Researchers Submit Patent Application, "Process and Method for Improving the Water Reuse, Energy Efficiency, Fermentation and Products of an Ethanol Fermentation Plant", for Approval
The patent's assignee is
News editors obtained the following quote from the background information supplied by the inventors: "The present invention relates to methods of ethanol fermentation.
"More specifically the present invention relates to processing stillage.
"Throughout this application, various publications, including
"Ethanol fermentation is the biological process by which sugars are converted into ethanol and carbon dioxide through yeast fermentation. Corn is one of the main feedstock materials used to produce ethanol. Dry milling has previously been used to produce ethanol from corn on other starch sources through fermentation (shown generally in FIG. 1, labeled 'Prior Art'). Corn is milled to flour, slurried, and treated with enzymes to convert the starch to sugars. The sugars are converted to ethanol in large fermenters. The ethanol is recovered through a distillation process. The residual spent grains, referred to as whole stillage, contains corn germ, corn bran, corn oil, unconverted starch, unfermented sugars, yeast cells, yeast metabolites, and other suspended and dissolved solids. The whole stillage stream is generally separated into wet distillers grain (WDG) and thin stillage. The wet distillers grains can be dried to produce Dry Distillers Grain (DDG). A portion of the thin stillage, referred to as backset, is recycled back to the front end of the ethanol process as make up water. The remaining thin stillage is evaporated to syrup, added to the wet distiller's grains and dried as Dried Distillers Grains with Solubles (DDGS). WDG, DDG, and DDGS are important co-products that are critical to the economic viability of the ethanol process. However, their value can be enhanced by extracting more valuable co-products from these streams. It has only recently been a goal to recover additional materials from the co-products for further use.
"Materials, such as oil, protein, and other solubles in the whole stillage are very valuable; however, recovery has shown to be inefficient and uneconomical. Recently, various methods have been attempted to recover the additional materials from stillage. These methods include traditional separation techniques such as heating the stillage stream and performing evaporation, using centrifugation, or using membrane filtration, in order to recover these additional materials. The result of each of these separation processes on stillage is a concentrate and a water phase wherein most of the solids have been removed.
"A number of methods have been developed involving heat treated stillage for the recovery of fermentation by-products, especially oil. U.S. Patent Application Publication No. 2009/0250412 and U.S. Pat. No. 7,608,729 to Winsness, et al. disclose methods for recovering oil from stillage concentrate including oil resulting from a process used for producing ethanol from corn. Winsness, et al. generally believe that filtration increases operating costs and therefore focus on separation by heating. In one embodiment, the method includes heating the stillage concentrate to a temperature sufficient to at least partially separate, or unbind the oil. The heating step includes heating to a temperature above 212 degrees F. but less than about 250 degrees F. The method also includes the step of pressurizing the heated stillage concentrate to prevent boiling. The method further includes recovering the oil from the treated stillage concentrate using a gravity separation process including centrifugation. The process disclosed by Winsness, et al. does not include treatment of unconcentrated stillage streams. While oil can be recovered from the method of Winsness, et al., there are many products in the thin stillage that are not recovered. For example, the process disclosed by Winsness et al. does not include recovery of a high solids-high protein fraction and a stickwater fraction (as defined below) nor the improved fermentative value and alternative uses of stickwater. Furthermore, it is generally accepted in the art that heating the thin stillage to higher than 250 degrees F. is harmful to proteins and other biological components.
"U.S. Pat. No. 6,106,673 to Walker discloses a process and system for the separation of a fermentation process byproduct into its constituent components and for the subsequent recovery of those constituent components. The process requires 1) mixing a starting mixture containing ethanol byproducts with a liquid (water) to form a diluted mixture, 2) heating of the diluted mixture containing the byproducts so as to separate the oil from a base component (fiber) of the byproduct to which the oil is bound at a temperature from about 140 degrees F. to about 250 degrees F., followed by 3) recovering oil, the base product (fiber), and possibly other substances such as molasses from the mixture. The process can be performed on a large scale and in a continuous fashion using a mechanical separator to recover fibers from the diluted heated mixture to produce a solids stream and a liquor stream and by then removing oil and insoluble substances from the liquor stream in an evaporator assembly. Energy consumption and water consumption are minimized through 1) the use of waste heat from the system's dryer as an energy source for the evaporator assembly and 2) the use of condensed liquids from the evaporator assembly to dilute the mixture. There is no disclosure in Walker '673 of recycle of recovered water or stickwater to fermentation or improvement of fermentation rate or yield by recycle of any or the entire liquor stream to upstream operations.
"Thus, while heating and mechanical separation described in prior art provides some separation of co-products, especially oil, it was not recognized that the use of all or a portion of hydrothermally treated stillage or stickwater can improve fermentation processes.
"Thermal hydrolysis has been investigated as a pretreatment step prior to anaerobic digestion of biomass, in particular the anaerobic digestion of waste activated sludge from biological waste water treatment facilities and the pretreatment of cellulosic biomass prior to enzymatic hydrolysis to liberate cellulosic sugars. The former has been commercially implemented while the latter remains a research and development endeavor. Camacho, et al. (Proceedings of the WEFTEC.RTM. 2008 Conference,
"Yu, et al. (
"Kim, et al. (including Ladisch) (Bioresource Technology 2008, 99, 5206-5215.) investigated the thermal hydrolysis of distiller's dry grains and solubles (DDGS) from a dry grind ethanol facility as a cellulosic pretreatment prior to enzymatic hydrolysis of the cellulosic biomass. The objective of the thermal treatment of Kim, et al. was to prepare the cellulose of DDGS for downstream enzymatic hydrolysis to glucose by cellulase and beta-glucosidase enzymes. U.S. Pat. No. 5,846,787 to Ladisch, et al. discloses use of thermal hydrolysis in the range of 160-220 degrees C. (320-428 degrees F.) as a pretreatment for cellulosic biomass prior to enzymatic treatment with cellulase.
"Other efforts have involved heat treatment and filtration of depleted lignocelluosic fermentation hydrolysate broth to separate undissolved solids from the liquid phase and create a low solids liquid (Hennessey, et al., U.S. Patent Application Publication No. 2012/0178976 and Hennessey, et al., U.S. Patent Application Publication No. 2012/0102823, assigned to
"It is recognized that the temperatures utilized for hydrothermal pretreatment of biomass prior to cellulosic ethanol fermentation and municipal waste prior to anaerobic digestion are greater (300 degrees F.-450 degrees F.) than those preferred for treating stillage in the present invention (220 degrees F.-300 degrees F.).
"Stillage has been investigated for enhancing biological processes. For example, in the prior art ethanol process of FIG. 1, stillage is recycled to the front end as make-up water in the slurry and is referred to as 'backset'. The proteins and nutrients in the stillage have been recognized as aiding fermentation; however, this benefit is marginal and the suspended solids in backset limit the amount of fresh grain solids that can be added to fermentation. Therefore, there is a need for treating stillage to increase its value in fermentation and other biological processes.
"A number of biological and non-biological methods have been developed for the improvement of thin stillage.
"Prior art processes have tried to remove suspended solids from thin stillage with various flocculating, coagulating or precipitating additives and chemical agents.
"Various filtration, microfiltration and ultrafiltration processes have been disclosed in the prior art. Bento, et al. in U.S. Pat. No. 5,250,182 assigned to
"Other prior art processes have described removal of solids from the clarified aqueous phase through the use of filters after separation of hot (140-212 degrees F.) concentrated thin stillage into a light oil phase and a heavy aqueous phase and treating the oil phase with alkali chemicals including spent clean in place (CIP) solutions (Woods, et al., U.S. Patent Application Publication No. 2011/0275845, assigned to Primafuel).
"None of these biological and non-biological prior art methods for treatment of stillage and solid-liquid separation (with or without benefit of additives) has been shown to improve fermentation by the surprisingly simple process of hydrothermally treating stillage and utilizing the treated stillage as a media component in a fermentation process.
"Various methods have been proposed for utilizing stillage for biological purposes other than ethanol fermentation.
"In summary of the prior art, methods for improving ethanol fermentation, fermentation of other products, or growth of non-alcohol producing microorganisms by addition of stillage which has been hydrothermally treated in the preferred range of 220 degrees F.-300 degrees F. of the present invention has not been described in patents or literature. It has been discovered for the first time that hydrothermally treating stillage and adding the treated stillage to a fermentation process increases fermentation rates and titers. Therefore, it is shown herein that the present invention provides a simple method for improving fermentation by the addition of hydrothermally treated stillage.
"While heating and filtration described in prior art provides some separation of co-products, recovery is limited and costs remain high. One advantage of the present invention is that hydrothermal fractionation of stillage produces a physicochemical alteration, which enables a facile separation allowing for improved recovery of co-products. With respect to the present invention, 'hydrothermal fractionation' means heating a substantially aqueous stillage stream to a temperature within a prescribed temperature range, and holding at temperature for a period of time within a prescribed residence time range. A saturation pressure is established and maintained during the hydrothermal fractionation step. Physicochemical alteration means that both physical and chemical changes are imparted to the stillage by the hydrothermal fractionation step. Manifest physical changes include changes in the rate of phase separation, relative phase volumetric fractions and phase densities, phase hydrophobicity and changes in color or appearance. Chemical changes include changes in the distribution of non-soluble protein, fat (oil) and carbohydrate (fiber) between the substantially liquid phase and the substantially solids phase. Other chemical changes include solubilization and/or hydrolysis of components to increase the levels bio-available protein and ammonia in the soluble phase. These physical and chemical changes are mutually dependent and hence the term physicochemical is applied.
"Thus heating of stillage has been performed as described in the prior art for recovery of corn oil and other by-products; however, it was not recognized that the hydrothermal treatment of stillage according to the present invention imparts physicochemical changes enabling facile separation into a low solids stickwater fraction, oil and high protein solids fraction. Furthermore and importantly, it will be shown herein that the low solids stickwater fraction provides an enhanced nutrient medium for ethanol and other fermentation processes, thus providing an economic advantage.
"Therefore, there is a need for a simple method of producing a physicochemical alteration that changes the co-products in stillage and enables facile separation of co-products in ethanol processing as well as providing streams suitable for improving biological production and recovery of valuable co-products, extracts, metabolites and treated water."
As a supplement to the background information on this patent application, NewsRx correspondents also obtained the inventors' summary information for this patent application: "The present invention provides for a method of hydrothermally treating stillage by heating stillage to 200 degrees F. to 350 degrees F., altering physicochemical properties of the stillage, enabling facile separation of the stillage, and creating unique product fractions.
"The present invention further provides for a method of performing ethanol fermentation by treating stillage to enable facile separation by heating the stillage to a temperature of 200 degrees F. to 350 degrees F., and separating the treated stillage to recover a high protein solids fraction, a stickwater fraction, and an oil fraction.
"The present invention provides for a method of performing ethanol fermentation by separating whole stillage into stillage and wet cake, hydrothermally fractionating the stillage to create unique product fractions by heating the stillage to a temperature of 200 degrees F. to 350 degrees F., separating the heat treated stillage into a high protein solids fraction, a first stickwater fraction, and a stickwater/oil emulsion, recovering oil from the stickwater/oil emulsion, recovering a second stickwater fraction from the stickwater/oil emulsion and adding the second stickwater fraction to the first stickwater fraction, and further processing the first and second stickwater fractions by a process selected from the group including recycling at least a portion of the stickwater to a front end of an ethanol plant, biological processing and chemical processing, and using the first and second stickwater fractions as growth media in the processing step.
"The present invention provides for a method of improving fermentation by heating stillage to a temperature of 200 degrees F. to 350 degrees F. resulting in hydrothermally treated stillage, using all or a portion of the hydrothermally treated stillage as a component of a media, and using the media for a process including fermentation and biomass production.
"The present invention also provides for a method of performing ethanol fermentation by separating whole stillage into wet cake and stillage, hydrothermally treating stillage by heating the stillage to a temperature of 200 degrees F. to 350 degrees F., and adding all or a portion of the treated stillage to the ethanol fermentation step or an operation upstream of fermentation.
"The present invention provides for a method of performing ethanol fermentation by separating whole stillage into a first cut solids stream and thin stillage, performing a particle size reduction step on all or a portion of the first cut solids, returning the reduced particle size solids to the thin stillage stream to produce thick stillage, hydrothermally treating the thick stillage by heating to a temperature of 200 degrees F. to 350 degrees F., and adding all or a portion of the treated stillage to the ethanol fermentation step or an operation upstream of fermentation.
"The present invention further provides for a method of increasing bioavailability of stillage components to microorganisms by hydrothermally treating stillage by heating the stillage to a temperature of 200 degrees F. to 350 degrees F., increasing the bioavailability of components in the stillage, and adding the hydrothermally treated stillage to media and providing to microorganisms.
"The present invention also provides for oil, stickwater, high protein solids fraction, high protein meal, metabolites, biomass, and media obtained from the methods above.
DESCRIPTION OF THE DRAWINGS
"Other advantages of the present invention are readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
"FIG. 1 is a flowchart of a prior art ethanol fermentation process;
"FIG. 2 is a flowchart of the hydrothermal fractionation process of the present invention;
"FIG. 3 is a flowchart of the hydrothermal fractionation process of the present invention added after separating whole stillage into stillage and wet cake, followed by stickwater separation and then oil separation from the high protein solids fraction, stickwater not recycled as backset and the high protein solids fraction are processed through the evaporators and recovered in DDGS;
"FIG. 4 is a flowchart of the hydrothermal fractionation process including the optional step of separating whole stillage into stillage and wet cake, followed by separation of treated stillage in a three-phase decanter known as a 'tricanter' giving an oil-water emulsion, stickwater, and high protein solids fraction, the oil-water emulsion can be centrifugally separated into oil and additional stickwater, and stickwater not recycled as backset and high protein solids fraction are recovered in DDGS;
"FIG. 5 is a flowchart of the hydrothermal fractionation process of the present invention added after separating whole stillage into stillage and wet cake, followed by hydrothermally fractionation of stillage, separation of stickwater from treated stillage and processing of stickwater by biological and/or chemical processing;
"FIG. 6 is a flowchart similar to FIG. 5 including biological and/or chemical processing of stickwater and further including dewatering of the high protein solids fraction to produce dewatered high protein solids to produce protein meal and a second stickwater fraction;
"FIG. 7 is a flowchart of the present invention added after separating whole stillage into thin stillage and a first cut solids stream which is forwarded to a particle size reduction step and re-combined with the thin stillage, the combined stream is further separated into second cut solids which are recovered in DDGS and thick stillage which is hydrothermally treated and fractionated into stickwater, oil and high protein solids;
"FIG. 8 is a graph showing the composition of untreated thin stillage and hydrothermally fractionated thin stillage after low G-force separation, FIG. 8 also includes photographs of centrifuge tubes to illustrate the facile separation of hydrothermally fractionated stillage under low-g separation;
"FIG. 9 is a chart showing central composite experimental design used in Example 4 to study the effects of time and temperature on hydrothermal fractionation;
"FIGS. 10A-10D are graphs of ammonia, soluble (BCA) protein, crude fat and change in suspended solids vs. thin stillage plotted against the reaction severity factor for the designed experiment of Example 4;
"FIGS. 11A-11C are graphs of ammonia, soluble (BCA) protein, crude fat, and change in suspended solids versus thin stillage plotted against the reaction temperature for the designed experiment of Example 4;
"FIG. 12 is a graph of Oil and Total Suspended Solids as percentages of whole stillage for whole, thick, and thin stillage samples prior to hydrothermal fractionation; and
"FIG. 13 is a semi-log plot of cell counts versus time for growth of Lipomyces starkeyi on stickwater versus thin stillage."
For additional information on this patent application, see: Bleyer,
Keywords for this news article include: Ammonia, Patents, Alcohols, Chemicals, Chemistry, Treatment,
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