Renewable Transportation Fuels Research Articles

Review of Methods for Converting Biomass into Biofuels

Thermochemical processes are among the most effective methods of obtaining hydrogen-rich gases from biomass. These technologies mainly include pyrolysis, gasification and hydrothermal liquefaction. Thermochemical conversion of dry biomass is similar to the conversion of fossil fuels using gasification and pyrolysis methods. Products obtained through thermochemical processes (CO and CH4) can be processed into other biofuels, e.g. syngas, a raw material for producing synthetic hydrocarbons, methanol and alcohols. In recent years, advanced research has been carried out using biomass to produce liquid fuels. The biomass pyrolysis process in the presence of a catalyst is based on the rapid heating of the biomass to a temperature of approximately 500°C in the so-called inert atmosphere in which there are no reactive gases. This process produces a liquid product: pyrolysis oil, gas and charcoal. The bio-oil produced in this process constitutes 60-75% of the mass of the biofuel and is thermally unstable because it contains up to 300 different chemical compounds. However, the bio-oil obtained in this way is incompatible with conventional liquid transport fuels (gasoline, diesel) due to its high oxygen content. Pyrolysis in the presence of a zeolite catalyst is a process that allows for the effective conversion of biomass in economic and ecological terms. A zeolite catalyst makes it possible to remove oxidized compounds in situ and modify the properties of the biofuel to ensure its compatibility with conventional transport fuels. The catalyst plays a crucial role in this process because it removes oxygen from oxygenates and, consequently, creates stable reaction products that can then be treated to obtain renewable transport fuels or other useful chemicals. The article presents methods of biomass conversion via pyrolisis, microorganisms usage, zeolite-based catalysis, biocatalysis and photo-fermentation, which poses a big possibility of diversification of renewable energy sources.

Recent Advances in Hydrodeoxygenation of Lignin‐Derived Phenolics over Metal‐Zeolite Bifunctional Catalysts

AbstractThe hydrodeoxygenation (HDO) reaction provides a promising catalytic strategy to remove oxygen in biomass‐derived bio‐oil to produce renewable transportation fuels and value‐added chemicals. The development of highly efficient and stable HDO catalysts plays an essential role in biomass valorization. Metal‐zeolite bifunctional catalysts have been well‐developed as the effective HDO catalysts in upgrading lignin‐derived phenolics due to their excellent activity, selectivity, and thermal and hydrothermal stability. However, clarifying the roles of the active sites and their synergistic effect, and establishing effective structure‐performance relationships in the HDO process still face challenges. In this review, we first survey the conventional catalysts applied in the HDO of bio‐oil, followed by thoroughly discussing the roles of metal centers, acid sites, supports, and their impacts on the HDO process of phenolic model compounds or bio‐oil. Finally, a discussion on the stability and deactivation of metal‐zeolite catalysts, especially in the aqueous‐phase HDO reaction, is provided. This critical review offers new insights into the development of state‐of‐the‐art metal‐zeolite bifunctional catalysts with well‐defined porosity and metal‐acid properties for viable biomass valorization.

The Word Shrinks, the World Expands.

Crises and urgencies are not new phenomena, as well as phases of expansion and contraction (or shrinkage). These dynamics are the essential base on which ground the Author of this paper reflected. His focus is specifically on the scientific and technological backgrounds of two quite different fields: petro-chemical geophysics and information technology, and their respective and opposite roles in “shrinking” or “expanding” the perceived and actual size, scale, and grain of the developed landscape. By putting together these two fields, planners can have the sufficient background to anticipate future land patterns that respond to the relocating effects of scarce, expensive, and renewable transportation and shipping fuels on the one hand, and the continued globalization of culture and corporate ownership on the other. This reflection, as highlighted in this special issue of CONTESTI, is pivotal in a context of a changing “new normal” of the 21st-century society. We must accept that the everyday life of people all over the world can be affected by unexpected disruptions, waves of crisis and recovery that may continuously create new equilibriums. Also, the world is, in some aspects, shrinking, but in other cases is expanding. How can we face such a situation? What can we expect as a result in terms of (re)configuration of cities and territories? In which world we would live in the (near) future?

Experimental study of droplet vaporization for conventional and renewable transportation fuels: Effects of physical properties and chemical composition

As part of the global energy transition, an increasing number of sustainable liquid fuels with a wide range of physical and chemical properties becomes available for gas turbine and IC engines. For an optimal design and operation of these engines, an improved understanding of the effects of fuel properties on atomization, vaporization and combustion kinetics is required. The present work provides a comprehensive experimental study of fuel effects on droplet vaporization for numerous conventional and alternative fuels. The study employs a recently developed flow channel, where free-falling droplets with initial diameters of D≈77μm vaporize under technically relevant gas temperatures Tg of up to 1300 K. The evolution of droplet diameters over travel distance and time is measured using microscopic shadow imaging. A total of 13 single fuel components, five bi- and tri-component mixtures, six conventional and alternative jet fuels and mixtures thereof, and three IC engine fuels and mixtures thereof have been tested under well-reproducible ambient conditions. The fuels represent a wide range of chemical classes such as n-alkanes, iso-alkanes, cycloalkanes, aromatics, alcohols and oxymethylene ethers, and most of them were measured for the first time with realistic D and Tg. The results for the single fuel components reveal in detail the temperature-dependent effects of physical properties such as boiling point Tb, liquid density ρl and enthalpy of vaporization Hv. In particular, it was found that for high gas temperatures of about 1250 K, the vaporization rate is almost completely determined by the product of Hv and ρl. By comparison with the results for single n-alkanes, the measurements for bi- and tri-component mixtures accurately characterize the preferential vaporization of individual fuel components over droplet lifetime. The results for various multi-component fuels reveal complex interplays of preferential vaporization and temperature-dependent influences of physical properties. It is shown that the vaporization for conventional and corresponding alternative fuels can differ significantly. Finally, the droplet vaporization is characterized for mixtures of PRF90+ethanol and ethanol+water, which exhibit a non-ideal vapor–liquid equilibrium.

Shifts in catalyst deactivation mechanisms as a function of surface coverage during Friedel-Crafts acylation in zeolites

The production of commodity chemicals from renewable resources is often accompanied by rapid catalyst deactivation rates. An important example is direct Friedel Crafts acylation, which can yield a range of valuable products from surfactants to renewable transportation fuels. Furanic acyl acceptors are among the most intriguing and promising possible acceptors; however, they undergo self-coupling reactions in the presence of Brønsted acid surface sites leading to rapid catalyst deactivation. In this contribution, we study 2-methylfuran acylation with acetic acid over HZSM-5 catalysts at temperatures ranging from 160 to 240 °C, revealing the remarkable shift in deactivation behavior as a function of surface coverage of acetic acid. We reveal that a surface saturated with acetic acid lowers the deactivation rate by blocking the direct access of furanic species to surface sites. However, on surfaces fully saturated with carboxylic acids, deactivation is revealed to proceed via reactions between adsorbed products with gas phase methylfuran reactants.

Toward the production of renewable diesel over robust Ni nanoclusters highly dispersed on a two-dimensional zeolite

Deoxygenation of bioderived lipids into renewable transportation fuels is a promising route to decreasing the dependence on fossil sources. Ni-based catalysts are high performing and cost-effective in deoxygenation reactions but suffer from severe sintering and aggregation. Herein, a ligand-chelating impregnation method was used to prepare highly dispersed Ni nanoclusters on a two-dimensional (2D) ITQ-2 zeolite. Comprehensive characterization was utilized to monitor the changes in the organometallic precursors during activation and to investigate their impact on the dispersion of the Ni nanoclusters on the ITQ-2 zeolite. The high external surface area and abundant surface defects of the 2D support enhanced the dispersion and immobilization of the Ni nanoclusters and outperformed conventional zeolites. The protection of the Ni2+ cations by the organic ligand suppressed the aggregation of Ni species during the activation processes, thereby leading to the formation of uniformly distributed Ni nanoclusters on the ITQ-2 zeolite. Due to the highly dispersed Ni nanoclusters and immobilization on the 2D zeolite, the Ni/ITQ-2-co material prepared by the ligand-chelating impregnation approach showed outstanding activity and stability for conversions of stearic acid or palm oil to diesel range alkanes. This work provides a rational design and precise modulation of metal-based catalysts for the production of renewable diesel.

Prospective life cycle assessment of alternatively fueled heavy-duty trucks

The development of renewable drop-in diesel fuels is essential for decarbonizing the diesel-dominated heavy-duty fleet in the short to medium term. Therefore, the project ‘Robust and Efficient processes and technologies for Drop In renewable FUELs for road transport’ (REDIFUEL), developed a novel renewable fuel production technology. The novel fuel, named REDIFUEL, consists of a mixture of high-cetane hydrocarbons and C6-C11 alcohols. This work presents a complete well-to-wheel environmental assessment of REDIFUEL use in heavy-duty mild hybrid and plug-in long haul hybrid trucks with prospective Life Cycle Assessment (LCA). In addition, the use of REDIFUEL is compared to trucks fueled with fossil diesel, conventional biodiesel, and battery electric trucks. The LCA results showed a reduction in climate change impacts of 40–55% in 2030, and 27–64% in 2050 when REDIFUEL displaces fossil diesel. The sensitivity analysis showed that the feedstock value, the payload, and the allocation factor were the most important parameters affecting the climate change results. For most environmental impact categories, plug-in hybrid and battery electric long haul trucks had higher impacts than mild hybrid trucks fueled with REDIFUEL.

Perspective on renewable fuels for public transport by bus in small and medium-sized Brazilian cities.

Perspective on renewable fuels for public transport by bus in small and medium-sized Brazilian cities.

Proton Affinities of Alkanes.

Chemical characterization of complex mixtures of large alkanes is critically important for many fields, including petroleomics and the development of renewable transportation fuels. Tandem mass spectrometry is the only analytical method that can be used to characterize such mixtures at the molecular level. Many ionization methods used in mass spectrometry involve proton transfer to the analyte. Unfortunately, very few proton affinity (PA) values are available for alkanes. Indeed, previous research has shown that most protonated alkanes (MH+) are not stable but fragment spontaneously via the elimination of a hydrogen molecule to form [M - H]+ ions. Here, the PAs of several n-alkanes and alkylcyclohexanes containing 5-8 carbon atoms, n-pentane, n-hexane, n-heptane, n-octane, cyclohexane, methylcyclohexane, and ethylcyclohexane, were determined via bracketing experiments by using a linear quadrupole ion trap mass spectrometer. Monitoring the formation of the [M - H]+ ions in reactions between the alkanes and protonated reference bases with known PAs revealed that the PAs of all the alkanes fell into the range 721 ± 20 kJ mol-1. In order to obtain a more accurate estimate of the relative PAs of different alkanes, two alkanes were introduced simultaneously into the ion trap and allowed to react with the same protonated reference base. Based on these experiments, the longer the alkyl chain in an n-alkane or alkylcyclohexane the greater the PA. Further, when considering alkanes with the same number of carbon atoms, the PAs of those with a cyclohexane ring were found to be greater than those with no such ring.

Renewable Drop-in Fuels for Heavy-duty Transport

Renewable Drop-in Fuels for Heavy-duty Transport

Reductions in greenhouse gas emissions through innovative co-production of bio-oil in combined heat and power plants

Integrating fast pyrolysis into existing biomass-based combined heat and power (CHP) plants offers an innovative opportunity for plant operators to acquire an additional heat sink and produce a renewable transport fuels feedstock. This technology is particularly interesting in Sweden, where biobased heat and power constitute an important part of the energy system. It is important to establish the GHG emissions reduction of the production, through e.g. substitution effects in the transport sector, to ensure coherence with climate ambitions. In this study, the GHG emission avoidance methodology in the newly introduced EU Innovation Fund (IF) was adapted to determine whether integrating bio-oil production into an existing wood-fuelled CHP plant through fast pyrolysis would lead to a significant reduction in GHG emissions compared to the status quo. The results showed a reduction in GHG emissions of up to 0.24 MtCO2-eq per year, due mainly to the replacement of fossil fuels in the transport sector. A potential production volume in existing Swedish CHP plants was estimated to be 6.8–8.1 Mt of bio-oil annually, leading to a GHG emission avoidance of 8.6–10.3 MtCO2-eq/y, requiring a wood fuel input of 181–185 PJ/y. Sensitivity analysis indicated a significant potential for the reduction using input parameters for heating, electricity and hydrogen production whether pre-defined in the IF methodology or determined from case-specific conditions. However, the detailed results indicate that case-specific conditions should be used to reflect the fact that different European countries are at different stages in the transition to a fossil-free energy system. In conclusion, according to IF-based calculations, commercialisation of combined heat, power and bio-oil technology could lead to significant GHG emission avoidance across multiple sectors.

Technoeconomic analysis and environmental sustainability estimation of bioalcohol production from barley straw

European Union bioeconomy policy emphasizes that the production of renewable transportation fuels should replace fossil fuels as much as possible. In particular, the utilization of waste or side-stream lignocellulosic materials for fuel production is highly recommended. Moreover, future crises forcing a reliance on locally available sources for fuels and energy may become increasingly common. Barley straw, a common agricultural residue in northern Europe, is a potential raw material for bioalcohol production via fermentation. In this study, the technoeconomic and environmental sustainability of bioethanol and biobutanol production from barley straw were evaluated. When compared with fossil gasoline production and use, the greenhouse gas emissions reduction 77.6% and 72.1% were achieved for ethanol and butanol production, respectively. Thus, the emission reduction of 65% for biofuels demanded by the European Union renewable energy directive was achieved in both biofuel production processes evaluated. However, our results indicated that ethanol production from barley straw, a well-known and mature technology, was an economically feasible process (NPV positive, IRR 20%) but that butanol production with Clostridium species through acetone-butanol-ethanol fermentation has still technoeconomic challenges to overcome (NPV negative, IRR below 10%). This was mainly due to the low yield and high recovery costs of butanol.

Electrolysis Assisted Biomass Gasification for Liquid Fuels Production

Gasification is a promising pathway for converting biomass residues into renewable transportation fuels and chemicals needed to comply with the ambitious Swedish environmental targets. The paper investigates the integration of a molten carbonate electrolysis cell (MCEC) in biofuel production pathway from sawmill byproducts, to improve the performance of gas cleaning and conditioning steps prior to the final conversion of syngas into liquid biofuels. The energy, material, and economic performance of process configurations with different gasification technologies are simulated and compared. The results provide relevant information to develop the engineering of gas-to-liquid transportation fuels utilizing renewable electricity. The MCEC replaces the water-gas shift step of a conventional syngas conditioning process and enables increased product throughput by as much as 15%–31%. Depending on the process configuration and steam-methane reforming technology, biofuels can be produced to the cost range 140–155 €/MWh in the short-term.

Bioenergy with carbon capture and storage (BECCS) potential in jet fuel production from forestry residues: A combined Techno-Economic and Life Cycle Assessment approach

In this study, the economic and environmental feasibility of a process configuration based on the Bioenergy and Carbon Capture and Storage (BECCS) concept is assessed. The research analyses the production of jet fuel from forestry residues-derived syngas via the Fischer-Tropsch (FT) technology. Further, the CO2 removed in the syngas cleaning section is not released to the environment, instead it is permanently sequestrated. The produced Sustainable Aviation Fuel (SAF) has the potential to achieve negative emissions. The present research is a one-of-a-kind study for the jet fuel production within the BECCS concept. The process has been modelled within the Aspen Plus and Matlab software to obtain detailed and realistic mass and energy balances. Based on these balances, the technical, economic and environmental parameters have been calculated. Based on a plant that treats 20 dry-t/h of forest residues, 1.91 t/h of jet fuel are produced, while 11.26 t/h of CO2 are permanently stored. The inclusion of the CCS chain in the biorefinery increase the minimum jet fuel selling price from 3.03 £/kg to 3.27 £/kg. The LCA results for global warming show a favourable reduction in the BECCS case, in which negative emissions of −121.83 gCO2eq/MJ of jet fuel are achieved, while without CCS case exhibits GHG emissions equal to 15.51 gCO2eq/MJ; in both cases, the multi-functionality is faced with an energy allocation approach. It is, then, evident the significant environmental advantages of the BECCS process configuration. Nevertheless, financial feasibility can only be attained through the implementation of existing policy schemes and the formulation of new strategies that would reward negative emissions. The application of the UK’s policy “Renewable Transport Fuel Obligation” and a hypothetical scheme that rewards negative CO2 emissions, breaks-even the Minimum Jet fuel Selling Price (MJSP) at 1.49 £/kg for a certificate and carbon price of 0.20 £/certificate and 246.64 £/tonne of CO2.

DRIVERS OF LIQUID BIOFUEL PRICES IN POLAND

The general aim of the study was to determine the impact of legal regulations in force on the market of liquid biofuels and biocomponents in Poland on the prices of fatty acid methyl esters (so-called biodiesel or BIO100 biofuel). Therefore, we indicated the importance of legal regulations in shaping biodiesel prices in Poland based on empirical data from the period of 2008-2016 (the latest available data). An additional purpose was to assess the legal regulations as drivers of ecodiesel (diesel with an admixture of biodiesel) prices in Poland based on empirical data from the period 2004-2021. Institutional, legal and economic variables were distinguished, assuming that the biofuel market, like many other markets, is so heavily regulated that taking legal acts into consideration is crucial for its functioning. Multiple regression analysis was used. The sources of data were officially available databases (PKN Orlen Data, FRED Economic Research Data, as well as USD/PLN exchange rate quotations), while the sources of legal acts were the Journal of Laws of the Republic of Poland and the Official Journal of the European Union. The obtained results indicated that the prices of biofuels (specifically biodiesel) in Poland depend both on economic factors (the USD/PLN exchange rate and crude oil prices) and on some legal regulations, including domestic and EU regulations. We proved the importance of the EU directive 2003/30 on the promotion of the use of biofuels or other renewable fuels for transport, as well as acts on renewable energy sources (2015), on amending the act on liquid biocomponents and biofuels (2014) and on excise duty (2008).

Process Design for Biohydrogen Production from Waste Materials and Its Application

Biohydrogen is regarded as an attractive future clean energy carrier due to its high energy content and environmentally friendly conversion. Biohydrogen reactor is widely used in studies concerning the anaerobic co-digestion of food waste, sewage sludge, wastewater and other organic solids. Anaerobic digestion is a series of biological processes in which microorganisms break down biodegradable material (biomass or waste feedstock) in the absence of oxygen to produce biogas, which may generate electricity and heat, or can be processed into renewable natural gas and transportation fuels. This review article explains the scientific processes of anaerobic digestion process such as hydrolysis, acidogenesis, acetogenesis and hydrogenesis as well as methods to produce biohydrogen gas such as fermentation and biophotolysis for the waste management technology and sources of renewable energy and concludes with solutions that may allow anaerobic digestion to become more widely adopted throughout the developing countries to control the waste management system.

ICE Relevant Physical-chemical Properties and Air Pollutant Emission of Renewable Transport Fuels from Different Generations – An Overview

The fuel demand in transport sector seems to be raised on a short and also on a long term base in the European Union and worldwide as well. A constantly growing trend is foreseen through 2050 worldwide as for using bio-based energy or fuels. Questions can arise before using these kinds of fuels in connection with the use of clean water or in terms of soil degradation, plant nutrients. It is also questionable whether they can be useful regarding their usage. First-, and second generation liquid as well as third generation gaseous bio-based fuels will be in focus in this article. They will be analyzed from physical-chemical properties and pollutant emission points of view.

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.

Process Intensification in Bio-Ethanol Production–Recent Developments in Membrane Separation

Ethanol is considered as a renewable transport fuels and demand is expected to grow. In this work, trends related to bio-ethanol production are described using Thailand as an example. Developments on high-temperature fermentation and membrane technologies are also explained. This study focuses on the application of membranes in ethanol recovery after fermentation. A preliminary simulation was performed to compare different process configurations to concentrate 10 wt% ethanol to 99.5 wt% using membranes. In addition to the significant energy reduction achieved by replacing azeotropic distillation with membrane dehydration, employing ethanol-selective membranes can further reduce energy demand. Silicalite membrane is a type of membrane showing one of the highest ethanol-selective permeation performances reported today. A silicalite membrane was applied to separate a bio-ethanol solution produced via high-temperature fermentation followed by a single distillation. The influence of contaminants in the bio-ethanol on the membrane properties and required further developments are also discussed.

Bioethanol from autoclaved municipal solid waste: Assessment of environmental and financial viability under policy contexts

Globally, 2.01 billion tonnes of municipal solid waste (MSW) were generated in 2016, about 37% of which was disposed of into landfills. This study evaluates the environmental and financial viability of producing ethanol from autoclaved MSW via fermentation. Experimental screening of four different microorganisms (i.e., S. cerevisiae, Z. mobilis, E. coli, and S. pombe) and process modelling indicate that MSW-derived ethanol can significantly reduce greenhouse gas emissions relative to gasoline (84% reduction following EU Renewable Energy Directive accounting methodology, and by 156–231% reduction following the US Energy Independence and Security Act methodology). Utilisation of wastes for biofuel production in the UK benefits from policy support and financial support for renewable fuels (Renewable Transport Fuel Certificates). Financial analysis highlights that microorganisms achieving higher ethanol yield and productivity (S. cerevisiae and Z. mobilis) can achieve financial viability with higher cumulative net present value than E. coli, S. pombe. However, the positive net present value can be achieved primarily due to the benefit of gate fees received by diverting wastes to autoclave and ethanol production (64% of total revenues), rather than from revenues from ethanol sales (7% of total revenues). Key process improvements must be achieved to improve the financial viability of ethanol production from MSW and deliver a clear advantage over waste incineration, specifically improving hydrolysis yield, reducing enzyme loading rate and, to a lesser extent, increasing solid loading rate. The results provide significant insights into the role of policy and technology development to achieve viable waste-to-biofuel systems.