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Three delignification treatments of corncob residues (CCR), including NaOH, formic acid, and sulfite treatments, were compared at the respective optimized condition and in light of chemical compositions, sugar recovery, and ethanol production. NaOH and sulfite treatment can remove lignin in the CCR efficiently. Though NaOH treatment showed a superior ability of delignification, its solid cellulose recovery is lower than that of sulfite treatment. The sulfite treatment has the highest selectivity between delignification and cellulose conservation. The formic acid-treated CCR still had high lignin contents because formic acid also accelerated the solvation of cellulose. In fed-batch simultaneous saccharification and fermentation (SSF) with 25% substrate loading, the highest 77.1 ± 2.33 g/L ethanol was from NaOH-treated CCR, corresponding to a CCR-to-ethanol yield of 0.208 ± 0.0021 g/g. However, the sulfite pretreated CCR also produced 68.2 ± 2.22 g/L ethanol, with a higher CCR-to-ethanol yield of 0.219 ± 0.0012 g/g. The high substrate dosage is beneficial to ethanol concentration but not beneficial to CCR-to-ethanol yield. The optimal substrate dosage required for ethanol production depends on the targeted aim (ethanol concentration or CCR-to-ethanol yield). [ABSTRACT FROM AUTHOR]

Ethanol, a common renewable energy resource, can reduce greenhouse gas (GHG) emissions to resolve the problem of global warming worldwide. Various feedstocks such as corn, sugarcane, maize stover, and wheat straw can be utilized for ethanol production. They determine production operations and relevant costs. Although there are monetary incentives and government policies in different countries to increase ethanal use, it is still challenging to make its sales price competitive due to the inefficient supply chain of ethanol. Unlike fossil fuels such as coal, oil, and natural gas using a well-designed supply chain in the long history of mankind, additional efforts are needed to organize and stabilize the supply chain of ethanol efficiently. The goal of this study is to investigate how simulation modeling techniques can be applied to various supply chain management issues of ethanol. Particularly, application cases of three major simulation paradigms such as discrete-event simulation, system dynamics, and agent-based simulation are investigated by conducting a scientific literature review. The findings of this study will contribute to the expansion of simulation use in the field of biofuel supply chain management. [ABSTRACT FROM AUTHOR]

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Millions of hectares of cover crops are planted in the U.S. and European Union to manage soil erosion, soil fertility, water quality, weeds, and climate change. Although only a small percentage of cover crops are harvested, the growing cover crop planting area provides a new biomass source to the biofuel industry to produce bioenergy. Oilseed crops such as rapeseed, sunflower, and soybean are commodities and have been used to produce biodiesel and sustainable aviation fuel (SAF). Other cover crops such as cereal rye, clover, and alfalfa, have been tested on small or pilot scales to produce cellulosic ethanol, biogas, syngas, bio-oil, and SAF. Given the various biofuel products and pathways, this review aimed to provide a comprehensive comparison of biofuel yield from different cover crops and an overview of the technologies that have been employed to improve biofuel yield. It was envisioned that gene-editing tools might be revolutionary to the biofuel industry, the work on cover crop supply chain will be critical for system scaleup, and high-tolerant technologies likely will be needed to handle the high compositional heterogeneity and variability of cover crop biomass for biofuel. [ABSTRACT FROM AUTHOR]

Clostridium thermocellum is a natively cellulolytic bacterium that is promising candidate for cellulosic biofuel production, and can produce ethanol at high yields (75–80% of theoretical) but the ethanol titers produced thus far are too low for commercial application. In several strains of C. thermocellum engineered for increased ethanol yield, ethanol titer seems to be limited by ethanol tolerance. Previous work to improve ethanol tolerance has focused on the WT organism. In this work, we focused on understanding ethanol tolerance in several engineered strains of C. thermocellum. We observed a tradeoff between ethanol tolerance and production. Adaptation for increased ethanol tolerance decreases ethanol production. Second, we observed a consistent genetic response to ethanol stress involving mutations at the AdhE locus. These mutations typically reduced NADH-linked ADH activity. About half of the ethanol tolerance phenotype could be attributed to the elimination of NADH-linked activity based on a targeted deletion of adhE. Finally, we observed that rich growth medium increases ethanol tolerance, but this effect is eliminated in an adhE deletion strain. Together, these suggest that ethanol inhibits growth and metabolism via a redox-imbalance mechanism. The improved understanding of mechanisms of ethanol tolerance described here lays a foundation for developing strains of C. thermocellum with improved ethanol production. [ABSTRACT FROM AUTHOR]

In recent years, policy-makers and researchers have paid close attention to sustainable energy resources. Biofuel has emerged as a viable option among available alternatives in countries with excess agricultural production. India is also ramping up ethanol production. However, there is limited research available on enablers that can help boost production for enhanced blending, thereby assisting in the achievement of energy security and the transition to a low-carbon economy. Furthermore, India can capitalize on its excess agri-production for long-term energy security, increase farmer income, reduce import bills and foreign exchange outflows, encourage local business participation and accelerate its overall economic development while lowering its carbon footprints. The Decision-Making Trial and Evaluation Laboratory (DEMATEL) approach is used in this article to investigate the enablers for implementing a policy regime for increased ethanol production. The findings are important for policy-makers in India to identify areas for policy interventions, and they also lay the groundwork for future similar research on this evolving industry in the global markets. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the effect of cutting frequency in Cayman grass (Urochloa HYBRID) on biomass yield, moisture, ash, ethereal extract, neutral detergent fiber (FDN), acid detergent fiber (FDA), acid detergent lignin (LDA), crude protein (PC), calorific value, and theoretical bioethanol yield. Four cutting frequencies were established as treatments: 30, 60, 90, and 120 d, arranged in a completely randomized block design with three replications. Data were analyzed with GLM (SAS), and means were compared with the Tukey test (p ≤ 0.05). The highest biomass production (11.9 Mg ha-1 year-1), calorific value (15.1 MJ kg-1), and LDA (5.7 %) were obtained at the 120 d cutting frequency. The concentration of FDN (61.8 %), FDA (43.6 %), cellulose (38.1 %), and theoretical bioethanol production (218.4 L Mg-1 MS) were statistically different at the cutting frequency of 90 d. The values of hemicellulose (18. 7 %) and ethereal extract (1.8 %) were statistically different at the 60 d-cutting frequency; while PC (9.7 %) and ash (11.8 %) showed significant differences at the 30-d cutting frequency. Based on the biomass yield and calorific value of Cayman grass, it can be considered as a potential plant material for cellulosic ethanol production. [ABSTRACT FROM AUTHOR]

The commentary focuses on the current state of bioethanol production and lists some of the big bioethanol-producing facilities. Currently, starch and sugarcane molasses, which compete for their use in human food, are the major source of industrial ethanol. Cellulosic ethanol is discussed which is based on the raw material that is not used for human consumption. The plentiful agricultural residues rich in cellulose are not part of the food chain and are an inexpensive plentiful renewable substrate for ethanol production. The technology for ethanol production from cellulosic biomass needs improvement. With the current know-how, the production of ethanol from cellulose is commercially challenging. The innovative new technologies may be exploited to create yeasts to efficiently utilize pentose sugars and to secrete cellulose hydrolytic enzymes in high yields so that fermentation is efficient without adding external expensive cellulases and other enzymes. In India, bioethanol production at sugar mills is attractive. It will save foreign exchange, decrease pollution from crop residue burning, strengthen national energy security, enhance farmers' income and create rural employment. [ABSTRACT FROM AUTHOR]

The growing need to expand the use of renewable energy sources in a sustainable manner, providing greater energy supply security and reducing the environmental impacts associated with fossil fuels, finds in the agricultural by-product bioethanol an economically viable alternative with significant expansion potential. In this regard, a dramatic boost in the efficiency of processes already in place is required, reducing costs, industrial waste, and our carbon footprint. Biofuels are one of the most promising alternatives to massively produce energy sustainably in a short-term period. Lignocellulosic biomass (LCB) is highly recalcitrant, and an effective pretreatment strategy should also minimize carbohydrate degradation by diminishing enzyme inhibitors and other products that are toxic to fermenting microorganisms. Ionic liquids (ILs) have been playing an important role in achieving cleaner processes as a result of their excellent physicochemical properties and outstanding performance in the dissolution and fractionation of lignocellulose. This review provides an analysis of recent advances in the production process of biofuels from LCB using ILs as pretreatment and highlighting techniques for optimizing and reducing process costs that should help to develop robust LCB conversion processes. [ABSTRACT FROM AUTHOR]

Sorghum [Sorghum bicolor (L.) Moench] is an important crop for food, feed, and fuel production. Particularly, sorghum is targeted for cellulosic ethanol production. Extraction of cellulose from cell walls is a key process in cellulosic ethanol production, and understanding the components involved in cellulose synthesis is important for both fundamental and applied research. Despite the significance in the biofuel industry, the genes involved in sorghum cell wall biosynthesis, modification, and degradation have not been characterized. In this study, we have identified and characterized three allelic thick leaf mutants (thl1, thl2, and thl3). Bulked Segregant Analysis sequencing (BSAseq) showed that the causal mutation for the thl phenotype is in endo-1,4-β-glucanase gene (SbKOR1). Consistent with the causal gene function, the thl mutants showed decreased crystalline cellulose content in the stem tissues. The SbKOR1 function was characterized using Arabidopsis endo-1,4-β-glucanase gene mutant (rsw2-1). Complementation of Arabidopsis with SbKOR1 (native Arabidopsis promoter and overexpression by 35S promoter) restored the radial swelling phenotype of rsw2-1 mutant, proving that SbKOR1 functions as endo-1,4-β-glucanase. Overall, the present study has identified and characterized sorghum endo-1,4-β-glucanase gene function, laying the foundation for future research on cell wall biosynthesis and engineering of sorghum for biofuel production. [ABSTRACT FROM AUTHOR]

Renewable alternatives to fossil fuels are now a worldwide effort, and biofuels can play an essential role in a sustainable energy matrix. The great potential of lignocellulosic biomass as feedstock for bioethanol production has been underexplored due to technological barriers and the costs involved. However, a new chapter in this history has been written recently after eight different biomass-to-ethanol processes achieved the industrial scale, leading bioethanol technologies to a new step of maturity due to challenges faced and lessons learned. The pretreatment of biomass has been recognized as the most complex step in the cellulosic ethanol production processes and the reason for the failure of some industrial initiatives. Pretreatment represents an essential process to prepare lignocellulosic material for subsequent hydrolysis and fermentation, and this review aims to describe the early and recent efforts to scale-up pretreatment systems and the current challenges of pretreatment operations. Since the early 2010s, a global running for cellulosic ethanol resulted in eight industrial facilities around the world; agricultural residues like corn stover, corn cob, wheat straw, sugarcane bagasse, and sugarcane straw were used by POET-DSM, Raízen, Beta Renewables, GranBio, Abengoa, DuPont, Clariant, and Longlive Bio-tech as feedstock for bioethanol production. Pretreatment technologies, including diluted acid, steam explosion, dilute ammonia, and mechanical refining, were then experienced industrially through batch or continuous systems performed in one or two conversion stages. The pretreatment systems employed by each cellulosic biorefinery are analyzed in this review, and the process conditions and strategies applied are discussed based on public information available. Furthermore, a historical background of the early developments of acid hydrolysis of cellulose and the transition to the modern pretreatment concept is provided. Typical batch reactors employed during the 1900s were replaced by continuous reactors aiming for high productivity. An overview of digesting systems used by the pulp and paper industry is explored, which were initially developed for pulping and recently adapted to perform biomass pretreatment. Special attention is paid to describing vertical and horizontal continuous digesters and mechanical disc refiners, the leading equipment used in industrial pretreatment systems. Additionally, current pretreatment challenges are discussed based on pilot and industrial experience. Biorefineries faced low throughput capacity due to unstable operation and high wear damage to equipment caused by mineral impurities. The impact of feedstock quality and preconditioning processes on pretreatment operation is also reviewed. Feedstock collection, storage, and cleaning have been considered critical operations for a successful pretreatment process; best practices from the non-wood pulping industry are analyzed, providing an important reference for biorefineries. Challenges related to pretreatment uptime, throughput, and yield are considered, and the control of residence time in horizontal continuous reactors is discussed. Finally, recent biorefinery experiences resulted in significant progress for industrial pretreatment's learning curve; this review contributes to consolidating the knowledge generated by these pioneer initiatives while this unique technology continues to evolve. • Review of the leading industrial pretreatment technologies for cellulosic ethanol. • Background of the early developments to scale-up biomass conversion systems. • Description of the recent worldwide industrial pretreatment initiatives. • Review of the best practices from the non-wood pulping industry. • Discussion of the challenges and lessons from industrial pretreatment operations. [ABSTRACT FROM AUTHOR]

• Lignocellulosic biomass becomes the potential feedstock for biofuel production. • Cost-effective pretreatments fascinating for biochemical routes result high yield. • Biomass pyrolysis facilitates sustainable biofuel production and allied applications. Prolonged consumption of fossil fuels and emission of greenhouse gases necessitates the need of alternate fuels of eco-friendly nature. Abundance and less emission of pollutants make biomass as promising resource for energy production. Thermochemical and biochemical methods are the efficient technologies for the effective conversion of biomass into biofuel and biochemical products. Biomass is considered as the potential clean energy source but direct combustion of biomass leads to severe environmental concern hence advanced biomass conversion technologies become attractive to produce biofuel and various biochemical products such as hydrogen, ethanol, acetone, butanol, organic acids etc., Suitable pre-treatment methods ensure the effective utilization of lignocellulosic biomass into energy efficient biofuels and allied products. Through bio-electro chemical conversion, microbial fuel cells produce clean and effective bioenergy. Life cycle assessment of biomass in energy production evidenced less greenhouse emissions further it facilitates strategies to be incorporated to ensure sustainability. The present review throws light on advanced thermochemical and biochemical conversion technologies to produce first to fourth generation biofuel and various biochemical products. The review further summarizes the thermochemical and biochemical conversion reactors, bio-electrochemical conversion technologies, role of recombinant technologies and enzyme catalyzed thermochemical conversion processes. The biochemical and thermochemical conversion of biomass to produce biofuels addresses the United Nations Sustainable Development Goals (UNSDGs) such as SDG 07: Affordable and clean energy, SDG 09: Industry, Innovation and Infrastructure, SDG 12: Responsible consumption and production, SDG 13: Climate action. [ABSTRACT FROM AUTHOR]

Growing interest in sustainable sources of chemicals and energy from renewable and reliable sources has stimulated the design and synthesis of renewable Schiff-base (iminium) ionic liquids (ILs) to replace fossil-derived ILs. In this study, we report on the synthesis of three unique iminium-acetate ILs from lignin-derived aldehyde for a sustainable "future" lignocellulosic biorefinery. The synthesized ILs contained only imines or imines along with amines in their structure; the ILs with only imines group exhibited better pretreatment efficacy, achieving >89% sugar release. Various analytical and computational tools were employed to understand the pretreatment efficacy of these ILs. This is the first study to demonstrate the ease of synthesis of these renewable ILs, and therefore, opens the door for a new class of "Schiff-base ILs" for further investigation that could also be designed to be task specific. [ABSTRACT FROM AUTHOR]

Growth in population and thereby increased industrialization to meet its requirement, has elevated significantly the demand for energy resources. Depletion of fossil fuel and environmental sustainability issues encouraged the exploration of alternative renewable eco-friendly fuel resources. Among major alternative fuels, bio-ethanol produced from lignocellulosic biomass is the most popular one. Lignocellulosic biomass is the most abundant renewable resource which is ubiquitous on our planet. All the plant biomass is lignocellulosic which is composed of cellulose, hemicellulose and lignin, intricately linked to each other. Filamentous fungi are known to secrete a plethora of biomass hydrolyzing enzymes. Mostly these enzymes are inducible, hence the fungi secrete them economically which causes challenges in their hyperproduction. Biomass's complicated structure also throws challenges for which pre-treatments of biomass are necessary to make the biomass amorphous to be accessible for the enzymes to act on it. The enzymatic hydrolysis of biomass is the most sustainable way for fermentable sugar generation to convert into ethanol. To have sufficient ethanol concentration in the broth for efficient distillation, high solid loading ~<20% of biomass is desirable and is the crux of the whole technology. High solid loading offers several benefits including a high concentration of sugars in broth, low equipment sizing, saving cost on infrastructure, etc. Along with the benefits, several challenges also emerged simultaneously, like issues of mass transfer, low reaction rate due to water constrains in, high inhibitor concentration, non-productive binding of enzyme lignin, etc. This article will give an insight into the challenges for cellulase action on cellulosic biomass at a high solid loading of biomass and its probable solutions. [ABSTRACT FROM AUTHOR]

In this paper, we describe multiple scenarios to assess the techno‐economic results of producing hydrocarbon fuels from corn stover‐derived ethanol and the impact of co‐producing higher‐value, ethanol‐derived n‐butanol and 1,3‐butadiene to improve economic feasibility. In our baseline process, the stover‐derived lignin is burned for its energy content to raise process steam and electricity. We evaluated an alternative approach based on the same stover‐to‐ethanol process, but instead of burning residual lignin to produce heat and electricity, it was fed to a hydrothermal liquefaction process and converted into hydrocarbon fuel, while the ethanol from fermentation is used to make only butanol or butadiene. Our results indicate that the hydrothermal liquefaction pathways have significant cost advantages over the pathways that burn the lignin. For comparison purposes, two more scenarios were evaluated based on the assumption that ethanol was purchased at market prices and converted to butanol or butadiene exclusively. This comparison evaluates the economics for making higher‐valued chemicals which, in the absence of incentives, would be the most profitable approaches in our study. The results for these evaluations indicated that the ethanol‐to‐butanol economics were generally favorable and achieved or exceeded the 10% internal rate of return target. The butadiene process had less favorable economic performance in some years when the market price for butadiene was less than the selling price needed to achieve the internal rate of return. Economic incentives for low‐carbon chemicals and fuels were not considered in our analysis. © 2022 Battelle Memorial Institute. Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]

The finite nature of fossil fuels and the environmental impact of its use have raised interest in alternate renewable energy sources. Specifically, nonfood carbohydrates, such as lignocellulosic biomass, can be used to produce next generation biofuels, including cellulosic ethanol and other nonethanol fuels like butanol. However, currently there is no native microorganism that can ferment all lignocellulosic sugars to fuel molecules. Thus, research is focused on engineering improved microbial biocatalysts for production of liquid fuels at high productivity, titer, and yield. A clear understanding and application of the basic principles of microbial physiology and biochemistry are crucial to achieve this goal. In this review, we present and discuss the construction of microbial biocatalysts that integrate these principles with ethanol-producing Escherichia coli as an example of metabolic engineering. These principles also apply to fermentation of lignocellulosic sugars to other chemicals that are currently produced from petroleum. [ABSTRACT FROM AUTHOR]

Corn stalks have been traditionally disposed of by in-situ incineration or for the production of animal feed, due to the main crop residues in northeastern China. However, the conventional treatments of corn stalks have posed a great threat to the environment and resource utilization in recent years. Alternatively, biomass materials (corn stalks) can be widely expected to replace wood preparation in paper production. Different pretreatments can be utilized to improve the quality of pulp made from corn stover. The common-used pulping pretreatment can include various physical, chemical, and biological reactions. This study aims to explore the possibility and feasibility of a co-culture procedure of anaerobic microorganisms and yeast to pretreat the corn stalks. The culture medium was firstly prepared in the experiment, and then the resulting goat rumen fluid was filtered and centrifuged, where the centrifuged supernatant was used for the identification. After that, the supernatant of rumen fluid (anaerobic fungi: Pecoramyces sp.) and Saccharomyces cerevisiae S1145 were added to the medium for the simple co-culture. The components of the naturally air-dried corn stalks were separated, where the corn stalk husks were collected, crushed, and sieved, and the shredded husks (as a substrate) were added to the medium for the simple co-cultivation at 39°C for 72 hours. The results show that the Saccharomyces cerevisiae presented the ethanol in the metabolites of fermentation broth under the action of rumen fungi, indicating that the rumen fungi and yeast were co-cultured in vitro. The content of Saccharomyces cerevisiae was greatly contributed to the metabolism. The ethanol content in the product reached the maximum when adding 5ml of Saccharomyces cerevisiae, accounting for 32.09% of the total metabolite content. The ethanol content was increased by 23.04 percentage points with Saccharomyces cerevisiae, compared with the control without. The co-culture process of anaerobic fungi and Saccharomyces cerevisiae was utilized to pretreat the corn stalk bark, where the Saccharomyces cerevisiae was improved the ethanol production. The enzyme preparation was normally used to enzymatically hydrolyze plant cellulose in the conventional second-generation cellulosic ethanol production. Nevertheless, the enzyme preparation cannot be reused during processing, leading to the high production cost of cellulosic ethanol. Taking the rumen of ruminants as a bionic object, the living environment of anaerobic microorganisms was simulated in vitro to create the conditions for the sustainable production of cellulosic ethanol. Consequently, this experiment provided a new way to treat the corn stalks. The corn stalks after biological treatment can be used to produce the biomass pulp. The experiments have verified that the rumen anaerobic microorganisms and Saccharomyces cerevisiae can self-reproduce the corn in an artificial biomimetic environment, indicating the feasibility of straw to produce ethanol. The treatment and reuse of corn stalks can greatly contribute to the economic benefits of corn stalk pulping, while reducing the overall cost consumption for the high resource utilization. [ABSTRACT FROM AUTHOR]

Abstract The demand for fossil derivate fuels and chemicals has increased, augmenting concerns on climate change, global economic stability, and sustainability on fossil resources. Therefore, the production of fuels and chemicals from alternative and renewable resources has attracted considerable and growing attention. Ethanol is a promising biofuel that can reduce the consumption of gasoline in the transportation sector and related greenhouse gas (GHG) emissions. Lignocellulosic biomass is a promising feedstock to produce bioethanol (cellulosic ethanol) because of its abundance and low cost. Since the conversion of lignocellulose to ethanol is complex and expensive, the cellulosic ethanol price cannot compete with those of the fossil derivate fuels. A promising strategy to lower the production cost of cellulosic ethanol is developing a biorefinery which produces ethanol and other high-value chemicals from lignocellulose. The selection of such chemicals is difficult because there are hundreds of products that can be produced from lignocellulose. Multiple reviews and reports have described a small group of lignocellulose derivate compounds that have the potential to be commercialized. Some of these products are in the bench scale and require extensive research and time before they can be industrially produced. This review examines chemicals and materials with a Technology Readiness Level (TRL) of at least 8, which have reached a commercial scale and could be shortly or immediately integrated into a cellulosic ethanol process.

Switchgrass (Panicum virgatum L.) has been identified as a potential feedstock for cellulosic ethanol production in United States for its high biomass yield and adaptation to marginal lands. Composition of the cell wall plays an important role in bioethanol conversion. A total of 209 pseudo‐F1 testcross progenies obtained from a biparental cross, AP13 × VS16, were grown at three locations from 2008 to 2011. Near‐infrared spectroscopy was used to estimate cell wall composition from biomass harvested at maturity. A linkage map of the pseudo‐F1 testcross was constructed with 8,757 SNPs developed by genotyping‐by‐sequencing. Quantitative trait loci (QTL) analysis was performed on eight lignocellulosic traits, namely, klason lignin, sugar, glucose, xylose, hexose, ethanol, hexosoic ethanol, and cell wall ethanol conversion percentage. A total of 327 QTL were recorded for the eight lignocellulosic traits. We have identified 111 major regions in the switchgrass genome that underlie these lignocellulosic traits. Scanning of the genome sequence for genes flanking the QTL peaks, we identified 45 important genes that are involved in lignin biosynthesis, carbohydrate and sugar metabolism, and other biological and cellular functions. Identification of valuable genes associated with QTL along with pleotropic effects of the significant number of QTL suggests that simultaneous selection and genetic improvement of these traits are possible using marker‐assisted selection. [ABSTRACT FROM AUTHOR]

Coproduction of high-value bioproducts at biorefineries is a key factor in making biofuels more cost-competitive. One strategy for generating coproducts is to directly engineer bioenergy crops to accumulate bioproducts in planta that can be fractionated and recovered at biorefineries. Here, we develop quantitative insights into the relationship between bioproduct market value and target accumulation rates by investigating a set of industrially relevant compounds already extracted from plant sources with a wide range of market prices and applications, including <$10/kg (limonene, latex, and polyhydroxybutyrate [PHB]), $10 to $100/kg (cannabidiol), and >$100/kg (artemisinin). These compounds are used to identify a range of mass fraction thresholds required to achieve net economic benefits for biorefineries and the additional amounts needed to reach a target $2.50/gal biofuel selling price, using cellulosic ethanol production as a test case. Bioproduct market prices and recovery costs determine the accumulation threshold; we find that moderate- to high-value compounds (i.e., cannabidiol and artemisinin) offer net economic benefits at accumulation rates of just 0.01% dry weight (dwt) to 0.02 dwt%. Lower-value compounds, including limonene, latex, and PHB, require at least an order-ofmagnitude greater accumulation to overcome additional extraction and recovery costs (0.3 to 1.2 dwt%). We also find that a diversified approach is critical. For example, global artemisinin demand could be met with fewer than 10 biorefineries, while global demand for latex is equivalent to nearly 180 facilities. Our results provide a roadmap for future plant metabolic engineering efforts aimed at increasing the value derived from bioenergy crops. [ABSTRACT FROM AUTHOR]

Graphical abstract Based on a computable general equilibrium (CGE) model augmented with an explicit land allocation module (a), land use changes induced by China's bioethanol expansion are quantified. The simulation results of different land conversion scenarios (b) indicate that planting non-grain feedstocks on newly reclaimed marginal land could increase non-grain feedstocks by 10% and save 0.217% of croplands with no deforestation by 2020 (c). Highlights • Built a general equilibrium model incorporating an explicit land use module. • Different patterns of land use management were considered. • Quantified land use changes among alternatives induced by bioethanol expansion. • Planting energy crops on marginal land could alleviate cropland occupation. Abstract Biofuel plays an important role in the transition to low-carbon energy systems. However, the large-scale expansion of biofuels may cause drastic land use change (LUC) due to feedstock cultivation and further result in other sustainability impacts (e.g., food supply), which are the key concerns for policy makers when designing bioenergy policies. However, biophysical models omit the indirect LUC from interactions of economic agents, whereas economic models lack the depiction of heterogeneous land use types. Thus, through either technique, it has formidable challenges to simulate land conversions among alternative uses driven by socioeconomic activities, especially policy mandates. To bridge the gap between these models by simultaneously considering land heterogeneity and market mechanisms and to gain better insights into specific national/regional cases to supplement previous global biofuel and LUC analyses, in this study, we develop a national computable general equilibrium (CGE) model augmented with an explicit land allocation module and design a scenario approach to simulate different patterns of land use management. Food grains and dedicated energy crops are considered feedstock sources and marginal land is incorporated as a potential land supply. Using this model, the case study of China quantifies the direct and indirect LUC driven by the bioethanol (one of the main biofuels) expansion of the new nationwide E10 mandate (gasoline containing 10% ethanol) in 2020, as well as the further impacts on food security. The results show that a slight land reallocation occurs with decreases in the land supply for rice (−0.016%), other non-feedstock grains and crops, as well as forest and grassland (−0.023%). The land competition among existing croplands would be intense in the non-deforestation scenario. If marginal land is reclaimed for feedstock cultivation, the cropland competition could be softened. The results of sensitivity analysis indicate that the total LUC scale would be 4.0–5.9% with no corn stockpile serving as feedstock. Additionally, the bioethanol expansion would trigger higher food prices (around +0.1%). To alleviate the negative impacts on land resources and food security, planting energy crops on marginal land could increase non-grain feedstocks by 10% and save 0.217% of croplands; therefore, it may be one of the promising pathways for sustainable biofuel development in China. This study can lay a common foundation for further integrated impact assessments of biofuel expansion. [ABSTRACT FROM AUTHOR]

Biofuel production from cellulosic feedstocks may increase during the next century. To be sustainable, this production should protect environmental quality and biodiversity. Fertilized mixed‐species prairie can deliver substantial quantities of cellulosic ethanol per unit land area with minimal losses of NO3‐N in drainage water, but the long‐term maintenance of biodiversity in such systems has been uncertain.We report how nitrogen, phosphorus, and potassium fertilizer application, precipitation, and time affected the species composition and productivity of reconstructed prairie communities harvested annually as biofuel feedstocks over a 9‐year period.Results indicated that both precipitation and fertilizer application drove above‐ground biomass production, with the greatest response to fertilizer occurring in wetter than average years. Fertilization reduced species richness, but increased species evenness. Consequently, Simpson's diversity index did not differ between the fertilized and unfertilized communities, though it declined in both communities over time.A total of 59 plant species was recorded, with eight of them explaining most of the differences in vegetation cover between the fertilized and unfertilized treatments. After 9 years, the high fertility community was dominated by the C4 grass Andropogon gerardii, the C3 grass Elymus canadensis, and the non‐leguminous forbs Heliopsis helianthoides, Helianthus maximiliani, and Monarda fistulosa, whereas the low fertility community was dominated by the C4 grasses A. gerardii and Sorghastrum nutans, the C3 grass E. canadensis, and the non‐leguminous forb M. fistulosa. Fertilization increased the abundance of flowering forbs available to pollinators in the early, middle and late portions of the growing season.Synthesis and applications. Results of our study suggest that maintenance of reasonably high levels of productivity and biodiversity are possible in fertilized prairie communities harvested annually for bioenergy, with plant cover more evenly distributed among different functional groups. In the future, if policy and markets favour biofuels and better delivery of ecosystem services from harvested land, prairie‐based feedstocks could become part of a renewable energy portfolio that fosters biodiversity and contributes to the provision of floral resources for pollinators. Results of our study suggest that maintenance of reasonably high levels of productivity and biodiversity are possible in fertilized prairie communities harvested annually for bioenergy, with plant cover more evenly distributed among different functional groups. In the future, if policy and markets favour biofuels and better delivery of ecosystem services from harvested land, prairie‐based feedstocks could become part of a renewable energy portfolio that fosters biodiversity and contributes to the provision of floral resources for pollinators. [ABSTRACT FROM AUTHOR]

The sugarcane sector in Brazil has undergone a major modernization in the last thirty years. Embracing the biorefinery concept, this sector is investigating bioproduct diversification and mostly putting a lot of effort and investment on second generation ethanol production. In this context, the investigation of the integration of a third generation biofuel production using microalgae to the sugarcane biorefinery seems an important starting point. This study evaluates the integration of microalgae growth and processing to a sugarcane biorefinery producing first and second generation ethanol using process simulation tools. Microalgae are cultivated using CO 2 produced during fermentation of ethanol and it is processed using supercritical fluid extraction technology in order to obtain lipids rich in high added-value compounds, carotenoids. The results showed that the integration of microalgae biomass processing without previously drying with the sugarcane biorefinery is not attractive from the thermo-economic point. When considering the extraction of dried microalgae the extraction process could be thermal integrated to the sugarcane biorefinery producing ethanol without the need of buying external fuel. The amount of CO 2 used as solvent to the supercritical fluid extraction was the main factor that influenced the economic viability of the process. When microalgae pretreatment by cell disruption or co-solvent extraction was considered, it was possible to decrease the amount of CO 2 used in the process and an increase in process yields was consequently achieved. The use of a co-solvent in the extraction increased in 1.4 and 2.4 times lipids and carotenoids extraction, respectively, and presented a lower investment when comparing with microalgae extraction without cell disruption. [ABSTRACT FROM AUTHOR]

U.S. ethanol production from corn rapidly grew since the enactment of the Energy Policy Act of 2005 and the Energy Independence Act of 2007. Although many economists analyzed the relationships between food and fuel prices, the mechanisms between the price comovements and ethanol production have not yet been investigated with numerical models. We test the hypothesis that ethanol production strengthens the linkages between food and energy prices using the dynamic conditional correlations (DCC) -mixed-data sampling (MIDAS) model and wavelet coherence approach over the sample period 2005–2020. To the best of our knowledge, this research is the first to apply the combination of the DCC-MIDAS and wavelet methodologies to address the relevant issues. Our primary findings are as follows (1) the DCCs for the three pairs (i.e., ethanol-corn, crude oil-corn, and ethanol-crude oil): exhibited positive linkages in most of the sample period. (2) The ethanol-corn DCC positively and negatively affects ethanol production in the short and long run. (3) Ethanol production negatively and positively influenced the crude oil-corn DCC in the short and long term. The results suggest that U.S. biofuel policies foster the food-energy long-run linkages and enhance the probability of concurrent food and energy crises. [ABSTRACT FROM AUTHOR]

Replacing fossil fuels with renewable fuels derived from lignocellulosic biomass can contribute to the mitigation of global warming and the economic development of rural communities. This will require lignocellulosic biofuels to become price competitive with fossil fuels. Techno-economic analyses can provide insights into which parts of the biofuel production process need to be optimized to reduce cost or energy use. We used data obtained from a pilot biorefinery to model a commercial-scale biorefinery that processes lignocellulosic biomass to ethanol, with a focus on the minimum ethanol selling price (MESP). The process utilizes a phosphoric acid-catalyzed pre-treatment of sweet sorghum bagasse followed by liquefaction and simultaneous saccharification and co-fermentation (L+SScF) of hexose and pentose sugars by an engineered Escherichia coli strain. After validating a techno-economic model developed with the SuperPro Designer software for the conversion of sugarcane bagasse to ethanol by comparing it to a published Aspen Plus model, six different scenarios were modeled for sweet sorghum bagasse Under the most optimistic scenario, the ethanol can be produced at a cost close to the energy-equivalent price of gasoline. Aside from an increase in the price of gasoline, the gap between ethanol and gasoline prices could also be bridged by either a decrease in the cost of cellulolytic enzymes or development of value-added products from lignin. [ABSTRACT FROM AUTHOR]

[Display omitted] • The rise of cellulosic ethanol generates vast amounts of lignin-rich residues. • Unique opportunity to apply lignin depolymerization technologies at scale. • Lignin bio-oil is upgradable into liquid biofuels and aromatic biochemicals. • Biochar can be a valuable coproduct of lignin depolymerization. • Many research opportunities in this novel platform of biorenewables. Recent years witnessed the dawn of the cellulosic ethanol industry based on enzymatic hydrolysis of carbohydrates in lignocellulosic biomass. Meanwhile, new concepts have emerged to depolymerize lignin and upgrade the obtained lignin fragments into value-added fuels and chemicals. This review analyzes the convergence of these two fields, presenting the opportunities for applying such depolymerization technologies to the residual enzymatic hydrolysis lignin (EHL) now available at an industrial scale. Key characteristics of EHL are presented together with the most investigated technologies for EHL depolymerization (pyrolysis, hydrothermal, and solvolysis) to obtain lignin bio-oils. The review also discusses the prospects for upgrading lignin bio-oils for use as aviation and marine biofuels. Furthermore, it presents a more long-term vision that progressively valorizes the biochar by-product and adds the co-production of chemicals harnessing the aromaticity and oxygenation of the lignin moieties. In conclusion, EHL has a unique set of characteristics (cost, availability, transportability, degrees of oxygenation and purity, reactivity, among others) to produce lignin bio-oils, instigating research questions dedicated to this type of industrially relevant feedstock. [ABSTRACT FROM AUTHOR]