Advanced Biofuels Research Articles

An Assessment of Liquid Biofuel Value Chains from Heavy-Metal Contaminated Feedstock

The present work aims to identify alternative liquid biofuel value chain scenarios utilizing heavy metal (HM)-contaminated biomass feedstocks. The analysis is based on breaking down existing liquid biofuel value chains, focusing on the required adaptations needed for clean biofuel production. State-of-the-art and emerging liquid biofuel production options are reviewed. The potential implications caused by the HM load in the biomass feedstock are analyzed along the whole biofuel production chain, which includes pre-processing, conversion and post-processing stages. The fate of the most common HM species present in contaminated biomass is identified and graphically represented for advanced (second generation) biofuel conversion processes. This information synthesis leads to the description of alternative value chains, capable of producing HM-free biofuel. This work goes a step further than existing reviews of experiments and simulations regarding heavy metal-contaminated biomass (HMCB) valorization to biofuels since feasible value chains are described by synthesizing the findings of the several studies examined. By defining the adapted value chains, the “road is paved” toward establishing realistic process chains and determining system boundaries, which actually are essential methodological steps of various critical evaluation and optimization methodologies, such as Life Cycle Assessment, supply chain optimization and techno-economic assessment of the total value chain.

“A future beyond sugar”: Examining second-generation biofuel pathways in Alagoas, northeast Brazil

In this article, we examine an early example of lignocellulosic, or second-generation (2G), ethanol production amid wider efforts to address concerns over harmful socio-environmental effects of the bioethanol sector. Focusing on a bioethanol-from-cellulose refinery in Alagoas, northeast Brazil, and recent efforts in the region to enroll alternative sources such as eucalyptus as feedstock, our findings underscore the continued importance of primary crops as inputs for new enzyme development for 2G production, with potential to intensify monoculture agriculture pathways in Alagoas and other sites of expansion. Accordingly, we highlight the value of transdisciplinary approaches to shape the early stages of scientific research into novel enzyme applications, including the selection of potential new crops for feedstocks, their local socio-environmental consequences, and their wider linkages in a global agrarian economy. We argue that determining which, if any, varieties of biomass are best suited for enzyme development entails seeking the input of multiple stakeholders and sources of knowledge to avoid reproducing socioeconomic inequalities and injustices or endangering local environments.

Highly selective hydropyrolysis of lignin waste to benzene, toluene and xylene in presence of zirconia supported iron catalyst

The use of lignin to produce Benzene, Toluene and Xylene (BTX) is a promising pathway to strength the economic case, over the production of advanced bio-fuels alone. In this work, Ce, Na, Pd and Fe supported on zirconium oxide were evaluated for the ex-situ hydropyrolysis (HyPy)/hydrodeoxygenation (HDO) of Etek lignin under mild conditions (600 °C, 1 atmosphere) towards the production of BTX. Fe/ZrO2 was able to selectively produce BTX (67 area%) and cycloalkenes (13.5 area%) and strongly deoxygenate the HyPy oil to about 5 wt% oxygen content, resulting in an oil with a carbon distribution of 85.5 % in C5-C10 hydrocarbons. The high selectivity of Fe/ZrO2 was related to the iron oxophilicity, the strong reduction potential of zero-valent iron, the good dispersion of Fe nanoparticles on the support and the presence of mesopores and acid sites, which enhanced the interactions between the reacting species and the catalyst surface.

Identification of Key Drivers of Cost and Environmental Impact for Biomass-Derived Fuel for Advanced Multimode Engines Based on Techno-Economic and Life Cycle Analysis

Early stage research and development are needed to accelerate the introduction of advanced biofuel and engine technologies. Under the Co-Optima initiative, the U.S. Department of Energy is leveraging capabilities from its nine national laboratories and more than 35 university and industry partners including advanced computational tools, process design, data analysis, and economic and sustainability modeling tools to simultaneously design fuels and engines capable of running efficiently in an affordable, scalable, and sustainable way. In this work, we conducted techno-economic analysis (TEA) and life cycle assessment (LCA) to understand the cost, technology development, and environmental impacts of producing selected bioblendstocks for advanced engines such as multimode (MM) type engines at the commercial scale. We assessed 12 biofuel production pathways from renewable lignocellulosic biomass feedstocks using different conversion technologies (biochemical, thermochemical, or hybrid) to produce target co-optimized biofuels. TEA and LCA were used to evaluate 19 metrics across technology readiness, economic viability, and environmental impact and for each ranked on a set of criteria as favorable, neutral, unfavorable, or unknown. We found that most bioblendstocks presented in this study showed favorable economic metrics, while the technology readiness metrics were mostly neutral. The economic viability results showed potentially competitive target costs of less than $4 per gasoline gallon equivalent (GGE) for six candidates and less than $2.5/GGE for methanol. We identified 10 MM bioblendstock candidates with synergistic blending performance and with the potential to reduce greenhouse gas (GHG) emissions by 60% or more compared to petroleum-derived gasoline. The analysis presented here also provides insights into major economic and sustainability drivers of the production process and potential availability of the feedstocks for producing each MM bioblendstock.

The new era of advanced biofuels in the face of regulatory uncertainty and investment needed for production

Abstract At this moment, environmental protection is the subject of almost daily debate, both in European and global forums. The most important thing is to find ways for countries to limit their carbon footprint as quickly as possible. Moreover, it should also be borne in mind that it is not desired that these options affect the daily life of individuals. These variants must be in line with the standards of living and needs that society has now. Ideally, this transition between the current options and the future options should be as seamless as possible so as not to create resistance to change in society. The transition to the new sustainable options should be phased in over a longer period, although the situation calls for rapid change with a major impact. The situation becomes even more challenging as the COVID-19 pandemic has brought major changes for companies around the world in the last two years. Not all governments have managed this crisis as well, and this uncertainty is now being reflected in investments in most sectors. Investment in new technologies, as far as the fuel industry is concerned, has been in question because of the uncertainty and rapid changes that society has experienced. This article is intended to highlight the major importance that these advanced biofuels can have for the environment, as well as the long-term sustainability they offer. The methodology of the paper is based on studies and indicators. For example, the company Clariant, as its contribution is well highlighted by the business direction it has towards biofuel technologies. In terms of literature, the subject is quite popular, but articles and papers are limited in number.

Biorefinery upgrading of herbaceous biomass to renewable hydrocarbon fuels, Part 1: Process modeling and mass balance analysis

Process simulation has long been a well-established tool to track key operational, design, and mass and energy balance metrics for pre-commercial technologies such as advanced lignocellulosic biofuels. While tools such as this are well-documented in the public literature around 2nd-generation cellulosic ethanol technologies (which have been scaled up to commercial deployment to some degree over the past decade), such models and analysis information remain more sparse for more complex biorefinery pathways focused on producing drop-in hydrocarbon fuels and blend-stocks, particularly regarding information required to support air emissions or other environmental analysis. In this work, we summarize key details for an established “design case” modeling the conversion of herbaceous lignocellulosic biomass into a renewable diesel hydrocarbon blend-stock based on a representative lipid pathway from oleaginous yeast. The process is based on a biochemical deconstruction and upgrading approach utilizing deacetylation and dilute acid pretreatment, followed by enzymatic hydrolysis, fermentation, and catalytic upgrading of hydrolysate sugars to fuels. We provide key mass and energy balance outputs from the process models, with accompanying stream tables and component-level flowrates. A total of 12 model scenarios are presented spanning two feedstocks, three biorefinery scales, and two processing approaches for the lignin/residual solids waste streams. This “Part 1” manuscript presents the resulting impacts across the 12 cases on fuel yields and key output streams, focused here on direct biorefinery air emissions for selected components including CO 2 as well as sulfur (SOx) and nitrogen oxides (NOx). In the context of cleaner production, the latter focus on selected biorefinery air emission outputs establishes an initial baseline estimate and accompanying framework of the model cases, upon which an accompanying “Part 2” study will build to refine the values for these and other air pollutants across these scenarios, also considering mitigation options to comply with applicable regulatory standards. We also highlight further optimization opportunities based on potential tradeoffs identified here between air emissions versus life-cycle greenhouse gas profiles attributed to the disposition of lignin/residual solids.

Biorefinery upgrading of herbaceous biomass to renewable hydrocarbon fuels, Part 2: Air pollutant emissions and permitting implications

The development of advanced biofuel production facilities is still at a nascent stage, and the biorefineries could face challenges in obtaining air permits required for their construction and operation because they are novel emission sources. To fill gaps in knowledge regarding potential emissions, we perform a detailed federal regulatory analysis and estimate air pollutant emissions for an advanced biorefinery that produces renewable diesel blendstock (RDB) from lignocellulosic biomass via aerobic respiration documented in Part 1 of the paper. We evaluate 12 design permutations that include two feedstocks, a uniform format blend (UFB) and corn stover; three biorefinery scales, 2,000, 5,200, and 9,100 dry metric tons per day (dmtd) of lignocellulosic biomass feed; and two lignin uses, as either a boiler fuel or for pellet production. We also evaluate 6 additional design permutations by incorporating non-emitting renewable power, which could reduce up to 63% carbon monoxide (CO) and nitrogen oxides (NO x ) each, 21% volatile organic compounds (VOC), and 43% hazardous air pollutants (HAP) as opposed to on-site power production, for biorefineries that produce pellets, using either UFB or corn stover. Our results indicate that all 18 design permutations would be classified as a major source under the Clean Air Act's New Source Review program without additional emission controls. Compared to using lignin as a boiler fuel, diverting lignin for pellet production reduces the emissions of CO up to 88%, NO x up to 73%, sulfur dioxide (SO 2 ) up to 99%, VOCs up to 72%, and HAPs up to 66%. Additionally, we explore control options that could further reduce emissions and assess whether reductions are enough to achieve minor source classification. Insights from our analysis can help biorefinery developers and regulators develop permitting strategies to mitigate investment risks. • Air emissions from 12 biorefinery process design variations are quantified. • Biorefineries would be classified as major sources without additional controls. • Control options are available for compliance with applicable federal regulations. • Diverting lignin for pellet production could reduce air emissions by at least 66%. • Integrating non-emitting renewable power could help achieve minor source.

Hydrogen-free deoxygenation of industrial vegetable oil waste using Ce, Zr-NiAl catalysts for second-generation biofuels production

High acidic vegetable oil feedstocks and wastes are not suitable for conventional biodiesel production. These wastes could be used to produce cheap hydrocarbon-rich biofuels without affecting food production. In this work, we studied the hydrogen-free fast pyrolysis and deoxygenation of an acidic industrial vegetable oil waste for biofuels and chemicals production, assessing the effect of Ce or Zr on NiAl mixed oxides obtained from layered double hydroxides. Oily waste (OW) was pre-adsorbed on the catalysts using a Catalyst:OW mass ratio of 5:1. Without a catalyst, pyrolysis of OW, containing triglycerides and a high percentage of free fatty acids, produced mainly 1-alkenes, lower carbon chain fatty acids, and fatty acid esters. Catalytic pyrolysis increased hydrocarbons favoring 1-alkenes between propene and 1-heptadecene, as well as alkyl-benzenes. Linear alkylbenzenes are feedstock for the production of biodegradable surfactants. NiAlCe was most selective to polyenes, alkanes and ketones, while NiAl and NiAlZr catalysts were efficient in producing aromatics, alkenes and light hydrocarbons in the GLP and gasoline range (C3-C10). The combination of acidic and metallic properties on high surface area unsupported bulk mixed oxide catalysts can be used to maximize the production of specific-range hydrocarbons for second-generation drop-in biofuels and bio-based surfactant precursors, towards the decarbonization of industry.

Engineered Production of Isobutanol from Sugarcane Trash Hydrolysates in Pichia pastoris.

Concerns over climate change have led to increased interest in renewable fuels in recent years. Microbial production of advanced fuels from renewable and readily available carbon sources has emerged as an attractive alternative to the traditional production of transportation fuels. Here, we engineered the yeast Pichia pastoris, an industrial powerhouse in heterologous enzyme production, to produce the advanced biofuel isobutanol from sugarcane trash hydrolysates. Our strategy involved overexpressing a heterologous xylose isomerase and the endogenous xylulokinase to enable the yeast to consume both C5 and C6 sugars in biomass. To enable the yeast to produce isobutanol, we then overexpressed the endogenous amino acid biosynthetic pathway and the 2-keto acid degradation pathway. The engineered strains produced isobutanol at a titer of up to 48.2 ± 1.7 mg/L directly from a minimal medium containing sugarcane trash hydrolysates as the sole carbon source. To our knowledge, this is the first demonstration of advanced biofuel production using agricultural waste-derived hydrolysates in the yeast P. pastoris. We envision that our work will pave the way for a scalable route to this advanced biofuel and further establish P. pastoris as a versatile production platform for fuels and high-value chemicals.

The Analysis on the Current Situation of the Utilization Mode of Microalgal Biomass Materials

In recent years, global warming caused by the greenhouse effect has become one of the greatest threats to mankind. This will have a serious impact on the environment and human body, such as land desertification, increase in ocean acidity, sea level rise, and increase in pests and diseases; affect people’s normal work and rest; and make people feel dizzy and nauseated. Excessive emissions of carbon dioxide (CO2), the main component of the greenhouse gas, have contributed to the continued rise in Earth’s temperature. Although the world is vigorously developing clean energy to reduce carbon emissions, it will not replace fossil fuels in the short term. The conversion of biomass into energy is the most important way of energy utilization. Biomass energy refers to the solar energy stored in biomass in the form of chemical energy and is the fourth major energy source after oil, coal, and natural gas. At present, biofuels have gone through three developmental stages, which can be divided into first-generation biofuels, second-generation biofuels, and third-generation biofuels according to the types of raw materials and development history. The first generation of biofuels produced from food crops, such as bioethanol derived from sucrose and starch, has already entered the energy market. However, because the first generation of biofuels uses food crops as raw materials, there is a phenomenon of “competing with people for food,” and it is difficult to achieve large-scale application. To avoid the problem of food shortages, second-generation biofuels produced from nonfood crops, such as wood fiber, have been developed. Microalgae biomass energy is favored by governments and scholars all over the world because of its unique advantages of fast reproduction speed and high oil content. The cultivation of microalgae does not occupy traditional farmland, and the marginal land such as mountains, oceans, and deserts can cultivate microalgae, or develop microalgae cultivation in the air through the innovation of microalgae photosynthetic reactors. When municipal wastewater, food industry wastewater, and aquaculture wastewater are used as the medium for large-scale cultivation of microalgae, and waste gas from biogas power generation, flue gas from coal power plants, and industrial waste gas from fermentation are used as the CO2 gas source for large-scale cultivation of microalgae, it can be further reduced. The comprehensive production cost of microalgae bioenergy plays a significant emission reduction effect. Combining the above advantages, the use of microalgae to produce first- or second-generation bioenergy has become a new research direction. This study focuses on the review of microalgal biomass in fuel, nonfuel, wastewater treatment, and fuel cell.

Impacts of Palm Oil-based Biofuel Utilization Promotion Policy in the Thai Transport Sector

This paper aims to provide an analysis of the impacts of the promotion policy of palm oil-based biofuel utilization in the Thai transport sector for the period 2020–2037. For this purpose, three scenarios are developed to represent different proportions of palm oil-based biofuel blending implemented in Thailand and their impacts are analyzed through the application of the Low Emissions Analysis Platform (LEAP) model. The analysis reveals that an increase in the proportion of palm oil-based biofuel in a diesel mix would provide several noticeable benefits, for example, help reducing diesel consumption, decreasing crude oil requirement, and mitigating emissions of CO2 and PM2.5 – a major source of current environmental health problems. In addition, increased proportion of palm oil-based biofuel in the diesel mix would contribute to a growing demand for oil palm production and a plantation area to meet an increase in palm oil-based biofuel production. A high demand for oil palm production and plantation land requirement could, however, be emerging challenges. In order to address these challenges, the effective strategies could include a plan for agricultural crop zoning, crop breeding, the efficiency enhancement of biofuel conversion technology, the reduction of chemical fertilizers and pesticides, and the support from the government for research and development of second-generation biofuels. The analysis will be useful for Thai planners and policy makers to design policies to overcome the issues of energy and food security as well as climate change problems.

Biocrude production by catalytic hydrothermal liquefaction of wood chips using NiMo series catalysts

In this work, hydrothermal liquefaction of wood chips was studied for biocrude production using a mix of Ni–Mo nitrides and carbides. The catalytic materials were synthesized by a temperature-programmed reaction method at 800 °C under a hydrogen atmosphere with nickel loads from 0 to 20 wt%. Lignin contained in the lignocellulosic biomass was successfully release via Kraft process. Hydrothermal liquefaction was carried out in a batch reactor at 320 °C with an initial pressure of 1000 psi of H2. According to characterization results, nanostructured catalysts with a mix of Ni2Mo3N/Mo2C compo4unds were obtained. NiMo series catalysts composition varies with nickel loads. The catalytic activity shows a reduction in the amount of solid products and an increase in the production of gaseous products as a function of the increase Ni loadings on the catalyst. The most optimal production of biocrude was obtained with the NiMo-10 catalyst, since 81.43% of the total product corresponded to water soluble products (WPS) fraction and the oil fraction, while the solids fraction represented the 6.43% of the total product. Hydrothermal liquefaction catalytic processes were selective towards WSP fraction, improving biocrude quality and favoring biocrude conversion into advanced biofuels.

Biofuels Production and Processing Technology

The negative global warming impact and global environmental pollution due to fossil fuels mean that the main challenge of modern society is finding alternatives to conventional fuels. In this scenario, biofuels derived from renewable biomass represent the most promising renewable energy sources. Depending on the biomass used by the fermentation technologies, it is possible obtain first-generation biofuels produced from food crops, second-generation biofuels produced from non-food feedstock, mainly starting from renewable lignocellulosic biomasses, and third-generation biofuels, represented by algae or food waste biomass. Although biofuels appear to be the closest alternative to fossil fuels, it is necessary for them to be produced in competitive quantities and costs, requiring both improvements to production technologies and diversification of feedstock. This Special Issue is focused on technological innovations, which include but are not limited to the utilization of different feedstock; different biomass pretreatments; fermentation strategies, such as simultaneous saccharification and fermentation (SSF) or separate hydrolysis and fermentation (SHF); different applied microorganisms used as monoculture or co-culture; and different setups for biofuel fermentation processes.

N-Butanol or isobutanol as a value-added fuel additive to inhibit microbial degradation of stored gasoline

Biofouling of gasoline can occur during fuel storage caused by bacteria and fungi that form a biofilm at a fuel/water interface and that produce organic acids and sulfides. Fuel additives are applied to gasoline to prevent biofouling but are relatively expensive, are not always effective against biofilms, and do not contribute to the combustibility of gasoline. Bio-isobutanol is an approved, certified advanced biofuel and is added up to 16% (v/v) in gasoline blends “iBut16”; n-butanol blends are currently under review. Microorganisms are inhibited by n-butanol or isobutanol when the aqueous concentration reaches >2-3% (w/v). We determined that n-butanol partitions into the aqueous phase of a model gasoline/water system reaching concentrations of 42 g/L and up to 48 g/L from gasoline blends at 10% and 24% (v/v), respectively. Likewise, isobutanol blended in gasoline at 10% and 24% (v/v) partitioned into an aqueous phase at 45 g/L and 53 g/L, respectively. Several bacterial and fungal strains that originate from fuel storage tanks, or are known to be solvent tolerant, were evaluated for their potential growth in a range of n- and isobutanol concentrations. Growth rates for all strains tested were reduced by 40–100% relative to untreated controls in n- and isobutanol concentrations of 1.5 and 2.0% (v/v). No observable growth occurred for any of the microorganisms in solvent concentrations at 3.0% (v/v). T amphiphilic and chaotropic properties of n- or isobutanol help them inhibit microbial growth and could serve as effective biocides during fuel storage as well as being valuable fuel additives.

Logistics and Costs of Agricultural Residues for Cellulosic Ethanol Production

There is global pressure to make advanced biofuels profitable. For cellulosic ethanol, three aspects remain as bottlenecks: collection of feedstocks, pretreatment methods, and enzyme production. In this paper, the first aspect is investigated, by addressing the main challenges for the logistics of agricultural residues. A logistic supply chain of corn stover collection and utilization for cellulosic ethanol production in Mexico is proposed, and a cost structure is designed for its estimation. By applying a value chain methodology, seven links and a set of three minimum selling prices (MSPs) of agricultural residues were determined. Furthermore, the harvest index (HI), crop residue index (CRI), nutrient substitution by extraction of agricultural residues, and harvest costs of corn stover were also calculated for a case study. The main results were a HI of 0.45, a CRI of 1.21, and nutrient substitution potential of 7 kg N, 2.2 kg P2O5, and 12.2 kg K2O per ton of corn stover. The set of the three estimated MSPs for corn stover was: $28.49 USD/ton (for delivery to the biorefinery’s gate), $31.15 USD/ton (for delivery and storage), and $48.14 USD/ton (for delivery, storage, and nutrient replenishment). Given the impact of the feedstock cost on the profitability of cellulosic ethanol, knowing details of the logistical information and its costs is critical to advancing the field of biofuels in Mexico. We also found that only 20% of farmers currently sell their residues; however, 65% of farmers would be willing to do so, a significant percentage for cellulosic ethanol production.

Influence of nanoparticles inclusion on the production of bioethanol from corn stalks and leaves

Bioethanol is a viable alternative to petroleum-derived fossil fuels. It is renewable, low-cost, and the preferred fuel for most developing countries worldwide. Although it is possible to make bioethanol from corn stalks and leaves wastes, second-generation biofuels made from agricultural waste feedstocks represent a significant step forward. In the present research, nickel oxide (NiO) nanoparticles (NPs) were used as a biocatalyst to achieve maximum ethanol output. The pretreatment of 2% NaOH with NiO NPs, 15-min autoclave condition, showed the highest total and reducing sugar yield was 162.69 g/L and 43.75 g/L. After hydrolysis, the suitable total and reducing sugar yield of 185.43 g/L and 125.42 g/L was chosen for further fermentation with the expansion of Saccharomyces cerevisiae cells. Separate hydrolysis and fermentation (SHF) using corn stalk and leaf waste was significantly assisted by incorporating a nanocatalyst; ethanol concentration was increased to 15.8 g/L at 24 hours incubation period. The study revealed critical information regarding ways NiO NPs could be employed to improve the efficiency of the ethanol production bioprocess.

Catalysis and chemistry of lignin depolymerization in alcohol solvents - A review

The second-generation biofuel strategy aims to fully utilize lignocellulose, which is the major component of the plant cell wall and the most abundant form of renewable organic resources. Among three major components of lignocellulose, i.e. cellulose, hemicellulose and lignin, lignin has been the least utilized one up to now. Nevertheless, lignin depolymerization (LD) to produce aromatic chemicals and fuels has been intensely explored in the recent decade. Alcohols have been the mostly employed solvents in LD reaction, and are also involved into the LD reaction. This review provides an overview of the catalysis and chemistry of LD reaction in alcohols, especially in methanol, ethanol and isopropanol. The recent advances are firstly summarized, and then the roles of alcohol in LD reaction are outlined. The alcohol self-conversions are firstly discussed, and then the roles of alcohol are discussed in four subtopics: supplying hydrogen, depolymerizing lignin, hindering repolymerization and affecting monomer structure. Alcohol and alcohol-derived intermediates provide active hydrogen for reductive catalytic LD reaction carried out without hydrogen input, effectively break ether linkages but not C-C linkages in lignin, and also react with active intermediates and monomers, suppressing the repolymerization side reactions. In addition, alcohol also inhibits the hydrogenation of benzene rings and involves in the formation of products, affecting the structure of monomers. With these understandings, the challenges and opportunities of LD are proposed.

Science and Business Developments

Science and Business Developments

How can filtration optimise the production of biofuels?

As emission targets become more stringent and the Russia-Ukraine conflict sees countries move towards greater energy security, renewables are pivotal for sustainability. Are advanced biofuels a key part of a greener future?

Hydro-treated vegetable oil as a potential biofuel for self-ignition engines

Hydro-treating vegetable oils or animal fats is an alternative process to esterification for the production of biodiesel. Hydro-treated products are also called renewable diesel fuels. Hydro-treated vegetable oils (HVO) do not have the harmful effects of FAME biodiesel such as increased NOₓ emissions, deposit formation, storage stability problems, faster aging of the engine oil or poor cold performance. HVO are straight chain paraffinic hydrocarbons which are free of aromatic hydrocarbons, oxygen and sulphur and have a high cetane number. In the article below, the authors conduct a comprehensive analysis and evaluation of the possibility of running compression-ignition engine on the hydro-treated vegetable oil, which is a second-generation biofuel. On its basis, the information on the assessment of emissions of selected toxic components of exhaust gases and pollutants of the injection system when the engine is powered with this type of fuel, was systematized. The article ends with conclusions from the conducted analyses.