Cellulosic Ethanol Technology Research Articles

Bioconversion of corn fiber to bioethanol: Status and perspectives

Due to the rising demand for green energy, bioethanol has attracted increasing attention from academia and industry. Limited by the bottleneck of bioethanol yield in traditional corn starch dry milling processes, an increasing number of studies focus on fully utilizing all corn ingredients, especially kernel fiber, to further improve the bioethanol yield. This mini-review addresses the technological challenges and opportunities on the way to achieving the efficient conversion of corn fiber. Significant advances during the review period include the detailed characterization of different forms of corn kernel fiber and the development of off-line and in-situ conversion strategies. Lessons from cellulosic ethanol technologies offer new ways to utilize corn fiber in traditional processes. However, the commercialization of corn kernel fiber conversion may be hampered by enzyme cost, conversion efficiency, and overall process economics. Thus, future studies should address these technical limitations.

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.

Potentials, subsidies and tradeoffs of cellulosic ethanol in the European Union

The EU's revised Renewable Energy Directive (RED2) sets high mandates for advanced biofuels like cellulosic bioethanol from agricultural residues. However, many residues are used for ecological and economic purposes such as soil organic carbon regulation and livestock bedding and fodder. We use the global CGE model DART-BIO with a detailed representation of the bioeconomy to simulate the RED2 cellulosic bioethanol mandates and run sensitivity analyses regarding processing technology, straw and oil prices. We implement a latent cellulosic ethanol technology and develop new sectors for agricultural residues. We find that the RED2 cellulosic ethanol mandates will require enormous amounts of residues that could exceed the sustainable available potential in the EU. Agricultural residue utilization changes substantially and the cellulosic ethanol industry becomes the main residue consumer. Results show that output and price impacts of advanced biofuel targets are small, but there is reallocation of land towards cereals that enter the agricultural residue sector away from other crops in the EU. Moreover, the size of necessary cellulosic ethanol subsidies and the abatement costs per tonCO2eq are very sensitive to actual straw and oil prices.

Novel Heat-Integrated Hybrid Distillation and Adsorption Process for Coproduction of Cellulosic Ethanol, Heat, and Electricity from Actual Lignocellulosic Fermentation Broth

Cellulosic ethanol (CE) can not only be produced from a nonedible, cheap, and abundant lignocellulose feedstock but also can reduce carbon footprint significantly compared to starch ethanol. Despite great stimulation worldwide, CE production has not yet commercialized because of the complexity of lignocellulose. Therefore, intensive research and development are needed to improve CE technologies. In this study, a cost-efficient and sustainable design was proposed for the coproduction of CE, heat, and electricity from the actual lignocellulosic fermentation broth. First, a conventional coproduction process of CE, heat, and electricity based on hybrid distillation and adsorption (HDA) was simulated and optimized. Subsequently, various heat integrated (HI) techniques such as heat pump (HP), multi-effect distillation (MED), and combined HP-MED were evaluated to improve the CE process. The combined heat and power (CHP) process that utilized the combustible solids of the beer stillage was designed and integrated with the CE process. Structural alternatives were assessed for both economic and environmental impacts. The results show that the proposed HI-HDA process can save 36.9% and 33.6% of total annual costs and carbon footprint, respectively, compared to the conventional CE process. In the proposed HI-HDA coproduction process, the CE recovery process can be self-efficient in energy and the CHP can generate 12.0% more electricity than that in the conventional coproduction process.

Business Roundup

BUSINESS Business Roundup ShareShare onFacebookTwitterWechatLinked InRedditEmail C&EN, 2021, 99 (5), p 13February 8, 2021Cite this:C&EN 99, 5, 13AbstractRenewcell plans to open a 60,000-metric-ton-per year mixed waste–textile recycling plant—the first of its kind, it says—in Sundsvall, Sweden, in 2022. Renewcell will use equipment from the engineering firm Valmet to convert textile waste into a pulp ready for spinning into new fiber. Clariant has secured a licensing deal—its fifth overall—for its sunliquid cellulosic ethanol technology with Harbin Hulan Sino-Dan Jianye Bio-Energy. The latter will use Clariant’s technology to produce 25,000 metric tons of ethanol annually from corn stover in Heilongjiang Province, China. Mitsubishi Corp. will work with CarbonCure, a Canadian firm that sells technology to trap carbon dioxide in cement and concrete, to bring the low-carbon building material to Japan and other parts of Asia. The Japanese conglomerate also made an undisclosed investment in the company. Evonik Industries has invested in Chembid , a digital marketplace for chemicals based in Oldenburg, Germany. Evonik will discontinue its OneTwoChem chemical marketplaceView: PDF | Full Text HTML

Robust paths to net greenhouse gas mitigation and negative emissions via advanced biofuels

Biofuel and bioenergy systems are integral to most climate stabilization scenarios for displacement of transport sector fossil fuel use and for producing negative emissions via carbon capture and storage (CCS). However, the net greenhouse gas mitigation benefit of such pathways is controversial due to concerns around ecosystem carbon losses from land use change and foregone sequestration benefits from alternative land uses. Here, we couple bottom-up ecosystem simulation with models of cellulosic biofuel production and CCS in order to track ecosystem and supply chain carbon flows for current and future biofuel systems, with comparison to competing land-based biological mitigation schemes. Analyzing three contrasting US case study sites, we show that on land transitioning out of crops or pasture, switchgrass cultivation for cellulosic ethanol production has per-hectare mitigation potential comparable to reforestation and severalfold greater than grassland restoration. In contrast, harvesting and converting existing secondary forest at those sites incurs large initial carbon debt requiring long payback periods. We also highlight how plausible future improvements in energy crop yields and biorefining technology together with CCS would achieve mitigation potential 4 and 15 times greater than forest and grassland restoration, respectively. Finally, we show that recent estimates of induced land use change are small relative to the opportunities for improving system performance that we quantify here. While climate and other ecosystem service benefits cannot be taken for granted from cellulosic biofuel deployment, our scenarios illustrate how conventional and carbon-negative biofuel systems could make a near-term, robust, and distinctive contribution to the climate challenge.

Clariant sells fourth straw ethanol license

Clariant has sold a fourth license for its Sunliquid cellulosic ethanol technology to Eta Bio, a family-owned agricultural business based in Bulgaria. Eta will build a plant with an annual capacity for converting about 250,000 metric tons (t) of wheat straw into 50,000 t of cellulosic ethanol. Ongoing commercial interest in Clariant’s technology is in stark contrast to that of other cellulosic ethanol technologies, most of which have been shelved .

Development Status and Technical and Economic Analysis of Ethanol Gasoline for Automobile in China

With the shortage of petroleum resources and the aggravation of environmental pollution, the research of alternative fuel for automobile is paid more and more attention. As a relatively clean fuel, ethanol gasoline can significantly reduce the emission of harmful substances in automobile exhaust. Compared with ordinary gasoline, it has the advantages of high octane number, good antiknock performance and high oxygen content. But it also has disadvantages such as low combustion heat value, large latent heat of evaporation, corrosion to metals, poor and compatibility with some engine materials, etc. The three factors affecting the development of ethanol gasoline are resources, technology and economic benefits. Although China is the third largest ethanol production and consumption country in the world, its resource conditions are not as good as those of the United States and Brazil. Under the current market and industrial policy environment, the overall benefits of domestic fuel ethanol production enterprises are poor. Cellulosic ethanol technology is the key technology to restrict the development of ethanol gasoline. Only when the second generation of biofuels pass the economic test, can the use of ethanol gasoline be promoted nationwide.

Clariant and Anhui Guozhen and Chemtex announce licence agreement on Sunliquid cellulosic ethanol technology in China

Both non-alcoholic steatohepatitis (NASH) and alcoholic hepatitis (AH) can lead to cirrhosis and hepatocellular carcinoma. However, the rate of progression to cirrhosis and tumorigenesis in AH is greater than that in NASH. We asked whether there are differences between the two conditions in the expression levels of proteins involved in the pathogenesis of hepatocellular carcinoma. The proteins tested were presented at the 2017 American Association for the Study of Liver Diseases (AASLD) Liver Meeting as overexpressed in hepatocellular carcinoma: KLF4, SCL19A1, FANCG, HRH-1, DNMT1, DNMT3B, TNFR2, DUSP4, EGFR, Integrin α6, HDACII, PDE3A, BCL-XL, and MTCO2. The expression of these proteins was measured in liver biopsy sections from NASH and AH patients using immunohistochemical staining with fluorescent antibodies and then quantifying the fluorescence intensity morphometrically. In AH patients, levels of all tested proteins except HRH-1 were elevated compared to normal patients. In NASH patients, KLF4, SCL19A1, FANCG, HDACII, BCL-XL levels were increased compared to normal controls while HRH-1, DNMT1 and PDE3A levels were decreased. The relative expression of all proteins studied except BCL-XL was significantly higher in AH compared to NASH. In conclusion, proteins involved in hepatocellular cancer development are more highly expressed in AH compared to NASH and normal liver, which corresponds with the higher rate of tumorigenesis in AH patients compared to NASH patients.

DuPont divests its cellulosic ethanol technology

DuPont has sold its technology for converting cellulosic biomass into ethanol to the Princeton, New Jersey–based chemical process engineering firm Petron Scientech for an undisclosed sum. The deal includes patents and the Zymomonas bacteria strains that DuPont developed for a $200 million–plus ethanol plant in Nevada, Iowa. DuPont closed the plant in 2017, just 2 years after opening it, and sold it last year to Germany’s Verbio, which is revamping the site to make biomethane. Petron say the acquisition will expand its family of renewable fuel and chemical technologies.

Structural and compositional changes in sugarcane bagasse subjected to hydrothermal and organosolv pretreatments and their impacts on enzymatic hydrolysis

Economical sustainability of cellulosic ethanol technology still requires considerable improvements in efficacies of both pretreatment and enzymatic hydrolysis steps. In this work a number of physical techniques were applied to characterize sugarcane bagasse samples that underwent hydrothermal and/or organosolv pretreatments under variable conditions and to correlated the observed changes with the efficiency of enzymatic hydrolysis. Confocal and field emission scanning electron microscopy studies revealed morphological changes in lignin distribution in the plant cell wall. The hydrothermal pretreatment caused a disorder in the arrangement of the lignin, whereas organosolv pretreatment partially removed lignin from bagasse and fraction of it redeposited at the surfaces of cellulose fibers. The delignification process was also analyzed by both chemical composition analysis and nuclear magnetic resonance. Pretreatment conditions leading to a significant increase of the efficiency of enzymatic hydrolysis were identified. Our studies open avenues for further biophysical investigations of pretreated lignocellulosic biomass, which could lead to its improved enzymatic hydrolysis.

Clariant and Enviral announced first licence agreement on sunliquid cellulosic ethanol technology

For successful implementation of sustainability in industry, robust assessments of products and processes are necessary that quantify environmental aspects while also considering a product or processes’ total cost of ownership. Challenges exist as sustainability needs vary greatly according to region, market sector, customer-specific requirements, and stakeholder demands. BASF has developed a toolbox for Eco-Efficiency assessments that addresses the broad range of in-house and external needs, allowing flexibility while ensuring that relevant and sufficient environmental impact and costs are covered. The toolbox is based on standard practice for life cycle assessment but goes further to better support strategic decisions, product development, and marketing. Environmental impact assessment follows ISO 14040 and 14044. The underlying Eco-Efficiency methodology is based primarily on standard assessment models as implemented in the product environmental footprint methodology of the European Union (EU PEF). Impacts are aggregated to an overall environmental impact expressed in terms of person time. Life cycle costs are similarly determined and may be combined with environmental impact to an overall Eco-Efficiency Portfolio and Eco-Efficiency Index. The automated relevance check ensures coverage of main impact categories and environmental impact. Normalization with meaningful figures is applied as well as a weighting scheme that was developed together with the external partner TNS infratest by using a panel weighting approach. Weighting factors are updated on a regular basis and are applicable for all regions of the world. Eco-Efficiency results support strategic business decision-making and customer and external stakeholder engagement based on quantified, credible sustainability assessments.

The isolation of pentose-assimilating yeasts and their xylose fermentation potential

For the implementation of cellulosic ethanol technology, the maximum use of lignocellulosic materials is important to increase efficiency and to reduce costs. In this context, appropriate use of the pentose released by hemicellulose hydrolysis could improve de economic viability of this process. Since the Saccharomyces cerevisiae is unable to ferment the pentose, the search for pentose-fermenting microorganisms could be an alternative. In this work, the isolation of yeast strains from decaying vegetal materials, flowers, fruits and insects and their application for assimilation and alcoholic fermentation of xylose were carried out. From a total of 30 isolated strains, 12 were able to assimilate 30 g L−1 of xylose in 120 h. The strain Candida tropicalis S4 produced 6 g L−1 of ethanol from 56 g L−1 of xylose, while the strain C. tropicalis E2 produced 22 g L−1 of xylitol. The strains Candida oleophila G10.1 and Metschnikowia koreensis G18 consumed significant amount of xylose in aerobic cultivation releasing non-identified metabolites. The different materials in environment were source for pentose-assimilating yeast with variable metabolic profile.

Aemetis buys Edeniq for cellulosic fuel

Biofuels producer Aemetis has agreed to acquire cellulosic ethanol technology provider Edeniq for an undisclosed amount of cash and stock. Founded in 2008, Edeniq developed a process to convert cellulosic sugars from corn kernel fibers into ethanol. Six U.S. ethanol plants have installed the technology. Edeniq had raised $100 million from venture backers and Department of Energy grants.

DuPont and New Tianlong Industry Co Ltd sign historic deal to bring cellulosic ethanol technology to China

Low-duty-cycle mode is widely adopted in energy-critical wireless sensor networks (WSNs). Such mode greatly reduces the energy waste caused by idle listening. However, it brings many new challenges for broadcasting. This paper mainly focuses on the minimum cost broadcast problem for low-duty-cycle WSNs. We propose a novel opportunistic broadcasting transmission model, which makes full use of the broadcast nature of wireless media to reduce the total energy consumption for broadcasting. The key idea is to allow nodes to defer their wake-up slots to opportunistically overhear the broadcasting messages sent by their neighbors, which could reduce the total energy consumption for broadcasting but increase the average end-to-end broadcasting delay. In this paper, we define a generalized broadcasting cost function, which can make a flexible tradeoff between average end-to-end broadcasting delay and total energy consumption for broadcasting, to adaptively meet various broadcasting performance requirements. Our target is to utilize the opportunistic broadcasting transmission model to design an efficient broadcasting schedule for low-duty-cycle WSNs, so that the broadcasting cost function is minimized. First, we define the Receiver-Constrained Minimum Cost Single-hop Broadcast Problem (RC-MCSB) and propose an optimal solution with a polynomial running time. Next, we extend the solution of RC-MCSB problem to our target problem and present a novel and efficient bottom-up solution. The simulation results have verified the significant performance advantage of our proposed bottom-up solution over the existing top-down solutions and the other solutions.

Use of Byproduct from Cellulosic Ethanol Production as an Additive for Concrete: A Possible Win-win Strategy?

Technologists are facing increasing demands to achieve ecologically sustainable industrial practices. Currently the concrete industry is a significant contributor to greenhouse gas emissions. On the other hand, the scaling up of cellulosic ethanol technology has not been a very easy task. In this context, the integration of “greener” concrete with cellulosic ethanol technology may open up promising possibilities. The solid byproducts from cellulosic ethanol production process have been demonstrated to increase the strength of concrete structures when used as a partial cement replacement. Such a delicate integration can also lead to reduction in both carbon footprint and product cost. The possible commercialization of the integrated technologies would provide win-win benefits for both industries.

Use of combined UV and chemical mutagenesis treatment of Aspergillus terreus D34 for hyper-production of cellulose-degrading enzymes and enzymatic hydrolysis of mild-alkali pretreated rice straw

Microbial production of cellulose-degrading enzymes could be significantly improved using traditional mutagenesis treatment. Development of high-titre cellulase producing mutants drastically reduces the costs involved in cellulase production and downstream processing in commercial-scale enzyme production. Here, we have evaluated the efficacy of different Aspergillus terreus D34 mutants for hyper-production of improved cellulase enzymes utilizing locally available lignocellulosic biomass residues as growth substrates in solid state fermentation conditions. Further, enzymatic hydrolysis of mild-alkali pre-treated rice straw was performed using the improved cellulases. A 4.9-fold higher β-glucosidase activity was obtained from ethyl methyl sulphonate (EMS) treated mutant strain (EMS2) when grown on mixed rice straw/sugarcane bagasse (RSBG) biomass growth substrate. Similarly with the EMS2 mutant and BG-grown culture extract a 1.1-fold higher xylanase activity was observed. Irrespective of the growth substrates and the mutant strains, the maximum cellulase (FPase, carboxymethyl cellulase, avicelase, β-glucosidase) and xylanase activities (U mL−1) were 2.34, 39.8, 2.46, 19.9 and 655, respectively. Further, external supplementation of 20% bovine serum albumin (BSA), 3% tween 80 and 20% polyethylene glycol (PEG) 6000 to the crude enzyme extract increased the FPase activity nearly 4.0-, 2.8- and 2.2-fold. Addition of 0.05% sodium benzoate marginally increased the stability of cellulase enzyme and retained more than 60% of the initial activity after 96 h incubation at 37°C. While at 4°C, no loss in enzyme activity was observed even after prolonged incubation period (up to 90 days). Further, maximum reducing sugars of 0.842 g g−1 at a rate of 0.25 mM g−1 h−1 at 10% biomass loading of mild-alkali pretreated rice straw was produced using the BG-grown culture extract of EMS2 mutant strain. The extracellular protein production and corresponding cellulase activities of A. terreus D34 were significantly enhanced after combined UV and chemical mutagenesis treatments. In the present study, besides accelerating the rate of cellulase production, we have also demonstrated production of high reducing sugars by enzymatic saccharification of pretreated lignocellulosic biomass using hyper-produced cellulase enzymes. Due to high enzyme activity of the cellulase enzymes produced from the mutant strains, the volume of enzyme loadings in enzymatic hydrolysis could be reduced up to 7-fold. These studies clearly show the potential of the developed hyper-cellulase producing mutants in decreasing the overall process economics of cellulosic ethanol technology.

A Multi-Years Analysis of the Energy Balance, Green Gas Emissions, and Production Costs of First and Second Generation Bioethanol

Contemporary reports on the energy and environmental benefits of bioethanol have suggested that the cellulosic ethanol is significantly more efficient. To understand the development potential of energy crops in Taiwan, the present study has assessed the resources and cost inputs for the planning, harvesting, transporting, and storing procedures of the first generation energy crops during 2007–2010 with the perspective of LCA. In addition, a field investigation focusing on rice straw, the largest agricultural waste in Taiwan, has been conducted since 2010 to obtain fundamental data.This study further analyzes the first and second-generation feedstocks from the perspective of LCA based on field investigated data. Taiwan has not yet established an ethanol plant; therefore, this study established production data by simulating the production efficiency of an economical scale using parameters obtained through production trials, and proposed an evaluation model for the energy input, GHG, and production costs of bioethanol in Taiwan. The results of this study were cross-compared with foreign literature to explore the development potential of bioethanol in Taiwan. The results indicate that based on the current cellulosic ethanol technology in Taiwan, regarding the energy balance, GHG, and production costs, is less efficient than that of the first generation bioethanol.

Coping with technology uncertainty in transportation fuel portfolio design

In this paper, we present a stochastic programming model to cope with uncertainty brought by cellulosic ethanol technology evolvement in transportation fuel portfolio design problems. The model takes into account a range of possible technology evolvement scenarios, and identifies a solution to the energy portfolio, together with the corresponding infrastructure needs, that complies with existing environmental requirements and is cost-effective, reliable, and adaptable to future technology changes. Using a California case study, we demonstrate that the proposed stochastic model produces a more reliable solution than its deterministic counterparts.

Insights into the structure and function of fungal β-mannosidases from glycoside hydrolase family 2 based on multiple crystal structures of the Trichoderma harzianum enzyme.

Hemicellulose is an important part of the plant cell wall biomass, and is relevant to cellulosic ethanol technologies. β-Mannosidases are enzymes capable of cleaving nonreducing residues of β-d-mannose from β-d-mannosides and hemicellulose mannose-containing polysaccharides, such as mannans and galactomannans. β-Mannosidases are distributed between glycoside hydrolase (GH) families 1, 2, and 5, and only a handful of the enzymes have been structurally characterized to date. The only published X-ray structure of a GH family 2 mannosidase is that of the bacterial Bacteroides thetaiotaomicron enzyme. No structures of eukaryotic mannosidases of this family are currently available. To fill this gap, we set out to solve the structure of Trichoderma harzianum GH family 2 β-mannosidase and to refine it to 1.9-Å resolution. Structural comparisons of the T. harzianum GH2 β-mannosidase highlight similarities in its structural architecture with other members of GH family 2, reveal the molecular mechanism of β-mannoside binding and recognition, and shed light on its putative galactomannan-binding site. Coordinates and observed structure factor amplitudes have been deposited with the Protein Data Bank (4CVU and 4UOJ). The T. harzianum β-mannosidase 2A nucleotide sequence has GenBank accession number BankIt1712036 GeneMark.hmm KJ624918.