# US 9,434,961 B2 · Continuous process for the production of ethanol from lignocellulosic biomass

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- Number: US 9,434,961 B2
- Document ID: US9434961B2
- Status: Granted
- Kind: B2
- Application number: 13/291,659
- Filed: 2011-11-08
- Published: 2012-05-10
- Granted: 2016-09-06
- Earliest claimed: 2010-11-09
- Assignees: GreenField Specialty Alcohols Inc.
- Applicants: Frank A. Dottori; Robert Ashley Cooper Benson; Régis-Olivier Benech; Richard Romeo Lehoux; Christopher Bruce Bradt
- Inventors: Frank A. Dottori; Robert Ashley Cooper Benson; Régis-Olivier Benech; Richard Romeo Lehoux; Christopher Bruce Bradt
- Web page: https://patentgrep.com/patent/US9434961B2

## CPC

- C12P 7/10: substrate containing cellulosic material
- Y02E 50/10: Biofuels, e.g. bio-diesel
- C12P: FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE {(brewing of beer C12C; producing vinegar C12J; producing specific peptides or proteins C07K; producing enzymes C12N9/00; DNA or RNA concerning genetic engineering, vectors, e.g. plasmids, or their isolation, preparation or purification C12N15/00; measuring or testing processes involving enzymes or microorganisms C12Q; measuring or testing processes involving nucleic acid amplification reactions C12Q1/6844; fermentation processes to form a food composition, A21 or A23; compounds in general, see the relevant compound class, e.g. C01, C07)}
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

A continuous process for the recovery of ethanol from hemicellulose and cellulose from lignocellulosic biomass. Yield of fermentable sugars can be maximized by continuous operation of the pre-treatment system and careful selection of pretreatment conditions including the addition of only small amounts of dilute mineral acid and low pressure. With this approach, the xylose component that is mainly present in its unfermentable oligomeric form in known pre-hydrolysis Kraft processes can be recovered more efficiently and as a monomer that can be fermented by xylose fermenting yeasts and bacteria. Due to the use of only dilute acids, there is a very low loss of glucose and xylose hence very low production of toxic chemicals (e.g. HMF, furfural) in the pretreatment step. The resulting overall fermentation efficiency of both hexose and pentose sugars is 90% of the theoretical maximum.

## Claims

### Claim 1

A continuous process for converting carbohydrates from lignocellulosic biomass to ethanol, comprising the steps of:
a) cutting said lignocellulosic biomass to a prescribed size to obtain sized biomass;
b) steaming said sized biomass from step a) at atmospheric pressure for 10 to 60 minutes to obtain steamed biomass;
c) squeezing said steamed biomass from step b) to remove a first liquid stream and generating squeezed biomass, wherein said steamed biomass is compressed up to 6-1;
d) adding mineral or organic acid to said squeezed biomass from step c) in an amount of 0.5% to 0.9% w/w on an incoming biomass dry matter basis, and presteaming said squeezed biomass for 5 to 90 minutes to obtain acidified biomass;
e) adjusting a moisture content of said acidified biomass from step d) to 50% to 80% w/w water, to obtain moisture adjusted acidified biomass;
f) pretreating said moisture adjusted acidified biomass from step e) in a continuous treatment vessel by steam treatment under pressure at a preselected pretreatment temperature for a preselected pretreatment time and at a preselected pretreatment pressure, wherein said preselected temperature is 130° C. to 180° C., said preselected pretreatment time is 30 minutes to 4 hours, said preselected pretreatment pressure is 35-110 psi;
g) continuously purging under pressure from said continuous treatment vessel of step f) volatile components generated by the pressurized steam treatment and liquid condensate formed in the vessel and containing soluble biomass components;
h) submitting to explosive decompression said biomass exiting said continuous treatment vessel of step g) prior to or after the washing step to obtain pre-treated biomass;
i) extracting said pre-treated biomass from step h) with water to recover a cellulose rich solids stream and a liquid stream, wherein said cellulose rich solids stream contains 4% to 8% w/w xylose from remaining xylose, xylooligosaccharides and xylans in said pre-treated biomass;
j) heating the said liquid stream from step i) to simultaneously concentrate said liquid stream and remove inhibitory compounds by evaporation of volatile components, to obtain a concentrated liquid stream containing at most 6 g/L acetic acid, said evaporation being carried out at pressure and temperature conditions selected from the group consisting of: atmospheric pressure at a temperature of 90° C. to 100° C.; under vacuum of 50 mbar to 250 mbar at a temperature of 70° C. to 85° C., under pressure of 5 psig to 35 psig, and combinations thereof;
k) hydrolyzing xylooligosaccharides in said liquid stream from step i) before, during or after the concentrating step of step j);
l) hydrolyzing said cellulose rich solids stream from step i) with a mixture of cellulase and hemicellulose to obtain a hydrolyzed solid stream;
m) combining said hydrolyzed solids stream from step l) with said concentrated liquid stream to obtain a combined hydrolysate stream comprising hexose and pentose sugars;
n) co-fermenting said hexose and pentose sugars in said combined hydrolysate stream from step m) in a fermentation broth to produce ethanol;
o) distilling said ethanol from said fermentation broth from step n) to recover ethanol and a de-ethanolized slurry.

### Claim 2 (depends on 1)

The process of claim 1, wherein said moisture content of said acidified biomass is adjusted in step e) to 65% to 80% prior to continuous steam treatment of step f).

### Claim 3 (depends on 1)

The process of claim 1, wherein said moisture content of said acidified biomass is adjusted in step e) to 70% to 80% prior to continuous steam treatment.

### Claim 4 (depends on 1)

The process of claim 1, wherein said mineral or organic acid is added to said squeezed biomass in step d) in an amount of 0.7% to 0.9% w/w.

### Claim 5 (depends on 1)

The process of claim 1, wherein said mineral or organic acid is added to said squeezed biomass in step d) in an amount of 0.8% w/w.

### Claim 6 (depends on 1)

The process of claim 1, wherein said biomass is steamed at atmospheric pressure for 10 to 60 min prior to subjecting said acidified biomass to steam treatment under pressure in a continuous treatment vessel.

### Claim 7 (depends on 1)

The process of claim 1, further comprising the step of drying said de-ethanolized slurry.

### Claim 8 (depends on 7)

The process of claim 7, further comprising the step of recovering energy produced from said pretreatment and drying steps.

### Claim 9 (depends on 1)

The process of claim 1, wherein the amount of mineral acid added to said squeezed biomass in step d) is adjusted to achieve a pH of 1.8 to 2.5 in said acidified biomass.

### Claim 10 (depends on 9)

The process of claim 9, wherein said acidified biomass is adjusted at a pH of 2.0.

### Claim 11 (depends on 9)

The process of claim 9, wherein said mineral acid is selected from the group consisting of sulfuric acid, phosphoric acid, and sulfur dioxide.

### Claim 12 (depends on 1)

The process of claim 1, wherein a severity index of the continuous steam treatment step f) is between 3.5 to 3.7.

### Claim 13 (depends on 12)

The process of claim 12, wherein said severity index is between 3.5 to 3.6.

### Claim 14 (depends on 1)

The process of claim 1, wherein extraction step i) comprises squeezing, water washing, or a combination thereof.

### Claim 15 (depends on 12, 13)

The process of claim 12 or 13, wherein extraction step i) is carried out at a pressure between atmospheric pressure and the pre-treatment pressure.

### Claim 16 (depends on 1)

The process of claim 1, wherein said liquid stream extracted in step i) is concentrated in step j) by evaporation to a concentration of soluble solids between 100 to 300 g/L.

### Claim 17 (depends on 16)

The process of claim 16, wherein energy required for the concentrating step j) is derived from recovered energy from the continuous steam treatment step f).

### Claim 18 (depends on 16)

The process of claim 16, wherein vapors created in the concentrating step j) from said evaporation of the soluble solids are recovered.

### Claim 19 (depends on 1)

The process of claim 1, wherein a consistency of said cellulose rich solids stream obtained in step i) is adjusted within a range of 10% to 25% consistency.

### Claim 20 (depends on 19)

The process of claim 19, wherein said cellulose rich solids stream is adjusted to between 15% and 25% consistency.

### Claim 21 (depends on 19)

The process of claim 19, wherein said cellulose rich solids stream is adjusted to 17% consistency.

### Claim 22 (depends on 1)

The process of claim 1, wherein said combined hydrolysate stream is co-fermented to ethanol with bacteria or yeast that converts both glucose and xylose to ethanol.

### Claim 23 (depends on 7)

The process of claim 7, wherein said drying of said de-ethanolized slurry takes place in a dryer for recovering heat as low pressure steam for use in other parts of the process.

### Claim 24 (depends on 1)

The process of claim 1, wherein step j) is carried out at atmospheric pressure and a temperature of 98° C.

### Claim 25 (depends on 1)

The process of claim 1, wherein step j) is carried out under a vacuum of 150 mbar and a temperature of 80° C.

### Claim 26 (depends on 1)

The process of claim 1, wherein step j) is carried out at a pressure of 20 psig.

### Claim 27 (depends on 1)

The process of claim 1, further comprising an extraction step, comprising squeezing, water washing or a combination thereof, prior to explosive decompression in step h).