Clean Technology : Biofuels & renewable fuels


Enzymatic Depolymerization of Lignin

UW–Madison researchers provide the first demonstration of an in vitro enzymatic system that can recycle NAD+ and GSH while releasing aromatic monomers from natural and engineered lignin oligomers, as well as model compounds composed of similar chemical building blocks. Nearly 10 percent of beta-ether units were cleaved when the system was tested on actual lignin samples.

The relevant enzymes include dehydrogenases, β-etherases and glutathione lyases. In an exemplary version, the system uses the known LigD, LigN, LigE and LigF enzymes from Sphingobium sp. strain SYK-6. A newly discovered heterodimeric β-aryl etherase (BaeA) can be used in addition to or instead of LigE.

Recyclable Catalyst for Lower Cost Production of Fermentable Sugars and High Value Chemicals from Biomass

An assistant professor in chemical engineering at the University of Wisconsin-Stevens Point and former senior research scientist at the Montana State University Bio-Energy Center have developed a technology that reduces the processing cost and time to fractionate lignocellulose into fermentable sugars. The technology is centered on the use of a catalyst linked to a magnetic bead, which replaces the need for acids and enzymes in the pretreatment step of the production process. Because of its magnetic properties, the catalyst can easily be recovered from the reaction mixture and reused multiple times. It is also capable of functioning under cellulose loads as high as 50%, whereas loads for competing solid acid catalysts have been typically limited to less than 15%. The end result is a process that makes better use of carbon-neutral biomass by lowering production costs and increasing yield of desirable monomer sugars and high value chemical compounds such as vanillin, phenol, acetophenone.

Recombinant High-Lipid Microbe for Bioproduct & Biofuel Production

By combining genetic and bioreactor engineering, the researchers have developed R. sphaeroides strains capable of producing and secreting lipids at levels found in oleaginous microbes. In the process they isolated and characterized 10 different high-lipid strains.

Following a single genetic alteration, the best performing strain produced 1.3 g/L fatty acids, corresponding to 33 percent of DCW. The researchers are not aware of any previous examples of a microbe accumulating more than 20 percent of its biomass as phospholipid (triacylglycerol or wax esters are typical).

The novel properties of these high-lipid mutants suggest that similar changes in cell envelope structure could be used to increase production of lipids and associated bioproducts from other microbes.

Electrochemical Reductive Amination of Furfural

UW–Madison researchers have developed an electrochemical method for the reductive amination of furfural-based molecules including HMF and its derivatives. Using the new method, furfural-based molecules can be converted into amines via conversion of their formyl groups into amine groups. The use of water as the hydrogen source at ambient temperatures without requiring chemical reducing agents will decrease the cost and environmental concerns of the process.

Zip-Lignin™ Assay: An Analysis and Validation Tool

The researchers have now developed the most sensitive assay to date for detecting and quantifying Zip-lignin monomers in plants. They modified an existing lignin assay known as DFRC (Derivatization Followed by Reductive Cleavage) that has been in use for almost a decade. They incorporated several new features to improve the sensitivity of the assay, including extended incubation periods and an additional purification step.

The modified DFRC assay is currently the only known technique capable of determining levels of monolignol ester conjugates in plant lignin.

Modified Yeast with Enhanced Tolerance for GVL Biomass Solvent

UW–Madison researchers have developed a genetically modified strain of Saccharomyces cerevisiae that is more resistant to GVL toxicity and grows more than 1.5 times faster than wild yeast in the presence of GVL.

The researchers deleted two genes (Pad1p and Fdc1p) in the yeast that play a role in mediating GVL tolerance. The new strain is the first ethanol-producing yeast specifically tailored for GVL-based techniques.

Improved Biomass Conversion with GVL Co-Solvent

Building on their work, the researchers have now developed a process that utilizes an inexpensive co-solvent to replace a fraction of the GVL and also facilitates the separation of the organic solvents from the hydrolysate. Furthermore, the separated aqueous solution, rich in carbohydrates, contains a negligible amount of dissolved lignin.

The new method uses a relatively inexpensive solvent mixture, which also minimizes the separation cost. This improves the economic potential and additionally provides a valuable feedstock for production of aromatics (from lignin). This new improvement offers the opportunity to develop an economically viable process that combines catalytic lignin upgrading and carbohydrate production from biomass. The co-solvent mixture can be tailored for the production of C5 and C6 carbohydrates or degradation products such as furfural.

Modified Yeast to Boost Biofuel Yields

A UW–Madison researcher has developed an S. cerevisiae strain that is 80 percent more effective at fermenting xylose. He discovered that knocking out several genes (hog1, isu1, gre3, ira1/2) enables dramatically faster xylose fermentation under the anaerobic conditions favored by industry.

Platinum-Free Catalysts for Fuel Cells

UW–Madison researchers have developed a new scheme to improve the efficiency of oxygen reduction reactions in electrochemical cells. Their method combines a redox catalyst with a charge transfer mediator capable of transferring electrons and protons. Careful redox mediator/redox catalyst pairings avoid the need for expensive metal cathodes (or anodes). Favorable pairings include quinones with cobalt or iron-containing redox catalysts, and nitroxyl-type materials paired with nitric oxide-type redox catalysts.

Solar Cells for Reducing HMF to Valuable Platform Chemicals

UW–Madison researchers have developed a high yield method for reducing HMF to valuable furan alcohols including BHMF.

The new method uses electrochemical cells (ECs) or solar-powered photoelectrochemical cells (PECs) to drive the reduction reaction. The cells feature cost-effective catalytic electrodes made of silver film on copper. The reaction takes place at ambient temperature and pressure using water as the hydrogen source.

The process also can be used to produce linear ketones such as 5-MF (5-methylfurfural) using a zinc catalyst.

Solar Cells Turn HMF to Valuable Platform Molecules

UW–Madison researchers have developed a new method using solar cells to electrochemically oxidize HMF to highly prized furan compounds, specifically FDCA (2,5-furandicarboxylic acid) and DFF (2,5-diformylfuran). These important compounds are used to produce polymer materials, pharmaceuticals, antifungal agents, organic conductors and much more.

The reaction takes place at ambient temperature and pressure using a TEMPO mediator. Unlike previous methods, the process does not require a precious metal catalyst.

High Yield Method to Produce LGO from Biomass

UW–Madison researchers have developed a new method to produce LGO from cellulosic biomass under mild reaction conditions. The biomass material is reacted in a mixture comprising a polar aprotic solvent (e.g., tetrahydrofuran or THF) and an acid in the absence of water. The LGO can be separated out by routine downstream processes such as distillation and evaporation.

Glucose, levoglucosan, furfural and 5-hydroxymethylfurfural also are produced in small quantities.

Microbes Produce High Yields of Fatty Alcohols from Glucose

UW–Madison researchers have developed a method to produce fatty alcohols such as 1-dodecanol and 1-tetradecanol from glucose using genetically engineered microorganisms. The organism, e.g., a modified E. coli strain, overexpresses several genes (including FadD and a recombinant thioesterase gene, acyl-CoA synthetase gene and acyl-CoA reductase gene). Other gene products are functionally deleted to maximize performance.

The strain is cultured in a bioreactor in the presence of glucose.

Grass Modified for Easier Bioprocessing

The researchers have identified another gene of interest in rice, corn/maize and other grasses, called p-coumarate monolignol transferase (PMT). This is the first gene reportedly involved in the acylation of lignin monomers. In essence, interfering with this gene could make plants more amenable to biorefining.

More Efficient Water-Splitting Cells

UW–Madison researchers have developed a method for synthesizing nanoporous BiVO4 electrodes with large surface areas. The material is made up of a porous network of BiVO4 particles smaller than 150 nm and coated with oxygen evolution catalyst. The small size of the particles addresses prior drawbacks by increasing a property called electron–hole separation yield. The material is made by applying a vanadium solution to a type of bismuth crystal. The mixture is heated and converted into a porous network of BiVO4 particles.

Visible-Range Sunlight Drives CO2 Reduction Process for Cheaper Syngas

UW–Madison researchers have developed a new method of reducing CO2 to CO via a reverse water gas shift reaction using visible solar light. The reaction produces a syngas mixture which can be further converted to liquid fuels.

In this process, CO2 (which can be obtained from many industrial processes) is contacted with a plasmonic catalyst in the presence of hydrogen. The catalyst is exposed to visible-range sunlight so that it undergoes an optical phenomenon called surface plasmon resonance, which causes metal electrons to oscillate in a certain way and accelerates the rate of CO2 reduction.

The process results in CO2 being reduced to water and CO that can be collected for downstream products.

Preparing HMF from Biomass in Polar Aprotic Solvents

UW–Madison researchers have developed a method to prepare HMF from biomass under mild reaction conditions without the presence of water. The reaction can use any polar aprotic solvent (e.g., tetrahydrofuran). Yields are on par with those obtained using ionic liquids.

The reaction requires mild mineral acids and moderate temperatures (about 200 degrees C). In the process, cellulose decomposes to levoglucosan, which is then dehydrated to HMF. Glucose, levulinic acid and formic acid also are produced as a result of side reactions. HMF and the byproducts can be separated from the solvent using conventional methods like distillation and evaporation.

Concentrated C5 and C6 Sugars from Biomass

UW–Madison researchers have developed a process for producing C5 and C6 sugars from biomass at high yields (70 to 90 percent) in a solvent mixture of water, dilute acid and GVL (gamma-valerolactone). GVL is attractive because it is effective and derived from biomass.

The biomass and solvent system may be reacted at a temperature between 50 and 250oC for less than 24 hours.

The method yields liquid and solid fractions enriched in C5 and C6 sugar, respectively. The fractions are easily separated for post-treatment upgrading. This strategy is well-suited for catalytic upgrading to furans or fermentative upgrading to ethanol at near-theoretical yield.

Powerful New Enzyme for Transforming Biomass

UW–Madison researchers have engineered a multifunctional polypeptide capable of hydrolyzing cellulose, xylan and mannan. It is made of the catalytic core of Clostridium thermocellum Cthe_0797 (also called CelE), a linker region and a cellulose-specific carbohydrate binding module(CBM3).

C. thermocellum is a well-known cellulose-degrading bacterium whose genome has been sequenced, annotated and published.

Transgenic Lignin Easier to Break Down for Biofuel

UW–Madison researchers and others have developed methods to genetically alter the structure of plant lignin to be less resistant to chemical (mostly alkaline) degradation.

They have identified and isolated nucleic acids from the Angelica sinensis plant that encode feruloyl-CoA:monolignol transferase. This enzyme produces lignin rich in CAFA and similar chemicals, and thus contains ester bonds that cleave under relatively mild conditions.

Plant cells can be modified to contain the enzyme gene sequence using standard genetic techniques. Whole plants (and their seeds) then can be generated from these cells.

Extending Juvenile Stage of Plants for Biofuels and Feedstock

UW–Madison researchers have developed methods for locking plants in a juvenile state by modifying genes related to maturation.

The genes – GRMZM2G362718 or GRMZM2G096016 – have been analyzed by the researchers and shown to influence growth transition in corn. To alter plant development, these genes and their homologs could be knocked out or inhibited by small molecules or biologics. The process could involve additional genes known to affect juvenile to adult growth development.

Unleashing Biomass Sugars Using Bromine Salt

UW–Madison researchers have developed a process for hydrolyzing lignocellulosic biomass in concentrated aqueous solutions of inorganic bromine salt with a small amount of acid. The process breaks down the lignocellulose material (corn stover, saw dust, hardwood, softwood, etc.) into fermentable sugars without pretreatment.

The reaction works on the raw lignocellulosic biomass for 5-200 minutes at moderate temperatures, hydrolyzing cellulose and hemicellulose and releasing monosaccharides for subsequent biofuel or chemical production. Lignin separates from the product sugars and can be filtered out for use in co-products. The bromine salt, like LiBr or CaBr2, also can be recovered and reused.

Better Biomass Conversion with Recyclable GVL Solvent

UW–Madison researchers have developed a method for producing soluble C6 and C5 carbohydrate oligomers and monomers from biomass. These include glucose, xylose and other sugars.

In the process, lignocellulosic material is reacted with water and gamma-valerolactone (GVL) – an organic solvent derived from biomass. This occurs in the presence of an acid catalyst under moderate temperatures, and results in the conversion of water-insoluble to water-soluble carbohydrates. These desired products are partitioned into an aqueous layer, where they can be recovered, concentrated and purified. The GVL separates into another layer to be recycled.

Enhanced Biomass Digestion with Wood Wasp Bacteria

UW–Madison researchers have derived preparations from ActE secretions that highly degrade lignocellulose. The bacteria can be obtained from Sirex noctilio wasps and grown on a substrate containing mostly cellulose, hemicelluloses, xylan, wood or non-wood biomass, and chitin. The substrate may be pretreated for better results. The ActE are grown aerobically to maximize the secretion of both oxidative and hydrolytic enzymes capable of rapid deconstruction of matter. The secretions can be purified and added directly to biomass slurry.

Hibiscus Cannabinus Gene Discovery to Enable Altered Plant Lignin

Building on their work, the researchers have identified a gene that appears to have arisen independently during evolution in a different plant species (kenaf, or Hibiscus cannabinus). The gene produces a feruloyl-CoA: monolignol transferase (FMT) enzyme that could be harnessed to make modified, readily cleavable lignin.

Incorporation of FMT nucleic acids and/or polypeptides in plants can simplify the processes used for making biofuels and paper. Other cloned or isolated enzymes with these beneficial properties are not currently available.

Mild, Nontoxic Production of Fuels and Chemicals from Biomass

UW–Madison researchers have developed methods for producing furans, including HMF and furfural, from biomass carbohydrates using boronic acids that enhance conversion.

Generating furans from cellulose, lignocellulosic biomass or other sugars is catalyzed by a 2-substituted phenylboronic acid alone or in combination with a metal salt. The reactants are mixed and heated at a selected temperature. The reaction may be carried out in a suitable solvent other than an ionic liquid, with water optionally added to increase yield.

More Efficient Ethanol Production from Mixed Sugars Using Spathaspora Yeast

UW–Madison researchers have developed a method for producing ethanol using Spathaspora passalidarum yeast to ferment xylose or cellobiose, even when mixed with glucose.

The ethanol is converted from biomass or other lignocellulosic material from agricultural residues, fast-growing hardwoods and processing byproducts. Sugars, lignin and other components are first extracted from this feedstock using standard methods to form mixtures rich in different sugars. The mixture is contacted with a Spathaspora yeast cell under oxygen-limiting conditions suitable to allow the yeast to ferment a portion of the xylose and/or cellobiose into ethanol.

One- and Two-Phase Conversion of Biomass to Furfural

UW–Madison researchers have developed monophasic and biphasic systems to produce furfural from the C5 sugar fraction of biomass utilizing GVL, itself a product of the reaction, as a solvent. Both methods result in furfural that can be directly distilled out of, or converted into, GVL.

In the monophasic method, a single reaction medium comprises GVL and an acid such as nitric, sulfuric, or solid acid zeolite to minimize the use of water and eliminate the separation step required of mineral acids. Into this solution is introduced pretreated biomass xylose or hemicellulose. The GVL acts as a reaction solvent. By reducing or removing water from the process, less leaching of acid sites occurs and a significantly higher yield of furfural is produced.

The biphasic, or two-layered, method also utilizes GVL, but as an extraction solvent in the form of a suspended organic layer. The lower phase contains an aqueous, acidic solution with a solute such as sodium chloride or fructose. The saturated biomass material dehydrates into furfural, which spontaneously partitions into the upper GVL layer, thereby preventing further degradation via mineral acid catalysis in the aqueous phase.

Genes for Xylose Fermentation, Enhanced Biofuel Production in Yeast

UW–Madison researchers have identified 10 genes in yeast that are involved in xylose fermentation. These genes could be used to create an organism that can ferment both xylose and glucose for enhanced biofuel production.

Improved Method for Converting Biomass into Levulinic Acid for Renewable Fuel Sources

A UW–Madison researcher has developed an improved method of producing levulinic acid from biomass. The method comprises a two-stage, acid-catalyzed treatment. First, at least a portion of the pentoses present in the biomass feedstock are separated from the hexose sugars under mild acidic conditions to result in a biphasic sugar mixture consisting of a pentose-rich liquor and a hexose-rich solid. Then the pentose-reduced, hexose-rich biomass fraction is treated to yield levulinic acid. Utilizing this two-stage process, a maximum levulinic acid molar yield of about 66 percent based on the hexose content was obtained under optimized conditions. The method also may comprise separating the first aqueous acidic solution from hexose-rich solid so the pentoses in the solution can be converted into furfural or other compounds.

One-Step Process Turns Biomass into Hydrocarbon Building Blocks

UW–Madison researchers have developed a process for converting biomass to furfural-/HMF-ketone precursors that then may be turned into long-chain hydrocarbons.

The method, called HDA (Hydrolysis-Dehydration-Aldol condensation), streamlines several conversion processes into a single step. First, a ketone (like acetone) is used as a solvent with lithium bromide or other halide salt, water and acid. The mixture is reacted with biomass under mild conditions to yield furfural-/HMF-ketone adducts.

The adducts then may be converted into hydrocarbons by standard hydrodeoxygenation methods.

New Rheometer and Method for Efficiently Measuring Yield Stress in Biomass

UW–Madison researchers have developed a device and a method for measuring rheological properties of fluid that will effectively determine the yield stress of biomass materials. These measurements do not alter the material sample prior to measurement, allowing for more accurate data results and characterization.

The device comprises a cavity for receiving the fluid, an auger connected with an axial shaft, and a load cell sensor connected to the auger. The sensor measures the force on the auger from the fluid as the auger moves up and down. A linkage interconnected to the sensor translates motion to the auger.

Ethanol Tolerant Yeast for Improved Production of Ethanol from Biomass

UW–Madison researchers have developed a method of using the Elongase I (ELO1) gene to impart ethanol tolerance to yeast. ELO1 is an enzyme involved in the biosynthesis of unsaturated fatty acids in yeast.  This gene could be incorporated into an industrial yeast strain to increase the amount of ethanol produced from biomass.

Lignin-Metal Complex Formation to Enhance Biofuel Production Processes

UW-Madison researchers have developed a method of cellulose hydrolysis using metal compounds to prevent the non-productive adsorption of enzymes by lignin during biofuel production. Metal compounds such as ferrous, magnesium and calcium compounds are used to form lignin-metal complexes. The formation of the lignin-metal complex prevents adsorption of enzymes by deactivating the non-productive adsorption sites on lignin. As a result, more enzymes are available for efficient cellulose saccharification. The formation of a lignin-metal complex allows a pretreatment step with no high-volume wash involved, reducing the energy and water costs associated with the biofuel production process.

Bacteria Modified to Secrete Biologically Active Protein for Large-Scale Production

UW–Madison researchers have discovered E. coli mutations that substantially increase the amount of biologically active, recombinant protein secreted from cells.  The mutations disrupt genes in a YebF-mediated protein secretion pathway.  Bacteria modified to contain these mutations are useful for the production of secreted proteins.  They can be used to produce proteins that might otherwise not be expressed due to toxicity or folding errors.  They also can be used to produce secreted complexes of enzymes such as cellulases and xylanases for the manufacture of cellulosic biofuels.

Lignin from Transgenic Poplar Is Easier to Process

UW–Madison researchers and others have developed genetically modified poplars with lignin that is less resistant to alkaline degradation.

Having previously identified and isolated the gene for FMT, the researchers introduced the nucleic acid sequence into poplar tissue. The enzyme produced lignin rich in monolignol ferulates, including coniferyl ferulate and sinapyl ferulate. The transformed lignin thus contained ester bonds that cleaved under relatively mild ammonia conditions.

The poplar cells were modified using standard genetic techniques.

Reducing Overpotential Needed to Create Hydrogen by Water Electrolysis

UW–Madison researchers have developed an electrolyzer used to produce gas by electrolysis with a lower overpotential requirement than conventional electrolyzers. The electrolyzer includes a housing, an electrical power source and an electrode comprising a conducting support and a nanoporous oxide coating material.

The researchers also developed a method of using the electrolyzer to produce a gas such as hydrogen by contacting an aqueous solution such as water with the electrode and applying a voltage from an electrical power source. By appreciably reducing the amount of voltage required to convert water to hydrogen and oxygen, this technology enables on-demand hydrogen production for point of use or storage.

Cheaper Process Converts Biomass into Furan Derivatives like Furfural & HMF

UW–Madison researchers have developed a novel, cost-effective method for producing furan derivatives such as HMF, furfural, levulinic acid or gamma-valerolactone from biomass using alkylphenols as solvents. The overall strategy involves converting lignocellulosic biomass into value-added fuels and chemicals by partially removing oxygen to yield reactive intermediates such as HMF, furfural and levulinic acid. These platform molecules are valuable commercial products and can be converted into desirable final products, including liquid transportation fuels.

The acid-catalyzed process for converting biomass into furan derivatives uses a biphasic reactor containing a reactive aqueous phase and an organic extracting phase, which includes an alkylphenol. Alkylphenols are chemically distinct from previously reported extracting solvents. They offer efficient extraction of furan derivatives like levulinic acid and unique options for recovery and processing. For example, the researchers found that no butylphenol is transferred into the aqueous phase, minimizing solvent loss and contamination of the aqueous stream. Additionally, alkylphenols are inert under conditions relevant to levulinic acid processing, including distillation and selective hydrogenation in the presence of butylphenol to yield gamma-valerolactone.

Production of Levulinic Acid and Gamma-Valerolactone from Biomass-Derived Cellulose

UW–Madison researchers have developed a streamlined process for making and extracting levulinic acid from aqueous solutions. First, levulinic acid is produced through the acid-catalyzed deconstruction of biomass in an aqueous solution. Then the levulinic acid is extracted from the aqueous solution using one or more alkylphenol solvents (see WARF reference number P110124US01).

The levulinic acid can be separated from the solvent by distillation or another means or further processed, e.g., by hydrogenation, to yield derivatives such as GVL. Both levulinic acid and GVL are value-added platform compounds that find commercial use as intermediates or reactants in many industrially useful processes, including the production of liquid transportation fuels.

Fatty Acid-Producing Microbes for Generating Medium- and Long-Chain Hydrocarbons

UW–Madison researchers have developed genetically modified E. coli that are capable of overproducing fatty acid precursors for medium- to long-chain hydrocarbons. The modified bacteria were transformed with exogenous nucleic acids to increase the production of acyl-ACP or acyl-CoA, reduce the catabolism of fatty acid products and intermediates, and/or reduce feedback inhibition at specific points in the biosynthetic pathway.

The modified bacteria can be cultured in the presence of sugars to produce fatty acids. The fatty acid products formed during fermentation then can be separated from the fermentation media via a two-phase separation process or other method. The separated products can be used directly or as feedstock for subsequent reactions, including conversion to medium- and long-chain hydrocarbons.

Method and Electrocatalyst to Efficiently Produce Hydrogen Fuel over a Broad, Acidic pH Range

UW-Madison researchers have developed an improved method for generating oxygen and hydrogen with a cobalt-oxide electrocatalyst that uses fluorophosphate or a similar anion electrolyte as the electrolytic buffer in the electrolysis reaction. Using this method, an anode and a cathode are placed in an aqueous solution containing water, a cobalt cation and the anion electrolyte. Then an external source of energy (potentially derived from solar, wind or other renewable energy) drives the electrolysis reaction to generate oxygen and hydrogen. Alternatively, a catalyst containing cobalt, oxygen and the anion electrolyte can be deposited on the anode of the electrochemical cell prior to electrolysis in cobalt-free conditions.

This cobalt-oxide catalyst enables efficient oxidation of water at room temperature over a more favorable pH range. The reduction in overpotential makes it easier and less expensive to split water into hydrogen and oxygen, while the expanded pH range allows water oxidation to be coupled with desirable reactions such as reduction of carbon dioxide at the cathode. In addition, the electrolyte buffers are compatible with conventional materials used in electrochemical cells. The hydrogen gas output of this process can be collected and used as an alternative fuel source or as feedstock for conversion into other fuels or materials. The oxygen gas can be collected, dried and used for any process requiring pure oxygen.

Coating Extends Life of Catalytic System

UW–Madison researchers have developed a coating that helps catalyst support structures withstand harsh reaction conditions.

The coating is made of a chemically robust material such as niobium oxide that can be applied in extremely thin layers using a technique called ALD (atomic layer deposition). The coating may be selected purely for its structure-enhancing properties, or may comprise materials that are themselves catalytically active.

Improving Biomass Conversion Efficiency by Modifying Lignin so Plant Cell Walls Are More Digestible and Fermentable

Wisconsin researchers have demonstrated that lignin may be engineered to be more digestible and fermentable by structurally altering the lignin so its monomer complement incorporates coniferyl and/or sinapyl ferulate. This allows biomass polysaccharides to be utilized more efficiently and sustainably, which should reduce inputs for energy, pressure vessel construction and bleaching during papermaking, and lessen pretreatment and enzyme costs associated with biomass conversion.

High-Yielding Method for Converting Biomass to Fermentable Sugars for Biofuel Production

UW–Madison researchers have developed a new method for degrading lignocellulosic biomass to fermentable sugars.  This simple, high-yielding chemical process, which involves the gradual addition of water to a chloride ionic liquid, enables crude biomass to serve as the sole source of carbon for a scalable biorefinery.

In this method, biomass is mixed with a cellulose-dissolving ionic liquid and heated to form a solution or gel.  Then water and an acid catalyst are added and the resulting mixture is heated, typically to 105°C.  At specified time intervals, more water is added to the mixture until it contains more than 20 percent water by weight.  At this point, the mixture contains free sugars such as xylose and glucose and unhydrolyzed carbohydrate polymers, which often are not dissolved.  The insoluble materials, acid and ionic liquids are separated from the soluble sugars.  The soluble sugars then can serve as the sole carbon source for microorganisms such as E. coli KO11, an ethanologen.

Cell-Free System for Combinatorial Discovery of Enzymes Capable of Transforming Biomass for Biofuels

UW-Madison researchers have developed compositions and methods that expand the ability to make, express and identify target polypeptides, including enzymes capable of enhancing the deconstruction of biomass into fermentable sugars. 

This approach uses a cell-free system to express enzymes and other polypeptides in a combinatorial manner.  Because the system is cell-free, the enzymes can be assayed without intermediate cloning steps or purification of the protein products.  This system also is more reliable than conventional methods for analyzing biomass transformation because it does not utilize living systems, which could rapidly consume soluble sugars.

Specifically, the system compromises a cell-free extract for synthesizing the target polypeptide, a nucleotide sequence that encodes a fusion protein containing a cohesion domain and a biomass binding domain, and a nucleotide sequence that encodes a second fusion protein containing a dockerin domain and a polypeptide capable of catalyzing biomass transformation.  The system also may include additional polypeptides and fusion proteins.  The target polypeptides may be synthesized in the presence of different types of biomass to determine their effects on biomass deconstruction.

Producing Olefins for Use in Gasoline, Jet and Diesel Fuels from Chemicals Obtained from Levulinic Acid

UW-Madison researchers have developed a method and apparatus for producing olefins (unsaturated hydrocarbons) in the C8 to C16 range from GVL. The method involves two tubular flow reactors and an inter-stage separator in a single catalytic system. The chemical transformation proceeds via conversion of GVL to an n-butene, which is then introduced into a second reactor where the butene is converted via acid catalyzed oligomerization to higher molecular weight olefins (C8 and longer). High pressure CO2 is an additional by-product of the reaction.

In addition to GVL, lactones, hydroxyl-carboxylic acids, alkene-carboxylic acids, alcohols or a mixture thereof can be reacted using this method to produce longer-chain olefins. The olefins produced with this method are of carbon chain-length and molecular weight suited for use in gasoline, jet and diesel fuels.

Method and Electrocatalyst to Efficiently Produce Hydrogen Fuel for Storage of Renewable Energy

UW-Madison researchers have developed an improved catalytic method for generating hydrogen and oxygen gas via water electrolysis. The method uses novel electrocatalysts formed from cobalt, oxygen and fluoride. These unique catalysts result in an electrolysis reaction with a favorable shift in pH tolerance and altered overpotential, making it easier and less expensive to split water into hydrogen and oxygen and providing a more practical means of storing renewable energy.

To drive the electrolysis reactions, electricity can be generated using a renewable energy source such as a solar cell or wind turbine. The hydrogen gas that results from this process can be collected and used as an alternative fuel source for vehicles or other fuel-dependent applications or as a feedstock for conversion into other fuels or materials. The oxygen gas can be collected and used for any process that requires pure oxygen, such as steelmaking.

Piezoelectrochemical Effect Uses Wasted Mechanical Energy to Split Water for Hydrogen Production

UW-Madison researchers have developed a new technique for hydrogen production that utilizes direct water-splitting through the conversion of mechanical energy into chemical energy.  Certain materials, such as quartz, have intrinsic piezoelectric properties.  When mechanical force is applied to these materials, they create an electric response on their surface.  This electric charge then can interact with the surrounding chemical species.  In the current invention, the surrounding environment is aqueous and the interaction catalyzes a water-splitting reaction that produces hydrogen and oxygen gas.

Because the process requires simple mechanical force, many potential applications exist.  Some possible sources of mechanical energy include the forces exerted on roadways or walkways where cars or pedestrians pass over, or even the force of sound waves hitting a surface. 

Implementing such a system is made more cost effective by the fact that quartz, a possible piezoelectric material, is one of the most abundant minerals on Earth’s surface as well as environmentally friendly.  The technique also surpasses the inefficiencies of solar techniques and has shown hydrogen production rates 25 times greater than standard photocatalysis.

Producing Liquid Fuels from Biomass-Derived Carboxylic Acids

UW-Madison researchers have developed a cascading method to convert cellulose to liquid fuels and other chemical intermediates.  The method involves the conversion of aqueous solutions of levulinic acid and other biomass-derived carboxylic acids into gasoline components in a catalytic flow reactor.

The new process allows total conversion of levulinic acid into pentanoic acid, 5-nonanone or butene in a single reactor without the need for expensive separation technology.  These products can be converted to liquid fuels (e.g., C4, C9 and/or C18 alkenes) via catalytic upgrading methods.  The cascade approach provides a strategy for management and recycling of sulfuric acid in the cellulose degradation step, while minimizing the need for an external hydrogen source. Current processes achieve only 70 percent conversion and require complicated separation procedures.

Efficient, Lower Cost Chemical Transformation of Lignocellulosic Biomass into Fuels and Chemicals

UW-Madison researchers have developed a relatively low cost, high yielding method for converting sugars, starches and cellulosic biomass into furans, such as HMF or furfural.  They found that that using N,N-dimethylacetamide-lithium chloride (DMA−LiCl) as a solvent enables the efficient synthesis of HMF or furfural in a single step from carbohydrates and even lignocellulosic biomass. The HMF then can be converted to the fuel component 2,5-dimethylfuran (DMF) via hydrogenolysis, while the furfural can be converted to furan via decarbonylation.

This simple chemical transformation could become a highly attractive process for the conversion of biomass into an array of fuels and chemicals.  The method can utilize untreated lignocellulosic biomass, such as corn stover, poplar wood or switch grass.  It is relatively rapid and high yielding, and takes place under moderate conditions (ambient pressure and temperature less than 200 °C).  In addition, the conversion of cellulose to HMF or furfural is not hindered by the presence of other biomass components, such as lignin or protein.

Woody Biomass Sulfite Pretreatment to Overcome Lignocellulose Recalcitrance for Biofuel Production

UW-Madison researchers have developed an improved pretreatment process for robust conversion of biomass.  This process, known as Sulfite Pretreatment to Overcome Recalcitrance of Lignocellulose (SPORL), reduces the energy consumption needed for size-reduction processes, required before enzymatic hydrolysis, by more than tenfold.  The new method can employ a number of aqueous sulfite or bisulfite solutions over a wide range of pH values and temperatures to weaken the chemical structure of the plant material.  It is particularly suitable for woody biomass, softwoods such as pines and other conifers that dominate many forests in the U.S., Canada, Europe and New Zealand, and hardwoods such as poplar, willow and eucalyptus that dominate temperate and boreal forests around the world.

The improved SPORL approach is flexible and integrated easily into current pretreatment systems.  The pH of the pretreatment liquor can be adjusted by reagent, making SPORL easily incorporated into current dilute acid approaches to improve the efficiency of the pretreatment.  Mechanical size reduction steps such as disk or hammer milling can be implemented directly before or after SPORL depending on the stock material.  In addition, the final enzymatic hydrolysis can be coupled directly after the pretreatment with or without washing the material or adding a surfactant to aid in the process.  The pretreatment also can be employed with steam explosion, using bisulfite as a catalyst.  After pretreatment, the hydrolyzed biomass can be separated and the sugars fermented or catalytically converted into fuels while sulfonated lignin byproducts can be sold to established markets and other wastes burned to produce energy for the process.

The novel SPORL approach is a superior method of biomass pretreatment because of its versatility, simplicity and efficiency.  It also has excellent scalability to commercial production.  The method will increase the energy efficiency of ethanol fermentation and catalytic fuel production processes through decreased size-reduction energy requirements and maximized enzymatic cellulose conversion in a short period of time.  This increase in efficiency will allow biofuels and other bioproducts to become economically competitive with petroleum derived fuels and products.

An Efficient Method and Gasification Device for Producing Synfuel from Biomass

UW Madison researchers have created a more efficient gasification method and device that uses liquid metal to heat the organic feedstock and produce synthesis gas.  Feedstock or raw biomass comprised of any carbon-containing organic material, such as wood chips, may be used in this method. The process produces syngas at levels near the theoretical maximum for a gasification method.

This new gasification process begins with heating the feedstock in a bath of molten metal between 100 °C and 200 °C, a temperature that drives out all moisture without breaking down the organic components.  The dried biomass is then pumped into a hotter bath, generally 300 °C to 1,200 °C, of the same molten metal.  In this high temperature phase, water is added back in a controlled manner to drive fast pyrolysis, thereby releasing gas byproducts and leaving behind tar and char. 

In the final step, gases that were released in the second step may be pumped into the chamber to increase the temperature and pressure levels. Natural gas feedstock also may be added to aid in the gasification reaction and further improve the system efficiency. The char, tar and gases react to produce syngas, which consists mainly of hydrogen and carbon monoxide.  The syngas then is siphoned off and used in a Fischer-Tropsch synthesis to produce ethanol, methane, diesel or other fuel. The molten metal from the final bath is filtered and recirculated, and a portion of the product syngas may be used to heat the baths and drive the reactions to increase the self sufficiency of the system.

Converting Biomass-Derived Carbohydrates to High-Quality, Long-Chain Liquid Fuels

UW-Madison researchers have developed a practical and energy-efficient catalytic process for producing high-quality, long-chain liquid fuels from carbohydrates. The multi-stage process uses combinations of self- and crossed-aldol condensation reactions, dehydration reactions and hydrogenation reactions to yield alkane, alkene and ether products.

Preferably, this process starts with an acid-catalyzed dehydration of biomass-derived carbohydrates. Then an aqueous-phase aldol condensation reaction yields large organic compounds, which are converted into long-chain alkanes via dehydration and/or hydrogenation. The aldol condensation reaction takes place in the presence of a stable, recyclable and solid-base catalyst, which is comprised of magnesium, zirconium, oxygen and possibly palladium.

Low-Temperature Process to Produce Hydrocarbons from Oxygenated Substrates, Including Sugars

UW-Madison researchers have developed a method of producing hydrocarbons from oxygenated reactants such as glycerol, glucose or sorbitol. The method includes the steps of reacting water and a water-soluble oxygenated compound in the presence of a metal-containing catalyst. The reaction can take place in either the vapor phase or, preferably, in the condensed liquid phase. This method allows the production of hydrocarbons from oxygenated compounds ultimately derived from fully renewable plant biomass. 

Thermostable Barley Alpha-Glucosidase for Improved Ethanol Production

UW-Madison researchers have developed a mutant barley alpha-glucosidase with increased thermal stability. They developed thermostable forms of the enzyme using site directed mutagenesis. Sites for mutagenesis were selected through comparisons with the sequences of other, more thermostable, alpha-glucosidase proteins.

Low Temperature Hydrogen Fuel Production Using Renewable Starting Materials

UW-Madison researchers have developed a method to generate hydrogen fuel through low-temperature, catalytic steam reforming of oxygenated hydrocarbons, such as ethanediol, glycerol, sorbitol, glucose and ethanol. Unlike conventional starting materials for hydrogen production, which come from natural gas, oxygenated hydrocarbons can be derived from renewable resources, like plant biomass. Moreover, although the inventors’ method also produces carbon dioxide as a byproduct, the use of plant biomass should reduce the net release of CO2 to the atmosphere, because plants fix and store CO2 in their biomass during growth.

Modified Yeast Ferments Biomass Xylose

A UW–Madison researcher and others have developed an S. cerevisiae strain genetically engineered with xylose utilization genes from another yeast, Scheffersomyces stipitis. The new strain (GLBRCY35) has been made to express S. stipitis genes XYL1, XYL2 and XYL3, which are known to improve xylose fermentation.

Modified Yeast Show Improved Xylose Fermentation and Toxin Tolerance

A UW–Madison researcher and others have developed genetically modified S. cerevisiae strains capable of xylose fermentation and better able to tolerate toxins associated with biomass pretreatment. The strains, called GLBRCY73 and GLBRCY87, were evolved in the presence of increasing amounts of p-Coumaric and Ferulic acids. Desirable specimens were selected based on strong growth characteristics.

Measuring Lignin in Corn Stalks

UW–Madison researchers have developed an automated method to scan and analyze corn stalks. The algorithm extracts information about rind thickness, vascular bundles, density and size. The new method uses a flatbed scanner to image samples. The images are acquired as RGB color at a resolution of 800 dpi. Thresholding techniques are used to assess the outer ring boundaries and vasculature.