advances.sciencemag.org/cgi/content/full/3/6/e1603301/DC1

Supplementary Materials for

Increasing the revenue from lignocellulosic biomass: Maximizing

feedstock utilization

David Martin Alonso, Sikander H. Hakim, Shengfei Zhou, Wangyun Won, Omid Hosseinaei,

Jingming Tao, Valerie Garcia-Negron, Ali Hussain Motagamwala, Max A. Mellmer, Kefeng Huang,

Carl J. Houtman, Nicole Labbé, David P. Harper, Christos T. Maravelias, Troy Runge, James A. Dumesic

Published 19 May 2017, Sci. Adv. 3, e1603301 (2017)

DOI: 10.1126/sciadv.1603301

This PDF file includes:

Supplementary Materials and Methods

section S1. Biomass fractionation

section S2. Liquid/solid separation

section S3. High-purity cellulose production for dissolving pulp

section S4. Lignin recovery and precipitation experiments

section S5. Lignin recovery for carbon foam and battery anode production

section S6. Lignin characterization

section S7. Carbon foam production

section S8. Furfural production

section S9. Solvent stability study

section S10. Techno-economic model

fig. S1. Fractionation of white birch.

fig. S2. Lignin produced from white birch fractionation.

fig. S3. Lignin produced from white birch fractionation.

fig. S4. Thermal decomposition of lignin samples produced from white birch

fractionation at 70:30 GVL/water, 125°C, 3 hours, and 0.1 M sulfuric acid and

80:20 GVL/water, 130°C, 1 hour, and 0.1 M sulfuric acid.

fig. S5. Aromatic (left) and side chain (right) region of the 13C-1H (HSQC) spectra

of white birch, lignin samples produced from white birch fractionated at 70:30

GVL/water, 125°C, 3 hours, and 0.1 M sulfuric acid and 80:20 GVL/water,

130°C, 1 hour, and 0.1 M sulfuric acid.

fig. S6. X-ray diffraction patterns of carbonized and passivated GVL lignin

compared to the original lignin (top).

fig. S7. Carbon foam produced from lignin (initial white birch fractionation

conditions: 80:20 GVL/water, 130°C, 1 hour, and 0.1 M sulfuric acid).

fig. S8. Production of furfural in a batch reactor using 10 wt % xylose as

feedstock.

fig. S9. Production of furfural in a continuous flow reactor using xylose as

feedstock.

fig. S10. Gas chromatography–mass spectrometry (GC-MS) chromatogram of

GVL (top), tetrahydrofuran (THF) (middle), and ethanol (bottom) after 12 hours

at 130°C.

fig. S11. GC-MS chromatogram of GVL (top), THF (middle), and ethanol

(bottom) after 12 hours at 130°C.

table S1. White birch fractionation optimization.

table S2. Properties of bleached high-purity cellulose sample from white birch

wood chips to produce dissolving pulp.

table S3. Lignin solubility in GVL/water mixtures at room temperature.

table S4. Effect of water/GVL ratio on lignin precipitation.

table S5. Chemical composition and molecular weight of lignin samples.

table S6. Thermal properties of lignin samples.

table S7. Summary of NMR analysis of lignin samples.

table S8. Hydroxyl group content of lignin sample (70:30 GVL/water, 125°C, 3

hours, and 0.1 M sulfuric acid) obtained by quantitative 31P NMR spectroscopy

(mmol/g).

table S9. Liquid composition after 12 hours at 130°C.

table S10. Liquid composition after 12 hours at 130°C.

table S11. List of economic parameters and assumptions.

table S12. Mass and energy balances (basis: 2000 tons of white birch per day).

table S13. Energy requirements before and after heat integration (basis: 2000 tons

of white birch per day).

table S14. Capital and operating costs (basis: 2000 tons of white birch per day).

table S15. Process model development details.

References (32–43)

Supplementary Materials and Methods

section S1. Biomass fractionation

White birch chips (approximately 2.54 × 2.54 × 0.65 cm) were acquired from Flambeau

River Papers (Park Falls, WI). These chips are the same as used in their process to

produce paper pulp. The chips have a moisture content of ≈30% and were stored at −20

°C. These chips were used as-received for the large-scale fractionation. Smaller chips

were created for the 100 g scale fractionation to allow for more homogeneity. These

chips were produced using a DR model CST1450-CHP knife mill fitted with a 0.32 cm

screen after further drying to ~10% moisture. The chips were then screened with an 8 mm

sieve screen to remove large pieces.

The initial study to determine the optimal process conditions to fractionate white birch

chips was performed in a rotating digester with 3 stainless steel bombs placed inside (1 L

each). The reactor was externally heated to the desired temperature by saturated steam,

and mixing was achieved by rotating the reactor at 2 rpm for the first 30 minutes. At the

end of the fractionation, the steam supply was stopped, and the steam in the digester was

released to quench the reaction. The digester was opened and the bombs were further

cooled by immersion in cool water. After cooling, the pulping liquor was filtered from

the pulp solids using 42 grade Whatman filter paper in a Büchner funnel under vacuum

generated by a Welch 2511 Dry Vacuum Pump (Welch Vacuum Technology, Niles, IL).

The pulp solids were then removed and mixed with a solution of GVL/water (80/20) at

80°C to simulate solvent washing. Because the reactor effluent was cooled before the

washing step, the washing was repeated 3 times using a liquid:solid mass ratio of 4, 3, 3

using mixing times of 30, 20, 20 min, respectively. After solvent washing, the cake was

washed 2 more times using DI water at 80°C with a liquid:solid mass ratio of 5 using a

15 min mixing time. This washing procedure was designed to avoid any interference of

the washing step in the final cellulose purity.

The screened pulp moisture content was determined by placing the sample in an oven at

105°C following TAPPI-T258 om-02. Kappa numbers were measured using TAPPI

Standard Test Method TAPPI-UM246 (Micro kappa number), and the cellulose chain

lengths in the pulps were approximated by measuring CED viscosity using TAPPI-T230

om-04 (Viscosity of pulp (capillary viscometer method)). Alpha cellulose content of the

bleached pulp was measured by TAPPI-T203 (Alpha-, beta- and gamma-cellulose in

pulp). The chemical composition of the solid residue was analyzed following the

NREL/TP-510-42618, Determination of Structural Carbohydrates and Lignin in Biomass.

Experimental results are summarized in table S1.

section S2. Liquid/solid separation

Experiments to produce samples to study the liquid/solid separation step were carried out

in 60 mL high pressure glass reactors (Chemglass) placed in an oil bath. To fit the wood

chips inside the reactor, the size was reduced using a DR model CST1450-CHP knife

mill fitted with a 0.32 cm screen after further drying to ~10% moisture. The chips were

then screened with an 8 mm screen to remove large pieces. The final moisture content of

the white birch feedstock was ~5%.

In a typical experiment, 6 g of grinded white birch and 24 g of a liquid solution of

GVL/water 70/30 by weight and 0.1 M sulfuric acid were added to the reactor and heated

at 125°C for 3 hours. At the end of the reaction, the liquid was separated from the solid at

~80°C using a centrifuge filter or vacuum filtration. The remaining cellulose was washed

with an additional 24 g fresh GVL/water solution with the same composition as the one

used for the reaction to recover additional carbohydrates and lignin solubilized in the

liquid retained by the cellulose (i.e., solid cellulose containing 60-65 wt% liquid). After

15 minutes the liquid was separated from the cellulose using a centrifuge filter or vacuum

filtration. The cellulose was finally washed with water and analyzed to determinate its

chemical composition following the NREL/TP-510-42618 protocol, Determination of

Structural Carbohydrates and Lignin in Biomass. The liquid fraction was used to perform

a second fractionation. The liquid fraction from the second liquid/solid separation step

was used to treat 6 g of fresh white birch at the same conditions as indicated above. At

the end of the reaction, the liquid was separated from the solid at ~80°C using a

centrifuge filter or vacuum filtration. The remaining cellulose was washed with an

additional 24 g of fresh GVL/water solution. After 15 minutes the liquid was separated

from the cellulose using a centrifuge filter or vacuum filtration. The cellulose was finally

washed with water and analyzed as mentioned above. The liquid fraction was used to

perform another fractionation. The recycling was repeated 4 times.

The liquid fraction was analyzed by High Performance Liquid Chromatography (Waters

2695 system with a Bio-Rad Aminex HPX-87H column) equipped with an RI 410

detector (for carbohydrates, organic acids, GVL) and a UV detector (for furfural and

HMF). In addition, to convert soluble oligomeric carbohydrates into monomers, a

protocol similar to NREL/TP-510-42618 was followed. A portion of the liquid was

diluted 10 times with 4.4 wt% sulfuric acid and heated at 120°C for 1 hour. The sample

was analyzed by HPLC as mentioned above.

The results obtained using the recycled GVL/water solution were similar to those

obtained using fresh GVL/water (less than 5% difference), indicating that the presence of

biomass derived impurities, low concentrations of lignin, and/or carbohydrates do not

affect the fractionation process significantly (see fig. S1). By combining these two

solid/liquid separation stages we maximize the recovery of soluble C5 carbohydrates and

the lignin (>95%). The liquid fraction from the first stage contains the soluble C5 sugars

and lignin, and this stream is transferred to the lignin recovery step. Results from these

experiments were used in the technoeconomic model.

section S3. High-purity cellulose production for dissolving pulp

After optimizing the reaction conditions, a larger scale fractionation experiment was

performed in a 20 L twin-digester reactor to produce high purity cellulose for dissolving

pulp application, high purity lignin for carbon foam and battery anodes production, and

for furfural production. 2.5 kg of moist white birch chips were loaded in the reactor and

covered with a mixture of GVL/water (70/30 by weight) and 0.1 M sulfuric acid. The

excess of liquid was re-circulated for 3 h at 125°C. At the end of the reaction, the liquid

was collected to recover the lignin and to produce furfural. The cellulose was washed

inside the reactor 3 times with a hot GVL/water mixture and 2 additional times with hot

water. Before washing the cellulose, the reactor was cooled and depressurized. The

cellulose was then taken out of the reactor and screened. The final yield of the pulp was

42% and the kappa number before the bleaching step was equal to 20.

The bleaching method used was a modified version of the standard OD(EP)D sequence.

The first step was an acid treatment using 1 wt% sodium chlorite along with acetic acid

(0.33 mL acetic acid/g NaClO2). This treatment was performed at a solid consistency of

3% under effective mixing. A slow reaction was carried out at room temperature under

stirring for about 3-4 hours, after which, the liquid was drained and the pulp was

dewatered using a bladder press to obtain a dried pulp with 26% solid content.

In the second step, NaOH was added to water to obtain a pH solution of 11. During this

NaOH treatment, the temperature was kept above 50°C. Fluffed pulp was added under

stirring, and the reaction was carried out for an additional 2 hours. After the reaction, the

liquid was drained and the bleached pulp was washed multiple times with fresh water

until neutral pH was reached. The pulp was dewatered using a bladder press to obtain a

dried pulp with 26% solid content.

In the third and final step (D), chlorine dioxide bleaching was performed using heat-seal

plastic bags in a water bath. Chlorine dioxide was prepared through sulfuric acid

acidification of sodium chlorite and sodium hydroxide.

The final bleached pulp was characterized for physical properties, including solids

analysis, alpha cellulose content, pentosan content, ash content, acid insoluble lignin

content, viscosity, brightness and kappa number. The results are summarized in table S2.

section S4. Lignin recovery and precipitation experiments

Lignin solubility studies in GVL/water mixtures were performed in a flow-through

reactor. In a typical experiment, 8.5 g of dried white birch powder was placed inside of

an 1/2" stainless steel tubing. The biomass was heated to 130°C and a solution of

GVL/water and 0.15 M sulfuric acid was passed through the reactor at 0.13 ml/min and

1.4 MPa to saturate the liquid with lignin. To the first 5 g of liquid, collected at room

temperature, 45 g of water was added to precipitate the lignin. The precipitated lignin was

separated from the liquid by centrifugation, thoroughly washed with water to remove any

remaining impurities, and dried in a vacuum oven overnight at 40°C. Results are shown

in table S3. Up to 14.3 wt% lignin was soluble in a 60/40 GVL/water and 0.15M sulfuric

acid solution.

The lignin precipitation study was performed using a GVL/water hydrolysate solution

produced in a 20 L twin-digester reactor. 2855 g moist white birch (2000 g dry) and 9092

g of liquid (biomass loading 18.2 wt%) were loaded into the reactor. The liquid was

80/20 wt% GVL/water and 0.1 M sulfuric acid. The reaction time was 60 minutes at

130°C and 30-35 psi, during which the liquid was recirculated through the white birch

chips to achieve mixing. At the end of the reaction, the liquid was drained and was used

to precipitate the solubilized lignin. Table S4 shows that simple addition of water is

sufficient to cause the precipitation of the lignin when the water/GVL mass ratio is above

1.5. At this ratio, lignin precipitates in small particles, and only 50% of the lignin

solubilized in the liquid is recovered by centrifugation. Also, the lignin contains high

amounts of GVL, and is recovered as a black dense viscous paste that can cause fouling

problems. After washing and drying, the recovered lignin still had a dark brown color

(fig. S2). Increasing the water/GVL ratio over 3 improves the lignin recovered to 80%.

Further increasing the water/GVL ratio does not increase the percentage of lignin

recovered, but decreases the amount of GVL retained by the lignin. The lignin

precipitation can be accelerated if the pH of the solution is below 1.5.

section S5. Lignin recovery for carbon foam and battery anode production

The liquid collected from the large-scale fractionation experiment (see section 3 of

supplementary materials) was utilized to recover the solubilized lignin. To 100 g of GVL

solution, 450 g of water were added to induce the precipitation of lignin (ratio water/GVL

≈8). The lignin was separated from the liquid by centrifugation. The liquid phase,

containing soluble C5 carbohydrates, was collected for further experiments (furfural

production). The lignin was washed 4 times with hot water (2 times the amount of lignin)

to simulate a countercurrent washing and dried under vacuum at 40°C. The lignin was

recovered as a light brown fine powder (fig. S3).

section S6. Lignin characterization

Two samples of lignin were characterized. Both samples were produced from white birch

chips as described in section 5. The difference between the samples was the reaction

conditions used during the biomass fractionation. The first sample was produced by

fractionating white birch chips at 125°C for 3 hours using a 70/30 GVL/water and 0.1 M

sulfuric acid solution, and the second sample was produced at 130°C for 1 hour using a

80/20 GVL/water and 0.1 M sulfuric acid solution.

a. Chemical composition and molecular weight

The chemical composition of the lignin was analyzed following the NREL/TP-510-42618

protocol. The molecular weight was analyzed after an acetobromination derivatization

procedure was applied. Approximately 2.5 ml of a mixture composed of 8 parts of acetyl

bromide and 92 parts (v/v) of glacial acetic acid were added to approximately 10 mg of

lignin. The sample was sealed and placed in a sand bath at 50°C for 2 h with continuous

magnetic stirring. The solvent was evaporated in a rotary evaporator connected to a high

vacuum pump and a cold trap. The residue was then dissolved in 5 ml of tetrahydrofuran

(THF) and analyzed by a size exclusion chromatography (SEC) system (Tosoh ECO

SEC) equipped with a UV detector (265 nm). The analysis was performed with THF as

the eluent at a rate of 0.32 mL per min with a Tosoh TSK gel Super Multipore HZ-M

column preceded with a TSK gel Super Multipore HZ-M guard column and calibrated

against polystyrene standards. The carbon, hydrogen and nitrogen contents of the sample

produced at 70/30 GVL/water ratio were measured in triplicate using a PerkinElmer

2400II CHNS/O combustion elemental analyzer.

The results are summarized in the table S5. Both samples have similar lignin purity

(>96%) which is expected as both samples were produced from the same feedstock and

using a similar recovery method. The sample produced at 125°C for 3 hours has a slightly

lower molecular weight than the sample produced at 130°C for 1 hour indicating that

reaction temperature and time influenced the lignin depolymerization.

b. Thermal properties

The glass transition temperature (Tg) was determined using a PerkinElmer Diamond

differential scanning calorimeter. Experiments were conducted under nitrogen

atmosphere using approximately 2 mg of lignin samples in triplicates. The lignin was first

heated from 25 to 140°C at a heating rate of 100°C/min and held at that temperature until

the change in thermal energy from the sample was zero to expel any moisture and erase

thermal history of the sample. The sample was then cooled and reheated to 200°C at the

same heating rate to calculate Tg.

Thermal decomposition of lignin samples was measured using a PerkinElmer Pyris 1

thermogravimetric analyzer. Experiments were conducted in duplicate using

approximately 5 mg specimens, heated from 20 to 105°C under a nitrogen atmosphere at

a rate of 10°C/min, and held for 10 min to remove moisture. The sample was then heated

to 950°C at the same heating rate.

The thermal properties are presented in the table S6. Both samples have similar properties

which can be attributed to the low degradation suffered by the lignin during the

fractionation. The samples have a high glass transition temperature, which is beneficial

for further processing. Thermal decomposition experiments (fig. S4) show a high thermal

stability with a small weight loss (2%) before 200°C.

c. NMR analysis

Pre-fractionated white birch was prepared as a gel for 2D HSQC NMR analysis following

the method of originally described by Mansfield et al. (32). Briefly, white birch was

milled to 40 mesh and extracted following the NREL method (33). The extractives-free

white birch sample was then ball milled and transferred to a 5 mm NMR tube. Dimethyl

sulfoxide-d6/ pyridine-d5 (4:1) was then added to NMR tube. After sonicating at 40°C

for 5 hrs, a gel was formed of the white birch cell wall. Bruker AV-II spectrometer

operating at 600.13 MHz was used to analyze the gel white birch sample.

Liquid state NMR analyses were carried out on a Varian 400-MR spectrometer. For 2D

(HSQC) spectroscopy, 100 mg of lignin was dissolved in 0.75 mL d6-DMSO, and all

samples were fully soluble. The NMR spectra were recorded at 25°C using the

(HC)bsgHSQCAD pulse program. The experiment collecting 32 transients and 512 time

increments in the 13C dimension. DMSO was used as an internal reference. The analysis

of the data was performed using Mnova version 10.0.1. HSQC cross-signals were

assigned by correlation with literature databases. Semi-quantitative analysis of volume

integrals was performed and interunit linkages were calculated as percentage of total side

chains. In the aromatic region, the relative abundance of syringyl (S), α-oxidized syringyl

unit (Sox) and guaiacyl (G) units were estimated from their C−H correlations.

As shown in Fig. 5S (top), the β-O-4 linkage (designated A) was the major lignin side-

chain interunit linkage present in the white birch prior to fractionation. NMR of the white

birch produced less pronounced lignin signals than those of solution NMR (Fig. 5S

middle, bottom). After GVL fractionated process, a qualititative analysis shows that GVL

fractionated lignin retains the majority β-O-4 linkages present in white birch.

Quantification of hydroxyl groups in lignin was carried out with 31P NMR by initial

derivatization with 100 µL of 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane

(TMDP). The derivatized samples (30 mg) were dissolved in 0.75 mL of pyridine and

deuterated chloroform (1.6:1 v/v) and mixed with 100 μL of a solution of N-Hydroxy-5-

norbornene-2,3-dicarboxylic acid imide (10 mg/mL) and chromium(III) acetylacetonate

(5 mg/mL) as internal standard and relaxation agent, respectively. 31P NMR spectra were

acquired using an inverse-gated decoupling pulse sequence with a 90° pulse angle, 25 s

relaxation delay and 256 scans.

Table S7 summarizes the NMR analysis of the lignin samples. In both cases, the isolated

lignin retained most of the β-O-4' bonds present in the native lignin, indicating a low

level of degradation. The NMR spectra are included in fig. S5.

Table S8 summarizes the hydroxyl group content of lignin sample (70/30 GVL/Water

125°C 3h 0.1 M SA) obtained by quantitative 31P NMR spectroscopy (mmol/g).

section S7. Carbon foam production

Carbon foam and nano-graphitic carbon-carbon composites were produced from the

lignin produced in section 5 and characterized in section 6 and denoted as GVL-lignin.

The dry GVL-lignin powder was exposed through a series of heat and processing

treatments for making a highly graphitic structure. The heating steps included a combined

thermal stabilization/pyrolysis step followed by passivation. A tube furnace (Thermo

Scientific Lindberg Blue M model) setup with inert gas conditions contained the lignin

powder in a ceramic crucible. During carbonization, lignin undergoes an irreversible

phase change and produces a rich carbon content material. The thermal stabilization step

increases oxygen (O) and carbon contents while decreases hydrogen (H2). Carbon content

continues to increase throughout the pyrolysis treatment. Finally, passivation stabilizes

the material with the introduction of hydrogen and removal of oxygen.

First, GVL-lignin powder was exposed to nitrogen (N2) with water vapor (H2O), in a tube

furnace for thermal stabilization and pyrolysis. The inert gas, N2, passed through a

bubbler at room temperature and fed into the furnace at a volumetric flow rate of 3 L min-

1. During the thermal stabilization and pyrolysis step, the furnace was heated from 30 to

1000°C at a rate of 10°C min-1 and then held at 1000°C for one hour producing a carbon

foam. Thermochemical decomposition of the organic material started at approximately

200°C. The effluent gases, which include steam, nitric oxide (NO), carbon monoxide

(CO), carbon dioxide (CO2) and sulfur oxides (SOx), were released from the system and

trapped for odor control. To increase surface area and improve resulting structure, the

foam was broken up into smaller pieces in two steps. First, the carbon foam was

grounded into a micro powder with a blender for five minutes. Second, the carbon

material was milled with a planetary ball mill (PM100 RETSCH model), resulting in

particle sizes in the nanometer range. The ball-milling process used a stainless-steel

grinding container with a mixture of 2 and 10 mm diameter stainless steel balls. One-

third of the container was filled with sample and grounded at 350 revolutions per minute

(rpm) for three hours, composed of alternating 15 minute periods of ball milling and

holds at ambient temperature for cooling. After ball milling, the material was sieved to

separate the grinding balls from carbon material. The furnace is setup with an argon-

hydrogen (Ar-H2) gas mixture (3 L min-1) for the passivation step. Passivation is

conducted by heating at 10°C min-1 to a temperature of 1050°C with a one hour hold

prior to cooling.

To identify the degree of crystallinity in the processed lignin carbon, x-ray diffraction

(XRD) scans were performed at room temperature using a PANalytical Empyrean

diffractometer. XRD scans with Cu-kα (λ = 0.154 nm) ranged from 5 to 115 two theta

degrees with a continuous step size of 0.013 at 45 kV and 40 mA. Using Highscore Plus

software (34), the scanned data was refined based on peak fitting to obtain the full-width

at half-maximum and the interlayer spacing (or d-spacing). The crystal size was

determined using the Debye-Scherrer equation (35). Crystallographic planes (hkl) were

indexed for a graphite standard pattern based on carbon graphite with a hexagonal

structure, i.e., a non-cubic system. Thermal treatments show the evolution of lignin to

form graphene sheets at 1000°C to graphitic content after passivation (fig. S6).

Figure S7 shows light microscopy and SEM images of the carbon foam produced from

lignin. The fractionation conditions were 80/20 GVL/water; 130 °C; 1 h; 0.1 M sulfuric

acid.

section S8. Furfural production

Initial experiments to study the production of furfural in GVL/water solution were

performed in 10 mL high pressure glass reactors (Alltech). The reactors were loaded with

a solution of 80/20 GVL/water, commercial xylose and the catalyst. The reactors were

mixed with a magnetic bar and heated to the reaction temperature in an oil bath. After the

indicated time, the reactor was taken out of the oil bath and cooled to room temperature

in a water bath. The liquid was analyzed by HPLC (Waters 2695 system with a Bio-Rad

Aminex HPX-87H column, RI 410 detector (carbohydrates, organic acids, GVL) and a

UV detector (furfural and HMF).

Figure S8 shows that the maximum furfural yield achieved using sulfuric acid as catalyst

at 170°C is 65%. The furfural yield can be increased to 80% if HCl is used as catalyst or

KCl is added to the system. In addition, the reaction time to obtain the maximum yield is

reduced from 30 min to 15 min when Cl- ions are introduced in the system, indicating

that the presence of Cl- ions not only increases the selectivity but also increases the

reaction rate.

The continuous production of furfural was studied in an up-flow reactor. A 0.635 cm

tubular stainless steel reactor was completely filled with fused SiO2 to fill the reactor

volume and improve heat and mass transfer. The reactor was mounted inside an

aluminum block heated by a heating tape. The reaction temperature was monitored at the

reactor wall by a Type K thermocouple (Omega) mounted within the aluminum block

and controlled by a Series 4B temperature controller (Love Controls). The pressure was

kept at 2.07 MPa to prevent water vaporization. The liquid feed was introduced in the

reactor using an HPLC pump (Lab Alliance Series I). The effluent was analyzed by

HPLC (Waters 2695 system with a Bio-Rad Aminex HPX-87H column, RI 410 detector

(carbohydrates, organic acids, GVL) and a UV detector (furfural and HMF).

Using a continuous reactor operating at 225°C, furfural yields over 80% can be achieved

with 0.05 M sulfuric acid as catalyst (feed is 2 wt% xylose in a GVL/water 80/20

solution). If the catalyst is replaced by HCl, yields over 95% can be achieved with a

similar feedtstock, indicating that the presence of Cl- ions reduces the degradation of the

furfural. If the xylose concentration is increased to 10 wt% the furfural yield decreases

slightly (fig. S9).

The liquid solution recovered after the lignin precipitation (see section 6) was

concentrated by evaporating the water to a ratio GVL/water of 80/20. This liquid contains

soluble C5 carbohydrates that were converted to furfural at 90% yield (225°C for 1 min).

The catalyst was the residual sulfuric acid from the fractionation step.

section S9. Solvent stability study

Experiments to study the solvent stability during the fractionation step were performed in

10 mL high pressure glass reactors (Alltech) placed in an oil bath. Three solvents were

used for the study: gamma-valerolactone (GVL), tetrahydrofuran (THF), and ethanol

(EtOH). Glycerol was initially considered for the study; however, it degraded

significantly, producing large quantities of black carbon deposit and no further studies

were performed. All the solvents were analytical grade from Sigma-Aldrich and were

used without further purification. The conditions used for the study were: solvent/water

(w/w) 80/20, 0.1 M sulfuric acid, 130°C and 12 hours. The experiments were performed

in triplicates. In addition to pure solvent stability, additional experiments were performed

by adding 5 wt% of acetic acid to the solution, to simulate the effect of biomass derived

impurities.

Table S9 shows that GVL is the most stable solvent of those studied. Both, GVL and

THF undergo ring opening in the presence of water and acid catalyst. In the case of GVL,

the products formed are isomeric pentenoic acids, 4 hydroxypentanoic acid and small

amounts of levulinic acid (fig. S10). In the case of THF, the main product observed was

1,4 butanediol (fig. S10). In both cases, the ring opening is an equilibrium reaction and

no further losses are expected once the equilibrium is reached. Ethanol was less stable

than the other solvents as it reacts to produce diethyl ether.

In the case of the experiments with 5 wt% acetic acid present (table S10), GVL stability

is similar to the previous case. This is expected as pentenoic acids do not react with acetic

acid and the esterification of the 4 -hydroxypentanoic acid is not favored (fig. S11). In the

case of THF and ethanol, the solvent loss increases as the THF-ring opening product, 1,4

butanediol, and the ethanol itself react with the acetic acid to produce esters (fig. S11).

section S10. Techno-economic model

To demonstrate techno-economic feasibility of the process to produce dissolving pulp,

furfural and technical lignin from lignocellulosic biomass, we developed a process model

based on the experimental results. The economic parameters and assumptions (table S11)

are similar to previous works by NREL (36) and Luterbacher (9). The feedstock, white

birch, was priced at $125 per MT according to the information obtained from the vendor

and Glucan Biorenewables LLC instead of utilizing the $80 per MT as suggested in

NREL studies. The selling price of dissolving pulp, furfural and lignin was fixed at $700,

$1000 and $500 per MT, respectively. Dissolving pulp prices range between $700-900

per MT and have reached up to $2000 in the recent years (37). Because of the initial

technical risk, we used the lower price for this study. Furfural price is mainly dominated

by Chinese producers, and it has ranged from $1000-1800 in the past years (38, 39). The

$1000 per MT price used in our study is competitive in the current market and could lead

to an expansion of the market if the quality and reliability of the product is demonstrated.

There is not a current market for lignin; however, based on the materials produced from

our lignin, carbon foam and battery anodes, we believe that $500 per MT is a

conservative price.

The cost of GVL has been estimated at $1000 per MT based on previous work (40–42)

that produced GVL as an intermediate molecule. The cost of other materials was taken

from the indicated references (table S11).

The internal tax of return has been set at 30% instead of the typical 10% to reflect the

higher risk of investing on a new technology.

Capital charge factor, calculated by discounted cash flow analysis, is 0.364.

Our techno-economic analysis follows three steps. The first step is the design of the

process that has been divided in 5 sections as shown in Fig. 2: 1) biomass fractionation,

2) lignin recovery, 3) furfural production, 4) pulp cleaning and bleaching and 5) heat and

power generation. The process models of these sections were developed using ASPEN

Plus Process Simulator (V7.3 Aspen Technology) based on the experimental data. The

storage, utilities and wastewater treatment, were scaled based on the NREL model (30).

The mass and energy balances for the main streams are presented in table S12.

The second step is the heat integration to optimize energy use using Aspen Energy

Analyzer (V7.3 Aspen Technology). Our process has heating requirements (536.1 MW)

mainly due to the evaporation of water after the lignin precipitation and the evaporation

of GVL during the GVL-recovery step. After heat integration, we obtained significant

energy recovery, thereby reducing the heating requirements of the process to 40.5 MW

(table S13). The remaining heating requirements are satisfied by the heat generated from

the combustion of the biomass residues (lignin and humins) along with natural gas. In

addition to thermal fluid heating, hot combustion gases are also used to produce

superheated steam for power generation, which meets electricity requirements of the

process (14.6 MW). The cooling requirements of the process are estimated to be 81.4

MW after the heat integration. The remaining cooling requirements are satisfied by using

cooling water.

The third step we performed was the equipment sizing and cost analysis using Aspen

Process Economic Analyzer (V7.3 Aspen Technology) based on the simulation results.

The capital and operating costs of the wastewater treatment, storage, and utilities sections

were scaled based on the NREL model (30). Table S14 shows the capital costs and

operating costs for all processing sections. Total project investment is estimated to be

$539.4 million. The total operating costs is $130.2 million.

fig. S1. Fractionation of white birch. 20 wt% biomass loading, 125°C, 3h 70/30

GVL/water by weight, 0.1 M sulfuric acid. The soluble products were analyzed after

treating the sample at 120°C for 1 h in 4.4 wt% aqueous sulfuric acid as indicated by

NREL (NREL/TP-510-42618). XMGA stands for the combination of xylose, mannose,

galactose, and arabinose monomers; LA for levulinic acid and HMF for 5-

hydroxymethylfurfural.

fig. S2. Lignin produced from white birch fractionation. 20 wt% biomass loading,

125°C, 3 h, 70/30 GVL/water by weight, 0.1 M sulfuric acid. The lignin was precipitated

by adding water at a water/GVL ratio = 3 and separated by centrifugation.

Fresh GVL/water Reutilization 1 Reutilization 4 0

10

20

30

40

50

60

70

80

90

100

Yie

ld (

%)

XMGA Furfural Glucose LA+HMF

fig. S3. Lignin produced from white birch fractionation. 20 wt% biomass loading,

125°C, 3 h, 70/30 GVL/water by weight, 0.1 M sulfuric acid. The lignin was precipitated

by adding water at a water/GVL ratio = 8 and separated by centrifugation.

fig. S4. Thermal decomposition of lignin samples produced from white birch

fractionation at 70:30 GVL/water, 125°C, 3 hours, and 0.1 M sulfuric acid and 80:20

GVL/water, 130°C, 1 hour, and 0.1 M sulfuric acid.

Temperature (°C)

200 400 600 800

Weig

ht

(%)

20

40

60

80

100

Deri

vati

ve w

eig

ht

loss (

%/m

in)

-6

-5

-4

-3

-2

-1

0

80/20 GVL/water

70/30 GVL/water

fig. S5. Aromatic (left) and side chain (right) region of the 13C-1H (HSQC) spectra of white

birch, lignin samples produced from white birch fractionated at 70:30 GVL/water, 125°C,

3 hours, and 0.1 M sulfuric acid and 80:20 GVL/water, 130°C, 1 hour, and 0.1 M sulfuric

acid. (A) β–O–4ʹ aryl ether linkages; (B) phenylcoumaran; (C) resinol; (D) spirodienone; (E)

dibenzodioxocine; (OMe) methoxyl groups; (S) syringyl; (G) guaiacyl; (Sox) α-oxidized syringyl;

(Gox) α-oxidized guaiacyl; (H) p-hydroxyphenyl.

OMe

Aα

Cα Polysaccharides

Polysaccharide

anomeric region

S2,6

S

(ox)2,6

G2

G5

G6

Aγ

Pyridine

Pyridine Whole biomass

S

2,6

S(ox)2,6

G2

G5

G6

G(ox)2

H2,6

OMe

Aγ

Cγ C

γ

Aα

Aβ

Dα E

α (?)

Bα C

α

S2,6

S2,6

S(ox)2,6

S(ox)2,6

G(ox)2

G(ox)2

G2

G2 G

5

G5

G6

G6

H2,6

OMe

OMe

Aγ

Aγ

Cγ C

γ

Cγ C

γ

Aα

Aα

Aβ

Aβ

Cα

Cα

Dα

Dα

Bα

Bα

80/20 GVL/Water (GB_WB_Cent._L1)

70/30 GVL/Water

80/20 GVL/Water (second batch)

H2,6

fig. S6. X-ray diffraction patterns of carbonized and passivated GVL lignin

compared to the original lignin (top). Thermal treatments show the evolution of lignin

to form graphene sheets at 1000°C to graphitic content after passivation. The original

lignin was produced from white birch fractionation at 70/30 GVL/Water, 125°C, 3 h, 0.1

M sulfuric acid.

fig. S7. Carbon foam produced from lignin (initial white birch fractionation

conditions: 80:20 GVL/water, 130°C, 1 hour, and 0.1 M sulfuric acid).

fig. S8. Production of furfural in a batch reactor using 10 wt % xylose as feedstock.

Reaction temperature: 170°C. (■) 0.05 M HCl, (▲) 0.05 M H2SO4, (●) 0.05 M H2SO4 +

0.25 M KCl.

fig. S9. Production of furfural in a continuous flow reactor using xylose as feedstock.

Reaction temperature: 225°C. (■) 0.05 M HCl, 2 wt% xylose; (●) 0.05 M H2SO4, 2 wt%

xylose; (▲) 0.05 M H2SO4, 10 wt% xylose.

0 5 10 15 20 25 30 35 40 45 50 55 60 650

10

20

30

40

50

60

70

80

90

100

0.05 M HCl 0.05 M SA 0.05 M SA + 0.25 M KCl

Furf

ura

l yie

ld (

%)

Reaction time (min)

0 20 40 60 80 100 120 1400

10

20

30

40

50

60

70

80

90

100

Furf

ura

l yie

ld (

mo

lar

%)

Reaction time (seconds)

fig. S10. Gas chromatography–mass spectrometry (GC-MS) chromatogram of GVL

(top), tetrahydrofuran (THF) (middle), and ethanol (bottom) after 12 hours at

130°C

fig. S11. GC-MS chromatogram of GVL (top), THF (middle), and ethanol (bottom)

after 12 hours at 130°C. Solvent/water mass ratio 80/20. Catalyst: 0.1 M sulfuric acid.

Acetic acid concentration 5 wt%.

table S1. White birch fractionation optimization. Effect of process conditions on solid

yield, purity and degree of polymerization.

Entry T

(°C)

GVL/

Water

ratio

Reaction

time

(h)

Liquid/

Solid

ratio

Yield

(wt%)

Hexosan

(wt%)

Pentosan

(wt%)

Kappa #/

Lignin+ash

(wt%)

Degree of

polymerization

1* 125 70/30 2 4 46.3 88.1 6.8 26.4/4.8 421

2* 125 70/30 3 4 44.1 90.6 4.8 17.5/2.5 1178

3* 125 80/20 2 4 44.3 20.9 540

4* 125 80/20 3 4 42.8 89.8 5.6 20.4/3.1 763

5† 125 80/20 3 4 35.3 33.5 1354

6† 125 80/20 3 4 33.5 43.8 1343

7* 125 90/10 3 4 41.8 25.3 642

8* 125 95/5 3 4 37.8 38.5 294

9* 130 80/20 2 4 41.7 88.3 4.6 11.3/1.7 447

10* 130 80/20 3 4 41.9 14.8 562

11* 140 80/20 2 4 35.7 94.5 1.3 19.1/2.9 139

12* 150 80/20 2 4 30.4 93.6 0.7 23.3/3.5 <100

13† 125 70/30 3 6 37.6 26.2 1152

14† 125 80/20 3 6 40.9 47.4 1732

* chipped, † wood chips. Initial composition of white birch (dry weight): hexosan = 43.5 wt%, pentosan =

23.9 wt%, lignin+ash = 22.0 wt%

table S2. Properties of bleached high-purity cellulose sample from white birch wood

chips to produce dissolving pulp.

Pulp Property

Alpha Cellulose

(Tappi 203) 91.2%

Hemicellulose

(Tappi 203) 3.9%

Pentosans

(NREL/TP-510-

42618)

3.1%

Acid Insoluble n/d or zero

Ash n/d or zero

Viscosity

(Tappi T230) 15.08 ± 0.08 cps

Brightness

(%ISO) 90

Kappa number n/d or zero

n/d = not detected

table S3. Lignin solubility in GVL/water mixtures at room temperature.

GVL/water ratio

(0.15 M sulfuric acid) Lignin solubility (wt%)

80/20 9.8

60/40 14.3

table S4. Effect of water/GVL ratio on lignin precipitation.

Water/GVL mass ratio Amount of soluble lignin

precipitated (wt%)

GVL retained in the

lignin (wt%)

0.5 No precipitation

1 No precipitation

1.5 50 20

3 79 20

6 82 15

8 80 12

14 80 8

table S5. Chemical composition and molecular weight of lignin samples.

Fractionation conditions 70/30 GVL/Water,

125°C, 3h, 0.1 M SA

80/20 GVL/water,

130°C, 1h, 0.1 M SA

Lignin purity (wt%) 96.6 96.2

Acid soluble lignin (wt%) 1.3 1.5

Acid insoluble lignin

(wt%) 95.3 94.7

Cellulose (wt%) < 0.05 0.7

Hemicellulose (wt%) 0.5 0.4

Ash (wt%) 0.2 0.01

GVL (wt%) 0.9 0.3

Mn (g/mol) 1144 970

Mw (g/mol) 7212 8431

PDI 6.3 8.7

Carbon (%) 64.1 −

Hydrogen (%) 6.16 −

Nitrogen (%) 0.18 −

table S6. Thermal properties of lignin samples.

Fractionation

conditions

70/30 GVL/Water, 125°C,

3h, 0.1 M SA

80/20 GVL/water, 130°C,

1h, 0.1 M SA

Tg (°C) 148 144

Delta Cp (J/g °C) 0.43 0.32

DTG peak temperature

(°C) 377 375

DTG Peak value

(%/min) −5.54 −5.77

Mass at 200°C (%) 98.1 97.5

Temperature at 5%

mass loss (°C) 270 261

Temperature at 10%

mass loss (°C) 308 304

Char (%) 34.5 34.9

table S7. Summary of NMR analysis of lignin samples.

S/G Sox/S

Lignin interunit linkages* (%)

A (β-O-4') B (β-5') C (β-β') D (β-1')

70/30 GVL/Water, 125°C,

3 h, 0.1 M SA 6.24 0.08 47.6 8.10 36.6 7.65

80/20 GVL/Water, 130°C,

1 h, 0.1 M SA 5.20 0.13 47.6 8.35 34.8 9.29

* Percentage of total interunit linkages involved.

table S8. Hydroxyl group content of lignin sample (70:30 GVL/water, 125°C, 3

hours, and 0.1 M sulfuric acid) obtained by quantitative 31P NMR spectroscopy

(mmol/g).

Carboxylic

acid OH

(COOH)

Phenolic OH Total

phenolic

OH

Aliphatic

OH p-

Hydroxyphenyl

C5

Substituted Guaiacyl Syringyl

0.14 0.02 0.30 0.44 1.85 2.61 2.48

table S9. Liquid composition after 12 hours at 130°C. Solvent/water mass ratio 80/20.

Catalyst 0.1 M sulfuric acid.

GVL THF Ethanol

Solvent 99.40 ± 0.08 % 97.98 ± 1.15% 95.12 ± 1.00%

Pentenoic acid 0.03 ± 0.0077%

4-Hydroxy pentanoic acid

+ Levulinic acid 0.27 ±0.013 %

Butanediol

1.49 ± 0.07%

Other products 0.31 ± 0.26% 0.53 ± 1.08% 4.88 ± 1.00%

table S10. Liquid composition after 12 hours at 130°C. Solvent/water mass ratio

80/20. Catalyst: 0.1 M sulfuric acid, 5 wt% acetic acid.

5% Acetic Acid GVL THF Ethanol

Solvent 99.16 ± 0.51% 91.40 ± 0.56% 93.18 ± 0.43%

Pentenoic acid 0.04 ± 0.0140%

4-Hydroxy pentanoic acid

+ levulinic acid 0.35 ± 0.019%

Butanediol

1.48 ± 0.08%

Other products 0.46 ± 0.48%

Esters + Others

7.12 ± 0.49%

Ethyl Acetate

10.34 ± 1.80%

table S11. List of economic parameters and assumptions.

White birch price ($ per ton)* 125.0

Sulfuric acid ($ per ton) (30) 22.6

Gamma-valerolactone price ($ per ton)* 1000.0

Sodium Chloride price ($ per ton) (43) 182.0

Disposal of ash cost ($ per ton) (30) 35.4

Boiler chemicals ($ per ton) (30) 1260.4

Flue gas desulfurization lime ($ per ton) (30) 50.3

Wastewater treatment nutrients ($ per ton) (9) 7953.4

Dissolving pulp price ($ per ton)* 700.0

Lignin price ($ per ton)* 500.0

Furfural price ($ per ton)* 1000.0

Natural gas price ($ per ton) (36) 239.0

Cooling tower chemicals ($ per ton) (30) 755.4

Internal rate of return (%)* 30.0

Tax rate (%)(30) 35.0

Depreciation period (years) (30) 7.0

Assumptions:

Capital investment is spread over 3 years at a rate of 8%,

60%, and 32% in the first, second, and third years,

respectively.

Working capital is 5% of fixed capital investment.

Capital charge factor, calculated by discounted cash flow

analysis, is 0.364.

* Value provided by Glucan Biorenewables LLC

table S12. Mass and energy balances (basis: 2000 tons of white birch per day).

Major Process Step Stream

Number

Mass Flow

(ton/h)

Pressure

(atm)

Temp.

(°C)

Energy

Requirement

(MW)

Biomass

fractionation 1 292.4 3.4 125.0

Electricity:

0.02

2 292.4 3.4 125.0

3 92.7 3.4 144.8

4 54.1 1.0 153.6

22 2.0 1.0 25.0

23 163.5 3.4 125.0

Lignin separation 8 199.0 3.4 125.0

Cooling: 34.9

Electricity:

14.5

9 17.0 4.5 149.8

10 13.0 3.4 140.7

11 1009.8 4.5 149.8

13 843.6 3.4 138.8

Furfural production 12 166.2 4.5 149.8 Heating: 40.5

Cooling: 46.4

Electricity: 0.1

16 166.8 20.4 225.0

18 11.5 1.2 167.7

20 107.4 1.0 210.1

Pulp

cleaning/bleaching 7 33.5 1.0 194.7

Heat and power

gen. 19 10.5 1.0 208.0

21 9.3 1.0 194.7

table S13. Energy requirements before and after heat integration (basis: 2000 tons

of white birch per day).

Energy required (MW) Before After

Heating 536.1 40.5

Cooling 576.9 81.4

table S14. Capital and operating costs (basis: 2000 tons of white birch per day).

Process step Capital cost (MM$) Operating cost

(MM$/yr)

Biomass Fractionation *, † 163.0 98.1

Furfural Production *, † 28.6 2.4

Lignin Separation *, † 155.7 0.4

Pulp Cleaning/Bleaching ‡ 39.0 9.4

Wastewater Treatment * 34.2 0.7

Storage * 14.2 0.0

Heat and Power Generation * 95.9 4.3

Utilities * 8.9 0.0

Fixed cost * 14.9

Total installed equipment

cost 284.4

Total capital investment 539.4

Total operating cost 130.2

Operating cost of each process step includes raw material cost (e.g., sulfuric acid,

natural gas), cooling utility cost (i.e., cooling water), waste disposal cost (e.g., ash

disposal), and fixed cost (e.g., salaries, property insurance).

*Estimated based on value reported in Davis et al. (30)

† Determined using Aspen Process Economic Analyzer (V8.8 Aspen

Technology).

‡ Estimated based on value obtained from Troy Runge (2016).

table S15. Process model development details.

Process step Equipment Design basis

Biomass

Fractionation

Biomass

Fractionation

Reactor

Experimental Results (Section 1 in SM). 20 wt% biomass

loading, 70/30 GVL/water 0.1 M SA. 3h at 125°C.

Biomass composition: C6 carbohydrate (45 wt%), C5

carbohydrate (25.3 wt%), lignin (21.7%) and others (8

wt%). Fractionation results using recycled GVL (see

Section 2 in SM): C6 carbohydrate yield (5.8%), C5

carbohydrate yield (80.1%), furfural yield (10.8%),

levulinic acid yield (0.8%), HMF yield (0.2%). Acetic

acid yield: 6.08 kg /100 kg of biomass. Formic acid

yield: 1.9 kg/ 100 kg of biomass. Model assumes 30 wt%

biomass loading.

Liquid/Solid

Separator

Washing based on experimental Results (Section 2 in

SM). Solid cake assumes: 40% solids/60% moisture.

Overall product recovery in this step is 95%

Furfural

Production

Furfural Reactor Experimental Results (Section 8 in SM). Furfural yield:

90%. Obtained at 225°C, 30 second residence time using

C5 sugars obtained from the biomass fractionation after

precipitating the lignin and concentrating the solution.

Furfural yield without removing the lignin was 86%.

Furfural

Distillation

The technoeconomic analysis has used Aspen Plus

database to design the distillation. We have distilled

furfural in the lab to >99% purity.

GVL Recovery Aspen Plus database (99% GVL recovery based on

simulated distillation). Lab experiments indicate GVL

stability >99.5%).

Lignin

Recovery

Lignin

Precipitation

Experimental Results (Section 4 in SM). 8 kg-of-

water/kg-of-GVL. 80% of lignin precipitated.

Concentrator Aspen Plus database.

Lignin Washing Experimental Results (Section 5 in SM). The lignin

contains 11 wt% GVL before washing and 0.8 wt% after

the washing step. 2 kg of water per kg of lignin were

used to wash the lignin.

Pulp

Cleaning

/Bleaching

Cellulose

Washing

Experimental Results (Section 2-3 in SM). After

evaporating the GVL, the cellulose contains 3wt% GVL.

Pulp Bleaching Experimental Results (Section 3 in SM).