Pretreatment of Biomass: Processes and Technologies

261 Pages·2014·13.14 MB·English

by  Ashok Pandey

PRETREATMENT
OF BIOMASS
PROCESSES AND TECHNOLOGIES
Edited by
A P
SHOK ANDEY
CentreforBiofuels&BiotechnologyDivision,CSIR-NationalInstitutefor
InterdisciplinaryScience&Technology,Trivandrum,India
S N
ANGEETA EGI
DepartmentofBiotechnology,MotilalNehruNationalInstituteof
Technology,Allahabad,India
P B
ARAMESWARAN INOD
CentreforBiofuels&BiotechnologyDivision,CSIR-NationalInstitutefor
InterdisciplinaryScience&Technology,Trivandrum,India
C L
HRISTIAN ARROCHE
InstitutPascal,PolytechClermont-FerrandUniversityBlaisePascal
Clermont-Ferrand,France
AMSTERDAM(cid:129)BOSTON(cid:129)HEIDELBERG(cid:129)LONDON(cid:129)NEWYORK(cid:129)OXFORD
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List of Contributors
YoungHoonJung DepartmentofBiotechnology, M. Morales-Otero Laboratory of Environmental
Korea University Graduate School, Seoul, Microbiology and Biotechnology, School of
RepublicofKorea Environmental & Natural Resources Engi-
Parameswaran Binod Centre for Biofuels, Bio- neering, University of Valle, Santiago de Cali,
technologyDivision,CSIReNationalInstitute Colombia
for Interdisciplinary Science and Technology, Ajay Kumar Pandey Department of Bio-
Trivandrum,India technology, Motilal Nehru National Institute
He´le`ne Carre`re INRA, UR0050, Laboratoire de ofTechnology,Allahabad,UttarPradesh,India
Biotecnologiedel’Environnement,Avenuedes Ashok Pandey Centre for Biofuels, Bio-
Etangs,Narbonne,France technologyDivision,CSIReNationalInstitute
Wei-Hsin Chen Department ofAeronauticsand for Interdisciplinary Science and Technology,
Astronautics, National Cheng Kung Trivandrum,India
University,Tainan,Taiwan,RepublicofChina Min S. Park Department of Chemical &
Jinghuan Chen Beijing Key Laboratory of Biomolecular Engineering, Korea Advanced
Lignocellulosic Chemistry, Beijing Forestry Institute of Science and Technology, Yuseong-
University,Beijing,China gu, Daejeon, Republic of Korea; Advanced
Biomass R&D Center, Yuseong-gu, Daejeon,
J.L. Colodette Pulp and Paper Laboratory,
RepublicofKorea
Department of Forestry Engineering, Federal
UniversityofVic¸osa,Vic¸osa,MinasGerais,Brazil Fabiana Passos GEMMA e Group of Environ-
Ivet Ferrer GEMMA e Group of Environmental mental Engineering and Microbiology,
DepartmentofHydraulic,MaritimeandEnvi-
Engineering and Microbiology, Department
ronmentalEngineering,UniversitatPolite`cnica
of Hydraulic, Maritime and Environmental
deCatalunya$BarcelonaTech,Barcelona,Spain
Engineering, Universitat Polite`cnica de
Catalunya$BarcelonaTech,Barcelona,Spain S. Bolado-Rodrı´guez Department of Chemical
Engineering and Environmental Technology,
C. Marangon-Jardim Pulp and Paper Laboratory,
UniversityofValladolid,Valladolid,Spain
Department of Forestry Engineering, Federal
UniversityofVic¸osa,Vic¸osa,MinasGerais,Brazil Raveendran Sindhu Centre for Biofuels, Bio-
technologyDivision,CSIReNationalInstitute
So-Yeon Jeong Department of Forest Products
for Interdisciplinary Science and Technology,
and Technology, Chonnam National
Trivandrum,India
University,Gwangju,RepublicofKorea
Shao-Ni Sun Beijing Key Laboratory of
Kyoung Heon Kim Department of Bio-
Lignocellulosic Chemistry, Beijing Forestry
technology,KoreaUniversityGraduateSchool,
University,Beijing,China
Seoul,RepublicofKorea
Run-Cang Sun Beijing Key Laboratory of
Jae-WonLee DepartmentofForestProductsand
Lignocellulosic Chemistry, Beijing Forestry
Technology, Chonnam National University,
University, Beijing, China; State Key Labo-
Gwangju,RepublicofKorea
ratory of Pulp and Paper Engineering, South
Sangeeta Negi Department of Biotechnology,
China University of Technology, Guangzhou,
MotilalNehruNationalInstituteofTechnology,
China
Allahabad,UttarPradesh,India
vii
viii
LISTOFCONTRIBUTORS
R.Travaini DepartmentofChemicalEngineering Jian Xu National Key Laboratory of Bio-
and Environmental Technology, University of chemical Engineering, Institute of Process
Valladolid,Valladolid,Spain Engineering, Chinese Academy of Sciences,
Enrica Uggetti GEMMA e Group of Environ- Beijing, China
mental Engineering and Microbiology, Ji-Won Yang Department of Chemical &
DepartmentofHydraulic,MaritimeandEnvi- Biomolecular Engineering, Korea Advanced
ronmentalEngineering,UniversitatPolite`cnica Institute of Science and Technology, Yuseong-
deCatalunya$BarcelonaTech,Barcelona,Spain gu, Daejeon, Republic of Korea; Advanced
Kun Wang Beijing Key Laboratory of Ligno- Biomass R&D Center, Yuseong-gu, Daejeon,
cellulosic Chemistry, Beijing Forestry Uni- RepublicofKorea
versity,Beijing,China Gursong Yoo Department of Chemical & Bio-
Donghai Wang Department of Biological and molecular Engineering, Korea Advanced Ins-
Agricultural Engineering, Kansas State Uni- titute of Science and Technology, Yuseong-gu,
versity,Manhattan,KS,USA Daejeon,RepublicofKorea
Feng Xu Department of Biological and Agricul-
tural Engineering, Kansas State University,
Manhattan,KS,USA
C H A P T E R
1
Introduction
Parameswaran Binod, Ashok Pandey
Centre for Biofuels, Biotechnology Division, CSIR e National Institute
for Interdisciplinary Science and Technology, Trivandrum, India
1.1 OVERVIEW
Lignocellulosic biomass is a promising feedstock for future renewable fuels. It consti-
tutes a substantial renewable substrate for bioethanol production that does not compete
with food and animal feed. Lignocellulosic materials predominantly contain a mixture of
carbohydrate polymers such as cellulose and hemicelluloses and lignin. Cellulose is an
unbranched linear polymerof glucose. Hemicelluloses belong to a group of heterogenous
polysaccharides containing both 6-carbon and 5-carbon sugars. Lignin is a very complex
molecule with phenylpropane units linked in a three-dimensional structure. Lignocellu-
losicplantmaterialsalsocontainotherproteinsandextractivesrepresentaminorfraction
(between 5% and 15%). Extractives contain large numbers of lipophilic and hydrophilic
constituents.
The amount of cellulose, hemicelluloses and lignin depends on the type of material.
Usually the cellulose content may vary between 30% and 50%, hemicelluloses 20e40% and
lignin 10e30%. Pretreatment is the first and most important step in lignocellulosic biomass
processing. It is the key process by which the recalcitrant lignocellulosic biomass could be
modified so as to make it amenable to further processes or reactions in order to convert it
into biofuel orother products.
The carbohydrate polymers in the lignocellulosic material are to be converted to simple
sugars before fermentation. There are several hydrolysis methods are available for this
conversion; they can be broadly classified into physical, chemical and biological. Among
these, biological means of hydrolysis using enzymes is the preferred one due to its several
advantagesovertheothertwo methods.Duetotheheterogenousandverycomplex nature
of the lignocellulosic biomass, enzymatic hydrolysis is not an efficient method for native
biomass.Hencethebiomasshastobepretreatedsoastomakeitamenabletoenzymeaction.
This book describes various methods of pretreatment generally adopted for removing the
recalcitrance of thelignocellulosic biomass.
PretreatmentofBiomass
http://dx.doi.org/10.1016/B978-0-12-800080-9.00001-3 3 Copyright(cid:1)2015ElsevierB.V.Allrightsreserved.
4
1. INTRODUCTION
Theenzymatichydrolysisoflignocellulosicmaterialsislimitedbyseveralfactors,suchas
cellulose crystallinity, degree of polymerization, moisture content, surface area and lignin
content.Decreasedparticlesizeimprovestheavailablesurfacearea,whichinturnimproves
theenzymatichydrolysis.Theporesizeofthesubstrateinrelationtothesizeoftheenzymes
is another limiting factor in enzymatic hydrolysis. Removal of hemicelluloses during
pretreatment (mainly by acid pretreatment) increases the mean pore size of the substrate
andtherebyimprovesthehydrolysisprocess.Dryingofpretreatedbiomassathighertemper-
atures generally decreases the sugar yield during enzymatic hydrolysis because of the
collapse in pore structure. Hence it is highly recommended to dry the pretreated biomass
at lower or ambient temperatures. The presence of lignin in the biomass limits the rate of
hydrolysis as lignin irreversibly binds with cellulases. Hence the pretreatment method has
toaddressmostoftheseissuesrelatedtotheenzymatichydrolysissoastomaketheprocess
moreeconomical.
1.2 THE ROLE OF PRETREATMENT
Pretreatment generally refers to the disruption of the naturally resistant carbohydrate-
lignin shield that limits the accessibility of enzymes to cellulose and hemicelluloses. The
choice of pretreatment technology is very significant. The pretreatment must take into
accountthesugarreleasepatternsandsolidconcentrationsforeachpretreatmentinconjunc-
tionwiththeircompatibilitywiththeoverallprocess,feedstock,enzymesandorganismsto
be applied. The economics of the whole process must be considered while selecting a pre-
treatment method. The need for chemicals in pretreatment and subsequent neutralization
and prefermentation conditioning should be minimal and inexpensive. Because milling of
biomass to small particle sizes is energy-intensive and costly, pretreatment technologies
that require limited size reduction are desirable. High yields of fermentable hemicellulose
sugars of close to 100% should be achieved through pretreatment. The concentration of
sugars from the coupled operations of pretreatment and enzymatic hydrolysis should be
highenoughtoensurethatethanolconcentrationsareadequatetokeeprecoveryandother
downstream costs manageable. Pretreatment reactors should be low in cost through mini-
mizing their volume, not requiring exotic materials of construction due to highly corrosive
chemicalenvironmentsandkeepingoperatingpressuresreasonable.Theliquidhydrolysate
from pretreatment must be fermentable following a low-cost, high-yield conditioning step.
However,itishighlydesirabletoeliminateconditioningtoreducecostsandtoreduceyield
losses.Thechemicalsformedduringhydrolysateconditioninginpreparationforsubsequent
biological steps should not present processing or disposal challenges (e.g. gypsum). Cellu-
lose from pretreatment should be highly digestible, with yields of greater than 90% in less
than five and preferably less than three days with low cellulase loadings of less than
10FPU/g cellulose. Lignin and other constituents should be recovered for conversion to
valuable co-products and to simplify downstream processing. The distribution of sugar
recoverybetweenpretreatmentandsubsequentenzymatichydrolysisshouldbecompatible
with the choice of organisms to ferment the sugars in hemicellulose. The heat and power
demands for pretreatment should be low and/or be compatible for being thermally
integrated with therestof the process[1].
A.LIGNOCELLULOSICBIOMASS
5
1.3 METHODSOFPRETREATMENT
1.3 METHODS OF PRETREATMENT
Avarietyofphysical(comminution,hydrothermolysis),chemical(acid,alkali,solvents,
ozone), physicochemical (steam explosion, ammonia fiber explosion) and biological
pretreatment techniques have been developed to improve the accessibility of enzymes
to cellulosic fibers [2].
Acid pretreatment involves the use of sulfuric, nitric or hydrochloric acids to remove
hemicellulose components and expose cellulose for enzymatic digestion while alkali
pretreatment refers to the application of alkaline solutions to remove lignin and various
uronic acid substitutions on hemicellulose that lower the accessibility of enzymes to the
hemicellulose and cellulose. Generally, alkaline pretreatment is more effective on materials
having high lignin content. Peroxide pretreatment enhances enzymatic conversion through
oxidative delignification andreduction of cellulosecrystallinity.
Hydrothermaltreatmentscanbeconductedoverwiderangesofoperatingconditions.The
treatmenttimecanalsovarywidely(fromafewsecondstoseveralhours).Suchisalsothecase
withtheliquid/solidratio,whichcanbesetatvaluesfrom2to40gwater/gmaterialbutusu-
allyfallswithintherange8e10g/g.pHhasastronginfluenceoncellulosedegradation.
Amongthephysicochemicalprocesses,steamingwithorwithoutexplosion(autohydrol-
ysis)hasreceivedsubstantialattention.Thepretreatmentremovesmostofthehemicellulose,
thus improving the enzymatic digestion. In steam explosion, the pressure is suddenly
reducedand makes the materials undergoan explosive decompression. High pressure and
(cid:1)
consequently high temperature, typically between 160 and 260 C, for a few seconds
(e.g.30s)toseveralminutes(e.g.20min),areusedinsteamexplosion.Thesteamexplosion
process is well documented and was tested in laboratory and pilot processes by several
research groups and companies. Its energy cost is relatively moderate, and it satisfies all
the requirements of the pretreatment process. Steam pretreatment can be performed with
addition of sulfur dioxide (SO ); the aim of adding this chemical is to improve recovery of
2
both cellulose and hemicellulose fractions. The treatment can be carried out by 1e4% SO
2
(w/w substrate)at elevated temperatures,e.g. 160e230(cid:1)C,for a periodof e.g. 10min.
Ozonationisanotherattractivepretreatmentmethodthatdoesnotleavestrongacidic,basic
ortoxicresiduesinthetreatedmaterial.Theeffectofozonepretreatmenthasbeenfoundtobe
essentiallylimitedtolignindegradation.Ozonationhasbeenwidelyusedtoreducethelignin
content of both agricultural and forestry wastes. The pretreatment is usually carried out at
room temperature and does not lead to the generation of inhibitory compounds. However,
ozonolysismightbeexpensiveduetotherequirementoflargeamountsofozone.
Theuseofmicrowaveenergyinthepresenceofachemicalreagentisanothermethodof
pretreatment. This is a more effective pretreatment than the conventional heating chemical
pretreatmentintermsofacceleratingreactionsduringthepretreatmentprocess[3].Theenzy-
matichydrolysisofpretreatedricestrawshowedthatthepretreatmentbymicrowave/acid/
alkali/H O hadthe highest hydrolysisrate and glucose content inthe hydrolysate [4].
2 2
Microorganisms can also be used to treat the lignocelluloses and enhance enzymatic
hydrolysis.Theappliedmicroorganismsusuallydegradeligninandhemicellulosebutverylit-
tlecellulose,sincecelluloseismoreresistantthantheotherpartsoflignocellulosestothebiolog-
icalattack.Severalfungi,e.g.brown-,white-andsoft-rotfungi,havebeenusedforthispurpose.
A.LIGNOCELLULOSICBIOMASS
6
1. INTRODUCTION
White-rotfungisuchasPhanerochaetechrysosporium,Trametesversicolor,Ceriporiopsissubvermis-
poraandPleurotusostreatusareamongthemosteffectivemicroorganismsforbiologicalpretreat-
ment of lignocelluloses. Low energy requirement, no chemical requirement, and mild
environmental conditions are the main advantages of biological pretreatment. However, the
treatmentrateisverylowinmostbiologicalpretreatmentprocesses.
Torrefaction is a relatively mild thermochemical process that uses low temperature,
generally 200e300(cid:1)C, and inert gas atmosphere to produce homogenous solid fuels with
higher hydrophobicity and lower oxygen content relative to the feed biomass [5]. During
this process, cellulose, hemicelluloses and lignin present in the biomass undergo different
chemical transformations because of their distinct chemical and thermal reactivity. It has
been reported that compared to cellulose and lignin fractions, most of the hemicelluloses
degradeintovolatilecomponentsatlowtorrefactiontemperatures[6].Duetothefuelvalue
oftorrefiedbiomass,ithasbeenusedasareplacementforcoal,inco-combustionwithother
fuels andin the production ofpellets or briquettes.
1.4 SUMMARY
Pretreatmentofbiomassplayakeyroleinthedevelopmentofbioprocessesandproducts
fromlignocellulosicandalgalbiomass,workingontheprincipleofbiorefinery.Theproduc-
tionofbioethanol(second-generationbiofuel)fromlignocellulosicfeedstock,otherthanfood
materials,hasbeendevelopedinrecentyearsandthird-generationbiofuelsareconsideredto
be a technically viable alternative bioenergy resource devoid of major drawbacks. Marine
resources have played an important role in biotechnology, particularly in the past decade.
Thereareseveral macro-algae that contain intracellularcarbohydrates and have a potential
forproductionofbiofuels,e.g.bioethanolandbio-oil.Differentpretreatmentmethodologies
areto beadopted to derivethe useful components fromthealgal biomass.
Acknowledgment
TheauthorsacknowledgethefinancialsupportfortheCentreforBiofuelsbytheTIFAC,NewDelhiandMNRE,
NewDelhi.
References
[1] Bin Y, Charles WE. Pretreatment: the key to unlocking low-cost cellulosic ethanol. Biofuels Bioprod Biorefin
2008;2:26e40.
[2] MoiserN,WymanC,DaleB,ElanderR,LeeYY,HoltzappleM,etal.Featuresofpromisingtechnologiesfor
pretreatmentoflignocellulosicbiomass.BioresourTechnol2005;96:673e86.
[3] Binod P, Satyanagalakshmi K, Sindhu R, Janu KU, Sukumaran KR, Pandey A. Short duration microwave
assistedpretreatmentenhancestheenzymaticsaccharificationandfermentablesugarproductionfromsugar-
canebagasse.RenewEnergy2012;37:109e16.
[4] Vani S, Binod P, Kuttiraja M, Sindhu R, Sandhya SV, Preeti VE, et al. Energy requirement for alkali assisted
microwaveandhighpressurereactorpretreatmentsofcottonplantresidueanditshydrolysisforfermentable
sugarproductionforbiofuelapplication.BioresourTechnol2012;112:300e7.
[5] ParkJ,MengJ,LimKH,RojasOJ,ParkS.Transformationoflignocellulosicbiomassduringtorrefaction.JAnal
ApplPyrolysis2013;100:199e206.
[6] PengYY,WuS.Thestructuralandthermalcharacteristicsofwheatstrawhemicellulose.JAnalApplPyrolysis
2010;88:134e9.
A.LIGNOCELLULOSICBIOMASS
C H A P T E R
2
Analysis of Lignocellulosic Biomass
Using Infrared Methodology
Feng Xu, Donghai Wang
Department of Biological and Agricultural Engineering,
Kansas State University, Manhattan, KS, USA
2.1 INTRODUCTION
Lignocellulosicbiomassforbiofuelproductionhasattractedmuchattentionbecauseofits
abundance and renewability [1]. The three major components of lignocellulosic biomass,
cellulose, hemicellulose and lignin, could be candidates for further biological/chemical
utilization [2]. Second-generation ethanol, or bioethanol, for example, is being developed
from polysaccharides with microbial fermentation [3,4]. Lignin, a phenolic polymer, is also
an important material in industrial applications such as development of adhesive resin
[5,6] and lignin gels [7,8]. Lignin and cellulose are being utilized in the synthesis of
biodegradable polymers [9]. Biomass composition varies by variety and production
location/conditions [10], which, in turn, significantly affects processing strategies; for
example, alkali pretreatment is more effective in biomass with low lignin content [11].
Biomass composition changes significantly during processing [12], so a fast and accurate
determination of biomass composition iscritical to accelerating biomass utilization.
Current biomass composition analysis methods are unable to meet the requirements of
high-throughput biomass processing. Classic wet chemical methods of biomass determina-
tion, which employ two-step sulfuric acid hydrolysis, have been used for over a century,
and improvements have adapted them to different objects and conditions [13,14]. The
NationalRenewableEnergyLaboratorydistributedaseriesofproceduresforbiomassdeter-
minationthathavebecomethedefactoprocessforbiomassanalysis[15].Thesewetchemical
methods providereliable informationabout biomass composition andhave been proven to
work well with both wood and herbaceous feedstock, but they are labor-intensive, time-
consuming and expensive, which makes them inappropriate for industrial applications or
large numbers of samples; for example, a complete analysis using wet chemical methods
costs$800e$2000persample[16].Recentdevelopmentsinthewetchemicalmethodinclude
PretreatmentofBiomass
http://dx.doi.org/10.1016/B978-0-12-800080-9.00002-5 7 Copyright(cid:1)2015ElsevierB.V.Allrightsreserved.
8
2. ANALYSISOFLIGNOCELLULOSICBIOMASSUSINGINFRAREDMETHODOLOGY
a small-scale, high-throughput method that is able to processa largenumberof samplesin
less time [17], but the instruments/devices (e.g. powder/liquid-dispensing systems) are
costly, and these methods requirefurtherrefinement because some components of biomass
(e.g. acid-soluble lignin and ash) are not determined. Other disadvantages of wet chemical
methods are that they require preconditioning to remove extractives, and they generate
reliable results only from samples within a certain range of particle size [18]. In addition,
chemicalmethodsareunabletodifferentiateamongtypesofhemicellulose,suchasxyloglu-
canandarabinoxylan[19].Thus,areliablelow-cost,time-savingmethodisurgentlyneeded
for biomass analysis.
Infraredspectroscopy(IRS)hasbeenwidelyusedforqualitativeandquantitativeanalysis
in various areas, such as the food and pharmaceutical industries [20e23]; for example, the
composition of protein and oil in meat products, cereal crops and food products was
predicted successfully using near-infrared spectroscopy(NIRS) [24e26], as wereBrix value
andstarchcontentinfruits[27].ThecostofanalysisofgrainmaterialsusingNIRS($13per
sample)islowerthanthatusingfeedanalysis(over$17persample)[28].IRSalsohasbeen
proven able to produce qualitative and quantitative results for biomass application [16,29];
for example, Fourier transform infrared spectroscopy (FTIR) has been used successfully
forcompositionalanalysisoflignocellulosicbiomass[30].ThemainadvantagesofIRStech-
nologyarethatsamplepreparationissimple,analysisisfastandprecise,andmanyconstit-
uentscanbeanalyzedatthesametime.Thus,thecostofbiomasssampleanalysiscouldbe
reducedtoabout$10foreachsample[16].OneexclusivecharacteristicoftheIRSmethodis
that it is nondestructive, so the sample could be used for other analysis after IRS measure-
ment.IRSanalysisalsousesnohazardouschemicals.AcomparisonofIRSandwetchemical
methods in biomass analysis is shown in Figure 2.1. In addition to determining the major
polysaccharides in biomass, IRS is capable of providing other structural information.
Sample IRS method
Biomass MV-PLS
IR spectra Model
model
measurement prediction
construction
Size reduction
Composition
105 °C drying
Insoluble
Extraction Extracted solid
fraction
575 °C drying
Extractives Acid Soluble HPLC
Filtration
hydrolysis fraction UV-Vis
Acid method
FIGURE2.1 Comparisonofthecompositionalanalysismethodsforbiomass(IR:infrared;MV-PLS:multivariate
partial least squares regression; HPLC: high-performance liquid chromatography; UVeVis: ultravioletevisible
spectroscopy).
A.LIGNOCELLULOSICBIOMASS