 to 213.63 MW. The unit exergoeconomic costs founded for glycerol, biodiesel, and electricity were all lower than the market costs, the bio-jet fuel costs, from hydrotreatment, were nearly the same as those from the Brazilian market 0.49 and 0.46 USD/L, respectively. However, the costs of upgrading ethanol were the highest found and way higher than the market rate at 5.15 USD/L. Environmentally, the selected configuration of biorefineries provides all produced biofuel environmental gains compared to conventional non-renewable fuels. Biodiesel and bio-jet fuels would avoid emission of 324.65 kgCO2eq/t and 3092.45 kgCO2eq/t, respectively.

Pyrolysis of 2-methylfuran/jet fuel surrogate blends: An experimental and kinetic modeling study

Owing to significant advantages over traditional biofuels, 2-methylfuran (MF) has arisen extensive interest as next generation biofuels. Atmospheric pressure pyrolysis of a 1:1 blend of MF with a three-component (3C) surrogate jet fuel was conducted in a flow tube using synchrotronphotoionization and molecular beam mass spectrometry techniques within a temperature range of 898–1223 K. Therein, the 3C surrogate fuel consists of 66.2% n-dodecane (NC12H26), 18.0% 1,3,5-trimethylcyclohexane (T135MCH) and 15.8% n-propylbenzene (NPB, A1C3H7). The detailed kinetic model including 579 species and 3474 reactions was developed via validating against both measured and literature data with reasonable agreement. MF exhibits no obvious influence on the 3C components pyrolysis. However, 3C mixtures play an important roles in MF decomposition: lower initial temperature and different decomposition pathways. In the meantime, n-propylbenzene (NPB) pyrolysis curve in 3C and 3C+MF significantly transfers to low temperature zone after 1000 K in contrast to pure NPB, while smaller change was found in the decomposition curve of n-dodecane. Compared with 3C pyrolysis, 3C+MF blends have less formation of aromatic species and light hydrocarbons except for vinylacetylene (C4H4) and acetylene (C2H2). Allyl radical (C3H3) has significant roles in benzene ring formation. The combination of allyl radical with propargyl radical producing benzene and H radical (aC3H5 + C3H3 = A1 + 2H) has the highest contribution to the benzene formation in both 3C and 3C+MF. Moreover, most of naphthalene (A2) formation is also related to C3H3 radical via reaction: A1CH2 + C3H3 = A2 + H, rather than via HACA (hydrogen abstraction carbon addition) reaction. Interaction of fuel blends was mainly presented through the common and important sensitive reactions which are much to do with CH3 and H radicals. The overview of product distribution was investigated by providing comparisons of carbon conversion rates during the pyrolysis of 3C and 3C+MF. These results will be helpful to better understand the pyrolysis properties of MF/jet fuel surrogate blends and could contribute to developing new generation biofuels for aviation.

Conversion of Oil Palm Empty Fruit Bunch (EFB) Biomass to Bio-Oil and Jet Bio-Fuel by Catalytic Fast-Pyrolysis Process

Oil palm empty fruit bunch (EFB) biomass is a potential source of renewable energy. Catalytic fast-pyrolysis batch process was initially performed to convert oil palm EFB into bio-oil, followed by its refinement to jet bio-fuel. Crystalline zeolites A and Y; synthesised from rice husk ash (RHA), were applied as heterogeneous catalysts. The catalytic conversion of oil palm EFB to bio-oil was conducted at a temperature range of 320-400°C with zeolite A catalyst loadings of 0.6 - 3.0 wt%. The zeolite catalysts were characterised by XRD, FTIR and FESEM. The bio-oil and jet bio-fuel products were analysed using GC-MS and FTIR. The batch fast-pyrolysis reaction was optimised at 400°C with a catalyst loading of 1.0 wt%, produced 42.7 wt% yields of liquid bio-oil, 35.4 wt% char and 21.9 wt% gaseous products. Analysis by GCMS indicates the compound distribution of the liquid bio-oil are as follows: hydrocarbons (23%), phenols (61%), carboxylic acids (0.7%), ketones (2.7%), FAME (7.7%) and alcohols (0.8%). Further refinement of the liquid bio-oil by catalytic hydrocracking over zeolite Y produced jet bio-fuel, which contains 63% hydrocarbon compounds (C8-C18) and 16% of phenolic compounds.

Synthesis of High-Density Aviation Biofuels from Biomass-Derived Cyclopentanone

Herein, we describe a three-step synthesis strategy starting with a chemical kinetics-governed one-pot two-step reaction. A series of biomass-derived molecules have been converted into ring-structured alkanes suitable for use as transportation fuels or jet fuels with high overall isolated yields of 68–90%. Various biomass-derived molecules can be used as starting materials, which include molecules with different functional groups such as carbonyl groups, benzene and furan rings, olefins, and so forth. Efficient and green reactions, including one-pot two-step reactions and solvent-free reactions, with common reagents and catalysts under mild reaction conditions or even under room temperature, were developed to produce bi(cyclopentane)-based biofuels with diversified and selective structures in good to excellent yields. The obtained products exhibit high densities of 0.87–0.94 g/cm3 and high net volumetric heating values of 38.3–41.4 MJ/L. Besides, they also have other fuel properties comparable to some well-known commercial synthetic fuels such as JET A, JET A-1, JET B, JP-10, and RJ-4. Some of the obtained biofuels have low freezing points of −58 and −80 °C. This general synthetic approach could be extended to a range of precursors with different carbon numbers, which allows the selective generation of high-energy content ring-structured alkanes with carbon numbers of C11–C26.

Fischer–Tropsch Synthesis as the Key for Decentralized Sustainable Kerosene Production

Synthetic fuels play an important role in the defossilization of future aviation transport. To reduce the ecological impact of remote airports due to the long-range transportation of kerosene, decentralized on-site production of synthetic paraffinic kerosene is applicable, preferably as a near-drop-in fuel or, alternatively, as a blend. One possible solution for such a production of synthetic kerosene is the power-to-liquid process. We describe the basic development of a simplified plant layout addressing the specific challenges of decentralized kerosene production that differs from most of the current approaches for infrastructural well-connected regions. The decisive influence of the Fischer–Tropsch synthesis on the power-to-liquid (PtL) process is shown by means of a steady-state reactor model, which was developed in Python and serves as a basis for the further development of a modular environment able to represent entire process chains. The reactor model is based on reaction kinetics according to the current literature. The effects of adjustments of the main operation parameters on the reactor behavior were evaluated, and the impacts on the up- and downstream processes are described. The results prove the governing influence of the Fischer–Tropsch reactor on the PtL process and show its flexibility regarding the desired product fraction output, which makes it an appropriate solution for decentralized kerosene production.

Exergoeconomic and Environmental Analysis of a Palm Oil Biorefinery for the Production of Bio-Jet Fuel

The production of biofuel from biomass is a viable option, due to the availability of biomass and its renewable character. This work aims to explore the production of bio-jet fuel via different routes in the context of a biorefinery in which the production of the bio-jet fuel is integrated with a palm oil mill and a transesterification plant for the production of biodiesel. In addition to handling the extraction and transesterification phases, the system has also a second-generation ethanol plant and facilities for the production of bio-jet fuel via HEFA and ATJ. The biorefinery has a cogeneration plant that is responsible for supplying all the processes with thermal and electric energy. The system is evaluated using the first and second laws of thermodynamics, and is shown to have efficiencies of 37% and 55%, respectively. An exergoeconomic and economic analysis is also carried out in this study. The thermodynamic analysis highlights the immature character of the bio-jet fuel production chain, due to the irreversibilities, in the HEFA scenario, 47 MW, and in the for the combination of 2G-ethanol and ATJ plants, 82 MW. In the ATJ process, the highest thermoeconomic costs were found for the biofuels. However, although the surplus of electricity produced had a higher cost than for any other product, at 65.53 US$/MWh, this was within the margins of market competitiveness in Brazil. The economic analysis showed that the project was not attractive due to the high initial investment required. From an environmental standpoint, the production of bio-jet fuel is an alternative that can mitigate the effects of global warming compared to fossil jet fuel, with reductions in emissions of 84.7% and 72.8% for HEFA and ATJ bio-jet fuels, respectively. In summary, it is shown that although diversification of the biorefinery’s products can contribute to the finances of the plant, the production chains are not fully prepared, and the processes of bio-jet acquisition has low production yields and a high level of irreversibility.

Estimating induced land use change emissions for sustainable aviation biofuel pathways

Sustainable aviation fuels (SAFs) are expected to play an essential role in achieving the aviation industries' goal of carbon-neutral growth. However, producing biomass-based SAFs may induce changes in global land use and the associated carbon stock. The induced land use change (ILUC) emissions, as a part of the full life-cycle emissions for SAF pathways, will affect whether and to what extent SAFs reduce emissions compared with petroleum-based jet fuels. Here, we estimate the ILUC emission intensity for seventeen SAF pathways considered by the International Civil Aviation Organization (ICAO), covering five ASTM-certified technologies, nine biomass-based feedstocks, and four geographical regions. We introduce the SAF pathways into a well-established computable general equilibrium (CGE) model, GTAP-BIO, and its coupled emission accounting model, AEZ-EF, to study economy-wide implications of SAF production and estimate ILUC emissions intensity for each pathway. The estimated SAF ILUC emission intensities, using a 25-year amortization period, range from -58.5g CO2e MJ-1 for the USA miscanthus alcohol (isobutanol)-to-jet (ATJ) pathway to 34.6g CO2e MJ-1 for the Malaysia & Indonesia palm oil Hydrotreated Esters of Fatty Acids (HEFA) pathway. Notably, the vegetable oil pathways tend to have higher ILUC emission intensities due to their linkage to palm expansion and peatland oxidation in Southeast Asia. The cellulosic pathways studied provide negative ILUC emissions, mainly driven by the high carbon sequestrations in crop biomass and soil. Using the core life-cycle emissions established by ICAO, we show that fifteen of the assessed pathways have a lower full life-cycle emission intensity than petroleum-based jet fuels (89g CO2e MJ-1), offering promising options to reduce aviation emissions.

Bio-jet fuel range in biofuels derived from hydroconversion of palm olein over Ni/zeolite catalysts and freezing point of biofuels/Jet A-1 blends

According to the regulation announced by International Air Transport Association to reduce greenhouse gas emissions, there are many attempts to produce bio-jet fuels from natural oils to replace, at least in part, the fossil fuels. However, bio-jet fuels usually suffer from poor cold flow properties. Hence, this research aimed to convert palm olein to bio-jet fuel range with high content of iso-alkanes via hydroconversion over nickel (Ni)/zeolite-based catalysts. The levels of liquid biofuels classified as bio-gasoline, bio-jet and green diesel, including the selectivity for chemical compositions were evaluated. Under 40 bar initial H2 pressure at 360 °C for 4 h, the use of Ni/NH4-Beta catalysts (Ni content = 10 wt%) provided the maximum iso-/n-alkane ratio at 1.67 with a bio-jet yield of 20.8 wt%. The schematic reaction mechanism for this process was also proposed. The incorporation of platinum (Pt) into the Ni/NH4-Beta catalysts to a Pt/(Pt + Ni) wt ratio of 0.24 increased the bio-jet yield to 28.7 wt% with iso-/n-alkane ratio of 1.02. Differential scanning calorimetry thermograms indicated that the freezing temperature (Tf) of the biofuels decreased with increasing iso-/n-alkane ratio, where the Tf of the liquid biofuels with iso-/n-alkane ratio > 1.00 was not observed. For the biofuels/fossil jet fuel (Jet A-1) blends, the use of biofuels having iso-/n-alkane ratio of 1.67 could be blended with Jet A-1 up to 50/50 (v/v) and the Tf of the blended jet fuel was found at ca. −80 °C, which was lower than the limitation according to ASTM D1655-04a (−47 °C).

Sustainable coastal halophyte farming for biofuel in arid regions: site and feedwater screening using geochemical modeling

Halophyte agriculture in marginal soils using saline water offers a sustainable solution for generating biomass feedstock for carbon-neutral aviation biofuels. A full-scale sustainable energy and agriculture system (SEAS) demonstration is planned for the Abu Dhabi coast, where evaporitic gypsiferous soils pose a challenge to long-term operation because of the potential for land degradation. In this study, geochemical modeling on the Geochemist’s Work Bench (GWB®) platform was employed to (1) evaluate the feasibility of using coastal groundwater versus seawater as irrigation feedwater, (2) determine the change in agricultural return water salinity through site-specific soils upon different seawater irrigation rates, and (3) assess mineral deposition effects in the soil column as a function of site-specific soil characteristics at candidate sites over a 1-year period of continuous seawater irrigation. Evaporation modeling was used to evaluate potential feedwater sources while varying feedwater composition and electrolyte activity coefficient models. 1-D saturated–flow advection–precipitation/dissolution modeling was utilized to assess return water quality and mineral deposition as a function of both the electrolyte activity coefficient model and the mineral composition of site-specific soils. Results pointed to seawater as the more viable feedwater option compared to coastal groundwater because of slower onset of precipitation. This effort demonstrated that soil type did not influence agricultural return water salinity (except for strongly gypsic soils) but influenced mineral precipitation under surficial evaporation conditions. Porosity loss correlated with layers of mineral deposition. The study points to the need for careful screening of land and saline water resources for the sustainable farming of halophytes.

A Comparison Study of Soot Precursor and Aggregate Property Between Algae-Based Aviation Biofuel and Aviation Kerosene RP-3 in Laminar Flame

Abstract Algae-based aviation biofuel shows the potential to reduce soot emission in flight. A comparison study of soot precursor and aggregate property between algae-based biofuel and aviation kerosene RP-3 in laminar flame was conducted to investigate the reason of biofuel’s less soot formation. The soot precursors were determined by the fringe lengths of soot particles. At a typical dimensionless height DH = 0.50 of both flames, the geometric mean fringe lengths of biofuel and RP-3 are measured to be 0.67 and 0.73 nm, respectively, approximating to the size of five-ringed (A5) and seven-ringed (A7) poly-aromatic hydrocarbon, respectively. An A5 growth mechanism was then added to biofuel surrogate mechanisms for soot formation simulation. Since the carbon number component of biofuel is wide and difficult for comprehensive mechanism development, two surrogate mechanisms were developed. One is based on the C8–C16 n-alkane that covers biofuel’s main components, and the other one is based on biofuel’s average carbon number to simplify the mechanism. Meanwhile, an A7 growth mechanism was added to a popular RP-3 mechanism. The soot formation simulation with the combination mechanisms for both fuels provides a better agreement with the measured primary particle diameter and suggests that the reason for less soot production by biofuel is its less soot precursor production that weakens soot nucleation and growth. Lastly, the soot fractal dimension of biofuel is smaller than that of RP-3, indicating that biofuel has a looser soot aggregate.

Transition to the bioeconomy – Analysis and scenarios for selected niches

Bio-based innovations do not evolve independently from each other, but are interrelated and may enjoy synergies, but also compete for resources (i.e. biomass, skills). Therefore, we explore possible transition pathways that distinct bio-based niches could follow during a joint transformation process. We apply the Multi-Level-Perspective’s transition pathways to the four distinct niches of (i) bioplastics, (ii) biolubricants and of biofuels for (iii) road and (iv) aviation. A subsequent scenario exercise that combines possible transitions paths of these niches enables us to explore the special relation between the individual niches and to detect possible synergies or conflicts. The scenarios show that diverse developments between bio-based niches in terms of scale and type of transition in the future are highly plausible. Finally, based on the results we derive conclusions about appropriate governance arrangements for the bioeconomy.