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Pretreatment Methods for Biomass Conversion into Biofuels and Biopolymers

National Renewable Energy Laboratory

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Technology Marketing Summary

Hydrolysis of lignocellulosic biomass using an acid catalyst to produce sugars has been known for decades but can be costly and requires special equipment. The hydrolyzed sugars themselves are somewhat labile to the harsh hydrolysis conditions and may be degraded to unwanted or toxic byproducts. If exposed to acid for too long, the glucose derived from cellulose degrades into hydroxymethlylfurfural, which can be further degraded into levulinic acid and formic acid. Xylose, a hemicellulose sugar, can be degraded into furfural and further to tars and other degradation products.

After a century of research and development, the dilute acid hydrolysis process has evolved into a highly efficient process of converting biomass into ethanol. Hydrolysis occurs in two stages to maximize sugar yields from the hemicellulose and cellulose fractions of biomass. The first stage is operated under milder conditions to hydrolyze hemicellulose, while the second stage is optimized to hydrolyze the more resistant cellulose fraction. Liquid hydrolyzates are recovered from each stage, neutralized, and fermented to ethanol.

Description

Patents: 6,660,506, 6,423,145
This technology is a set of processes to convert lignocellulosic biomass to ethanol, comprising hydrolyzing lignocellulosic materials by subjecting dried lignocellulosic material in a reactor to a catalyst composed of a dilute solution of a strong acid and a metal salt to lower the activation energy (i.e., the temperature) of cellulose hydrolysis and ultimately obtain higher sugar yields. The lower temperatures achieved reduces the need for costly steam and specialized equipment and enables the hydrolysis of both hemicellulose and cellulose, when used with hydrolyzer feeders that do not compact the biomass feedstock to achieve higher sugar yields. The liquid hydrolyzates are recovered from each stage and fermented to alcohol. Residual cellulose and lignin left over in the solids from the hydrolysis reactors serve as boiler fuel for electricity or steam production.

Benefits

NREL’s intellectual property in the area of pretreatment, can be beneficial to your company’s pretreatment steps in a number of ways, including the following:

 

  • Lower required activation temperature for hydrolysis of both hemicelluloses and cellulose can reduce the cost of steam and equipment
  • Increase fermentable sugar yields
  • Recover water soluble sugars
  • Requires less sever pH, temperature, and time than conventional prehydrolysis.
  • Greater extraction of cellulose and hemicelluloses
  • Reduced nutrient requirements
  • Fermentation method in 00-52 eliminates the need for washing the second-stage hydrolysate to recover soluble sugars.
  • Requires a less severe combination of pH, temperature, and time than conventional prehydrolysis.
Applications and Industries
  • Bio-fuels
  • Pulp & paper
  • Food & feed processing
  • Textile processes
Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Date
Patent 6,423,145
Patent
6,423,145
Dilute acid/metal salt hydrolysis of lignocellulosics
A modified dilute acid method of hydrolyzing the cellulose and hemicellulose in lignocellulosic material under conditions to obtain higher overall fermentable sugar yields than is obtainable using dilute acid alone, comprising: impregnating a lignocellulosic feedstock with a mixture of an amount of aqueous solution of a dilute acid catalyst and a metal salt catalyst sufficient to provide higher overall fermentable sugar yields than is obtainable when hydrolyzing with dilute acid alone; loading the impregnated lignocellulosic feedstock into a reactor and heating for a sufficient period of time to hydrolyze substantially all of the hemicellulose and greater than 45% of the cellulose to water soluble sugars; and recovering the water soluble sugars.
National Renewable Energy Laboratory 07/23/2002
Issued
Patent 6,660,506
Patent
6,660,506
Ethanol production with dilute acid hydrolysis using partially dried lignocellulosics
A process of converting lignocellulosic biomass to ethanol, comprising hydrolyzing lignocellulosic materials by subjecting dried lignocellulosic material in a reactor to a catalyst comprised of a dilute solution of a strong acid and a metal salt to lower the activation energy (i.e., the temperature) of cellulose hydrolysis and ultimately obtain higher sugar yields.
National Renewable Energy Laboratory 12/09/2003
Issued
Technology Status
Development StageAvailabilityPublishedLast Updated
DevelopmentAvailable01/14/201007/16/2010

Contact NREL About This Technology

To: Eric Payne<Eric.Payne@nrel.gov>