Revealing the chemistry of biomass pyrolysis by means of tunable synchrotron photoionisation-mass spectrometry

Article abstract of DOI:10.1039/c3ra40486b

Imaging biomass conversion: pyrolysis is the first reaction involved in all thermal processes for biofuels and green chemicals production. Synchrotron light ionisation and mass spectrometry is used for the first time to investigate biomass pyrolysis. The soft and tunable ionisation source coupled with ab initio calculations reveals chemical mechanisms and new major intermediate species. This methodology could be extended to the thermal and catalytic conversion of all other materials. Primary volatile products are analysed online as a function of photon energy, biomass composition (cellulose, xylan, lignin), reactor temperature and time of conversion. Hydroxyacetaldehyde was detected at very minor yields for cellulose pyrolysis confirming that it is a secondary product. The effect of cellulose structure and ash content on primary tar formation was also studied. The mechanism of levoglucosan dissociative photoionisation is depicted. A new major intermediate product which could be a precursor of furanone-based species from cellulose is evidenced thanks to the soft ionisation and MSMS structural analysis of ions. Different lignin markers and evolutions upon time of conversion are shown for miscanthus and oak pyrolysis.

Full text of DOI:10.1039/c3ra40486b

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Revealing the chemistry of biomass pyrolysis by means
of tunable synchrotron photoionisation-mass
spectrometry3
Cite this: RSC Advances, 2013, 3,
4786
Anthony Dufour,*a Junjie Weng,b Liangyuan Jia,b Xiaofeng Tang,b Baptiste Sirjean,a
a
a
c
a
a
´
´
Rene Fournet, Herve Le Gall, Nicolas Brosse, Francis Billaud, Guillain Mauviel
and Fei Qi*b
‘‘Imaging’’ biomass conversion: pyrolysis is the first reaction involved in all thermal processes for biofuels
and green chemicals production. Synchrotron light ionisation and mass spectrometry is used for the first
time to investigate biomass pyrolysis. The soft and tunable ionisation source coupled with ab initio
calculations reveals chemical mechanisms and new major intermediate species. This methodology could be
extended to the thermal and catalytic conversion of all other materials. Primary volatile products are
analysed online as a function of photon energy, biomass composition (cellulose, xylan, lignin), reactor
temperature and time of conversion. Hydroxyacetaldehyde was detected at very minor yields for cellulose
pyrolysis confirming that it is a secondary product. The effect of cellulose structure and ash content on
primary tar formation was also studied. The mechanism of levoglucosan dissociative photoionisation is
depicted. A new major intermediate product which could be a precursor of furanone-based species from
cellulose is evidenced thanks to the soft ionisation and MSMS structural analysis of ions. Different lignin
markers and evolutions upon time of conversion are shown for miscanthus and oak pyrolysis.
Received 5th November 2012,
Accepted 29th January 2013
DOI: 10.1039/c3ra40486b
www.rsc.org/advances
sis4 and (iii) in situ spectroscopic analysis.5 One of the main
issues is to sample and analyse reactive volatiles with a well
Introduction
Ligno-cellulosic biomass such as wood and agricultural wastes
offers an important potential for a sustainable development.1
Its thermo-chemical conversion could be an attractive route
for the production of biofuels and value-added chemicals.2
The main issue for these processes is to optimize the
conversion of lignocellulosic feedstocks of low energy density
into more suitable liquids or gas by gasification or liquefac-
tion. The first and main reaction in all the processes is
pyrolysis. Consequently, it is of high importance to better
understand and optimize the selectivity of pyrolysis.
known thermal history. This could be achieved by Molecular
Beam Mass Spectrometry (MBMS).4a,d This approach is
complementary to other techniques with condensation of
products followed by chemical analysis such as GC-MS, LC-MS
(etc.). The main drawback of MBMS is the difficulty to be
quantitative. The intensity of ions peaks depends on sampling
conditions (as design of the sampling train), ionisation
method, conditions of ions transfers and detections. But this
disadvantage is in part offset by the ability to sample directly
the volatile species from their reactive environment. Indeed,
condensation of volatiles followed by liquid evaporation in a
GC injector could affect the composition of pyrolysis products.
Mass spectra from MBMS give a ‘‘fingerprint’’ of volatiles
composition. The ionisation method should be as soft as
possible to obtain more easily interpretable mass spectra with
few or no fragment ions.4a,6 Extensive works have been
conducted by using vacuum ultra violet (VUV) single photo
ionisation (SPI) to reduce fragmentation.7 Synchrotron light
offers a unique accurate, soft and tunable VUV-SPI source.8
Synchrotron VUV-SPI has been yet only used to study the
ionisation and fragmentation mechanisms of biomass model
compounds, i.e. sugars9 and methoxyl-phenols.10
Pyrolysis of biomass has been extensively studied mainly by
(i) thermo-gravimetric analysis,3 (ii) mass spectrometry analy-
aReactions and Processes Engineering Laboratory, CNRS, Lorraine University, ENSIC,
1 rue Grandville, B.P.20451, 54000 Nancy Cedex, France.
E-mail: anthony.dufour@ensic.inpl-nancy.fr
bNational Synchrotron Radiation Laboratory, University of Science and Technology of
China, Hefei, Anhui 230029, P. R. China. E-mail: fqi@ustc.edu.cn
cLERMAB, Lorraine University, B.P.239, 54506 Vandoeuvre les Nancy Cedex, France
Electronic supplementary information (ESI) available: 1. Mass spectra for
3
miscanthus, xylan and lignin pyrolysis. 2. MSMS analysis of key ions. 3.
Ionisation thresholds of some lignin markers and effect of photon energies on
peak areas for lignin ions. 4. Table with the main identified species ranked by
elemental formula. 5. Cartesian coordinates of the optimised geometry of
levoglucosan and m/z = 128 (5-methyl-4-oxotetrahydrofuran-2-carbaldehyde). See
DOI: 10.1039/c3ra40486b
To the best of our knowledge, we report the first use of
synchrotron VUV-SPI to ionise volatile products from biomass
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Fig. 2 Mass spectrum of volatile products from the pyrolysis of cellulose
extracted from miscanthus (350 uC).
Fig. 1 Mass spectrum of the volatile products from microcrystalline cellulose
pyrolysis with a photon energy set at 9 eV and pyrolysis reactor at 350 uC.
It is known that cellulose can be thermally converted
through two main pathways: (i) transglycosylation producing
mainly levoglucosan and (ii) glycosidic rupture producing
mainly 5-hydroxy-methylfurfural (HMFU).12 The relative
importance of these two pathways depends on cellulose
structure13 and mineral content.14 A mass spectrum obtained
with cellulose extracted from Miscanthus is shown in Fig. 2.
The experimental procedure for cellulose extraction was
previously presented in ref. 5a. The main product from
Miscanthus cellulose is HMFU (m/z = 126) with very few
products from transglycosylation (m/z 162, 144, 98, etc.). One
can notice the very simple mass spectrum for Miscanthus
cellulose due to the soft and accurate ionisation. Lighter
species analysed in other works4a,7c,15 for cellulose pyrolysis
could be produced by secondary reactions (during pyrolysis or
sampling and analysis) of the labile primary volatiles.6,16
pyrolysis. Ions are analysed by a triple quadrupole time-of-
flight MS (QTOF-MS). Experimental results are supported by ab
initio calculations. First, minimum ionisation thresholds and
fragmentation mechanisms of key cellulose tars (such as
levoglucosan) are presented. Second, the molecular structure
of a possible new intermediate compound during cellulose
pyrolysis is evidenced. Third, the evolution during biomass
pyrolysis of ‘‘markers’’ from lignin, xylan and cellulose is
studied.
Results and discussion
Main primary products from two different celluloses
Experiments were conducted on different biomass samples
(see experimental section) and as a function of photon energy
from 8.5 to 12 eV. An example mass spectrum obtained for
microcrystalline cellulose pyrolysis is displayed in Fig. 1.
Some major species from cellulose pyrolysis are given in
Table 1 with their zero-point corrected adiabatic ionization
energy, computed at the CBS-QB3 level of theory.11 The
estimated uncertainty for these calculations is close to 0.06
eV (1.5 kcal mol21).
Pyrolysis of miscanthus (mass spectrum given in ESI ) also
3
shows very few transglycosylation products [consistent with
ref. 4a] and the same marker (HMFU) as the extracted
cellulose. On the contrary, more levoglucosan parent ions
were analysed for oak pyrolysis (not shown). m/z = 60
(hydroxyacetaldehyde-HAA, Table 1) was always detected at
very minor yields confirming that HAA is a secondary
product.15
Table 1 Molecular structure and adiabatic ionization threshold of some major cellulose primary tars calculated from the CBS-QB3 method
Molecular structure
Name
Molar mass (g mol21
60.05
)
Adiabatic ionization threshold (eV)
9.88
Hydroxyacetaldehyde
Furfural
96.08
9.19
8.76
5-Hydroxymethyl-furfural (HMFU)
126.11
1,4: 3,6-Dianhydro-glucopyranose
144.13
162.14
9.02
8.86
Levoglucosan (LVG) or 1,6-anhydro-b-D-glucopyranose
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Fig. 4 Structural differences between neutral and cation levoglucosan. CBS-QB3
level of theory (B3LYP/6-311G(d,p) geometries).
Fig. 3 Evolution of peak areas of some major ions from microcrystalline cellulose
as a function of photon energy (8.5 to 10 eV).
levoglucosan, we explored the water elimination mechanism
of ionized levoglucosan at the CBS-QB3 level of theory.11
Stationary points of the potential energy surface (PES) of the
cation were optimized and shed a new light on a possible
water elimination route. The PES presented in Fig. 5 shows
that water elimination in ionized levoglucosan can occur in
three steps.
The ring opening of the levoglucosan cation (noted 1 in
Fig. 5) is expected to be easy upon ionization, with a saddle
point computed to lie 0.07 eV above the calculated ionization
energy. The opening of the ring leads to the formation of
cation 2 which is more stable than the levoglucosan cation by
0.08 eV. While simulations of a-pyranose water elimination by
Ghosh et al., showed that H2O can be eliminated directly from
the opened structure, our calculations indicate that an
additional step is needed in the case of the levoglucosan
cation before the water elimination step. From cation 2, the
transfer of the OH group (O(4)H(15) in Fig. 4) to carbon C(3)
yielding cation 3 is found to be a necessary rearrangement in
our calculation. From cation 3, the transition state for water
elimination, yielding cation 4 (with m/z = 144) and neutral
water, is computed to lie 1.34 eV above the ionization energy
threshold. The OH-group transfer in cation 2 leads to a
structure which is similar to that of the opened a-pyranose
Effect of ionisation energy on cellulose primary products
ionisation and the mechanism of levoglucosan dissociative
photoionisation
More low molecular weight ions (mainly m/z 57, 60, 73, 98, etc.)
than in Fig. 1 were analysed for cellulose pyrolysis in ref. 4a,7c
due to higher ionisation energy (IE) and fragmentation.4a,16
Fig. 3 shows the evolution of peak areas of some key ions as a
function of photon energy.
Major cellulose primary tar exhibits an experimental
ionisation onset at a lower photon energy than the theoretical
adiabatic threshold (Table 1). The species produced from
biomass pyrolysis and ionised after the first skimmer would
harbor internal energy and thus would have a lower IE.10,17
The increase of the peak area of ions (but not m/z 162) from 8.5
to 10 eV is due to a better ionisation combined with a
fragmentation of higher m/z ions (especially m/z 162 and 144)
into lighter species.
Levoglucosan is one of the main products from microcrystal-
line cellulose pyrolysis12 but the signal of m/z 162 is weak even
at low photon energy (Fig. 1 and 3). It can be explained by a
dissociative photoionisation of levoglucosan ions but not from
secondary thermal conversion. Indeed pyrolysis was con-
ducted under low pressure (2.8 Torr) hence minimizing gas-
phase residence time and secondary thermal reactions.
Moreover, levoglucosan conversion is slow at 350 uC.18 The
low intensity of the levoglucosan parent ion (m/z 162) close to
threshold is consistent with what occurs for a-pyranose.9 Upon
ionisation, even at threshold, a fragmentation of m/z 162 into
144 (water elimination) occurs, followed by a subsequent
fragmentation of m/z 144 into 126, 97, 98 ions (etc.). An
increase of the C(3)–C(9) bond length from the levoglucosan
molecule to the cation is evidenced by ab initio calculation
(Fig. 4). The same observation was found for a-pyranose with
DFT calculations.9 Water elimination is the dominant frag-
mentation channel for both compounds.
Ab initio molecular dynamics simulations performed by
Ghosh et al.9 showed that water elimination upon ionization of
a-pyranose occurs via the opening of the ring, followed by a
rearrangement of the opened structure through internal
rotations that further favors the elimination of water. Since
significant structural differences exist between a-pyranose and
Fig. 5 Potential energy surface of water elimination in ionized levoglucosan.
Energy at 0 K calculated at the CBS-QB3 level of theory.
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cation observed by Ghosh et al. In these structures, OH-groups
linked to C(3) and C(2) are separated by one carbon atom, i.e.,
water elimination occurs through a 6-membered ring. The
water elimination step is computed with an energy barrier of
10.20 eV relative to neutral levoglucosan. Note that using the
less accurate energy values computed with DFT at the B3LYP/6-
311G(d,p) level of calculation, an energy barrier of 9.2 eV is
computed for the water elimination. This value is close to that
proposed by Ghosh et al. (9.8 eV), using DFT, for the same
process in a-pyranose. The overall bottleneck of the PES is the
transition state for OH-group transfer that lies 1.69 eV above
ionized levoglucosan. Dynamic effects should be taken into
account to firmly conclude on the feasibility of the mechanism
proposed in Fig. 5 and on the fate of cation 4. However, this
kind of study remains beyond the scope of this work.
Fig. 7 Evolution of some typical markers for lignin, xylan and cellulose during
miscanthus pyrolysis as a function of time (from biomass introduction in the
preheated reactor at 550 uC, 10.5 eV photon energy). TIC (Total Ion Current).
A potential new intermediate from cellulose pyrolysis is
evidenced
To the best of our knowledge, the m/z 128 compound
evidenced in Fig. 1 has not been previously reported4a,7c
maybe because the ionisation energy was too high4a,7c,16 or
this species is very thermally unstable and is favoured by the
low vacuum. We noticed a reduction in the signal of m/z 128
from 10 eV compared to 9.5 eV. It could be a new intermediate
species (or primary product) from cellulose pyrolysis. The
aforementioned mechanism of levoglucosan fragmentation
excludes its formation from levoglucosan photoionisation.
The proposed structure for m/z 128 (5-methyl-4-oxotetrahy-
drofuran-2-carbaldehyde or position isomers, Fig. 6) is
chemistry of biomass pyrolysis4a,d,21 and to monitor pro-
cesses.22 Fig. 7 displays the evolution of the main markers of
cellulose, xylan and lignin as a function of time. The time scale
starts from the biomass injection time in the preheated
furnace.
Lignin is the first polymer in the native miscanthus which
produces volatile products (Fig. 7). This finding is consistent
with thermogravimetric analysis.5a Light gases are also
produced from lignin at higher temperature after cellulose
degradation.23 In miscanthus, cellulose is the most stable
polymer. The structure of the xylan marker (m/z = 114) is
deduced from the MSMS spectra (in ESI ). Some other m/z
3
deduced from MSMS analysis (see ESI ) in agreement with ref.
3
128 species were detected in ref. 19 but at very minor yields
and with a chemical structure not compatible with the MSMS
spectra. The proposed chemical structure (and position
isomers) could be a precursor of furanone-based species
detected at major yields in ref. 4a, 19, 20 and in this work (see
4a, 20b. m/z = 114 is also produced from cellulose (Fig. 2) but
its main contribution comes from xylan. m/z = 114 has been
also chosen as a xylan marker in other works.4a,d We did not
yet reveal the chemical structure of pure xylan markers
(presented in Fig. S2, ESI ). For miscanthus, the main lignin
3
ESI ). Possible formation pathways from cellulose pyrolysis of
3
markers are the following: 120 (4-vinylphenol), 180 (4-
vinylsyringol), 150 (4-vinyl guaiacol), 210 (sinapyl alcohol)
(etc.). The chemical structures of markers are in close
agreement with extensive 13C NMR and 31P NMR analyses of
the functional groups in miscanthus lignin.5a,24 As usual in
monocotyledonous plants, miscanthus lignin is highly acy-
lated with p-coumaryl and acetyl groups.24 p-coumaryl moi-
eties form 4-vinyl phenol during pyrolysis. The other markers
at m/z 150 and 180 resulted from the deconstruction of lignin-
core units (respectively Guaiacyl and Syringyl units). Markers
(m/z = 150, 4-vinyl guaiacol, m/z = 124, guaiacol) were also
identified for a wheat straw lignin (not shown) consistent with
ref. 22b. A much lower phenol peak (m/z = 94) was observed in
all our experiments probably due to secondary reactions in the
pyrolysis process in ref. 22b.
this potential new intermediate species are beyond the scope
of this paper.
Evolution of cellulose, xylan and lignin markers during
miscanthus and oak pyrolysis
The effect of photon energy and reactor temperature on xylan
and lignins products have been also studied (not shown, MS
spectra given in ESI ). Ionisation thresholds were determined
3
by the CBS-QB3 method for key lignin markers (see ESI ).
3
Markers of polymers (cellulose, xylan, lignins) were selected
and are listed in ESI. Markers are useful to understand the
3
We did not notice a different apparent devolatilisation rate
as a function of time for the different lignin markers in
miscanthus (Fig. 8).
Oppositely, we noticed three groups of lignin markers
during oak pyrolysis (Fig. 9).
The first group of lignin markers involves sinapic aldehyde
(m/z = 208) and syringaldehyde (m/z = 182). It is produced at
the early step of oak conversion. The peak at m/z = 180 is most
Fig. 6 Proposed chemical structure (or position isomers) for m/z = 128, a
potential new intermediate from cellulose pyrolysis. Energy calculation
computed at the CBS-QB3 level of theory.
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Fig. 8 Evolution of some typical lignin markers during miscanthus pyrolysis as a
function of time (from biomass introduction in the preheated reactor at 550 uC,
10.5 eV photon energy).
Fig. 10 Scheme of the set-up including a pyrolysis reactor, a sampling train and
synchrotron VUV photoionisation QTOF-MS.
probably vinylsyringol for oak, even if in hardwood we cannot
exclude totally coniferyl alcohol. It is produced during the
whole conversion time of oak. The third group of markers
involving syringol (m/z = 154) and 4-methylsyringol (m/z = 168)
is produced at the end of oak conversion and even after
cellulose markers (not shown). The same finding was
previously noticed for pine.4a The formation of the third
group of lignin markers becomes significant from a reactor
temperature of 450 uC (Fig. 9a). The evolution of lignin
markers is consistent for miscanthus, oak and with ref. 4a. All
early predominant markers exhibit a double bond on the
aromatic ring functions (Fig. 8 and 9a). The formation of a
double bond function would be easier because of a minimum
need for transferable hydrogen.4a The later group which
reaches its maximum production rate at the end of oak
pyrolysis (m/z 154, 168 in Fig. 9) is formed in a hydrogen-
deficient matrix.4a,5a This matrix can mainly undergo cross-
linking reactions and devolatilisation by hydrogen transfer to
form more stable aromatic species. Further works are needed
to better understand the formation of volatile products in
relation with our in situ 1H NMR analysis of mobile-
transferable hydrogen.5a
Experimental
Pyrolysis set-up
The unique set-up developed in Hefei (USTC, China)25 is
presented in Fig. 10.
It couples:
–a pyrolysis tubular reactor where solid samples are
introduced,
–a sampling train for volatiles (through skimmers),
–an ionisation region by the synchrotron VUV light,
–and the analysis of ions by a triple quadrupole time-of-
flight MS (QTOF-MS).
The QTOF-MS consists of three quadrupoles, Q0, Q1 and Q2,
followed by a reflecting TOF mass analyzer with orthogonal
injection of ions.
Nitrogen was used as a carrier gas to bring the gas phase
products to the Q0 chamber (first quadrupole in the QTOF-MS)
with an optimal flow rate of 10 standard cm3 min21 (SCCM),
which was controlled by
a mass flow controller (MKS
Instruments, Andover, MA, USA). A quartz sample rod of 6
mm diameter was used to introduce about 50 mg of biomass
materials into the middle of the preheated tubular reactor.
Fig. 9 Evolution of some typical lignin markers during oak pyrolysis as a function
of time (from biomass introduction in the preheated reactor, 10.5 eV photon
energy) a) reactor temperature at 450 uC, b) at 550 uC.
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The temperature of the furnace was controlled by a
temperature controller (SKY Technology Development Co.
Ltd., Shenyang, China) and measured with a K-type thermo-
couple.
The gas phase products passed through the first heated
skimmer (200 uC, home made) with 0.5 mm inner diameter
aperture and entered the photoionization region. The design
of the first skimmer is close to the optimized design proposed
in ref. 26. The pressure of the pyrolysis region and
photoionization chamber was 2.8 Torr and 1.8 mTorr
respectively.
growing crop with a high potential for biofuels and chemicals
production.28 These samples were extensively characterized by
elemental and ash analysis, thermogravimetry, XRD (for
cellulose crystallinity), gel permeation chromatography (for
molecular weight distribution of cellulose and lignin), 13C and
31P NMR (for lignin functional groups), in situ 1H NMR (for
mobile protons development) (etc.). The main characteristics
can be found in ref. 5a, 24. The procedures for cellulose and
lignin extraction (by the ethanol organosolv process) from
miscanthus have been optimised to be close to the native
polymers.5a,24
The ions produced by SVUV were guided into the QTOF
mass spectrometer by a repeller plate and the second skimmer
as shown in Fig. 10. In this work, the optimal voltages applied
to the repeller plate and the second skimmer are 50 and 2 V,
respectively. The optimal distance from the outlet of the
furnace to the aperture of the first heated skimmer is 2 mm.
The SVUV light path has a distance of 4 mm away from the
repeller plate and 2 mm from the tip of the second skimmer.
Nitrogen was also used for collisional cooling and focusing
the ions entering the instrument in the Q0 quadrupole. The
optimal flow rate of nitrogen is 150.0 SCCM. It provides both
radial and axial collisional damping of ion motion. The ions
are thermalized in collisions with neutral gas molecules,
reducing both the energy spread and the beam diameter and
resulting in better transmission into and through both the
quadrupole and TOF analyzers. In a word, ion cooling in Q0 is
used for better transmission into the quadrupole, while ion
cooling in Q2 is used for better transmission into TOF. The
other use for collisional Q2 is for MSMS. Q1 is operated in the
mass filter mode to transmit only the parent ion of interest.
The ion is then accelerated to an energy of between 10 and 80
eV before it enters the collision cell Q2, where it undergoes
collision induced dissociation (CID) after the first few
collisions with neutral gas molecules (usually argon or
nitrogen). The resulting fragment ions (in addition to the
remaining parent ions) are collisionally cooled and focused as
described above.
Conclusions
The development of tunable synchrotron photoionisation
mass spectrometry coupled with ab initio calculations is
presented for the first time to study biomass pyrolysis.
Numerous biomass samples at different photon energies and
temperatures were studied. This methodology is a powerful
tool for revealing the chemical mechanism of biomass thermal
conversion and is also of practical interest for selecting
markers and ionisation conditions for on-line monitoring of
thermochemical reactors. Ionisation and consequent fragmen-
tation depend on sampling (skimmer geometry, pressures,
etc.) and ion transfer conditions (repeller tension, etc.). For
cellulose primary products, fragmentation of levoglucosan
cannot be avoided by a photoionisation method. A photon
energy of around 9.5 eV seems to be a trade-off between ions
intensity and fragmentation. For lignin markers, photon
energy should be lower than 10.5 eV to reduce their
fragmentation.
This work could lead to further uses of synchrotron VUV
photoionisation for studying thermal or catalytic conversion of
other solid materials.
The mass spectra were collected at different photon energies
and temperatures. They were accumulated during the whole
pyrolysis experiments or every 10 s for an m/z curve as a
function of time. A background test was performed before
each experiment by measuring a blank sample at the same
condition (injection of an empty rod at the same temperature
and ionisation energy) and subtracted. Background signal was
very low due to the optimized design of the first skimmer that
is heated.
Acknowledgements
Dr F. Battin-Leclerc and Dr P. A Glaude (CNRS, Nancy) are
acknowledged for promoting this study. P. Beaurain, Y.
Niedergand (CNRS, Nancy) are acknowledged for their
technical support.
A part of this work was financially
supported by the ANR french agency through the ‘‘PYRAIM’’
project.
We are aware that devolatilisation rate may be limited by
heat transfer and ions evolutions upon time are not a purely
chemically kinetic pattern. The temperature mentioned in this
paper refers to the one of the pyrolysis reactor but not to the
temperature of biomass decomposition.27
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lose (Sigma Aldrich), xylan from birch (Sigma Aldrich),
cellulose and lignin extracted from miscanthus, miscanthus
(Miscanthus x Giganteus), and oak. Miscanthus is a fast-
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