Quantifying Sugar Removal from Willow Biomass Using HotHot-Water Extraction, Based on
Densification Methods
Neil Sprenkle, Amy Falcon, Xinfeng Xie, Jingxin Wang
Division of Forestry and Natural Resources
West Virginia University
Morgantown, WV, USA
Abstract
Lignocellulosic biomass is the most widely available source of
carbohydrates, however, this feedstock is not readily fermentable. The
structure of the lignin surrounding the cellulose and hemicellulose
impedes the breakdown of cellulose and hemicellulose into their
component sugars. To overcome this difficulty, lignocellulose structure
must be modified through pretreatment. The extracted sugars are
then available for conversion to biofuels or other bioproducts. A major
factor inhibiting the process of extracting the sugars from being
economical is the inherent cost of mechanically pretreating woody
biomass. Densified wood is an ideal feedstock because of its lower cost
and long term storage abilities compared to wood chips or dust. In
this research, sugar is extracted from densified wood pellets and
compared to the quantity of sugar extracted from ground wood. The
results from this study determined that it is feasible to use pelleted
wood as a feedstock for extracting sugars from woody biomass,
however the grinding of biomass did not optimized sugar recovery.
Upon completion of the study, it was determined that pelleting raw
ground biomass does not significantly influence the quantity of
fermentable monosaccharides extracted post thermohydrolysis and
acid hydrolysis. Additionally, the acid soluble lignin percentage was
observed to be similar as well. Due to the similarities relative to the
results, it was determined that the purchasing densified woody
biomass would be an preferred option as the cost of biomass
transportation is reduced through densification technologies and
through said technologies companies are able to avoid costly
mechanical pretreatments used to process raw biomass.
Determination of Sugars
During hydrolysis the polymeric carbohydrates are hydrolyzed into the monomeric forms,
which are soluble in the hydrolysis liquid. Aliquot from samples post acid hydrolysis are
measured at 540 nm using a spectrophotometer. The absorbance value obtained was used in
conjunction with the derived trend line equation to calculate the concentration of reducing
sugars prevalent within the sample.
Reducing Sugar Concentration (mg/L)
Ground
SX61
Owa
9.875
5.366
10.587 10.547
9.654
8.352
6.528
7.625
5.261
9.057
7.745
11.792
6.166
8.625
5.326
8.562
7.147
Average 11.589
7.523
7.083
6.863
9.391
8.182
Quantification of Lignin
This procedure uses a two-step acid hydrolysis to fractionate the biomass into forms that are
more easily quantified. The lignin fractionates into acid insoluble material and acid soluble
material. The acid insoluble material may also include ash and protein, which must be
accounted for during gravimetric analysis. The acid soluble lignin is measured by UV-Vis
spectroscopy at 240 nm.
Analysis
A UV Spectrophotometer was used to determine the absorbance values of glucose
standards. There is a linear relationship between the absorbance read and the concentration
of glucose in solution at 540 nm. The equation of this line can be used to calculate unknown
glucose concentrations at measured absorbance. Glucose Standards were tested at 50, 100,
150, 200, 300, 400, and 500 grams/liter and the linear relationship can be seen in Figure 1.
Pellet
SV1
14.623
Average
SV1
SX61
Owa
Table 1: Utilizing the trend line equation derived from the standard curve produced,
the absorbance values obtained at 540 nm was used to determine the amount of
glucose within the liquid samples. The data displayed indicates no optimization with
regards to sugar recovery when biomass undergoes the densification procedure.
Glucose concentrations (mg/L) vary within the range of 5.261 to 14.623, however no
significant amount of reducing sugar is observed within either ground or pellet
aliquots. The results suggest that densification does not increase overall extraction
yields but instead contributes approximately the identical amount as raw ground
biomass.
Acid Soluble Lignin Content
Ground
SV1
SX61
Owa
Pellets
SV1
SX61
Owa
4.232% 6.131% 5.790%
6.689% 5.264% 8.142%
7.681% 5.373% 6.558%
5.359% 6.295% 5.823%
6.694% 7.778% 4.063%
6.498% 5.101% 6.415%
Objectives
• Determine quantity of sugar removed from willow wood particles
for conversion to fuels
Average 6.202% 6.427% 5.470% Average 6.182% 5.553% 6.793%
• Determine quantity of sugar removed from densified willow wood
pellets for conversion to fuels
• Compare sugar quantities from densified and non-densified wood
and draw conclusions as of the efficacy of using densified material as
a fuel source for sugar extraction without further mechanical
pretreatment
Materials and Methods
• Hybrid willow, three (3) genotypes:
— Belleville SV1 Rep1
— Belleville SX61 Rep 2
— Belleville Owasco 99207-018 Rep 2
Figure 1: Standard curve displaying the linear relationship between glucose concentration (g/L) and their
absorbance values at 540 nm
Hydrolyzed Biomass
• Analysis of liquid extract post pre-hot water treatment must further be
investigated in addition to the solid extract from pretreatment. Liquid extract
contains a great amount of fermentable monomers due to the cleavage of
glycosidic bonds within the hemicellulose polymers and would contribute to the
desired extraction yields more than monomers obtained from the solid extract.
• Ground material (12% MC) was pelletized using a Pellet Press Model
• Hot water pre-treatment through Parr Batch Reactor on samples
under the following parameters:
• Solid loading of 10% (w/w) with water
• Target temperature: 200°C
• Hold time: 9 minutes
• Ramp rate: 15°C/min
• Mass of solid hydrolyzed during pre-hot water treatment must be looked into to
demonstrate the effectiveness of the pretreatment
Conclusions
• NREL-LAP: Determination of Structural Carbohydrates and Lignin in
Biomass (1).
Extraction Process
Future Work
• To obtain significant reducing glucose yields, experimental procedure may have
to be adjusted to prolong the oxidation of monomers due to either the high
concentration of sulfuric acid used or the length of time samples were allowed
undergo hydrolysis within the autoclave.
• Processed raw willow chips through Pulverisette 25, Fritsch Power
Cutting Mill. Particles of 1 millimeter or less.
• Somogyi-Nelson Method for the determination of reducing sugars
Table 2: No significant deviations in acid soluble lignin (ASL) is observed amongst
the two categories. Quantity of ASL in the ground and densified SV1 genotype is
almost identical whereas ASL % in the SX61 and Owa genotypes differ by 0.874%
and 1.323%, respectively. ASL % for all three genotypes ranged from 5.470% to
6.793% with no real observable trends with regards to what ASL % would
characterize a specific genotype. The desired outcome would be to have a higher
quantity of acid soluble lignin compared to acid insoluble lignin as the insoluble
lignin aids in the impeding of monosaccharide extraction due to its close
association with other cellulosic polymers which prevents said polymers from
hydrolyzing into their monomeric components.
Figure 2: Displays the amount of biomass hydrolyzed after each acid hydrolysis procedure.
Although there are deviations between the ground and densified genotypes, there are no
observable trends regarding the amount of biomass hydrolyzed between the two categories.
• % of biomass hydrolyzed upon acid hydrolysis is not correlated
with the type of mechanical pretreatment the biomass
undergoes prior to treatment.
• Densified biomass yielded an approximately identical amount of
fermentable sugars and ASL percentage as the ground biomass
samples.
• Pelleting the biomass has no observable effect on sugar yields
from to the solid extract derived from thermohydrolysis.
• Sugars released via acid hydrolysis may have been oxidized prior
to the Somogyi-Nelson procedure. This may account for the low
reducing sugar yields.
• No negative implications due to pelleting, a more economically
beneficial option.
References
1. Ruiz, R, Scarlata, C., Sluiter, J. & Templeton, D. (2008). Determin. of Struc. Carbs. and
Lignin. National Renewable Energy Laboratory
2. Serapiglia, M. J., et. al. (2013). Enzymatic sacchari. Of shrub willow genotypes with
differing biomass composition for biofuel production. Frontiers in Plant Science. 4.