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Ulla Lassi and Bodil Wikman (ed.)

KOKKOLAN YLIOPISTOKESKUS CHYDENIUS

BIOMASS GASIFICATION TO HEAT,ELECTRICITY AND BIOFUELS

HighBio Project Publication

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BIOMASS GASIFICATION TO HEAT,ELECTRICITY AND BIOFUELS

HighBio Project Publication

Edited by Ulla Lassi and Bodil Wikman

University of JyvskylKokkola University Consortium Chydenius

Kokkola 2011

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Layout: Pivi VuorioCover photo: Yrj Muilu

ISBN 978-951-39-4316-5 (pbk)ISBN 978-951-39-4317-2 (pdf)

Forsberg RahkolaPietarsaari 2011

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P

Renewable energy and the use of biomass in energy production promotessustainable development and decreases the use of fossil fuels. Biomass, e.g.wood chips can be used in the production of heat and electricity, as wellas being used as a biofuel component and novel product for the chemicalindustry. E cient utilisation of biomass requires a high level of knowledgeand the development of new processes to create a new way of thinking. Inthis process, international co-operation plays a signi cant role.

The aim of the HighBio project was to produce new information on biomass gasi cation and the utilisation opportunities of product gas

in biofuel and biochemicals production. The project was also aimed atstudying utilisation properties of biogasi cation ashes in distributedenergy production. Small-scaled CHP plants can be used for simultaneousheat and power production by gasifying wood chips and by burningenergy intensive product gas. Compared with thermal combustion,particulate emissions from gasi cation are lower, which also contributesto the EUs ever tightening emission legislation. Several small and middlescale companies in the Northern part of Finland and Sweden have workedwith biomass gasi cation, and during the project, the birth of new ones has been seen. In this development stage, researchers of the HighBio projecthave also been strongly involved.Increased use of renewable energy opens up new possibilities forentrepreneurship and the birth of new companies, especially in ruralareas. In order to enable these opportunities, we need research datafrom the universities, novel innovations, and especially their successfulcommercialisation. The HighBio project has also contributed to tacklingthose challenges by arranging research seminars and meetings to companiesand other interest groups, as well as by establishing research activitiesand collaborations. Regional collaboration combined with national andinternational research networks has made a strong basis for this activity.

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HigHbio project publication

Finally, we would like to express our deepest gratitude to all of youwho have participated in the HighBio project; researchers, companiesand other interest groups, nanciers and active participants in ourseminars and meetings. You have made this project very interestingand challenging, but most importantly having made the project havea signi cant e ect upon our society.

Kokkola, 12th of May, 2011

Ulla Lassi Bodil WikmanProfessor, Applied Chemistry Project coordinatorLeader of HighBio project

Within the HighBio project seminars and study tours have been arranged bydi erent partners. The picture presents the Finnish HighBio delegation visitingSmur t Kappa kra liner and bioenergy production site in Pite, Sweden withinthe framework for a project seminar in May 2010.

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5

CDECENTRALISED ENERGY PRODUCTION

Decentralised Energy Production 9Ulf-Peter Gran

BIOMASS GASIFICATION ETC-HighBio Contributions 19 Magnus Marklund and Olov hrman

Centria Downdra Biomass Gasi er for Small Scale 31 CHP ProductionYrj Muilu and Kari Pieniniemi

Gasi cation and Analysis of the Product Gas 41Kari Pieniniemi and Yrj Muilu

Future of Gasi cation Technology 50 Jukka Kon inen

Gasi cation Technology from a Users Perspective 53Pen i Etelmki

BIOFUELS AND UTILISATION OF SYNTHESIS GAS

Biofuels of the Future 59Kirsi Partanen and Ulla Lassi

Syngas into New Chemical Products and New Applications 68Henrik Romar, Pekka Tynjl and Riikka Lahti

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UTILISATION OF GASIFICATION BY-PRODUCTS

Chemical Studies for Utilisation of Bioashes 81Sari Kilpimaa, Toivo Kuokkanen and Ulla Lassi

TECHNO-ECONOMICAL EvALUATION

Small-scale Biomass Based Combined Heat and Power 91Production Economic Conditions Joakim Lundgren

HighBio Project Info 98

Publications and Reports Related to the HighBio Project 101Financiers 104

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DECENTRALISEDENERGY PRODUCTION

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D E PUlf-Peter Gran

In terms of national energy production, it is important in the future thatsmall-scale decentralised solutions come closer to the raw materials andconsumers. Unfortunately, in Finland big companies are still makinguse of their resources to hamper small-scale local solutions. Hopefully,common sense will prevail and decentralised energy production can bedeveloped in small units. In particular, small-scale CHP units (combinedheat and power) can contribute to the development of sustainable energyproduction.

D CHP-

Finland and Sweden possess large amounts of unused biomass resources inthe form of forests. These resources could be exploited in the production ofelectricity and heat. In addition, they o er raw materials for the productionof transportation fuels and chemicals. Due to rapid progress in technicaldevelopment, the research is globally focused on the simple and robustsolutions for the re ning processes.Small-scale solutions with regards to the re ning of biomass forconsumers in a nearby region do not have the desirable resources requiredfor development. The nancial support from national and EU sources offunding are o en awarded to the big actors due to their be er visibility.The authorities and decision-makers have not been interested or have nothad the competence to see the considerable potential of small-scale energyproduction, such as thermal power production.

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FIGURE 1 . Decentralised energy production.

S R

The scheme illustrated below describes in general the re ning of biomass- based raw materials.

Biomass-based raw material can originate from forest, agriculture,manure or agricultural waste, municipal waste, or wastes from the processindustry.

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decentralised energy production

FIGURE 2. Processing of biomaterials.

CHP

Decentralised CHP units for heat and electricity can be comprised bymany di erent ways depending largely on the volume of the electricity to be generated. An important factor is the cost of electricity or an electricitysubsidy.

Examples of di erent types of units:Direct combustion of wood chips/pellets + Stirling engineDirect combustion of wood chips/pellets + Organic Rankine Cycle(ORC)Direct combustion of wood chips/pellets + Small steam turbineGasi cation + Direct combustion + Gas engine or micro turbine Gasi cation + Direct combustion + ORCGasi cation + Gas engine (piston engine)Gasi cation + Micro turbineBiogas + Gas engineBiogas + Micro turbineCombination of bio-syngas and biogas + Gas engine or microturbine

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FIGURE 3 . Bio-based raw materials for processing.

FIGURE 4 . Forest biomass for gasi cation.

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B

Forest and agricultural based raw materials for green energy can originatefrom several di erent resources, as described below:In general,biomass from forest contains:

Fuel wood , di erent size wood from forest clearance andthinningLogging residues , branches and tops from a logging areaEnergy forest , or short rotation forestry, e.g cultivation of downy birch

Energy plants cultivated in eldsReed canary grass, hemp ( bre hemp for biomass), elephant grassetc.Willow, bri le willow, cultivated mainly in elds; is an intermediate form of energy forest

From agriculturestraw, grass and other plants cultivated for biogas production

Wet biomassManure and bio waste, such as spoiled silage in bales or from silo

Oil plantsTurnip rape, oilseed rape, sun ower, mustard, ax etc. yield bio-oils, which can be converted to biodiesel by the esteri cationprocess

G I

The concept of small-scale decentralised re ning of biomass has thepotential to exhibit a key role in the regional environmental thinking. Thestudy of novel technologies suitable for decentralised re ning processesenables the re ning of the biomass-based raw material for customersand consumers in local andneighbouring areas. A growing interest

for the integration of di erent re ning processes exists, to increase theconsolidation and create positive synergy e ects.

G

Gasi cation of biomass produces useful product gas which is an interestinggaseous resource. It can be utilised as a fuel in direct combustion or as araw material for further processing. Amongst all the available gasi cationoptions in terms of production of fuels and chemicals, forest-based

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biomasses as raw materials is the most interesting. Synthesis gas (syngas)or product gas can be used in further processing a er puri cation andconditioning.

Application areas include:Direct combustion for heat productionDirect combustion in CHP unit for heat and electricityproductionGas fuel for electricity production CHP with:

piston engine/gas enginegas turbinefuel cell (in the future)

Processing and upgrading to

transportation fuels chemicals

I

Coordination of activities between operators of heating units in the regioncan be performed in di erent ways and evolve over time. Therefore it isalready important in the planning phase to try to locate units so that futureplans can be implemented easily. This includes suitable land area, logisticsas well as cables and pipe lines for electrical and thermal connectionsrespectively.

Some examples of the possible activities for integration include:Drying of the wood chipsCHP unitEnergy terminals, with integrated treatment of biomass rawmaterial and processed materialGasi cation of biomass

Solar energy Geo energyManufacturing of pelletsProduction of biogas from farmsProduction of biogas from nearby communitiesProcessing of raw materials for the production of transportationfuels

Activities depend primarily on local development and interests.

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FIGURE 5. Local and integrated energy production.

O en integration evolves gradually, and is dependent on what stage thepieces that are used in the development of local activities will be introduced.The priority is mainly due to, for example, needs and demands of the localenergy cooperation and neighbouring area.

G

By a chemical re ning of syngas or product gas it is possible to producea variety of raw materials and products. The greatest expectations areassociated to the transportation fuels as a replacement for fossil fuels. This

is bene cial for the utilisation of forest-based biomass as a raw materialsince it does not compete with food production.Through the development of green chemistry it is possible to reduce the

dependence of oil products. In addition, as local resources are exploitedmore e ciently it can only improve the employment and self-su ciencyin the region.

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S

A good alternative is to locate gasi cation and re ning units close to aCHP plant, which allows the e cient utilisation of heat and distribution ofproduct gas obtained from the gasi cation process. It ensures that productgas of low quality and heat can be exploited in a CHP unit and districtheating network respectively.

It is appropriate for smaller gasi cation units based on biomassgasi cation to combine with local CHP plants, especially if the gasi ers,that can use moist or dry biomass to produce product gas free of tarparticles, are available. In order to produce product gas economically, a

CHP unit, which requires the drying of fuels and e cient puri cation oftars, must be large enough.

Decentralised energy production already o ers considerable potential toutilise local bioenergy resources through small-scale re ning, promotinga sustainable de elopment.

FIGURE 6. Green chemistry - potential of gasi cation of biomassa.

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BIOMASSGASIFICATION

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ETC-H B C Magnus Marklund and Olov hrman

ETC, Pite, Sweden

P -

An increase in the use of biomass based energy resources, both nationallyand globally, will help to reduce the demand of fossil fuels and limitlong-term greenhouse e ects. Besides the generation of electricity andheat, biomass can e ciently be converted into valuable materials, such aschemicals and biofuels through so-called biore nery concepts. Material

ow of the annual logging of biomass in Sweden, where about 45% is inthe form of logging residues (equivalent to approximately 70 TWh), ispresented in Figure 1.

Energy Technology Centre in Pite (ETC, Pite, Sweden) is currentlyworking on a pilot project for the gasi cation of biomass which has also been a part of the HighBio project. The project has involved the design,construction and commissioning of the pilot plant, which is based onPressurised Entrained ow Biomass Gasi cation (PEBG) for the productionof synthesis gas from wood waste and other biomass that the industryhas no use for. The technology concept is based on high temperature (>1200 C) gasi cation of powdered biomass in a pressurised entraineddown ow gasi er with a low production of tar and other hydrocarbons.The disadvantage of this concept in comparison with gasi cation at lowtemperatures and a long residence time is that the fuel must be ground toa ne powder (

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Concerning the slagging issue, Table 1 shows the di erent features whichmake up the tree. It clearly shows that the proportion of extractives andash is higher in the needles and bark in comparison with ordinary wood.This means that logging residues from forestry has a higher content ofextractives and ash content due to increased amounts of needles and barkthat comes with this material.

FIGURE 1 . Harvested annually material ow of biomass in Sweden in 2004.

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bioMass gasiFication

TABLE 1. Approximate percentages of cellulose, hemicellulose,lignin, extracti e and ash in Pine and Spruce.

Cellulose Hemi-cellulose

Lignin[wt-%] drybasis

Extracti es Ash

Pine (about 70 years)Stem wood 41 27 28 3 1Bark, inner 36 26 29 4.5 2Bark, outer 25 20 48 3.5 2Branches 32 32 31 3.5 1Wood needles 29 25 28 13 5

Spruce (about 110 years)Stem wood 43 27 28 0.8 1Bark 36 20 36 3.8 4Branches 29 30 37 1.7 2Wood needles 28 25 35 6.1 5

The PEBG plant at ETC was inaugurated as the IVAB gasi er at theSolander Symposium in November 2010 (see Figure 2 for a side view ofthe plant). The facility is currently being commissioned (April 2011) where

all subsystems have been systematically tested, and initial combustiontests have been carried out.

FIGURE 2 . PEBG pilot plant at ETC (titledIVAB gasi er) was put into operation inApril 2011.

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The initial gasi cation experiments will focus on atmospheric gasi cationof stem wood with a synthetic air mixture to ensure safe operation. Furtheron, experimental campaigns will be focused on pressurised conditions andwith an increased oxygen concentration for various fuels (bark, stumpsand other wood residues). The plant is designed for a load and pressure of1 MWth and 10 bars respectively. The nominal operation conditions will be500 kWth at 5 bar absolute pressure.

F

Supply of biomass in powdered form can be problematic due to thebrous structure of the biomass. Powder from biomass is mainly in the

form of small chips that tend to stick together and form arches and bridgeswhen the powder is transported. A robust and reliable feeding system isa necessity for all types of processes that handle powders from biomass,especially when biomass is used for combustion and gasi cation (e.g.in PEBG process). In these applications, a steady and stable supply ofpowder is required. There are a variety of pneumatic powder transportsystems available on the market for atmospheric processes, but theseare not suitable for pressurised conditions due to the large amounts oftransport gas required. The most suitable powder supply for pressurisedgasi cation is a lock hopper based concept with dual fuel storage tanksthat can alternate with lling and feeding to maintain a continuousoperation. For the PEBG plant, such a concept has been constructed anddemonstrated with good performances in the initial tests.

The rst tests of the feeding system in the PEBG plant were carried outwith three di erent fuels (a bark powder and two stem wood powderswith di erent size distributions) under atmospheric conditions. The feederwas calibrated by the use of a scale that could log the rate of fuel powder being transported every second. The linearity of the weight increase inproportion to the feeding rate can be used as a stability measure of the

powder feeder. Furthermore, impact of fuel type, size distribution andchoice of fuel on the stability were also examined. Figure 3 shows thelinear relationship between the measured fuel ow and the used feedingrate for a powder originating from stemwood.

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FIGURE 3. Relation between the measured ow of feedstock and the feedingrate.

F P

In recent decades, pellet manufacturing and powder combustion hassteadily increased. In both processes, a signi cant issue is the grinding of biofuels. This also applies to biomass gasi cation in plants where woodpowder is used, e.g. in a cyclone gasi er or entrained ow gasi er. Therequirements for the powder, however, di er between these applications.For example, pellet production is suitable for particles with a diameter

up to 3 mm whilst this size must be reduced to less than 1 mm in powdercombustion and gasi cation. Furthermore, another requirement is that aportion of the particles, about 10% of the powder, should be less than 100mm. This is an important requirement considering ame stability.

The grinding of biofuel is a more complicated process and requiresmore energy than coal grinding. This is because coal is more bri le,and therefore, more easy to break down. Previous studies have shownthat coal grinding requires 7-36 kWh/t of energy, which is less than theenergy reported for biomass (20-200 kWh/t). The grinding of pellets forpulverising normally requires most powders to be less than 1 mm, and

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a certain amount below 0.2 mm. Table 2 shows a number of pelletisingcompanies operating in Sweden. Bionorr distinguishes themselves with ahigh energy consumption of about 74 kWh / t. This is due to the fact thatBionorr uses a special process where grinding takes place before drying.Normally, drying is carried out before grinding and as a result reducesthe demand for electricity. Values presented in Table 2 are partly basedon estimates (e.g. grinding capacity and engine e ciency), and therefore,results presented are not comparable directly. It is, anyhow, reasonable toassume that the average energy consumption for milling of biomass is 25kWh/t (moisture content of biomass being 10-12%).

It is widely known that energy consumption increases markedly withthe moisture content of biomass. Bionorr uses about three times as muchenergy for grinding compared with the maximum energy consumption

at any other facilities. Bionorr uses raw chips with a moisture content ofabout 50 % whereas other facilities grind dried wood chips or sawdustwith a moisture content of about 12 %. Previous experience has shownthat the following factors, in addition to moisture, impact the energyconsumption in grinding:

1. Sieve density2. Sieve plate area3. Structure of the materials

Another pre-treatment technology is torrefaction, which is a thermalpretreatment process of biomass to convert it from hydrophilic tohydrophobic materials. The process takes place at 250-300 C in an inertenvironment (fumes). At these temperatures during the heat treatment ofdry wood, the connecting structure between the cellulose, hemicelluloseand lignin (wooden main components) changes. Hemicellulose is the leastheat stable component of wood and is the source of most of the substancesproduced by torrefaction. The degradation of hemicellulose also initiatessome structural changes in the lignin, the cellulose, however it is notsigni cantly a ected.

Table 3 shows a list of various references that report mass and energyexchanges in torrefaction and the boundary conditions that were used inthe trials. Table 3 also shows that the mass exchange varies between 43 and87 % depending on the wood type, temperature and reaction time. Energyoutput also possesses wide variations. The lowest energy yield is 50 %while the highest is about 93 %. However, there are some results whosevalues that are even higher than these.

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TABLE 2. various milling techniques used in Sweden.

Owner Mark Sie e(mm)

Produc-tion(t/h)

Motore ect(kW)

Energy(kWh/t)

Type ofraw mate-rial

Moisturecontent %

1. Glom-mers

Russian(un-known)

6 1,6 25 15,6 Dry chips 9-15

2. SCABionorr

ABB windterm

10 736 73,6 Greenchips

45-55

3. Lax Pel-lets

AndritzSprout

2,5 8 200 25,0 Pine /sprucescip

10

4. LuleBioenergi

Buhler 3 (7-10) 24,7 Chips 10-15

5. DeromeBioenergi

Buhler 4-6 5 118 24,0 Sawdusts 12

6. Lant-mnnensAgroenergiAb

AndritzSprout

4-6 10 315 31,5 Processedchips(max 15mm)

11

7. Vida Pel-lets

AndritzSprout

5 16 200 12,5 Chips 12

TABLE 3. Mass and energy exchange from torrefaction.

Material Mass ex-change (%)

Energyoutput (%)

Calori c value (MJ/kg)

Temp(oC)

Reactiontime (min)

Wheat straw 72.0 77.0 20.7

270 30Reed canarygrass71.0 78.0 20.8

Willow 80.0 86.0 21.7Wheat straw 55.1 65.8 22.6

290 30Reed canarygrass 61.2 69.0 21.8Willow 72.0 79.2 21.9Willow 87.0 95.0 19.4 250 30Willow 67.0 79.0 21.0 300 10Wood waste 56.0 65.0 22.8

27030

Wood waste 54.0 62.0 23.0 60Wood waste 43.0 50.0 23.1 90Birch 68.9 88.3 21.1

280 120Pine 72.1 92.9 22.3Bagass 64.7 82.8 19.8

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Wood possesses three main components: cellulose, hemicellulose andlignin. These three substances are polymers with weak chemical bounds.During the heat treatment of dry wood at temperatures above 200 C, thestructure of these chemical bonds changes. There are also di erences inhemicelluloses between so and hard wood. For example, hemicellulosepresent in hardwood contains 80-90 % xylan, while so wood contains60-70 % glucomannan and 15-30 % arabinogalactan. Xylan is more heatsensitive than the other wood components, and this explains the highermass loss during torrefaction of hardwood and straw.

P

The gasi cation of biomass produces a synthesis gas consisting of H2 ,CO and CO2. In addition to these components, raw synthesis gas cancontain small amounts of pollutants such as H2S, COS, mercaptans, heavyhydrocarbons (tar) and particulates. It may also contain traces of halidesand HCN. Depending on the application where the synthesis gas is to beused, demands for puri cation di er. In general, if synthesis gas is usedfor catalytic synthesis of transportation fuel it requires a higher level oftreatment compared if the gas is used for power generation. Many di erentgas puri cation technologies exist today. The techniques that can be relevantfor puri cation of synthesis gas from a biomass gasi er are as follows:

Physical and chemical scrubbers (absorption)AdsorptionThermal or catalytic conversionMembranes

A

When a gas dissolves in a uid absorption takes place. There are two types

of absorption, chemical and physical. An example of chemical absorptionis amine wash that can be used to clean synthesis gas from H2S and CO2.There are many di erent types of amines used. The general reactions thattake place are:

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Alkaline solutions can also be used to clean synthesis gas. O en thesolutions are Na2CO3 or K2CO3 at pH 9-11. The reactions that take placeare:

An example of puri cation of H2S from synthesis gas produced fromgasi cation of black liquor is shown in Figure 4. The graph shows theamount of H2S and CO2 that can be removed from the synthesis gas by

means of short-term contactors containing dilute liquor, which is a kindof alkaline wash. In the experiment 78 % of the H2S was removed from thesynthesis gas with three short term contactors.

FIGURE 4 . Treatment of H2S using diluted liquor at 50 C.

Examples of commercial processes that use alkaline solutions includeBen eld, Catacarb, Flexsorb, Giammarco-Vetrocoke, Seabord, VacuumCarbonate, Vacasulf and Alkacid etc.

When large amounts of impurities have to be removed from the gasphase, a natural absorption might be more appropriate. For example,organic solvents such as methanol are used to absorb impurities.Furthermore, puri ed synthesis gas as well as clean gas streams consisting


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of e.g. H2S and CO2, are readily available from the plant. Examples ofcommercial technologies are Selexol, Sepasolv, Purisol and Rectisol.

Sul nol and Amisol are two di erent processes in which both chemicaland physical absorption takes place. The physical absorption is used toremove most of the impurities and the chemicals to purify the nal content.In such Amisol processes methanol is used for physical absorption andalkyl amine as a chemical solvent.

A

Adsorption usually takes place at low temperature, and can either bephysical or chemical in nature. The adsorption of a gas bounds to the

surface of a material with high surface area e.g. 500 m2

/g. Examples ofmaterials used in adsorption are activated carbon or zeolites. Activatedcarbon is used to adsorb heavier hydrocarbons from a gas stream whilstzeolites can be used to remove CO2 from the synthesis gas. Regenerationof adsorbents can be achieved by heating or using pressure. For example,ZnO can be used to remove H2S from a gas stream since H2S reacts withZnO to form ZnS at elevated temperatures. However, ZnS is di cult toregenerate. For this reason it is used only to remove small amounts ofpollutants before the gas is injected into the catalysts for the production oftransportation fuels.

T

Contaminants can also be removed via thermal or catalytic conversion.Odours and volatile organic impurities can be oxidised thermally whilstvia catalytic conversions, impurities are removed at lower temperatures.

MMore recently, membranes have been used in gas puri cation. A zeolitemembrane or polymer electrolyte membrane is used to selectively separateout a particular component into a gas stream. ETC in Pite, Sweden, hassuccessfully tested CO2 selective zeolite membranes at high pressure. Themembranes have great potential to be used in biofuel production becausethe synthesis gas from a biomass gasi er needs to be puri ed from CO2.

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FbioMass gasiFication

S

Several research projects are underway in this area. In the BioDME project,currently performed at ETC in Pite, DME is produced on a pilot scale (4tons/day) from synthesis gas that is produced from gasi cation of blackliquor, which could also easily be further converted into gasoline. Similarly,diesel can be produced from synthesis gas. In Finland there are on-goingresearch and development activities around this process. Synthesis gas hasfor a long time been converted into many di erent products. For biomassgasi cation, it is important that the formed synthesis gas can be puri edto a suitable quality for existing technologies. In addition, there should be room for innovations in gas cleaning and catalytic synthesis of customsynthesis gas from biomass gasi cation, such as zeolite membranes for thepuri cation of synthesis gas.ETC has a bench scale plant for the catalytic synthesis of methanol andDME. During 2010, the rst synthesis of methanol was achieved fromsynthesis gas via black liquor gasi cation. The gas from the black liquorgasi er was puri ed rst from benzene with a carbon lter (adsorption)and then from sulphur components with a layer of zinc oxide. The clean gaswas then introduced into a catalytic reactor where the gas was convertedinto methanol. Figure 4 shows the plant used for methanol synthesis.Totally, approximately 0.6 dm3 of liquid bio-methanol was produced, seeFigure 6.

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FIGURE 5. Plant used for the catalytic synthesis of methanol from syngas. Theplant includes the reactor with the addition of carbon, zinc oxideand a catalyst.

FIGURE 6 . Methanol is drained from the facility, made from gasi ed blackliquor.

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C D B G S S CHP P

Yrj Muilu & Kari PieniniemiCentral Ostrobothnia University of Applied Sciences

CENTRIA R&D, Ylivieska, Finland

During the past few years, gasi cation of biomass has become a populartopic of industrial and scienti c interest. Product gas or synthesis gas, as aresult of biomass gasi cation, can be used in small-scale CHP (combinedheat and power) units for heat and power (electricity) production.Moreover, the product gas can also be used in production of biofuels andchemicals. Small-scale CHP can be de ned as combined heat and powergeneration systems with electrical power less than 100 kW. Micro-scaleCHP is also o en used to denote small-scale CHP systems with an electriccapacity smaller than 15 kWe (Dong L. 2009).

The Centria downdra gasi er studied in the HighBio research project,as shown in Figure 1, is based onpatented EK gasi er technology. Thermaland electrical output power of the Centria research gasi er is 100 kWth and50 kWe respectively.

The Centria downdra gasi erconsists of a feeding system for woodchips, air pre-heater and supply, gasi er with ash removal and a gas cleaning

system (Figure 1). Centria research gasi er is based on a traditional woodgasi cation process, but it has some distinct technical improvements thatmake it unique and more versatile in distributed CHP production. In theEK-technology based biomass gasi cation process the quality of the fuelis not as critical as in traditional gasi ers and (for example) in air dried(moisture content 3040%) wood chips (containing bark) made from birch,pine etc which can be fed in to the gasi er.

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FIGURE 1. CENTRIA downdra gasi er is based on patented EK gasi cationtechnology.

Process conditions during the stable operation of the Centria downdragasi er is presented in Table 1 and the process ow diagram in Figure 2.

TABLE 1. Process conditions during the stable operation of theCentria downdra gasi er

Property alueFeedstock mass ow, kg/h 45Air ow, Nm3/h 52Air temperature, C 16Reactor temperature, C 1200Bo om ash removal rate, kg/h 0.4Product gas ow,Nm3/h 78

Research at the Centria R&D renewable energy laboratory aims to providea more comprehensive understanding of the operational conditions,produce di erent gas or syngas compositions and study the heat andelectricity coproduction (CHP) optimisation from syngas generated bygasi cation of renewable energy sources. This includes wood chips andsmall size thinnings as well as other agricultural biomasses. The aim of thestudy is in good accordance with the EU strategy to reduce the dependence

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on fossil fuels, reduce greenhouse gas emissions and meet the tough CO2 reduction targets.

In biomass-fuelled CHP systems combustion and steam turbinetechnologies are the most widely used, particularly for large and medium-scale biomass-fuelled CHP systems (Table 2). Gasi cation based CHPsystems can potentially have a higher electricity e ciency than a directcombustion CHP. The gas obtained by gasi cation can be utilised in diesel,gas, Stirling or dual fuel engines, or in a gas turbine. (Verigan 2009)

TABLE 2. Major energy con ersion technologies for biomass-fuelledCHP systems (Dong L., 2009)

Primary technology Secondary technology

Combustion producing steam, hotwater Steam engine; steam turbine; Stirlingengine; Organic Rankine Cycle (ORC)

Gasi cation producing gaseous fuelsInternal combustion (IC) engine; micro-turbine; gas turbine; fuel cell; Stirlingengine

Pyrolysis producing gaseous andliquid fuels Internal combustion engine

Biochemical/biological processesproducing ethanol, biogas Internal combustion engine

Chemical/mechanical processes pro-ducing biodiesel Internal combustion engine

Downdra gasi cation can be considered as one of the most suitabletechnologies for distributed small-scale biomass based combined heat andpower production up to about 1 MWth. All together there are about 50commercial gasi cation plant manufacturers in Europe, the United States,and in Canada from which 75% uses a xed-bed downdra design, 20%

uidised-bed systems, 2.5% updra and the remaining 2.5% are variousother designs (H. Knoef 2000).

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FIGURE 2. Process ow diagram of the Centria R&D renewable energylaboratory gasi er

S

Speci c gas production of the Centria R&D renewable energy laboratorygasi er and wood gas fuel consumption of the modi ed IC engine wasdetermined using di erent electric loads of 9 kW, 18 kW and 27 kW (Figure3).

Moisture content and measured higher and lower heating values of thewood chip used in this study are represented in Table 3. Moisture of chipswas rather high at 44.6 %.

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FIGURE 3. Study of the gas production and fuel consumption of the modi ed8 litre 6 cylinder IC engine. Electrical power loads of 9 kW used inthe experiment (le ) and IC gas engine (right)

TABLE 3. Measured properties of the wood chips used in theexperiment

Wood chip property Unit Measuredvalue

Moisture as received % 44.6Ash (dry basis) % 1.9Higher heating value (HHV(dry)) MJ/kg 19.71Lower heating value (LHV(dry)) MJ/kg 18.3Lower heating value as received(LHV)

MJ/kg9.5

Speci c gas and wood consumption of the IC engine was determined byincreasing the electric load from a no-load situation to 27 kW by 9 kWsteps using 9 kW electric heaters (Figure 3). Speci c gas consumption ofthe IC engine in a no-load situation is rather high at 70.4 Nm3 of wood gasto produce 1 kWh of electrical energy compared to an under load situationwhere 2.63.0 Nm3 is required to produce 1 kWh of electrical energy. (Table4)

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TABLE 4. Measured data for the determination of wood gasconsumption of the IC engine

Measurement Unit Test run 1 Test run 2 Test run 3 Test run 4

Averageproduct gasvolume owrate

Nm3/h 70 94 124 151

Wood chipconsumption kg/h 39.78 - 58.84

Heat power kW 22 45 52.5Electric energy kWh 0 9 18 27Speci c gasconsumption Nm

3

/kWh 70.4 2.6 3.0 3.0

Speci c wood chip consumption was estimated from measurementspresented in Table 4 to be 1.06 kg/kWh whilst the speci c gas productionwas calculated to be 2.45 - 2.83 Nm3/kg.

Wood chip consumption was also determined using an Oilon naturalgas burner modi ed for wood gas usage. The same burner can also beused in a Sterling engine CHP unit (Figure 6). According to collectedmeasurements air dry (moisture 35 %) wood chip consumption was 57

litre / h, which equates to about 16 kg / h (approx speci c gravity: 280 kg/m3). (Figure 4) Wood gas production was measured using a gasometerand found to be 7.49 Nm3/h, which according to this measurement, wouldproduce 3.6 Nm3 for 1 kg of wood chips. This is rather high compared tovalues presented in Table 5.

FIGURE 4. Evaluation of speci c gas production using a gas burner. Wood gasfuelled gas burner (le ) and test facility (right).

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Measured wood chip consumption of the Centria CHP unit as a functionof electrical energy produced is presented graphically in Figure 5.

FIGURE 5. Wood chip consumption (kg/h) as a function of electrical energy(kWh).

Measured speci c gas production and fuel consumption are in goodagreement with the values presented in literature (Table 5)

TABLE 5 Measured gasi cation parameters compared to typicalalues presented in literature

Gasi cation parameter Unit Measured values(Centria gasi er)

Typical values(Knoef 2005)

Speci c gas production Nm3/kg 2.52.8 23Speci c gas production Nm3/kWe 2.63.0 23

Speci c fuelconsumption

kg/kWe 1.06 11.3

Speci c load kg/m2.hr 2510 5002000

It should be noted that the moisture content of wood chips used in thisexperiment was about 45 %, which is much more than the literature valuegiven for the highest acceptable moisture content (25 %) for a downdragasi er (H. Knoef 2005). Lower heating value of the wood chips used inthis experiment was about 9.0 MJ/kg, which is considerably lower than


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the literature value provided (13.5 MJ/kg) for wood chips with a moisturecontent of 25 %.

U

High temperature biomass gasi cation (1200 1400 C) results in biosyngas(H2 to CO ratio 2:1), a raw material that can be used in the chemical industryto produce liquid fuels (e.g. ethanol, methanol, and FT-diesel), to generateheat and power or synthesise other chemicals and produce H2.

Low temperature biomass gasi cation (800 1000 C), on the otherhand, results in product gas that contains mainly CO, H2 , CO2 , H2O, CH4 ,N2 , some higher hydrocarbons and tars, which can be used as fuel for

gas or in a Stirling engine to produce electricity along with heat. A er tarcracking, cleaning and reforming, product gas can be used like biosyngasin several applications e.g. as a feedstock for synthetic natural gas (SNG)production.

The addition of steam or oxygen to the biomass gasi cation processresults in steam reforming and produces a biosyngas, which can be usedas the feed to a Fischer-Tropsch reaction to make higher hydrocarbons, orto a water gas shi reaction (WGS) for hydrogen production. Currently,hydrogen is primarily used in the chemical industry, but in the future itcould become a signi cant fuel used in cars for example. (Holladay, et al.2009).

S E M -CHP CR D

A Stirling engine coupled with a biomass gasi er is the latest installationin the Centria R&D renewable energy laboratory.

A Stirling engine is a heat engine which operates by cyclic compressionand expansion of air or other gas, the working uid, at di erenttemperature levels such that there is a net conversion of heat energyto mechanical work. The Stirling engine is noted for its high e ciencycompared to steam engines, quiet operation, and the ease with which itcan use almost any heat source. This compatibility with alternative andrenewable energy sources has become an increasingly signi cant methodfor reducing the dependence on fossil fuels and to reduce CO2 emissions.(h p://en.wikipedia.org/wiki/Stirling_engine)

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FIGURE 6. Installation of the SOLO Stirling 161 Combined Heat and Power tothe Centria R&D renewable energy laboratory

The heat from the combustion of fuel is transferred from the outside to theworking gas at a high temperature (typically 700C - 750C) and the extraheat, which is not converted into work on the sha , is rejected into thecooling water at 40C - 85C.

There are some important bene ts from using the Sterling miro-CHP units compared to conventional IC engine combined heat powerproduction. For instance service intervals for Stirling engines are muchlonger compared with O o engines, being typically 5000 to 8000 hourswhilst the emission of harmful substances from current Stirling burnerscan be 10 times lower than the emission from gas- red O o engines witha catalytic converter. (SOLO STIRLING GmbH version 1.9, July 2003)The capacity of the Stirling engine is 9 and 26 kW for electric power andthermal power respectively, whilst a total e ciency of over 95 % can beachieved.

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R

Dong L., Liu H. and Ri at S. Development of small-scale and micro-sca-

le biomass-fuelled CHP systems A literature review. Applied ThermalEngineering 29 , 2009: 21192126.Holladay, J.D., J. Hu, D.L. King, and Y. Wang. An overview of hydrogen

production technologies.Catalysis Today 139. 2009. 244 260.Knoef, H.Inventory of biomass gasi er manufacturers and installations. En-

schede: Final Report to European Commission, Contract DIS/1734/98-NL, Biomass Technology Group BV, University of Twente, 2000.

Knoef, H.A.M., ed.Handbook Biomass Gasi cation.BTG Biomass Technolo-gy Group BV, The Netherlands, 2005.

SOLO STIRLING GmbH.Technical Documentation. Solo Stirling 161 Com-bined Heat and Power (CHP) Module. Silde ngen: www.stirling-engine.de, version 1.9, July 2003.

Verigan, H.J. Advanced Techniques for Generation of Energy from Bio-mass and Waste.ECN publication. , 2009: Available from: h p://www.ecn.nl/ leadmin/ecn/units/bio/Overig/pdf/Biomassa_voordelen.pdf.

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G A P G

Kari Pieniniemi & Yrj MuiluCentral Ostrobothnia University of Applied Sciences

CENTRIA R&D, Ylivieska, Finland

B

Gasi cation is a thermal treatment process based on drying, pyrolysis,oxidation, and char gasi cation, which results in gaseous productsand small quantities of organic impurities, char and ash. Gasi cation isperformed at high temperatures in order to optimise gas production. The

resulting gas, known as the producer gas or product gas is a mixture ofcarbon monoxide (CO), hydrogen (H2), and methane (CH4), together withcarbon dioxide (CO2), nitrogen (N2) and some organic impurities (tar)along with dust, HCl, H2S, NH3 ect. (Figure 1)

biomass + O2 (or H2O) CO, CO2 , H2O, H2 , CH4 + other hydrocarbons tar+char+ash HCN, NH3 , HCl, H2S + other sulphur gases

FIGURE 1. Product gas formed from biomass gasi cation.

Pyrolysis is the rst step in all thermochemical biomass conversions.Conventional slow pyrolysis (carbonisation) has been utilised forthousands of years primarily for the production of charcoal. Fast pyrolysisproduces mainly liquid bio-oils (6075 wt%), some solid char (1525 wt%),and non-condensable gases (020 wt%). Flash pyrolysis is considered to be an improved version of the fast pyrolysis, with reaction times of few toseveral seconds. (Table 1)

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TABLE 1. Pyrolysis conditions in slow, fast and ash pyrolysis

Slow pyrolysis Fast pyrolysis Flash pyrolysisPyrolysis temperature(C)

300700 6001000 8001000

Heating rate (C/s) 0.11 10200 >1000Particle size (mm) 550

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TABLE 2. Tar compounds can be divided into ve di erent classes(Li C., 2009)

Tarclass

Class name Property Representati ecompounds

1 GC-undetectable Very heavy tars, cannot be detected by GC (GasChromatography)

Determined by subtract-ing the GC-detectable tarfraction from the totalgravimetric tar

2 Heterocyclicaromatics

Tars containing heteroatoms; highly watersoluble compounds

Pyridine, phenol, cresols,quinoline, isoquinoline,dibenzophenol

3 Light aromatic (1ring)

Usually light hydrocarbons with single ring;do not pose a problemregarding condensabil-ity and solubility

Toluene, ethylbenzene,xylenes, styrene

4 Light PAHcompounds (23rings)

2 and 3 rings com-pounds; condense atlow temperature evenat very low concentra-tion

Indene, naphthalene,methylnaphthalene, biphenyl, acenaphthalene,

uorene, phenanthrene,anthracene

5 Heavy PAHcompounds (47rings)

Larger than 3-ring,these componentscondense at high-temperatures at lowconcentrations

Fluoranthene, pyrene,chrysene, perylene, cor-onene

Gasi cation, even at high temperatures of 800-1000 C produces a signi cantamount of tar, which is still the main problem in gasi cation processes andtherefore tar removal is regarded as one of the greatest technical problemsfor the development of gasi cation technology.

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FIGURE 3. Example of some common tar compounds

Composition and the amount of tar, which has been de ned as a collectionof organic contaminants with a molecular weight larger than that of benzene, depends on the biomass type, gasi er and operation conditionsof the gasi er. Average concentration of tars are approximately 100 g/Nm3 in an updra gasi er, 10 g/Nm3 in a uidised bed gasi er and 1g/Nm3 in adowndra gasi er (Nee J. 1999) (Figure 3)

FIGURE 4. Typical particulate and tar loadings in biomass gasi ers (tar B.P. >150 C) (Stlberg P. 1998)

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Most important tar decomposition processes are cracking, steam and dryreforming (Figure 5).

Cracking: p CnHx q CmHy + rH2.Stream reforming: CnHx + n H2O (n + x/2) H2+ n CODry reforming: CnHx + n CO2 (x/2) H2 + 2n CO.Carbon formation: CnHx n C+(x/2) H2.CnHx represents tar, and CmHy represents hydrocarbon withsmaller carbon number than CnHx

FIGURE 5. Most important tar decomposition processes.Tar can be reduced in the gasi er itself by modifying the gasi cationconditions or gasi er design ( primary measures) or by mechanical separationor through thermal or catalytic cracking a er the gas formation (secondarymeasures). In the EK gasi er technology tar is reduced primarily by a novelgasi er design while secondary measures for gas cleaning involves only awet scrubber.

A

The analysis of impurities of the product gas such as tars is most o enperformed by gas chromatography (GC) or gravimetrically. Sampling of thetar analysis methods are most o en based on trapping the tar in an organicsolvent or by adsorption on a suitable sorbent. (Li C. 2009). Traditionaltar sampling methods are based on cold trapping coupled with solventabsorption in impingers. Various solvents are used to sample tar, but2-propanol was recommended by the Tar Protocol (Neef 2005). (Figure 6)

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FIGURE 6. Light tars can beanalysed by gaschromatographywhile heavy tarsare analysedgravimetrically(Reinikainen 2009)

In addition to the tar protocol, we have used a SPA (Solid Phase Adsorption)method for the determination of the total tar content of the product gasfrom the gasi er in CHP production. Biomass used in this experiment wasin the form of wood chips possessing a moisture content of about 30 %.Tar samples were adsorbed on the solid sorbent (XAD) and the sorbentwas extracted with DCM (dichloromethane) using the Soxhlet apparatus.DCM extract was evaporated and the resulting residue was weighed viathe gravimetric method. Measured tar content of the producer gas duringhalf and full load was 143 g/Nm3and 138 mg/Nm3 respectively (Table 3).

TABLE 3. Total tar concentration of the Centria R&D pilot gasi erproduct gas before and a er cleaning

Power Tar content of the product gasmg/m 3n (dry, STP: 0C, 1 atm )

50 % 143 100 % 138

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FIGURE 7.Centria R&D renewable energylaboratory FTIR gas analyser GasmetDx4000N

Product gas from the gasi er contains mainly permanent gasesCO, H2 ,

CO2 , CH4 and N2. Permanent gas concentrations and quality of the productgas can be continuously followed by measuring CO, CO2 , CH4contents andethane and ethylene concentrations together with benzene by a FTIR gasanalyser (Gasmet Dx4000N). Fourier Transformed Infra Red spectroscopy(FTIR) is a spectroscopic method that compares the absorbed energy froman infra red source of light. Diatomic gases (hydrogen and nitrogen) can be analysed continuously by micro-GC. Hydrogen can also be measured by a Drger X-am 3000 ue gas analyser a er dilution of the product gassince the measuring range of the ue gas analyser is only up to 0.5 vol %

of H2.During the total tar sampling (Table 3) the product gas was alsocontinuously monitored by the FTIR gas analyser and the measuredconcentrations of the permanent gases are given in Table 4.

TABLE 4. FTIR analysis of the Centria R&D gasi er product gas(STP 0C, 1 atm). Concentration of the main gaseouscomponents (permanent gases)

Power H2Ovol%

CO2vol%

CO mg/Nm3

CH4 mg/Nm3

50 % 7.0 11.0 138 9100 % 6.3 9.4 171 11

Typical composition and concentrations of the product gas from theCentria research gasi er are presented in Table 5. Typical gas compositionwas measured by gas chromatography a er sampling in Tedlar sampling bags.

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TABLE 5. Typical composition and concentrations of the product gasfrom Centria R&D pilot gasi er.

Product gas component ol-% g/Nm 3

(STP 0C, 1 atm)CO 15 187H 2 15 14CH 4 2.5 18CO 2 15 295N 2 50Other gaseous compounds 2.5

During the total tar sampling (Table 3) theemissions of the internalcombustion engine (IC engine) was continuously monitored by measuringO2 , CO2 , CO, NOx and SO2 concentrations in the ue gas. Continuousemission measurements on dry basis, were based on paramagnetism (O2),IR absorption (CO, CO2), UV- uorescence (SO2) and chemiluminescence(NOx). Results of the continuous emission measurements with theestimated combined uncertainty are presented in Table 6.

TABLE 6. Composition and concentration of the ue gas maingaseous components during the tar sampling along withthe estimated total combined uncertainty

Measured ue gascomponent

Measured ue gascomposition

Concentration(dry, STP: 0C, 1 atm))

O2 0.4 0.04 vol% -CO2 172 vol% -CO 56863 ppm 170 19 mg/Nm3SO2 81 ppm 25 4 mg/Nm3NOx 16237 ppm 332 37 mg/Nm3

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FIGURE 8.IC gas engine emission measurement

R

Ellio , DC. Relation of reaction time and temperature to chemical com-position of pyrolysis oils.Proceedings of the ACS symposium series 376, pyrolysis oils from biomass.1988.

Li C., Suzuki K. Tar property, analysis, reforming mechanism and mo-del for biomass gasi cationAn overview.Renewable and SustainableEnergy Reviews , 2009: 594604.

Nee , J.P.A. Rationale for setup of impinger train as used in the TechnicalSpeci cation of Sampling and Analysis of Tar and Particles in the Pro-duct Gases of Biomass Gasi cation.Technical background document CEN BT/TF 143. Organic contaminants(tar). January 2005. h p:\\www.tar-web.net\.

Nee J., Knoef H., Onaji P. J. Nee , H. Knoef, P. Onaji, Behaviour of Tar in Bio-mass Gasi cation Systems, Tar Related Problems and Their Solutions.ReportNo. 9919, Energy from Waste and Biomass, 1999.

Nee , J.P.A,. Rationale for setup of impinger train as used in the Techni-cal Speci cation of Sampling and Analysis of Tar and Particles in theProduct Gases of Biomass Gasi cation.Technical background documentCEN BT/TF 143 Organic contaminants (tar) , 1999.

Reinikainen, M. Synthesis Gas Characterization at VTT laboratories andtest facilities. VTT Finland , 2009.

Stlberg P., et.al.Sampling of contaminants from product gases of biomass ga-si ers, VTT Research Notes 1903.Technical Research Center of Finland,1998.

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F G T Jukka Kon inen

University of Jyvskyl, Finland

In Finland biomass gasi cation has been studied for the last 30 years (Salo,2009) with an increased focus in the early 1990s on heat and power (CHP= Combined Heat and Power) from gasi cation. There was talk about a so-called IGCC technology (Integrated Gasi cation Combined Cycle), wherethe biomass raw material is gasi ed at high pressure and temperature andthe resulting gas is puri ed and directed to a CHP plant. A combined powerplant consists of a gas and steam turbine in combination with a waste

heat boiler (Kurkela, 2006). In Finland, there were two commercial-scale biomass-IGCC demonstration projects planned, but neither of them wasput into practice. At the same time the low cost of rival energy production,including oil and natural gas, made solid fuel based plant investmentsunviable. In addition, it can be said that customers (Forest Industrycompanies), despite the aid of large public investment, were not willingto on take the risk of developing IGCC technology for pulp mills. IGCCtechnologies were also developed for fossil raw materials (coal, oil).

As we approached 2010 the availability and price uncertainties of fossilcrude oil, greenhouse gas emission issues and the forest industrys needto develop alternatives for paper and paperboard products has made biomass gasi cation-based biore nery interesting. In practice, all majorFinnish forest companies, such as UPM Kymmene Oy, Stora Enso Oy, andMetslii o have their own biore nery project in the commercialisationphase. This also includes Neste Oil Oy and Vapo Oy (Kurkela, 2009).These projects aim to demonstrate the potential of biomass in pressurisedgasi cation, gas puri cation as well as catalytic processing of synthesisgas to biofuels. The fuel biodiesel is the most interesting, and the mostlikely, based on the fact that the synthetic production technology of diesel

from coal or natural gas has already been demonstrated.

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New catalytic processes for conversion of synthesis gas from gasi cationare already under development. For example in Sweden, the companyChemrec is currently building a DME (dimethyl ether) and a methanolproduction and distribution plant at Pite. Supporting this project isthe car manufacturer Volvo (Gebart, 2011). Biomass-based gasi cationdemonstration plants for the production of liquid biofuels are beingdeveloped across the Nordic countries as well as in Central Europe andNorth America (Bacovsky, 2009). In Austria, a gasifying plant currentlyin operation implements the REPOTEC process. The plant is based oncombined heat and power production from woody biomass gasi cation, butthe produced synthesis gas is also demonstrated in advanced productionof biodiesel and SNG (synthetic natural gas). SNG can also be used as fuelfor transport like natural gas. In Sweden REPOTEC technology is being

introduced in a larger scale in a so-called CoBiGas project (Rauch, 2011).By 2020, worldwide production of liquid biofuels is expected to increase by 3-6 times (Sohlstrm, 2010). On an industrial scale, liquid biofuelproduction is likely to constitute a signi cant share of the gasi ed biomassraw material processing, the so-called second-generation technology.The advantage of gasi cation is the use of raw materials that do notdisadvantage food production.

In the so-called decentralized scale gasi cation of wood biomass andsolid waste can bring signi cant increases in CHP production also ondecentralised scale, namely electricity generation from 10 to 1000 kWe.There is also talk about the so-called small- or micro-CHP technology.Gasi cation-based applications are currently being developed across theNordic countries and Central Europe, for example based on down-dra -gasi er (Kon inen, 2011). While small scale-CHP is not the solution forthe basic power production at a national level, it however can bring new business and jobs to rural municipalities and improve Finlands energyself-su ciency and security. In addition, it may provide new technologicalexport products. Small scale CHP units can also be combined with otherrenewable forms of energy production as a hybrid solution, such as biogas,solar and wind power.

In Lahti, Finland, waste fuel is capitalized in a large-scale gasi cationCHP plant (160 MWth) as a replacement for use of coal fossil fuel. Since1998, the plants waste and biomass gasi er has been connected to apulverized coal boiler (Lahti Energia, 2011). The potential of biomass- based IGCC has not disappeared either (Kurkela, 2006).

In addition to the price trends of competing energy sources, the lackof successful demonstrations has contributed to the slow progress in thecommercialisation of gasi cation technologies. In all the above mentionedtechnology projects based on gasi cation, the challenges are still the

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demonstration of long term operation as well as providing competitiveprices of electricity, heat and liquid biofuel. The most critical technologicaldevelopment for the future is gas puri cation.

R :

Bacovsky, N.: Overview on Wide Spread Implementation of 2nd Gen Bio-fuel Demonstration Plants in the World. 4th BTLtec, Graz, Austria, Sep-tember 2009.

Gebart, R.: Swedish Research on Forest Biomass Gasi cation and SyngasConversion into Second Generation Motor Fuels. Swedish-Finnish Fla-me Days, 2011, Pite, Sweden, January 2011. h p://www. rc. /Flame-Days_2011/Session_4_Gasi cation/27gebart.pdf

Kon inen, J.: Onko jo pien-CHP:n aika? Motiva bioenergy days, Varkaus,December 2010.h p://www.motiva. / les/3765/Varkaus_Kon inen.pdf

Kurkela, E.: Biomassan ja j een kaasutus. Liekkipiv 2006, Turku, Ja-nuary 2006. h p://www.tut. /units/me/ener/IFRF/Liekkipaiva2006_BiomassaJateKaasutus_KURKELA.pdf

Kurkela, E. : Gasi cation R&D Activities in Finland. Finnish-Swedish Fla-Finnish-Swedish Fla-me Days 2009, Naantali, January 2009.h p://www.tut. /units/me/ener/IFRF/FinSweFlameDays09/Kurkela.pdf

Lahti Energia,www.roskatenergiaksi.. 4.4.2011Rauch, R.: Development of the biomass CHP Gssing to a biosyngas plat-

form; Kra werk Gssing GmbH & Co KG; Austria. GREENSYNGASworkshop, Gssing, Austria February 2011.

Salo, K. (Carbona Oy): Private conversation, 2009.Sohlstrm, H.: Biore neries UPM and Biofuels. FOREST BIOENERGY

conference, Tampere, September 2009.

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G U P

Pen i EtelmkiKeski-Pohjanmaan metsnomistajien lii o ry, Finland1

Keski-Pohjanmaan Metsmarkkinointi Oy2

Lohtajan energiaosuuskunta3

1 The Forest Owners Union of Central Ostrobothnia2 Forest Marketing Company of Central Ostrobotnia Ltd

3 Lohtaja Energy Cooperative

Thermal energy enterprises and cooperatives typically operate in the 0.32.0 MW plant size category. So far, they have focused almost exclusivelyon the production of heat for their customers. In cost-e ective solutionscustomer groups are large, relative to the plant size, and very close tothe heat units. Larger plants usually have more customers, as such theheat transfer canal is wider and heat production is in the form of districtheating. Customers are mainly municipalities, cities, churches and other businesses. Heat production has led to contract agreements with users thatalready have an existing water circulating heating system, for exampleschools, industry, apartments, retirement homes, etc. Wood chips are themain source of fuel, but peat is o en used in peat parishes whilst a mixtureof the two can also be used during high heat consumption. However, anumber of the energy cooperatives are commi ed to using only wood astheir raw material. Energy Cooperatives were established from the early

1990s up to the early 2000s but in recent years, hardly any co-operativeshave been set up. It is clear now that plants, only producing heat, willcontinue with its life cycle with existing machines until a point when a newsolution will be needed. The EU and Finlands energy policy for renewableenergy targets will lead to an increase in new investment in downstreamenergy. In this development CHP plants are one solution.

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The expectations of CHP plants by thermal energy enterprises andcooperatives are high. Technical solutions should be functional, be madeas simple as possible, and easily administered in the control system. Ifnecessary, modularity should be an asset when adding and removingcomponents. The base size should match the current 0.3 - 2.0 MW heatproduction of electric power, whilst heat production and electric power/gas output should be approximately 50 % more than this. The plantsequipment is expected to reach their full potential a er 3000-4000 hours ofuse, e.g. the plant, size 0.3 MW, should produce annually about 600 MWhof heat and about 300 MWh of electricity / gas as its minimum output.The introduction of new technology should be exible whilst equipmentsuppliers could guarantee the security of supply solutions such as leasing,or an extensive service network. The investment recovery charge should

be closer to ve years rather than ten years.When it comes to the generation of electricity and related energy, itcan be assumed that there will always be potential customers, who areprobably all using more than 100 000 kWh combined with heating orcooling recovery. This threshold will decrease further when electricity becomes more expensive and incentives favouring small plants are o ered by the Central European model. The competitiveness of heat production isimproved when competing forms of energy such as light fuel oil becomesmore expensive. Beyond incentives, alternatively, there is also investmentaid and so loans for nancing. Local Energy is mentioned in a number oforganisations strategies including i.e. MTK. Small plants have undeniableadvantages when it comes to transportation and employment for ruralareas.

Wood gasi cation process allows the manufacturing and implementationof a number of higher re ned energy products locally. Gas can be utilisedin a wide range of technologies for engines and generators Renewableelectricity and gas are easy to move and sell in a local area. In comparison,the heat transfer is less favourable due to expensive thermal canal andinvestment losses.

In traditional heat production, small plants possess an annual e ciencyof 75-85 %. This value is dependent on the plants design (peak load),heat transmission length, average quality of fuel, boiler cleaning and thecombustion process itself. During the summer (as expected) e ciency ismuch lower than during the winter. Furthermore, it was also found thattwo boilers connected in series provide be er fuel e ciency as one large boiler. For example, a 1 MW plant has an improved e ciency with two 0.5MW boiler, one of which is cold for most of the year. Thermal plants ownelectricity consumption is about 1-2 % of the heat energy, so the electricity

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generated in the CHP energy production from cooperatives / self-heatingwould largely go on sale.

The fuel e ciency of wood chips can also be improved when themoisture content of raw material is reduced. This decreases the total costdue to lower chip consumption, chipping / transportation expense andfewer failures. Wood chips with a moisture content of 3035 % are goodmaterial for the production of heat. Energy co-operatives members have been trained to achieve the objective of this quality for many years. Finally,as I understand it, the chip quality requirements (humidity) in the CHPgeneration should be in the same category.

The Finnish government has drawn up a number of obligations, one ofwhich is to increase renewable energy usage at a speci c rate until 2020. Toachieve these goals the government has decided to increase energy taxes

on fossil fuels, including peat. Unfortunately, actual incentives, includingfeed-in tari s, bonuses paid for certain heat production, emission trade-tiedsupport for power generation, energy support for small wood productionand for investments and support for changes in thermal systems, haveyet not been nally approved. New and existing small plants have been mistreated due to size limits and minimum production quantities.Furthermore, the Central European model of the di erential feed-in tariis not being implemented. The quarterly review also predicts speculativesolutions if the situation remains this way.

It is desirable that versatile related energy production is encouraged by reasonable elements. This would achieve positive e ects in terms ofemployment, technological development, bio-processing, forestry, a risk-free energy production and lower environmental loading.

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BIOFUELS AND UTILISATIONOF SYNTHESIS GAS

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B FKirsi Partanen1 , Ulla Lassi1,2

1University of Oulu, Department of Chemistry, 2Kokkola UniversityConsortium Chydenius, Finland

bioFuels and utilisation oF syntHesis gas

I

Energy demand is estimated to grow more than 50 % by 2025 if growthcontinues at its current rate. Growth in energy consumption is largely dueto the emerging economies of countries that possess growing consumptiondemands. Reduction of fossil fuels and their life expectancy in the worldmarket has forced enterprises, research institutes and policy makers to

seek alternative solutions to use alongside transportation fossil fuels.The EU Directive (Directive 2003/30/EU) outlines targets that willincrease the use of biofuels in the European Union. In accordance with theobjectives of the directive, the share of biofuels in transport fuels should be 2 % by the end of 2005 and 5.75 % by the end of 2010. Many countries,including Finland, have so far not been able to meet these objectives.

The biofuel debate, research and its production has so far focusedmainly on bio-ethanol and diesel (ethers) production. However, the energydensity of ethanol compared to existing fossil-fuels (gasoline, diesel) issigni cantly lower. Because of this, it is also important to consider otherpossible transportation fuels, such as alcohols, butanol, pentanol, as wellas furfural and furans.

The bene ts of butanol compared to ethanol are signi cant. It isestimated that about 0.7 litres of butanol is equivalent to the energy densityin one litre of ethanol. In addition, butanol has a be er air-fuel ratio andis suitable for use in the existing fuel engines. The main problem with themanufacturing of butanol so far has been the low yields, especially in theproduction of butanol from bio-based raw materials.

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5-hydroxymethylfurfural has previously only been producede ciently from fructose, but the use of ionic solvents and catalysts for itspreparation from glucose has also been found to be e ective. For example,2,5-dimethylfuran has a 40 % higher energy density than ethanol. Therefore,furfural production is an interesting alternative for the production of biofuels, bringing a new perspective for biomass recovery.

T

The most common used transportation fuels are fossil fuels, such as gasolineand diesel of which almost ve trillion litres are consumed worldwideeach year. 97 % of the worlds cars use fossil fuels as their energy source

with alternative fuels accounting for remaining 3 %, of which 1-2 % isproduced from renewable energy sources.By developing alternative and renewable fuels the dependence on fuel

oil can be reduced, or by developing vehicles and engines that can exploit amore diverse range of energy sources. The alternative transportation fuelscurrently used and those that are designed for use in the future includethe following; biodiesel, natural gas and biogas, lique ed petroleum gas,alcohols such as methanol, ethanol and butanol, furfural derivatives, aswell as hydrogen.

Amongst liquid and gaseous fuels, other sources have also been examinedsuch as lithium-ion ba eries for cars. The rst of these applications arealready on the market and almost every vehicle manufacturer possesses anexisting concept of a hybrid vehicle. Electric cars reduce the dependence onliquid fuels; however, it is worth remembering that the energy of electriccars will also need to be produced.

The physical and chemical properties of transport fuels

Table 2 contains the chemical and physical properties of gasoline, diesel andalcohol fuels. The most commonly used ethanol has a considerably lowerenergy density than, for example butanol, and 2.5-dimethylfuran (DMF).The total energy of ethanol-gasoline-mixture does not reduce signi cantlycompared to other fuel mixtures, because the maximum allowed ethanolconcentration is currently set at 10 vol-%.

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TABLE 1. The chemical and physical properties of gasoline, dieseland alcohol fuels. (Gautam et al., 2000)

Fuel Energydensity(MJ/l)

RON MON Solubility( % )

Air-fuelratio

viscosity,( 20oC)

Gasoline 32 9199 8189 Insigni -cant

14.6 0.40.8

Diesel 35.5 - - Insigni -cant

(60100)14.7

4 (40oC)

n-Pentanol 27.8 Low Low 0 11.68 -n-Butanol 29.2 96 78 7 11.12 3.64Ethanol 19.6 130 96 100 8.94 1.52

Methanol 16 136 104 100 6.43 0.642,5-dimethylfuran 30 119 2.3 - -

EU legislation on fuels

The European Union has regulated the properties of tra c biofuels andtheir concentrations of di erent substances. The directive of the Europeanfuels (2007) and European standard EN 228 - quality standard (2008) allow

oxygen content up to 3.7 m-% for biofuels, so alcohols and furans arenot suitable for transport biofuels, but these biofuels are o en mixturescontaining di erent substances. Also, E85 - fuel with higher ethanolcontent, is recommended speci cally for fuel referred cars. In Table 2 theEuropean fuel directive de ned by various parameters and the maximumvalues is presented.

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TABLE 2. European fuel directive with di erent parameters andtheir maximum alues. (Directi e of the European fuels,2007)

Parameter Unit Maximum limitVapour pressure, summer season * kPa 60.0**Ole nes vol- % 18.0Aromatics vol- % 35.0Benzene vol- % 1.0Oxygen mass- % 3.7Methanol vol- % 3.0Ethanol vol- % 10.0Ether (e.g. DMF) vol- % 22.0

Other oxygenates vol- % 15.0* ) Begin at the latest 1.5. and ends at the earliest 30.9. Member States witharctic or severe winter conditions, will start at the latest 1.6. and ends at theearliest 31.8.** ) Countries with severe winter conditions during the summer period of upto 70 kPa.

In the production of biofuels other factors must also be considered. Forexample, an oxidation resistance of the fuel mixture, since the maintenanceof fuels may come into contact with oxygen in air. Oxygenation can result inprecipitated particles that can block car engine lters. For security reasons,the ashpoint of biofuels must not be less than 55 C. (Motiva, 2006)

In December 2008, the European Parliament adopted a directive forrenewable energy use (COM 2008/19) in which it was stated that renewableenergy should make up 20 % of total energy consumption by 2020. Biofuelfeedstocks should favour organic waste materials, non-food biomass andlignocellulosic materials, such as pulp liquors. If the biofuel raw materialcan be produced from soil, which is unsuitable for food production, a bonus for carbon emissions can be awarded. The directive on the use ofrenewable energy has also set national objectives for each Member State.

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Utilisation of biomass in fuel production

Biomass suitable for food has traditionally been used in biofuel productionand food production has been reduced globally because of this fact. Sucha policy, fortunately, has started to be less popular. As a result of thepolicy, poverty has increased, and food prices have risen. Furthermore,a change in the cost of biofuels production has reversed the direction ofresearch to residue bioenergy and municipal waste materials. In Finland,the production of biofuel can be based on forest industry residues, whichnormally have a high cellulose content and energy, as well in the foodindustry waste masses.

The use of residue biomasses in biofuel production is problematic, sincethey o en contain a lot of di erent fragments and unused chemicals from

processing. These factors will have a negative impact on the manufacturingprocess. The residual materials should be handled in an environmentallyfavourable manner, so that their use would be ecological. Residue biomass possesses high energy content and is well suited, for example,to gasi cation (Sricharoenchaikul et al., 2002). Gasi cation of biomassreduces the required pretreatment, but gas cleaning is important.

A

Alcohol-based fuels can be used to replace fossil fuels to combustionengines and -cells. Alcohols used as fuels, or their components, aremethanol, ethanol, propanol and butanol. A number of long-chain alcoholscould be used as fuel given their chemical and physical properties, butthe manufacturing of alcohols for this purpose is not yet commerciallypro table. The use of ethanol has been extensively researched mostlythanks to its low toxicity and well-known manufacturing methods.(Minteer, 2006)

Ethanol as a transport fuel

Bioethanol is the most commonly used alcohol-based transportation biofuel. It is generally used in mixtures with gasoline and despite ithaving been criticized for its poor e ciency, the use of ethanol and itsmanufacturing as fuel are well known. Ethanol production has causedconsiderable environmental damage in countries such as those in SouthAmerica, where valuable rain forests have been destroyed to make wayfor biofuel plantations.

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Butanol as a transport fuel

n-Butanol is a monovalent alcohol. It is suitable for use either directly orwith a small engine adjustment, in existing gasoline car engines as fuel,either alone or alongside fossil fuels. Due to the high manufacturing costsof butanol, the only commercial markets that are viable, for now, arein industrial chemicals and solvents. Butanol has the advantage of lowsolubility in water, which reduces the side e ects if it comes into contactwith groundwater. Furthermore, due to the low vapour pressure of butanol, lling up can be achieved in existing distribution fuel networks.(Ramey et al., 2000)

Other AlcoholsAlternatives to ethanol include the use of heavier alcohols astransport fuel due to their higher energy density and low watersolubility. Branched-chain alcohols have higher octane numberscompared with the same amount of carbon-containing straight-chain alcohols. Branched-chain alcohols currently cannot besynthesised enough economically by using natural micro-organisms.Methanol has not been studied as a transportation fuel as much as ethanol.Research on methanol has mainly focused on gas-phase methanol synthesisand the use of fuel cell applications. Methanol is currently used with otherfuels, mainly as raw materials and additives. (Minteer, 2006)

Furfurals and furans as a transport fuels

Furfural and furans have recently been identi ed as biofuel alternativesdue to their reasonable successes in being manufactured from sugarsvia existing methods. Moreover, they possess good qualities as fuel. For

example, 2,5-dimethyl furan (DMF) energy density is about 40 % higherthan ethanols. 2,5-DMF production has been performed, mainly fromfructose, but a new method also allows the use of glucose as a raw material.This enables for example the utilisation of cellulose containing residuesfrom forest industry. (Romn-Leshkov et al, 2007)

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P

Alcohols are generally produced by fermentation of sugars by enzymecatalysts. Catalytic methods, where the biomass is rst gasi ed to synthesisgas, are developed in large amounts and the rst commercial producersare already found within the Americas.

Preparation of Alcohols using Enzyme Catalysts

The preparation of alcohols by an enzyme catalyst is well known. Forexample, fermentable sugars have been utilised in the production ofvarious alcoholic beverages for many years. The best known method is

to produce ethanol from sugar-based raw materials by Saccharomycescerevisiae - an enzyme of yeast. (Glazer et al., 1995; Helle et al., 2004;Lawford et al., 2002)

Preparation of Ethanol

Yeast uses sugar as an energy source (carbon source), for example in thiscase, occurring through anaerobic (oxygen-free) fermentation. Chemicallyit is a redox reaction, where there is no net oxidation or reduction. Thefermented end product results in nal compounds which cells secrete totheir surroundings. Ethanol is separated from the aqueous solution bydistillation, however not all water is removed and it may be necessary touse various drying chemicals.

Preparation of butanol

Butanol is manufactured using a particular family of bacteria,Clostridium.

Preparation of butanol occurs in three stages. The rst step is the so-calledacidogenic phase, where the pH is neutral and the products are acetic and butyric acid. The second step is the solventogenic phase, carried out atlow pH (about 4.3 to 4.4). The products of the second step are acetone, butanol and ethanol. The third step is known as the algogenic stage, whereproducts butanol, acetone and ethanol are separated.

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Catalytic preparation of biofuels

Catalytic methods are quite common in the processing of crude oil. Inthis case, reaction temperatures may be several hundred degrees and thereactions take place in the gas-solid interface. Biomasses thermal stabilityis signi cantly lower than crude oil. Therefore, biomass processing shouldtake place in the liquid phase or very carefully in the gas phase if thedecomposition of biomass into synthesis gas is to be prevented. In thiscase, the processes are slower and require larger reactor volumes. (Klass,2004)

The worlds the rst commercial technologies have already beendeveloped for the production of biofuels from biomass by gasi cationand the converting of gas catalytically. These companies, for example:

Choren, Coscata and Range Fuels, mainly produce ethanol and alkanes.The gasi cation process is currently not selective enough for long chainalcohols and alkanes production (Lin et al., 2009). The best known processesare methanol synthesis and Fischer-Tropsch synthesis. Converting biomass into synthesis gas requires several steps, which include biomassgasi cation, gas cleaning, (in most cases, a water-gas-shi unit) andsynthesis gas conversion. (Klass, 2004)

C

The conversion of sugars into transportation biofuels still requires muchresearch and development. Fermentation of ethanol is well known, butalternative biofuels and new preparation methods are required. Physicaland chemical properties of butanol and some furans compared to ethanolare signi cant, but preparation methods are not currently economical.

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R

Directive 2003/30/EU. O cial journal of the European Union, L123/42,

17.5.2003, DIRECTIVE 2003/30/EC OF THE EUROPEAN PARLIAMENTAND OF THE COUNCIL, on the promotion of the use of biofuels orother renewable fuels for transport, Available at: h p://ec.europa.eu/energy/res/legislation/doc/biofuels/en_ nal.pdf 26.4.2011

Directive of the European fuels (2007). Commission of the European Com-munities. COM (2007) 18 nal. Available also: h p://eur-lex.europa.eu/LexUriServ/site/en/com/2007/com2007_0018en01.pdf, 26.4.2011.

Directive for renewable energy use (COM(2008)19), 24.8.2009, h p://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=COM:2008:0019:FIN:FI:PDF

European standard, En 228:2008, Automobile fuels Unleaded petrol Requi-rements and test methodsGautam, M., Martin II, D.W., Proc. Inst. Mech. Engrs,2000 , 214 A, 497Glazer, A.N. ja Nikaido, H.; Microbial Biotechnology: Fundamentals of Applied

Microbiology , W.H. Freeman and Company. USA,1995 , 327358Hadlington S. Chemistry World, news, 2007Helle, S.S., Murray, A., Lam, J., Cameron, D.R., Du , S.J.B, Bioresour.

Technol.2004 , 92, 163Klass, D.L,in Encyclopedia of Energy , ed. C.J. Cleveland, Elsevier, London,

2004 , 193-212Lawford, H.G., Rosseau, J.D., Appl. Biochem. Biotechnol.,2002 , 98-100, 429

Lin, Y-C, Huber, G.W., Energy and Environmental Science,2009 , 2, 68Minteer, S., Alcoholic fuels , 1st edition, CRC Taylor & Francis Group, Boca

Raton,2006, 1-3Motiva, 2006.Vaihtoehtoiset pol oaineet ja ajoneuvot opas , On internet

29.3.2010: h p://www.motiva. / les/2131/Vaihtoehtoiset_pol oaineet_ ja_ajoneuvot.pdf

Ramey, D., Yang, S-T,Production of Buturic Acid from Biomass, Final Report ,for U.S. Department of Energy, Morgantown, WV,2000Romn-Leshkov, Y., Barre , C.J., Liu, Z.Y., Dumesic, J.A. Nature,2007 , 447,

982Sricharoenchaikul, V., Agrawal, P., Frederick, W.J., Jr., Ind. Eng. Chem.

Res.2002 , 41, 5640Zhao, H., Holladay, J.E., Brown, H., Zhang, Z.C. Sciencemag.,2007 , 316,

1597

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S N C P N A

Henrik Romar1 , Pekka Tynjl1,2 , Riikka Lahti1,21Kokkola University Consortium Chydenius, 2University of Oulu, Finland

B -

Biomass is a renewable resource that has great potential for conversionto bio-based fuels. By thermal treatment of biomass (gasi cation) gasesare obtained that can be used as precursors for the production of fuels

and chemicals. Much intensive research is being undertaken in order tond new, bio-based vehicle fuels to replace the fossil fuels currently in usetoday. Both globally and within the EU targets have been set in order toincrease the share of bio-based fuels. The EU aims to increase the portionof bio-based fuels from 5.75 % in 2010 to 10 % in 2020. In the current climate(2009), the proportion was 1.4 %.

F - -

Biofuels are divided into rst- and second-generation fuels depending onthe raw materials used in production. Raw materials for rst-generation biofuels are wheat, maize and sugar cane, or other materials that could beused to produce food (see Table 1).

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TABLE 1. First-generation biofuels.

First-generation biofuels

Fuel Name Ingredient ProcessBioethanol Conventional bioethanol

Sugarcane, beetwheat, corn

Hydrolysis + fermenta-tion

Vegetable oil Pure plant oil Oilseed rape,turnip rape

Cold-pressingExtraction

Biodiesel RME (rapeseed-oil-methylester)FAME (fa yacid-methylester)

Oilseed rape,turnip rape

Cold-pressingExtraction Transesteri-cation

Biodiesel Biodiesel from

waste

Waste fats and

oils, animal fats

Transesteri cation

Biogas Upgraded biogas (Wet) biomass MetabolismBio-ETBE Bioethanol Chemical synthesis

For second-generation biofuels, lignocellulose waste is the prominentraw ingredient mainly found in cu ing waste, waste from agriculture,demolition wood and specially grown energy crops such as reed canarygrass. To some extent, residues from the food industry, such as starchywaste from the potato industry can also be used as raw materials. Theidea behind second-generation fuels is that they do not compete with foodproduction, using waste and residues instead.

Since the material consists of lignocellulose a harder treatment isrequired. Techniques used include enzymatic or acid hydrolysis into freesugars followed by fermentation, or direct gasi cation of biomass which isconverted into hydrogen and carbon monoxide, known as product gas.

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TABLE 2. Second-generation biofuels.

Second generation biofuels

Fuel Name Ingredient ProcessBioethanol Cellulose basedBioethanol

Lignocellulose Advanced hydroly-sis + fermentation

Synthetic biofuel

Biomass-to-liquid(BTL)Fisher-TropschdieselBiomethanolMixed alcoholsBio-dimethylether

(Bio-DME)

Lignocellulose Gasi cation +synthesis

Biodiesel Hydro treated Bi-odiesel

Plant oilsAnimal Fat

Hydration

Biogas SNG (syntheticnatural gas)

Lignocellulose Gasi cation +synthesis

Biowaste Biowaste Lignocellulose Gasi cation +Synthesis orBiological processes

W ?

For a large-scale production of biofuels the process should be assessedthroughout from several points of views as the fuel is introduced into amarket dominated by fossil fuels. In particular, four criteria are important,namely: e ciency, economy, e ects on environment and end use.Moreover, there are also several other considerations that have to be takeninto account:

The fuel produced through a gasi cation process is able to treat1. various types of biomass, as well as wood-based agriculturaland municipal wasteThe manufacturing process allows exible production of both2. bio-based materials as well as fossil-basedThere is an existing infrastructure for distribution3.Biofuels are mixable with existing fuels4.

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