b i om a s s a n d b i o e n e r g y 3 4 ( 2 0 1 0 ) 1 4 7 1e1 4 8 0

Avai lab le a t www.sc iencedi rec t .com

ht tp : / /www.e lsev ier . com/ loca te /b iombioe

Use of Hesperaloe funifera for the production of paper andextraction of lignin for synthesis and fuel gases

R. Sanchez a, A. Rodrıguez a, E. Navarro a, J.A. Conesa b, L. Jimenez a,*aChemical Engineering Department, Campus of Rabanales, Building C3, University of Cordoba, 14071 Cordoba, SpainbChemical Engineering Department, University of Alicante, Spain

a r t i c l e i n f o

Article history:

Received 27 November 2009

Received in revised form

15 April 2010

Accepted 17 April 2010

Available online 14 May 2010

Keywords:

Hesperaloe funifera

Pulp

Paper

Lignin

Pyrolysis gas

Fuel gas

* Corresponding author. Tel.: þ34 957 21 85 8E-mail address: iq1jiall@uco.es (L. Jimene

0961-9534/$ e see front matter ª 2010 Elsevdoi:10.1016/j.biombioe.2010.04.019

a b s t r a c t

In this work, we characterized Hesperaloe funifera; pulp and paper obtained by subjecting

the plant raw material to soda, sodaeanthraquinone, ethanolamine, ethyleneglycol and

diethyleneglycol cooking. In addition, the solid fractions extracted by acidifying the

cooking liquors, rich in lignin, were used to obtain synthesis and fuel gases.

The contents in lignin, a-cellulose, holocellulose, hemicellulose, ethanolebenzene

extractives, hot water solubles, 1% NaOH solubles and ash of H. funifera were found to be

7.3%, 40.9%, 76.5%, 35.6%, 4.0%, 13.5%, 29.5% and 5.9%, respectively. The mean fibre length,

4.19 mm, exceeds those for some non-wood materials.

Hesperaloe pulp obtained by cooking with 10% NaOH and 1% anthraquinone at 155 �C for

30 min exhibited good values of yield (48.3%), viscosity (737 mL g�1), Kappa number (15.2),

tensile index (83.6 Nm g�1), stretch (3.8%), burst index (7.34 kN g�1) and tear index

(3.20 mNm2 g�1).

Acidification to pH 6 of the liquor resulting from the soda pulping of 500 g of plant raw

material provided an amount of 13.90 g of lignin-rich solids pyrolysis of which gave a gas

mixture containing 1.13% H2, 31.79% CO and 1.86% CH4 by weight. Gasification of the same

sample provided a mixture containing 0.18% H2, 24.50% CO and 17.75% CH4, also by weight.

ª 2010 Elsevier Ltd. All rights reserved.

1. Introduction testifies to the growing significance of the latter as cellulose

The paper industry currently produces more than five

hundred types of paper for over three hundred uses. More

than 30% of the paper types used at present did (e.g., filter,

chromatographic, interleaving, electrotechnical paper) not

even exist only ten years ago and have emerged in response to

new social needs [1]. The increasing variety of paper types and

uses has resulted in a substantial increase in production, from

187 Mt in 2000 to 195 Mt in 2007 (i.e., a 4.3% rise) [2]. Pulp

production from wood species over this period has grown by

3.1%; by contrast, the use of non-wood species for this

purpose has risen much more markedly (18.1%) [2], which

6; fax: þ34 957 21 86 25.z).ier Ltd. All rights reserved

raw materials. This phenomenon can be ascribed to non-

wood plants providing an effective alternative to wood, paper

and cellulose pulp imports for developing countrieswith scant

forest resources; also to the added value acquired by agrifood

residues used for pulping; and also to the special chemical

composition and morphological characteristics of non-wood

raw materials (e.g. their less compact, more porous structure,

more readily accessible tissues and weaker fibrilefibril bonds)

reduce energy requirements and reagent consumption in

cooking and bleaching processes.

A promising non-wood raw material is Hesperaloe funifera.

Although the fibre morphology of H. funifera plants is

.

b i om a s s an d b i o e n e r g y 3 4 ( 2 0 1 0 ) 1 4 7 1e1 4 8 01472

especially suitable for making cellulose pulp [3], little research

in this direction appears to have been conducted. In the few

exceptions, the material was subjected to alkaline sulphite-

eanthraquinone or sodaeanthraquinone pulping [4,5] and the

resulting paper sheets found to have very high tensile, burst

and tear indices e and hence to be highly suitable for making

special paper.

In this work, we characterized H. funifera in physico-

chemical terms and subjected it to soda and organosolv

processes in order to obtain paper pulp, taking advantage of

the lignin simultaneously to obtain synthesis gas or combus-

tible gases.

Soda and sodaeanthraquinone processes have been used

to pulp non-wood raw materials with good results [6e8].

These processes have some advantages such as the following:

a high production resulting from the use of relatively short

pulping times; good yields; applicability to both wood and

non-wood raw materials; reusability of the cooking liquors;

and increased yields, more expeditious cooking and reduced

Kappa numbers by effect of the joint use of soda and

anthraquinone.

Organosolv processes have been widely used at the labo-

ratory scale [9,10] and applied to various alternative raw

materials including Cynara cardunculus, wheat straw,

Paulownia fortunei, vine shoots, cotton stalks, Leucaena leuco-

cephala and Chamaecytisus proliferus [11e15]. The most salient

advantages of these processes are as follows: economy at the

small and medium scale, and efficient recovery of solvents

and by-products, in relation to kraft processes; reduced water,

energy and reagent consumption; reduced pollution and easy

recovery of bleaching effluents; applicability towood and non-

wood raw materials; production of pulp with properties on

a par with those of kraft pulp in addition to higher yields,

lower lignin contents, higher brightness, and easier bleaching

and refining; and the need for no additional investments if

kraft pulping facilities are available as it suffices to use high-

boiling solvents (glycols, ethanolamines) to exploit them.

Interest in exploiting plant rawmaterials in full rather than

specific fractions such as those used to obtain cellulose for

papermaking purposes has grown considerably in recent

years. In fact, researchers have sought methods to addition-

ally obtain hemicellulose and lignin, which are usually burnt

instead. This has led to the development of biorefining, which

is concerned with the separation of plant components (lignin,

hemicellulose and cellulose, mainly) with a view to obtain

various products from them [16e21].

Hydrolysing polysaccharides in plant raw materials with

water at a high temperature provide a liquid fraction con-

taining oligomers [13,22e26] which can be further hydrolysed

and fermented to obtain food additives or sugar substrates

[27,28]. The fractionation method used causes structural

alterations in some compounds and detracts from quality in

the final pulp; the problem, however, can be overcome by

using an appropriate hydrothermal treatment for the plant

material and improving the strength-related properties of the

pulp by beating [13,23,24].

One other use of biorefining is for isolating lignin from

residual cooking liquor. Lignin removed by organic solvents is

ofamuchhighervalue than ifusedasa fuel in thekraftprocess.

In fact, lignin can be used to obtain phenoleformaldehyde

resins, polyurethanes, acrylates, epoxides and composites

[29e31]. One special use of lignin is for the production of

synthesis by pyrolysis [32e34] or fuel gases by gasification

[35e38].

In this work, we characterized H. funifera in terms of major

components (cellulose, hemicellulose, lignin and extractives),

and also of hot water solubles, 1% NaOH solubles and ash, by

using conventional chemical methods. Following character-

ization, H. funifera samples were subjected to soda, soda-

eanthraquinone, ethyleneglycol, diethyleneglycol,

ethanolamine and diethanolamine pulping, and the resulting

pulp and paper sheets analysed for the usual quality-related

parameters. Finally, the cooking liquors were acidified to

separate solid fractions that were subjected to pyrolysis and

gasification in order to obtain synthesis and fuel gases.

2. Experimental

2.1. H. funifera

H. funifera is a plant of the family Agavaceae up to 80 cm tall

and 1.0e1.2 m wide with long leaves up to 5 cm wide and

2e3 cm thick. All species in its genus originated in Mexico and

its neighbouring USA regions, where it is used mainly for

ornamental purposes. Hesperaloe has very modest irrigation

requirements by effect of its using the acid metabolism of

Crassulaceans (CAM) for photosynthesis. Its plants fix carbon

dioxide and transpire water more strongly at night than

during the day; also, because their coefficient of transpiration

is lower at night, they use water highly efficiently. Based on

these properties,Hesperaloemight be an effective cellulose raw

material in arid zones precluding cultivation of other species

[39] or in areas with scant water resources. The first crop takes

five years to develop in full and the plant gives a new crop

every three years afterwards. High-density plantations

(27,000 stem ha�1) can yield 205 t of fresh biomass per hectare

per crop, which amounts to approximately 20 tons of dry

biomass per hectare, crop and year after the initial crop [4].

These crop yields can be increased by careful control of plant

flowering and the use of higher planting densities [39].

2.2. Raw material characterization

Samples of H. funifera fibre for educational and research

purposes were kindly supplied by the Hesperaloe Project

research team at the University of Arizona. Following drying

at room temperature, the H. funifera was cold ground in

a Retsch SM 2000 mill to avoid alterations in its components.

The ground productwas sieved and the 0.25e0.40mm fraction

(sieves No. 60 and 40 in the Tyler series) saved for analysis. In

fact, particles larger than 0.40mmare inefficiently attacked by

chemical reagents and those smaller than 0.25 mm can

interfere with filtering operations.

The contents in lignin, a-cellulose, ethanolebenzene

extractives, hot water solubles, 1% NaOH solubles and ash of

the raw material were determined in accordance with the

following Tappi standards: T-222, T-203 0S-61, T-204, T-257, T-

212 and T-211. The content in holocellulosewas obtainedwith

the method of Wise [40].

Table

1e

Pulpin

gco

nditionsfrom

Hesperaloefunifera,andpro

pertiesofpulpsandpapersh

eets

from

pulpsobtain

edwithvariousreactive.

Pulp

Reactive

Tem

peratu

re,

� CTim

e,

min

Conce

ntration,

%(o.d)

Yield,

%Kappa

num

ber

Visco

sity,

cLg�1

Beating

grade,SR

Tensile

index,

Nm

g�1

Stretch,

%Burstindex

,kN

g�1

Tearindex

.m

Nm

2g�1

P1

Soda-anth

raquinone

155

30

10

48.3

15.2

73.7

65.1

83.6

3.8

7.34

3.20

P2

Soda-anth

raquinone

170

60

15

41.3

12.5

58.6

62.0

70.7

4.0

5.34

3.22

P3

Soda-anth

raquinone

185

90

20

31.9

7.3

29.6

32.4

23.8

2.2

1.09

1.00

P4

Soda

155

30

10

46.6

20.4

73.0

62.4

83.8

4.4

6.93

3.47

P5

Soda

170

60

15

40.0

13.1

53.2

66.9

68.4

4.4

5.28

3.48

P6

Soda

185

90

20

30.3

7.2

18.3

36.4

34.3

2.7

2.59

1.29

P7

Eth

anolamine

160

30

60

53.8

22.5

74.0

70.6

81.6

3.0

5.41

2.09

P8

Eth

anolamine

170

60

70

52.3

22.3

69.5

60.5

64.3

2.7

5.33

3.11

P9

Eth

anolamine

180

90

80

51.1

27.2

53.1

68.0

59.8

3.6

4.81

3.45

P10

Dieth

anolamine

160

30

60

55.1

20.7

78.8

54.9

79.0

3.0

6.82

3.01

P11

Dieth

anolamine

170

60

70

53.3

20.1

81.4

56.0

73.9

3.3

5.55

3.00

P12

Dieth

anolamine

180

90

80

49.6

20.1

81.1

42.6

63.8

3.7

5.62

5.22

P13

Eth

yleneglyco

l160

30

60

59.6

30.5

73.2

40.0

74.5

2.6

6.09

2.92

P14

Eth

yleneglyco

l170

60

70

46.9

31.9

54.4

52.6

43.4

3.5

0.38

4.37

P15

Eth

yleneglyco

l180

90

80

45.7

35.1

32.3

22.3

13.8

1.6

3.96

0.95

P16

Dieth

yleneglyco

l160

30

60

56.6

29.9

58.5

45.1

79.5

2.8

5.82

2.67

P17

Dieth

yleneglyco

l170

60

70

49.3

29.3

60.8

58.2

47.6

3.3

3.55

2.51

P18

Dieth

yleneglyco

l180

90

80

47.9

34.0

43.4

34.9

18.3

1.8

0.45

0.91

b i om a s s a n d b i o e n e r g y 3 4 ( 2 0 1 0 ) 1 4 7 1e1 4 8 0 1473

The fibre length distribution of H. funifera was determined

by using a Visopan projection microscope.

2.3. Pulping

The raw material was cooked in a 15 L batch reactor that was

heated by means of an outer jacket and stirred by rotating the

vessel via amotor connected through a rotary axle to a control

unit including the required instruments formeasurement and

control of pressure and temperature.

Table 1 shows the temperature, time and concentrations

of reagent (soda, anthraquinone) or solvent (ethyleneglycol,

diethyleneglycol, ethanolamine, diethanolamine) used in

the pulping experiments. The liquid/solid ratio was always

8:1. After each process was completed, cooked material was

unloaded from the reactor, washed with 4 L of water at room

temperature to remove residual cooking liquor and fiberized

in a disintegrator at 1200 rpm for 30 min, which was followed

by beating in a SprouteBauer refiner. Finally, the fiberized

material was passed through a filter of 0.16 mm pore size to

remove uncooked particles.

2.4. Pulp and paper sheets characterization

The pulp samples obtained were characterized in terms of

yield (gravimetrically), and also for Kappa number, viscosity

and beating grade e in a ShoppereRiegler apparatus e

according to the UNE standards 57-034, 57-039 and 57-025,

respectively.

Paper sheets were obtained with an Enjo-F39-71 former

and analysed for tensile index, stretch, burst index, tear index

and brightness in accordance with the following UNE stan-

dards: 57-054, 57-028, 57-08, 57-033 and 57-062.

2.5. Processing of residual liquor

The liquors from the different pulping processes were treated

with sulphuric acid at pH 6, 4 and 2 to obtain various solid

fractions which were then dried at room temperature and

subjected to pyrolysis in a heliumatmosphere and gasification

with a 9:1 mixture of helium and oxygen.

The experimental system [41] consists in a quartz tube,

10 mm wide, where the sample is introduced uniformly

Table 2eChemical composition ofHesperaloe funifera andother raw materials.

Raw material Holocellulose,%

a-cellulose,%

Lignin,%

Hesperaloe funifera 76.5 40.9 7.3

Kenaf 78.9 49.5 15.6

Bagasse 73.9 45.3 21.7

Cotton stalks 72.9 58.5 21.5

Wheat straw 72.2 44.1 18.3

Paulownia fortunei 75.8 43.6 20.5

Sunflower stalks 66.9 37.6 10.8

Empty fruit bunches 84.7 60.6 16.9

Rice straw 60.7 41.2 21.9

Fig. 1 e Hesperaloe funifera fibre size distribution graph and

fibre photograph.

b i om a s s an d b i o e n e r g y 3 4 ( 2 0 1 0 ) 1 4 7 1e1 4 8 01474

occupying an appreciable length of the tube (approx.

350e400 mm). A horizontal actuator (servomechanism that

supplies and transmits a measured amount of energy for the

operation of another mechanism or system) introduces with

a constant linear velocity the tube with the lignocellulosic

material inside a furnace maintained at the desired temper-

ature (850 �C). The operating conditions used for gasification

have been selected among commonly used for similar ligno-

cellulosic material experiments.

The raw gas obtained from lignocellulosic material and

compost gasificationwas analysed by GCeTCD (Shimadzu GC-

14A Gas Chromatograph) and GCeFID (Shimadzu GC-17A).

Furthermore, experiments were performed in a thermoba-

lance with TG-DTA analyzer (Mettler Toledo, model TGA/

SDTA851e/LF/1600) coupled to a mass spectrometer (Pfeiffer

Vacuum,model Thermostar GSD301T) tomonitor the signal of

the volatile compounds evolved. The initial sample weight

was around 5 mg. Dynamic experiments were carried out at

10 K min�1 from 25 to 900 �C.

Table 3 e Properties of pulps and paper sheets obtained using

Abaca Phoenixdactilifera Soda dac

Yield, % 90.7 42.1

Kappa number 10.6 28.9

Viscosity, mL g�1 1428 814

Tensile index, Nm g�1 55.9 37.3

Stretch, % 5.12 e

Burst index, kN g�1 e 1.9

Tear index, mNm2 g�1 19.03 10.7

3. Results and discussion

3.1. Physico-chemical characterization of H. funifera

The contents in lignin, a-cellulose, holocellulose, hemi-

cellulose, ethanolebenzene extractives, hot water solubles,

1% NaOH solubles and ash of H. funiferawere found to be 7.3%,

40.9%, 76.5%, 35.6%, 4.0%, 13.5%, 29.5% and 5.9%, respectively.

Table 2 compares the holocellulose, a-cellulose and lignin

contents of this species with those of other non-wood mate-

rials [12,14,42e46]. As can be seen, H. funifera has the lowest

proportion of lignin and an a-cellulose content similar to

those of the other raw materials except EFB and cotton stalks,

which surpass it in this respect. A low hemicellulose content

can raise the necessary energy to obtain a given tensile

strength level with respect to conifer pulp [47].

Fig. 1 shows the fibre length distribution curve for H. funi-

fera and a photograph of a sample of fibres. The mean fibre

length, 4.19 mm, exceeds those for some non-wood pulping

raw materials such as kenaf (1.3 mm), reed (1.2 mm),

switchgrass (1.1 mm), miscanthus (1.0 mm), cotton stalks

(0.8 mm) and wheat straw (0.7 mm) [15]. Fibre length and

thickness are correlated with a number of mechanical prop-

erties of paper. Thus, long fibres have a favourable effect on

tensile index and tear index; also, thin-walled fibres of a small

diameter result in increased paper strength, bonding and ease

of sheet formation [47]. The long fibres of H. funifera are

extremely strong and possess a small linear mass, which

ensures the obtainment of paper with good physical

properties.

3.2. Characterization of pulps

Table 1 shows the results of the characterization of H. funifera

soda, sodaeanthraquinone and organosolv (ethanolamine,

diethanolamine, ethyleneglycol and diethyleneglycol) pulp

obtained under the conditions summarized in the same Table

1, in terms of yield, Kappa number, viscosity and beating

grade.

The pulping action of anthraquinone is well-known and

involves redox catalysis of some reactions occurring during

cooking of the raw material; electrons in the aldehyde

groups of carbohydrates present in its fibres are transferred

to the anthraquinone molecule and the aldehyde groups

transformed into carboxyl groups as a result; this stabilizes

different reactive of various raw materials.

Phoenixtilifera soda-AQ

Bagasse Rice straworganosolv

Kenaf

44.2 82.7 35.6e53 58.1

25.5 92.9 17.0e75.3 25.5

937 e 673e956 e

43.1 62.9 21.1e23.7 11.4

e e 1.95e1.99 0.68

2.2 2.8 1.0e1.2 2.4

10.0 6.0 0.3e0.4 11.8

Table 4 e Solid fractions extracted by acidification of the cooking liquor and overall proportions of gases obtained by theirpyrolysis and gasification.

Liquor pH for extractionof solid fraction

Amounts of solidsextracted (g) and proportionwith respect to the body

of fractions

Total amount of gases obtained(% with respect to theextracted fraction)

Pyrolysis Gasification

Soda pulping pH ¼ 2 0.23 (1.5%) e e

pH ¼ 4 (sample A) 1.14 (7.5%) 82.6 98.0

pH ¼ 6 (sample B) 13.90 (91.0%) 91.0 96.1

Diethanolamine

pulping

pH ¼ 2 (sample C) 1.81 (14.3%) 74.1 99,6

pH ¼ 4 (sample D) 8.01 (63.3%) 75.1 97.3

pH ¼ 6 (sample E) 2.84 (22.4%) 77.9 87.5

b i om a s s a n d b i o e n e r g y 3 4 ( 2 0 1 0 ) 1 4 7 1e1 4 8 0 1475

carbohydrates and increases pulp yield [48]. Our soda-

eanthraquinone pulp samples (P1eP3) exhibited better

yield, Kappa number and viscosity than those obtained in

the absence of catalyst. Thus, the Hesperaloe pulp obtained

by cooking with 10% NaOH and 1% anthraquinone at 155 �Cfor 30 min (P1) exhibited the highest yield (48.3%) and

viscosity (737 mL g�1) in addition to a fairly small Kappa

number (15.2).

Thepulpsamplesobtainedwith theamine solvents (P7eP12)

exhibited better yield, Kappa number, viscosity and beating

grade than those provided by the glycols. The highest yield

(59.6%) was that for the pulp obtained by using a 60% ethyl-

eneglycol concentration at 160 �C for 30 min (P13); diethanol-

amine provided pulpwith a similar yield but significantly better

values for the other properties. Thus, the best Kappa number

(20.1) was obtained by pulping with 70% diethanolamine at

170 �C for 60 min (P11) or an 80% concentration of the amine at

180 �C for 90min. The reaction conditions seemingly have little

influence on Kappa number; this should allow Hesperaloe pulp

with a comparable Kappa number to be obtained by using

a lower temperature, time and solvent concentration e and

hence with reduced production costs. This is also the case with

viscosity, which peaked in the pulp samples obtained with

diethanolamine (P10eP12); such samples differed by only

26 mL g�1 between the level obtained under the most and least

drastic conditions: 814 mL g�1 for P11 vs 788 mL g�1 for P10.

0,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

300 400 500 600 700 800 900 1000 1100 1200 1300T (K)

We

ig

ht fra

ctio

n

ABCDE

Fig. 2 e Mass loss of the solid fractions from H. funifera in

the absence of oxygen.

3.3. Paper sheets characterization

Table 1 shows the results of the characterization of paper

sheets made from the previous Hesperaloe pulp samples. As

can be seen, the sheets obtained from soda pulp possess

better physical properties than those obtained from soda-

eanthraquinone pulp. The best tensile index, stretch, burst

index and tear index were obtained under the mildest condi-

tions used (P4), i.e., with the least reagent and heating energy

consumption (low value of temperature).

The physical properties of the paper obtained from the amine

pulp samples were better than those for paper from the glycol

pulp samples. The best tensile index was achieved by using 60%

ethanolamine at 160 �C for 30 min. Also, the best brightness,

stretch, burst index and tear index were obtained with ethanol-

amine, both under mild and under drastic operating conditions.

Table 3 shows the results of the characterization of pulp

and paper sheets from other raw materials [7,45,48e50]. As

can be seen, Abaca surpasses Hesperaloe in yield, viscosity,

stretch and tear index. Oil palm surpasses Hesperaloe in tear

index and viscosity, and the opposite is true for the other

pulp and paper properties. Sugarcane bagasse provides

a better yield and tear index than Hesperaloe. Finally, rice

straw and kenaf are similar to Hesperaloe in yield, but provide

a worse tear index and better values of the other studied

properties.

0,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

300 400 500 600 700 800 900 1000 1100 1200 1300T (K)

We

gih

t fra

ctio

n

ABCDE

Fig. 3 e Mass loss of the solid fractions from H. funifera in

an oxidizing atmosphere.

Table 5 e Composition of evolved gases generated bypyrolysis and gasification of the solid fractions.

Process Samples Composicion, g/100 g sample

H2 CO CO2 CH4

Pyrolysis Sample A 1.54 16.30 19.00 1.81

Sample B 1.13 31.70 22.40 1.86

Sample C 0.97 13.60 16.80 3.70

Sample D 0.74 10.50 12.80 2.37

Sample E 0.64 13.00 14.80 1.55

Sample

(D þ E)

0.71 11.16 13.33 2.16

Gasification Sample A 0.17 32.40 67.20 17.66

Sample B 0.18 24.50 52.90 17.76

Sample C 0.15 53.40 51.60 16.01

Sample D 0.26 23.00 48.60 23.26

Sample E 4.92 20.40 38.40 14.01

Sample

(D þ E)

1.48 22.32 45.94 20.84

b i om a s s an d b i o e n e r g y 3 4 ( 2 0 1 0 ) 1 4 7 1e1 4 8 01476

3.4. Exploitation of residual liquors

The residual liquors from the sodaeanthraquinone (P1) and

diethanolamine (P10) processes, which proved the most effi-

cient methods for pulping H. funifera plant material, were

acidified with sulfuric acid 2 N in order to isolate lignin-rich

fractions. Table 4 shows the results obtained at different pH

values.

Fig. 4 e Concentration profiles for the synthesis and fuel

gases obtained from the solid fraction extracted from the

sodaeanthraquinone cooking liquor at pH 4 (sample A).

Soda cooking an amount of 500 g of H. funifera plant

material provided pulp in a 48.3% yield. Based on the lignin

contents of the raw material (7.3%) and pulp (3.07%), the

cooking liquor should have contained 29.09 g of lignin. This

amount, however, was much greater than the combination of

the three individual fractions: 15.27 g. Since the solid fractions

contain additional components such as hemicellulose and

ash, only part of the lignin in the liquors was recovered by

acidification. The diethanolamine pulping process provided

similar results: the amount of lignin obtained from the cook-

ing liquor was 18.15 g (pulp yield was 55.1% and the pulp

contained 6.66% lignin), but the solid fractions in combination

only contained 12.66 g.

As can be seen from Table 4, acidification of the soda liquor

at pH 6 extracted the highest proportion of solid fraction

(91.0%). Therefore, using lower pH values to obtain other solid

fractions may be counterproductive as they will add little to

the previous one and unnecessarily raise the cost of neutral-

izing the effluent. The main solid fraction in the liquor from

the diethanolamine process, which accounted for 63.3% by

weight, was obtained at pH 4; by contrast, only 14.3% was

extracted at pH 2. Using a pH below 4 may be counterpro-

ductive for the same reasons as with the soda liquor.

Thermal decomposition of the previous solid fractions in

an inert atmosphere (He) and an oxidizing atmosphere (9:1

He/O2) resulted in weight losses is shown in Figs. 2 and 3.

Fig. 5 e Concentration profiles for the synthesis and fuel

gases obtained from the solid fraction extracted from the

sodaeanthraquinone cooking liquor at pH 6 (sample B).

Fig. 6 e Concentration profiles for the synthesis and fuel

gases obtained from the solid fraction extracted from the

diethanolamine cooking liquor at pH 2 (sample C).

Fig. 7 e Concentration profiles for the synthesis and fuel

gases obtained from the solid fraction extracted from the

diethanolamine cooking liquor at pH 4 (sample D).

b i om a s s a n d b i o e n e r g y 3 4 ( 2 0 1 0 ) 1 4 7 1e1 4 8 0 1477

As can be seen from Fig. 2, approximately until 700 K the

weight loss curves for the solid fraction in the soda liquor

treated in the absence of oxygen, are higher than those

obtained for diethanolamine liquor, whereas above 700 K the

opposite happens. This suggests that pyrolysis of the solid

fractions obtained from the soda liquor produces smaller

amounts of carbonaceous residues and ash, and hence greater

amounts of evolved gases (see fourth column in Table 4).

As can be seen from Fig. 3, mass losses during the gasifi-

cation process decreased with increasing temperature up to

800e850 K; also, the solid fractions extracted at the lower pH

values provided smaller amounts of gases (see last column in

Table 4).

Samples of the different solid fractions (AeE in column 2 of

Table 4) were pyrolysed and gasified in a horizontal tubular

reactor and the resulting gases analysed by GC/FID and GC/

TCD. The results are shown in Table 5, and the concentration

profiles for the synthesis and fuel gases in Figs. 4e8.

A comparison of Figs. 4 and 5, and the data in Table 5,

reveals that pyrolysis of the solid fraction extracted by acidi-

fying the soda cooking liquor at pH 6 produced less H2 but

more CO than that extracted at pH 4. Also, gasification of the

solids extracted at pH 6 from the same liquor produced

slightly more H2 but less CO.

The amounts of H2 and CO obtained by gasifying the frac-

tion extracted from the soda cooking liquor at pH 6 were

smaller than those obtained by gasification. The opposite was

true for CH4 and CO2.

On the other hand, from the graphs of Figs. 4 and 5 it is

deduced that is not appropriate to operate at temperatures

above 800e900 K, because that range produces larger quanti-

ties of H2, CO and CH4, both pyrolysis and gasification.

A comparison of Figs. 6e8, and the data in Table 5, reveals

that pyrolysis of the solid fraction obtained by acidification of

the diethanolamine cooking liquor at pH 6 produced

decreased amounts of H2, CH4, CO and CO2 relative to pH 2;

and decreased amounts of H2 and CH4 and increased amounts

of CO and CO2 relative to pH 4.

On the other hand, gasification of fraction extracted at pH 6

produced increased amounts of H2, but decreased amounts of

CH4, CO and CO2, relative to pH 4 and 2.

A comparison of the amounts of gases obtained by gasifi-

cation and pyrolysis of the solid fraction extracted from the

diethanolamine cooking liquor at pH 4 reveals that gasifica-

tion produced less H2 but more CO, CO2 and CH4 than

pyrolysis.

As it can be clearly seen from Figs. 6e8, using temperatures

above 750e850 K resulted in no further increase in the

amounts of H2, CO and CO2 obtained by pyrolysis or

gasification.

Fig. 8 e Concentration profiles for the pyrolysis and fuel

gases obtained from the solid fraction extracted from the

diethanolamine cooking liquor at pH 6 (sample E).

b i om a s s an d b i o e n e r g y 3 4 ( 2 0 1 0 ) 1 4 7 1e1 4 8 01478

As can be seen fromTable 5, pyrolysis of the solids from the

soda cooking liquor provided increased amounts of H2, CO and

CO2 relative to thediethanolamine liquor.However, pyrolysis of

the soda liquor fractions extracted at pH 4 and 2 provided

decreased amounts of CH4 relative to diethanolamine.

Gasification provided very small amounts of H2 with all

fractions except that extracted from diethanolamine liquor at

pH 6. The fractions extracted at the lower pH values (samples

A and C) gave greater amounts of CO and CO2. Finally, the

largest amounts of CH4 were obtained from the diethanol-

amine liquor extracted at the intermediate pH.

Based on the foregoing, the solid fraction extracted from

soda liquor at pH 6 is the best source for producing synthesis

gases (H2 þ CO) by pyrolysis, and so is the fraction extracted

from diethanolamine liquor (sample C) for obtaining fuel

gases (H2 þ CO þ CH4) by gasification.

Table 5 shows the composition of the synthesis and fuel

gases obtained from the combination of the two fractions

extracted at pH 4 (samples D and E). As can be seen, pyrolysis

of sample B produced greater amounts of synthesis and fuel

gases than did the combination of D þ E; the actual difference

was even more marked than suggested by the results if one

considers that the amounts of B and CþD obtained from 500 g

of pulp were 13.90 and 10.85 g, respectively. On the other

hand, gasification of samples B and D þ E produced similar

amounts of synthesis and fuel gases; however, since the

amount of B extracted exceeded that of D þ E, the former

fraction is to be preferred as it provides greater amounts of

gases and requires less acid for extraction.

4. Conclusions

A comparison of the chemical properties of H. funifera with

those of non-wood raw materials including kenaf, bagasse,

cotton stalks, wheat straw, paulownia, sunflower stalks,

empty fruit bunches (EFBs) and rice straw confirms that H.

funifera provides an effective alternative raw material for

obtaining cellulose pulp and paper.

Based on the results of the characterization of pulp and

paper obtained by cooking H. funifera with soda, soda-

eanthraquinone, ethyleneglycol, diethyleneglycol, ethanol-

amine and diethanolamine, the best pulp from this alternative

raw material was that obtained by using 10% soda containing

1% anthraquinone at 155 �C for 30 min. These conditions

resulted in a good yield, Kappa number, viscosity, drainage

index, tensile index, stretch, burst index and tear index.

A comparison of the amounts of synthesis gases (H2 þ CO)

and fuel gases (H2 þ CO þ CH4) generated by pyrolysis and

gasification of the solid fractions obtained by acidifying the

liquors from the sodaeanthraquinone and diethanolamine

processes revealed that the best results were those for the

sodaeanthraquinone liquor extracted at pH 6. These condi-

tions allow efficient exploitation of lignin-rich fractions in the

residual cooking liquor.

Acknowledgements

The authors are grateful to Ecopapel, S.L. (Ecija, Seville, Spain)

for their support, to Spain’s DGICyT for funding this research

within the framework of Projects PPQ2007-65074-C02-01 and

TRACE2009-0064, and to the Ramon y Cajal programme

(Spain’s Ministry of Education and Science) for additional

funding.

r e f e r e n c e s

[1] Asociacion Espanola de Fabricantes de Pasta, Papel y Carton,www.aspapel.es [accessed May 2009].

[2] FAO, http://faostat.fao.org [accessed May 2009].[3] McLaughlin SP. Removing flowers stalks increases leaf

biomass production in Hesperaloe funifera (Agavaceae). J AridEnviron 2003;55:143e9.

[4] WongA,McLaughlinSP.AlkalinesulphitepulpingofHesperaloe,an arid-zone native fibre plant from northern Mexico. In:Proceeding Tappi Pulping Conference. Boston M.A.; 2000.

[5] Fairbank M, Detrick R. Hesperaloe funifera an excellentreinforcement fiber for mechanical paper grades. Tappi J2000;83(11):66.

[6] Labidi J, Tejado A, Garcıa A, Jimenez L. Simulation oftagasaste pulping using soda-AQ. Bioresour Technol 2008;99:7270e7.

[7] Jimenez L, Ramos E, Rodrıguez A, de la Torre MJ, Ferrer JL.Optimization of pulping condition of abaca. An alternative

b i om a s s a n d b i o e n e r g y 3 4 ( 2 0 1 0 ) 1 4 7 1e1 4 8 0 1479

raw material for producing cellulose pulp. Bioresour Technol2005;96:977e83.

[8] Jimenez L, Serrano L, Rodrıguez A, Sanchez R. Soda-AQpulping of palm oil empty fruit bunches and beating of theresulting pulp. Bioresour Technol 2009;100:1262e7.

[9] Lopez F, Alfaro A, Jimenez L, Rodrıguez A. Alcohols as organicsolvents for the manufacture of cellulose pulps. Afinidad2006;63(523):174e82.

[10] Rodrıguez A, Jimenez L. Pulping with organic solvents otherthan alcohols. Afinidad 2008;65(535):188e96.

[11] Ligero P, Villaverde JJ, Vega A, Bao M. Pulping cardoon(Cynara cardunculus) with peroxiformic acid (MILOX) in onesingle stage. Bioresour Technol 2008;99:5687e93.

[12] Ziaie-Shirkolaee Y, Mohammadi-Rovshandeh J, Rezayati-Charani P, Khajeheian MB. Influence of dimethyl formamidepulping of wheat straw on cellulose degradation andcomparison with kraft process. Bioresour Technol 2008;99:3568e78.

[13] Caparros S, Dıaz MJ, Ariza J, Lopez F, Jimenez L. Newperspectives for Paulownia fortunei L. Valorisation of theautohydrolysis and pulping processes. Bioresour Technol2008;99(4):741e9.

[14] Jimenez L, Perez A, de la Torre MJ, Moral A, Serrano L.Characterization of vine shoots, cotton stalks, Leucaenaleucocephala and Chamaecytisus proliferus and of theirethyleneglycol pulps. Bioresour Technol 2007;98:3487e90.

[15] Gominho J, Lourenco A, Curt M, Fernandez J, Pereira H.Characterization of hairs and pappi from Cynara cardunculuscapitula and their suitability for paper production. Ind CropProd 2009;29:116e25.

[16] Pan X, Arato C, Gilkes N, Gregg D, Mabee W, Pye K, et al.Biorefining of softwoods using ethanol organosolv pulping:preliminary evaluation of process streams for manufactureof fuel-grade ethanol and co-products. Biotechnol Bioeng2005;90(4):473e81.

[17] Towers M, Browne T, Kerekes R, Paris J, Tran H. Biorefineryopportunities for the Canadian pulp and paper industry. PulpPap Can 2007;108(6):26e9.

[18] Kelley SS. Lignocellulosic biorefineries: reality, hype, orsomething in between? ACS Syposium Series 2007;954:31e47.

[19] Covey G, Grist S. What is the role for biorefineries?. In: Appitaannual conference and exhibition, 62th; 2008. p. 1e18.

[20] Delmas M. Vegetal, refining and agrichemistry. Chem EngTechnol 2008;31(5):792e7.

[21] Kadam K, Chin CY, Brown LW. Flexible biorefinery forproducing fermentation sugars, lignin and pulp from cornstover. J Ind Microbiol Biotechnol 2008;35(5):331e41.

[22] Garrote G, Cruz JM, Domınguez H, Parajo JC. Valorisation ofwaste fractions from autohydrolysis of selectedlignocellulosic materials. J Chem Technol Biotechnol 2003;78:392e8.

[23] Caparros S, Ariza J, Lopez F, Dıaz MJ. Optimizing cellulosicpaper obtained from Arundo donax under hydrothermaltreatment. J Ind Eng Chem 2007;13(3):465e73.

[24] Caparros S, Ariza J, Lopez F, Nacimiento JA, Garrote G,Jimenez L. Hydrothermal treatment and ethanol pulpingof sunflower stalks. Bioresour Technol 2008b;99(5):1368e72.

[25] Alfaro A, Rivera A, Perez A, Yanez R, Garcıa JC, Lopez F.Integral valorization of two legumes by autohydrolysis andorganosolv delignification. Bioresour Technol 2009;100(1):440e5.

[26] Yanez R, Garrote G, Dıez MJ. Valorisation of a leguminousspecie, Sebatia grandiflora, by means of hydrothermalfractionation. Bioresour Technol 2009;100(24):6514e23.

[27] Boussarsar H, Roge B, Mathlouthi M. Optimization ofsugarcane bagasse conversion by hydrothermal treatment

for the recovery of xylose. Bioresour Technol 2009;100(24):6537e42.

[28] Dogaris I, Karapati S, Mamma D, Kalogeris E, Kekos D.Hydrothermal processing and enzymatic hydrolysis ofsorghum bagasse for fermentable carbohydrates production.Bioresour Technol 2009;100(24):6543e9.

[29] Sun RC, Tomkinson J. Fractional separation andphysico-chemical analysis of lignins from black liquorof oil palm trunk fibre pulping. Sep Purif Technol 2001;24:529e39.

[30] Gonzalez AM, Tejado A, Blanco M, Mondragon I, Labidi J.Agricultural palm oil tree residues as raw material forcellulose, lignin, and hemicelluloses production byethylene glycol pulping process. Chem Eng J 2009;148(1):106e14.

[31] Garcıa A, Toledano A, Serrano L, Egues I, Gonzalez M,Marın F, et al. Characterization of lignins obtained byselective precipitation. Sep Purif Technol 2009;68(2):193e8.

[32] Baumlin S, Broust F, Bazer-Bachi F, Bourdeaux T, Herbinet O,Touite-Ndiaye F, et al. Production of hydrogen by lignins fasepyrolysis. Int J Hydrogen Energy 2006;31(15):2179e92.

[33] Mani T, Muruga P, Mahinpey N. Determination of distributedactivation energy model kinetic parameters using simulatedannealing optimization method for nonisothermal pyrolysisof lignin. Ind Eng Chem Res 2009;48(3):1464e7.

[34] Murugan O, Mahinpey N, Johnson K, Wilson M. Kinetics ofpyrolysis of lignin using thermogravimetric and differentialscanning calorimetry methods. Energy Fuel 2008;22(4):2720e4.

[35] Osada M, Hiyoshi N, Sato O, Arai K, Shirai M. Reactionpathway for catalytic gasification of lignin in presence ofsulfur in supercritical water. Energy Fuel 2007;21(4):1854e8.

[36] Furusawa T, Sato T, Sugito H, Miura Y, Ishiyama Y, Sato M,et al. Hydrogen production from the gasification of ligninwith nickel catalysts in supercritical water. Int J HydrogenEnergy 2007;32(6):699e704.

[37] Yamaguchi A, Hiyoshi N, Sato O, Osada M, Shirai M. Ligningasification over supported ruthenium trivalent salts insupercritical water. Energy Fuel 2008;22(3):1485e92.

[38] Yamaguchi A, Hiyoshi N, Sato O, Osada M, Shirai M.Hydrogen production from woody biomass over supportedmetal catalysts in supercritical water. Catal Today 2009;146(1e2):192e5.

[39] McLaughlin SP. Properties of paper made from fibers ofHesperaloe funifera (Agavaceae). Econ Bot 2000;54(2):192e6.

[40] Wise LE, Murphy M, D‘Adieco A. Chlorite holocellulose itsfractionation and beating on summative wood analysis andon studies on the hemicellulose. Paper Trade J 1946;122(2):35e43.

[41] Conesa JA, Font R, Fullana A, Martın-Gullon I, Aracil I,Galvez A, et al. Comparison between the pollutant emissionin the pyrolysis and combustion of different wastes. J AnalAppl Pyrol 2009;84:95e112.

[42] Khristova P, Bentchera S, Karar I. Soda-AQ pulp blends fromKenaf and sunflower stalks. Bioresour Technol 1998;66:99e103.

[43] Wanrosli WD, Zainuddin Z, Lee LK. Influence of pulpingvariables on the properties of Elaeis guineensis soda pulp asevaluated response surface methodology. Wood Sci Technol2004;38:191e205.

[44] Rezayati-Charani P, Mohammadi-Rovshandeh J, Hashemi SJ,Kazemi-Najafi S. Influence of dimethyl formamide pulping ofbagasse on pulp properties. Bioresour Technol 2006;97:2435e42.

[45] Rodrıguez A, Serrano L, Moral A, Jimenez L. Pulping of ricestraw with high-boiling point organosolv solvents. BiochemEng J 2008;42:243e7.

b i om a s s an d b i o e n e r g y 3 4 ( 2 0 1 0 ) 1 4 7 1e1 4 8 01480

[46] Saim A, Yonghao N, Mehmet A, Ayhan T. Characterizationand evaluation of Paulownia elongata as a raw material forpaper production. Afr J Biotechnol 2008;7(22):4153e8.

[47] Garcıa JA. Fibras papeleras. Barcelona, Spain: UPC; 2007.[48] Khristova P, Kordsachia O, Kluider T. Alkaline pulping with

additives of date palm rachis and leaves from Sudan.Bioresour Technol 2005;96:79e85.

[49] Fuwape JA. Paper from Kenaf fibre. Bioresour Technol 1993;43:113e5.

[50] Rezayati-Charani P, Mohammadi-Rovshandeh J. Effect ofpulping variables with dimethyl formamide on thecharacteristics of bagasse-fiber. Bioresour Technol 2005;96:1658e69.