Lignocellulosic Ethanol Production Potential and Regional Transportation Fuel Demand

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Mälardalen University Press Licentiate Theses No. 143

LIGNOCELLULOSIC ETHANOL PRODUCTION POTENTIAL

AND REGIONAL TRANSPORTATION FUEL DEMAND

Lilia Daianova 2011

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ISSN 1651-9256

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Summary

Road traffic dominates in domestic Swedish transportation and is highly de-pendent on fossil fuels, petrol and diesel. Currently, the use of renewable fuels in transportation accounts for less than 6% of the total energy use in transport. The demand for bioethanol to fuel transportation is growing and cannot be met through current domestic production alone. Lignocellulosic ethanol derived from agricultural crop residues may be a feasible alternative source of ethanol for securing a consistent regional fuel supply in Swedish climatic conditions.

This licentiate thesis focuses on regional transport fuel supply by consi-dering local small-scale ethanol production from straw. It presents the results of investigations of regional transport fuel supply with respect to minimising regional CO2 emissions, cost estimates for transport fuel supply, and the

availability of lignocellulosic resources for small-scale ethanol production. Regional transport fuel demand between the present and 2020 is also esti-mated. The results presented here show that significant bioethanol can be produced from the straw and Salix available in the studied regions and that this is sufficient to meet the regions’ current ethanol fuel demand.

A cost optimisation model for regional transport fuel supply is developed and applied for two cases in one study region, one when the ethanol produc-tion plant is integrated with an existing CHP plant (polygeneraproduc-tion), and one with a standalone ethanol production plant. The results of the optimisation model show that in both cases the changes in ethanol production costs have the biggest influence on the cost of supplying the regional passenger car fleet with transport fuel, followed by the petrol price and straw production costs.

By integrating the ethanol production process with a CHP plant, the costs of supplying regional passenger car fleet with transport fuel can be reduced by up to a third. Moreover, replacing petrol fuel with ethanol can cut region-al CO2 emissions from transportation by half.

Keywords:

Agricultural by-products, Straw, Bioethanol, Transport system, Greenhouse gases (GHG), Polygeneration system, Combined Heat and Power (CHP), Mixed Integer Programming (MIP).

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Sammanfattning

Vägtrafiken dominerar i det inhemska transportsystemet i Sverige och är mycket beroende av fossila bränslen, bensin och diesel. För närvarande står användning av förnybara bränslen för mindre än 6% av den totala energian-vändningen inom transportsektorn. Efterfrågan på bioetanol som transport-bränsle ökar och kan inte tillgodoses genom nuvarande inhemsk produktion. Lignocellulosa baserad etanol från skörderester kan vara en möjlig alternativ resurs för etanol som därmed kan säkra en kontinuerlig regional bränsletill-försel vid svenska klimatförhållanden.

Denna licentiatavhandling fokuserar på den regionala bränsleförsörjning-en för transporter gbränsleförsörjning-enom lokal småskalig etanolproduktion från halm. Det regionala utbudet av transportdrivmedel beaktande minimering av koldiox-idutsläpp, kostnadsberäkningar för det regionala drivmedelsutbudet samt tillgängligheten av lignocellulosaresurser för småskalig etanolproduktion är analyserade och presenterade i avhandlingen. I avhandlingen har det region-ala behovet av drivmedel för personbilar uppskattas fram till år 2020. Resul-taten visar att en betydande volym av etanol kan framställas av den tillgäng-liga halmen och Salix i de studerade regionerna och att denna volym kan möta dagens regionala efterfrågan på etanolbränsle.

Kostnadsberäkningar för den regionala bränsleförsörjningen av personbi-lar utfördes i två fallstudier för en fristående etanolanläggning samt etanol-produktionen integrerad med ett befintligt kraftvärmeverk. Optimeringsre-sultaten i båda fallen visar att förändringar i etanolproduktionskostnader har en stor inverkan på kostnaderna för drivmedel, följt av bensinpriset och kostnader för importerad etanol.

Genom att integrera etanolproduktionsprocessen med ett kraftvärmeverk, kan kostnaderna för drivmedeltillförsel för transportbilar minskas med en tredjedel. Resultaten visar att genom att ersätta bensin med bioetanol kan CO2-utsläppen från transporter minska med hälften.

Nyckelord:

Halm; Bioethanol; Transportsystem; Växthusgaser, Kraftvärmeverk (KVV), Bioenergikombinat, Mixed Integer Programmering.

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Acknowledgements

I am grateful to my supervisors, Professor Jinyue Yan and Dr. Eva Thorin, for guidance and all help. I am very thankful for the opportunity to work on this project and for all the support and help. I would like to thank Dr. Erik Dotzauer for introducing me to the world of modelling and all the support he has provided.

I wish to thank all the staff, my colleagues and fellow PhD students at the School of Sustainable Development of Society and Technology at Mälarda-len University, and the head of the Division of Energy Technology, Benny Ekman, for warmth and support.

I am very grateful to the referees who reviewed the manuscripts of the papers and this thesis for their valuable comments and constructive recom-mendations. I wish to especially thank David Ribé who helped to improve the English language of Paper II and of this thesis.

I would like to express my sincere gratitude to my family, who are always in my thoughts but live so far away from MDH. Your love and support is helping me to get through all the things that are happening to me in my life. I wish to express my warm thanks to my little daughter for always trying her best, for being the most important person in my life.

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iv

List of Papers

This thesis is based on the following papers, which are referred to in this the-sis by their Roman numerals and are presented here in reverse chronological order.

Paper I

Daianova, L., Dotzauer, E., Thorin, E., & Yan, J. Evaluation of a regional

bioenergy system with local production of biofuel for transportation, inte-grated with a CHP plant. Applied Energy (2011), In Press; doi:

10.1016/j.apenenergy.2011.08.016. Paper II

Daianova, L., Thorin, E., Yan, J., & Dotzauer, E. Local production of

bio-ethanol to meet the growing demands of a regional transport system. In

Pro-ceedings of World Renewable Energy Congress 2011, May 2011, Linkö-ping, Sweden.

Paper III

Campana P.E., Daianova L., Yan J., & Desideri U. Bioethanol production

from lignocellulosic biomass – evaluation of the potential bioethanol pro-duction in three Swedish regions. 17th Biomass conference and Exhibition,

Conference Proceedings, Hamburg, 29 June to 3 July 2009.

Author’s contributions to the papers included in this thesis are as fol-lows:

Paper I Collection of input data for the optimisation model, perform-ing the optimisation and writperform-ing the paper together with the co-authors.

Paper II I am the main author of this paper, performed the data collec-tion, and wrote the paper with contributions from the co-authors.

Paper III Planned the paper, contributed to the summary and discussion, and wrote the paper together with the co-authors.

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Papers not included in this thesis

Starfelt, F., Daianova, L., Yan, J., Thorin, E., & Dotzauer, E. (2009)

In-creased Renewable Electricity Production in Combined Heat and Power Plants by Introducing Ethanol Production. The First International

Con-ference of Applied Energy, January 5–7, 2009 in Hong Kong.

Song, H., Starfelt, F., Daianova, L., & Yan, J. (2011). Influence of drying

process on the biomass-based polygeneration system of bioethanol, pow-er and heat. Applied Enpow-ergy, doi:10.1016/j.apenpow-ergy.2011.02.019, In

Press.

Starfelt, F., Daianova, L., Yan, J., Thorin, E., & Dotzauer, E. (2011). The

impact of lignocellulosic ethanol yields in polygeneration with district heating – A case study. Applied Energy, doi:10.1016/j.apenergy.

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List of figures

Figure 1. Relationships between the studies presented in this thesis ... 3 Figure 2. A simplified flowchart of a polygeneration system. ... 5 Figure 3. Input data collection pathway of the regional case study system ... 8 Figure 4 a. A simplified flowchart of the Case 1 study system of standalone

ethanol production (Paper I) ... 12 Figure 4 b. A simplified flowchart of the Case 2 study system of ethanol

production integrated with a CHP plant (Paper I) ... 12 Figure 5. Ethanol supply potential (P1-P3) and ethanol fuel demand

(D1-D3) in the Sala-Heby region (MWh). ... 17 Figure 6. Optimisation results for standalone ethanol production (Case 1). ... 18 Figure 7. Optimisation results for polygeneration system (Case 2). ... 19

List of tables

Table 1. Total CO2 eq. emissions factors by type of transport fuel

(Johansson and Fahlberg, 2009) ... 14 Table 2. Estimates of transport fuel demand in the Enköping region ... 15 Table 3. Estimate of straw based ethanol production in Sala-Heby region ... 16 Table 4. Estimates of ethanol and petrol fuel demand in the Sala-Heby

region ... 16 Table 5. Estimates of CO2 eq. emissions from passenger cars in the

Sala-Heby region ... 21

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x

Abbreviations

CHP Combined heat and power

MIP Mixed integer programming

LCB Lignocellulosic biomass

SSF Simultaneous saccharification and fermentation

GHG Greenhouse gases

DM Dry matter

LUC Land use change

iLUC Indirect land use change

EU European Union

CO2 eq. The amount of CO2 that is required to give the same

ef-fect as other gases with global warming potential (e.g. CH4, N20)

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Symbols

a i

c Straw production cost [€/MWh]

imp a

c

, _{Imported straw price [€/MWh]} eth

j

c

Ethanol production costs at the plant j [€/MWh]

gas

c

Biogas production costs [€/MWh]

imp eth

c , _{Imported ethanol price [€/MWh]} fossil

c Petrol fuel price [€/MWh]

heat j

i Plant j’s income from heat sold [€/MWh]

j

e The cost of building an ethanol plant j with maximal ethanol _capacity eth j

x

[€]

power j

i Plant j’s income from power sold [€/MWh]

exp , gas

i Income from biogas sold to other regions [€/MWh]

exp ,

a i

i

Income from biomass not used for ethanol or biogas produc-tion and sold to other regions [€/MWh]

fert

i Average fertiliser price [€/ton]

eth a

j i

b

,

, Biomass cultivated in a supply area i and delivered to ethanol _{plant j [MWh]}

gas a

j i

b

,

, The amount of crop used for biogas production at plant j _[MWh]

exp , a i

b _{Biomass exported from the region [MWh]}

imp a j

b

, _{Biomass imported from the region [MWh]}

eth j

x

Ethanol produced at plant j [MWh]

j

q Heat produced at plant j [MWh]

j

p Power produced at plant j [MWh]

draff j

z

The distiller’s residue from ethanol production at plant j [-]

gas

x The biogas produced in the region [MWh]

exp , gas

x _{The biogas exported from the region [MWh]} imp

gas x ,

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xii

fert

z The fertiliser co-product from biogas production [kg]

imp eth

x , _{The ethanol imported to the region [MWh]} fossil

x The petrol fuel used in the region [MWh]

j

u The binary variable indicating whether plant j is in operation ₍ j

u =1 means the plant j is in operation, otherwise

u

j=0)

B Straw-based ethanol production potential [kWh]

Si Cereals cultivation area [ha], where i is the type of cereal crop Yi Cereals yield in the respective county [kg/ha]

Ri Crop to residue ratio for each cereal type [-] A Straw availability [-]

YEtOH Ethanol production yield from straw [litre/kg] D Estimated ethanol fuel demand in the region [kWh]

Ni Number of vehicles in use in the studied region during a year Si Distance covered per vehicle in the respective county in a year _[km] Qi Fuel consumption per type of fuel and kilometre driven in each _{county [litre/km]} Ci The ratio of pure ethanol to petrol in each type of fuel blend _{used [-]} E Energy content of the fuel [kWh/litre]

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1 Introduction

Energy security and the mitigation of greenhouse gas emissions (GHG) are the driving forces behind the development of renewable fuel sources world-wide. According to the EU Directive, the target share of renewable energy sources as a percentage of gross final energy consumption in Sweden in 2020 is 49% (Directive 2009/28/EC). Currently, renewable energy use in the transport sector accounts for less than 1% of the final energy use (Swedish Energy Agency, 2010a).

Road transportation, which consists of private transport (mainly passenger cars), public transport and trucks, mostly uses the fossil fuels petrol and die-sel. In Sweden, the share of renewable liquid fuels (ethanol, fatty acid me-thyl ester, biogas, and renewable electricity) increased to 5.4% of the total energy use in transport by the end of 2009 (Swedish Energy Agency, 2010a). The relatively rapid development in bioethanol use in transportation has been driven by the implementation of national taxation regulations – biofuels are CO2 and energy tax exempt in Sweden. However, domestic bioethanol

production is currently unable to satisfy the growing demand for ethanol fuel.

Small scale ethanol production from agricultural residues can help smaller regions to meet their needs for transport fuel. Ethanol production from lig-nocellulosic biomass, straw, and the fast growing energy crop Salix have the potential to secure a consistent regional transport fuel supply in Swedish climatic conditions. Consequently, realising local small scale ethanol pro-duction can help regions to become more fossil fuel independent. It can also contribute to reducing local environmental impact caused by transportation when replacing petroleum fuel with renewable fuels. However, there are several hurdles that must be overcome in order to increase local lignocellu-lose-based bioethanol production, such as its higher market price compared to imported sugarcane ethanol.

This thesis focuses on regional transport fuel supply by realising local small-scale ethanol production from agricultural residues, cereals straw, and the fast growing energy crop willow (Salix). The possibilities for smaller

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gions to become self-sufficient in transport fuel supply are evaluated based on an analysis of current and potential regional biomass supply and transport fuel demand, not taking into account the details of ethanol production. In the thesis, the main cost drivers for supplying the passenger car fleet with etha-nol fuel are investigated for a regional system with an existing CHP plant. The thesis investigates the reductions in regional CO2 emissions that may be

possible by substituting petrol use with ethanol fuel mixtures.

1.1 Objectives of the thesis

The overall objective of this thesis is to present the research findings from investigations of the possibilities for a small region to become self-sufficient in transport fuels. The thesis provides results from an optimisation model developed for cost minimisation for regional transport fuel supply. It de-scribes aspects of the replacement of fossil fuels used in regional road traffic with alternative fuels produced locally from agricultural residues in a pol-ygeneration production system.

The objectives of Paper I are to perform cost optimisations and compare standalone ethanol and CHP plants with a polygeneration system that sup-plies the regional passenger car fleet with ethanol derived from straw, and to identify the main cost drivers for regional transport fuel supply. The main objective of Paper II is to analyse the potential for CO2 emissions savings in

the region by substituting petrol with ethanol fuel in transportation. The ob-jective of Paper III is to identify whether regionally cultivated Salix, agricul-tural residues and straw can meet the regional demand for local bioethanol production in two small regions.

1.2 Contributions

In this licentiate thesis, a static model of regional straw use for transport fuel production is developed for the case study region of Sala-Heby. This model estimates costs of supplying the regional passenger car fleet with transport fuels (bioethanol, biogas and petrol fuel) and evaluates the main cost drivers. The minimisation of CO2 emissions when replacing fossil fuels in road

traf-fic with bioethanol is also evaluated. Possibilities for regional energy sys-tems to become self-sufficient in ethanol fuel supply are addressed in the ap-pended papers.

It is challenging to realise a profitable small-scale ethanol production in-tegrated with an existing CHP plant. For this reason it is very important to use a systems approach and to investigate factors other than economic fac-tors that influence the future system performance, such as local environmen-tal impact or biomass resource availability.

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This thesis contributes with a method for and findings from a regional system optimisation study, that includes the use of agricultural residues for small-scale transport fuel production.

The thesis shows the possibilities for the study regions of Sala-Heby and Enköping to increase their utilisation of agricultural residues for fuel produc-tion, and addresses the possibilities for the regions to become self-sufficient in lignocellulosic biomass for fuel transport fuel production.

1.3 Thesis outline

This licentiate thesis is based on the content of three scientific papers (Pa-pers I–III). Figure 1 shows how the pa(Pa-pers relate to each other in this thesis.

Figure 1. Relationships between the studies presented in this thesis

This thesis focuses on the regional system for transport fuel supply, and con-siders the potential of cellulosic ethanol production (Papers I–III). The pa-pers included in the thesis share the common aim of investigating possibili-ties for smaller regions to reduce fossil fuel dependence and minimise local environmental impact by replacing fossil fuels with renewable fuels for transportation.

This licentiate begins with a description of the background and related work on optimisation of polygeneration systems and GHG emissions from transport fuel supply. This is followed by a description of the presented stud-ies, and by methods for evaluation of the regional biomass supply and transport fuel demand. The thesis then describes the optimisation model of the regional passenger car fleet fuel supply with locally produced straw-based ethanol, including a description of simplifying assumptions and limita-tions of the optimisation model study. The main results from the appended papers are then discussed and conclusions from the studies are presented.

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This licentiate thesis is comprised of the following six chapters:

Chapter 1 Introduces the present thesis, including its objectivities, meth-odology and a thesis outline.

Chapter 2 Provides background information and results from related re-search.

Chapter 3 Presents a regional study on the passenger car fleet with local-ly produced transport biofuels, including its limitations and describes the case study system.

Chapter 4 Provides the main results of the papers included in the thesis and outlines the main discussion points.

Chapter 5 Summarises the main conclusions of the thesis.

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2 Background and related work

2.1 Polygeneration

A polygeneration system integrates generation of products such as heat, elec-tricity, bioethanol and biogas. Figure 2 presents a simplified scheme of such a polygeneration system.

When integrating ethanol production with an existing CHP plant, the ex-cess heat from the ethanol plant can be used for district heating. At the same time, the steam needed for lignocellulosic biomass hydrolysis at the ethanol plant can also be supplied by the CHP plant (Starfelt et al., 2010). Ethanol production residues can also be further processed within the same system; lignin can be used as additional fuel for the CHP plant and distiller’s residue can be digested to biogas.

Biomass CHP plant Ethanol plant Biogas plant Biogas Ethanol Electricity Heat Polygeneration system Lignin Steam, Electricity Organic residues

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Starfelt et al. (2010) and Pfeffer et al. (2007) discuss the possibilities for in-tegration of ethanol production with combined heat and power (CHP) plants and improving the energy system performance. Several recent studies have described the technical performance of integration of ethanol production with existing CHP plants (Starfelt et al., 2010; Wingren et al., 2008; Seabra

et al., 2010). These studies on polygeneration systems demonstrate that the

efficiency of the production process can be increased by recirculation of mass and energy flows within the polygeneration system. Using residues such as lignin or organic residues from the ethanol production process, can reduce costs of ethanol production. This thesis describes the use of organic residues for biogas and fertiliser production. However, the model presented in this thesis does not include the use of lignin as additional fuel to the CHP.

2.2 Ethanol production and use

In Swedish transportation, ethanol is mainly used as low blend ethanol fuel (E5), which is petrol mixed with 5% ethanol, and as high blend ethanol mix-tures (E85, ED95). The share of E5 in all petrol fuel used in Sweden has in-creased from 45% to 95% over the period 2003–2009, according to the Swe-dish Energy Agency (2010a). This has resulted in an increasing demand for ethanol fuel.

Over the period 2001–2009, total ethanol use in the Swedish transport sector increased from around 42 000 m3_{to 391 000 m}3_{(SCB, 2010).}

Domes-tic commercial ethanol fuel production in 2009 was 221 150 m3_.

Lantmän-nen Agroetanol in Norrköping currently produces bioethanol by fermenta-tion of wheat grains, resulting in a capacity of 210 000 m3_{/year, which}

al-most meets the demand for low blend ethanol. SEKAB in Örnsköldsvik pro-duces 16 000 m3_{/year of ethanol from sugary liquor from sulphite pulp from}

Domsjö Factories, and the SEKAB pilot plant produces 150 m3_ethanol/year

from wood residues (Swedish Energy Agency, 2010b).

The technology for lignocellulosic ethanol production is under develop-ment and has not yet been commercialised. A number of recent studies worldwide focus on the process development of lignocellulosic ethanol pro-duction and in particular on process performance for straw based ethanol, e.g. Kaparaju et al. (2009), Gírio et al. (2010), Shinozaki and Kitamoto (2011), and Talebnia et al. (2010).

2.3 CO

2

emissions from transport

The use of alternative transport fuels is a way to reduce CO2 emissions from

the transport sector and has the potential to make transport systems less de-pendent on fossil fuels.

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Börjesson (2009) estimated GHG emissions for the current Swedish grain-based ethanol production and argues that GHG emissions savings can vary considerably depending on the structure of the studied system. His re-sults show that GHG emissions can be reduced by 80% relative to petrol fuel when using wheat grain-based ethanol produced in Sweden (Börjesson, 2009). The CO2 eq. emission factors presented in the study performed by

Jo-hansson and Fahlberg (2009), on which the calculations in this thesis are based, correspond to 76% total CO2 eq. emission savings for pure ethanol

compared with pure petrol fuel.

Sustainability of lignocellulosic ethanol production is discussed by Dahlquist et al. (2007), who analyse strategies for making the regional ener-gy system of the Mälardalen region in Sweden free from fossil fuels by 2030 from an energy system perspective. Possible strategies suggested by the re-sults of this study include reducing energy demand in the transportation sec-tor while concurrently developing use of regional forestland and farmland for Salix and sugar beet production. These products could be used for heat, power and ethanol production for regional needs (Dahlquist et al., 2007).

The Sala-Heby and Enköping regions presented in this thesis are part of the Mälardalen region. This thesis analyses the potential for CO2 emissions

savings by substituting regional petrol use with ethanol fuel mixtures, with-out considering the details of ethanol production.

2.4 Regional static MIP model

Mixed integer programming (MIP) models are widely used in cost optimisa-tion studies. As the majority of optimisaoptimisa-tion problems naturally involve a mixture of integer and continuous parameters, MIP models can provide a numerical solution. Leduc et al. (2010a, 2010b) and Schmidt et al. (2010) have used MIP models for modelling of optimal geographic locations for biofuel plants. In this thesis, the geographic location of plants is provided, and the focus is shifted to conditions under which the local transport fuel supply system can become independent of petrol fuel imports. The study fo-cuses on cost optimisation of small-scale ethanol production from regionally produced straw and analyses cost drivers for transport fuel supply.

In this thesis, a static MIP model assesses the regional car fleet supply of transport fuel (ethanol, biogas and petrol). The model is applied for two cas-es, one where the ethanol production plant is integrated with an existing CHP plant (polygeneration), and one with a standalone ethanol production plant. The model includes the production of ethanol, biogas, heat and power from locally available cereals straw. The MIP model is developed in General Algebraic Modelling System (GAMS).

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3 Methodology

This thesis analyses the regional transport fuel supply, comparing production technologies, the possibility of being self-sufficient in bioethanol and evalu-ating environmental impact reduction, and in particular CO2 emissions, when

replacing fossil fuels with alternative fuels for transportation. The input data in this thesis is predominantly obtained from databases presented by the state authorities Swedish Energy Agency, Swedish Board of Agriculture, and Sta-tistics Sweden, who are responsible for dissemination of statistical data. In-put data collection for presented case studies is performed according to the structure shown in Figure 3.

Figure 3. Input data collection pathway of the regional case study system

The economic optimisation of the regional car fleet supply with transport fuels is performed for a standalone ethanol production plant and the case of

Evaluation of biomass supply

(straw from spring and winter wheat, barley and oats) Data on cultivation areas for cereals crops, annual yields, straw availability

Processes

(stand-alone plants vs process integration – polygeneration) Plants’ efficiencies on heat, power and ethanol production

Products/Services

(heat, power, ethanol, biogas, fertilizers, lignin) Ethanol, biogas and fertilizers production yields

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the integrated production of multiple products – heat, electricity, bioethanol and biogas – which is an example of a polygeneration system (see Figure 2).

3.1 Description of the study region

Papers I and II involve a study on a small region with around 35 000 inhabit-ants, comprising of the Sala and Heby municipalities. The Enköping region, with around 39 000 inhabitants is also studied in Paper III. The Sala-Heby and Enköping municipalities are neighbouring regions situated around 100 km northwest of Stockholm. These regions are situated at the northern border of cereals cultivation in Sweden, and the regions’ cereals yields are lower than in the more southern parts of Sweden.

In each of the two regions, there is a CHP plant that supplies the region with heat and power. Both plants are fuelled solely by biofuels. The biomass currently used at the plants mainly originates from within the same region. The CHP plant in the Enköping region also utilises fast growing willow

(Sa-lix), which is mainly grown at the plant’s own plantations. The regional

de-mand for transport fuel is driven by the working population commuting to cities outside the region.

3.2 Biomass supply and ethanol production potential

In this thesis, cereals straw from wheat, barley, oats, and the fast-growing energy crop Salix are considered as a feedstock for ethanol production. The-se types of cellulosic biomass are the most commonly cultivated in the stud-ied regions (see input data description presented in Papers I–III). The analy-sis of availability of cereals straw and Salix in the two studied regions shows that there are more abundant willow resources in the Enköping region com-pared to the Sala-Heby region (see input data description in Paper II and III). This chapter presents results on straw availability in the Sala-Heby region and willow and straw availability in the Enköping region.

The ethanol production potential (P) in the Sala-Heby region is calculated for each cereal type (Paper II):

4 1 i

S

i

Y

i

R

i

A

Y

EtOH P (1)

where P is straw-based ethanol production potential (liter), Si is the cereals

cultivation area (ha), Yi is the cereals yield in the respective county (kg/ha), Ri is the crop to residue ratio for each cereal type, A is the straw availability, YEtOH is the ethanol production yield from straw (litre/kg), and i is the type of

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Future regional straw supply and ethanol production potential in the Sala-Heby region are analysed for the following scenarios:

Scenario 2020-P1 – all the parameter values remain the same except are-as for cereals cultivation. The total straw production is are-assumed to in-crease by 20% through the use of fallow land for ethanol straw cultiva-tion. Fallow land currently accounts for 29% of arable land for cereals production in the Sala-Heby region.

Scenario 2020-P2 – all the parameter values remain the same except the yield for ethanol conversion from straw, which is assumed to increase to 0.35 (litre/kg) (YEtOH) due to improvements in the process technology.

Scenario 2020-P3 – combines scenarios 2020-P1 and 2020-P2 (straw production increases and higher ethanol yields).

The ethanol production potential from willow and straw from wheat and oats is estimated for the Enköping regional system. The willow yield can vary be-tween 9–20 tonnes/ha depending on the soil type and willow variety (Sassner et al., 2008). Here it is assumed that the annual yield of willow is 12 tonnes/ha. This assumption relies on the results of the study by Dahlquist et al. (2007) on the same region. Based on the energy content of E85 and E100 ethanol fuel mixtures, the regional ethanol and petrol fuel demand is evalu-ated for two scenarios: E85 scenario and E100 scenarios.

3.3 Transport fuel demand

The studies presented in this thesis only consider fuel use by passenger cars as this is the dominant form of transport in regional road traffic. Buses are excluded from the current analysis as none of the buses currently run on eth-anol fuel and there are no plans for them to do so in future (Bergquist per-sonal communication, 2010; Backman, perper-sonal communication, 2010).

The use of motor fuel is calculated based on the numbers of passenger cars registered in the Sala and Heby municipalities, average distance covered per car and average fuel consumption per driven kilometre. Ethanol fuel de-mand (D) in the Sala-Heby region is estimated for E5 and E85 ethanol mix-tures:

2 1 i

N

i

F

i

Q

i

C

i

E

D (2)

where D is estimated ethanol fuel demand (kWh), Ni is the number of

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respec-tive county in a year (km), Qi is the fuel consumption per type of fuel and

kilometre driven in each county (litre/km), Ci is the ratio of pure ethanol to

petrol in each type of fuel blend used, and E is the energy content of the fuel (kWh/litre).

To evaluate current and future regional demand on transport fuel in the Sala-Heby region the following scenarios were analysed (Paper II):

Scenario 2020-D1 – all the parameters remain the same except the num-bers of passenger cars fuelled by petrol and ethanol fuels. The number of E85 fuelled cars increases and the number of E5 fuelled cars decreases, following the same trend as during the period 2006–2009 for each vehi-cle type.

Scenario 2020-D2 – all the parameters remain the same except the amount of ethanol blended with petrol fuel, which is assumed to increase from 5% to 10% of the petrol fuel mixture, meaning that passenger cars are fuelled with E10 instead of E5. Petrol fuel consumption per driven kilometre is assumed to decrease following the trend from 2006–2009 (-1.2%), and is 0.074 l/km in 2020.

Scenario 2020-D3 – this is the most extreme scenario, where it is as-sumed that all passenger cars are fuelled by E85 ethanol fuel.

In this thesis, it is assumed that all petrol fuel in the studied regions is cur-rently E5 fuel, as the share of low blend petrol in Sweden is 95% according to the Swedish Energy Agency (2010b), and more detailed data on the re-gional share of E5 fuel and petrol fuel is not available.

3.4 Modelling of regional car fleet supply with

transport fuel

In this thesis, the regional transport fuel supply for passenger cars is ana-lysed from a cost optimisation perspective (Paper I). The model considers the production of the alternative transport fuels bioethanol and biogas from regionally produced straw. It evaluates main cost drivers for replacement of current petrol use with straw based ethanol without considering the detailed process configuration of straw-to-ethanol production.

3.4.1 Case study description

The optimal costs for regional transport fuel supply are analysed for the fol-lowing two cases: standalone ethanol production (Case 1) and ethanol

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pro-12

duction integrated with a CHP plant (Case 2). Figures 4a and 4b present simplified schemes of the case study systems.

The Case 1 system includes heat and power production at the CHP plant and ethanol production from straw at the standalone ethanol plant. In the Case 2 system, the ethanol production is integrated with the CHP plant.

Figure 4 a. A simplified flowchart of the Case 1 study system of standalone etha-nol production (Paper I)

Figure 4 b. A simplified flowchart of the Case 2 study system of ethanol produc-tion integrated with a CHP plant (Paper I)

All straw and transport fuels exchanged between the study region and the surrounding regions are considered as imported or exported biomass and fuel. As in the case of petrol fuel imports, security of regional biomass sup-ply can become a central issue in many regions. This thesis addresses the possibility for the Sala-Heby region to become self-sufficient in straw sup-ply.

Both cases (Cases 1 and 2) only allow ethanol production from regionally grown straw. However, straw imports are not restricted. The imported straw

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can be used for biogas or fertiliser production. Straw can also be sold to oth-er regions.

Transport fuel imports and regional fuel production satisfy the need of the regional car fleet for transport fuels. In both cases (Case 1 and 2) imports of biogas are not allowed but petrol and ethanol fuel can be imported from oth-er regions. Biogas can be produced from regionally available and/or import-ed straw. Biogas can also be producimport-ed from ethanol production residues by anaerobic digestion or directly from straw if it is optimal for the system. Di-gestion residues can further be used for fertiliser production.

By using residues such as lignin and organic residues from the ethanol production process, lignocellulose-to-ethanol production costs can be re-duced. The use of lignin as additional fuel to the CHP plant is not permitted in the current version of the model. Here, the residual organic components from ethanol production are used for biogas and/or fertiliser production. In the polygeneration system, more effective use of excess heat and biomass re-sults in higher total efficiencies and lower production costs.

3.4.2 Optimisation model description

In this thesis, a static MIP model assesses the regional car fleet’s supply of transport fuel. The model is developed in General Algebraic Modelling Sys-tem (GAMS) (Rosenthal, 2008).

The model is described in Section 2.2 of Paper I. Input data for the opti-misation model is presented in Section 2.3 of Paper I.

Given the costs and incomes, the objective function is defined as

. ) , , , , , ( , , , , exp , exp , exp , 1 1 1 , , 1 1 exp , exp , 1 1 exp , , 1 , , fossil fossil imp gas imp gas imp eth imp eth fert fert gas gas gas gas gas P j j power j j heat j eth j eth j j j P j A a imp a j imp a S i A a a i a i S i A a a i gas a i P j eth a j i a i x c x c x c z i x i x x c p i q i x c u e b c b i b b b c u z p q x b f

(3) The MIP is defined as

( , , , , , )

min , , , , ,xqpzuf b x q p z u b (4) Variables non-negative

0,1, j P~. uj

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14

Solving the problem provides the economically optimal supply of biomass and regional ethanol production from straw.

The approach applied in this thesis selects a number of key parameters, varies each by +/-20% and analyses how these deviations influence the total cost of supplying the regional car fleet with biofuels. The selected key pa-rameters for the analysed scenarios are ethanol production costs, costs for imported ethanol and petrol fuel, heat and power prices, straw production costs, imported straw costs and straw availability in the region. The scenari-os are applied separately for standalone and integrated ethanol production plants.

3.5 CO

2

emissions from regional passenger car

trans-portation

This thesis analyses the potential for CO2 emissions savings in the

Sala-Heby region to be gained from substituting petrol with ethanol fuel in trans-portation, ignoring emissions from the bioethanol production process.

Estimates of CO2 eq. emissions from passenger cars are based on the

re-sults presented by Johansson and Fahlberg (2009). These emissions factors are lifecycle based and include emissions from fuel combustion, production and distribution (Johansson and Fahlberg, 2009). Table 1 presents CO2 eq.

emissions rates for E5, E85 and E10.

Table 1. Total CO2 eq. emissions factors by type of transport fuel (Johansson

and Fahlberg, 2009)

CO2 eq. emissions by type of fuel, (g/kWh)

E5 277.48

E10 269.34

E85 110.54

Regional CO2 eq. emissions from passenger car transportation are estimated

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4 Results and Discussion

This chapter presents the main results from Papers I–III and outlines the main discussion points.

4.1 Regional ethanol production and transport fuel

demand

As passenger cars are the dominant form of regional road traffic, the regional ethanol production and transport fuel demand are only estimated for passen-ger cars (see Papers I–III).

In Paper III, cereals straw from wheat and oats, and fast growing willow (Salix) are considered as potential cellulosic biomass sources for regional bi-oethanol production. Table 2 presents results for evaluation of transport fuel demand in the Enköping region.

Table 2. Estimates of transport fuel demand in the Enköping region

Parameter Unit 2006 E85 scenario E100 scenario Petrol demand MWh/year 343 920 74 467 0 Ethanol demand MWh/year 13 815 306 265 378 230 The estimates of ethanol production from regionally produced straw and

Sa-lix in the Enköping region show that 19 581 m3_{(122 185 MWh) and}

28 596 m3_{(178 439 MWh) of ethanol can be produced from C-5 and C-6}

sugars respectively. The results from Paper III show that available straw and

Salix are sufficient to satisfy the potential ethanol fuel demand in the

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16

Ethanol production from straw in the Sala-Heby region is estimated using Eq. 1. Table 3 presents results for the ethanol production potential from straw for different scenarios in the Sala-Heby region using the values for the energy content of the ethanol fuel (kWh/litre) presented in Table 4 of Pa-per II.

Table 3. Estimate of straw based ethanol production in Sala-Heby region

Parameter Unit 2009 2020-P1 2020-P2 2020-P3

Pethanol MWh/year 81 210 97 452 98 012 117 615

The average annual decrease in petrol fuelled passenger cars is 1.5%. Based on this rate the number of E5 fuelled passenger cars is estimated to be 13 251. The average annual increase in E85 fuelled cars in the 2006–2009 period is 39%, whereas the assumed average increase after 2014 is 20%. The results on regional ethanol and petrol fuel demand are presented in Table 4.

Table 4. Estimates of ethanol and petrol fuel demand in the Sala-Heby region

Parameter Unit 2009 2020-D1 2020-D2 2020-D3

Dethanol MWh/year 12 234 52 927 57 955 179 977

Dpetrol MWh/year 153 734 129 712 106 695 0

Dethanol+petrol MWh/year 165 968 182 639 164 650 179 977

Summarised results for straw-based ethanol supply and ethanol demand in the Sala-Heby region are presented in Figure 5.

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Figure 5. Ethanol supply potential (P1–P3) and ethanol fuel demand (D1–D3) in the Sala-Heby region (MWh)

The estimated potential ethanol production from currently produced bio-mass, straw and Salix is able to meet the current transport fuel demand in the Sala-Heby and Enköping regions. However, it is not sufficient for scenarios where all passenger cars are fuelled with E85.

Thus the regional transport system can become self-sufficient in ethanol fuel by implementing local small-scale ethanol production.

4.2 Cost optimisation of lignocellulosic ethanol

pro-duction

4.2.1 Standalone ethanol production

Effects of changing the individual factors on costs of supplying passenger cars in the study region with transport fuel are shown in Figure 6, where fac-tors are ranked in descending order, according to their impact on the total costs. Demand 2009 D1 D2 D3 D1 D2 D3 D1 D2 D3 Potential 2009 P1 P2 P3 0 20 000 40 000 60 000 80 000 100 000 120 000 140 000 160 000 180 000 200 000 M W h Total ethanol fuel demand Total ethanol potential

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18

Figure 6. Optimisation results for standalone ethanol production (Case 1)

The changes in ethanol and straw production costs have the biggest impact on the total cost of transport fuel production at the standalone ethanol plant. Interestingly, the increase in petrol fuel price does not have a substantial ef-fect on the total cost, but simply motivates increased biogas production by importing more straw to the region. Total costs for supplying passenger cars with transport fuel are practically unchanged compared to the base scenario (only a 0.58% increase).

The demand to supply regional transport fuel at the lowest possible cost leads to increased imports of ethanol and petrol fuel when the prices of these fuels falls. This scenario results in the largest decrease of the total fuel sup-ply costs (-9.1% and -8.3% respectively). It also results in a 10% decrease in regional straw production compared to the base scenario.

In the case of standalone ethanol production, the regional transport fuel system becomes independent of petrol fuel imports in four scenarios: when the cost of imported ethanol decreases, petrol fuel prices increase, straw pro-duction costs decrease, or the cost of imported straw decreases.

When the cost of imported ethanol decreases it simply becomes more profitable for the system to import ethanol fuel. In other scenarios, for a self-supplying fuel system the solution is to significantly increase straw imports in order to increase biogas production. It should be noted that in all scenarios ethanol production from straw is restricted to 85 140 MWh/year, the theoret-ical ethanol production from regionally produced straw. This assumption is

-10,0% -8,0% -6,0% -4,0% -2,0% 0,0% 2,0% 4,0% 6,0% 8,0% 10,0% ethanol production costs straw production costs petrol fuel

price importedethanol costs

heat price imported

straw costs availablestraw powerprice

changes in t ot al c os t cost drivers

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applied both in the case of standalone ethanol production and the polygener-ation system.

4.2.2 Polygeneration system

In the course of optimisation, the values for heat and power production re-main unchanged, as in Case 1. However, these values are much higher than in Case 1. Heat production in the polygeneration system increases to 61 301 MWh/year compared to 14 474 MWh/year in Case 1. The values for power production in Cases 1 and 2 are 7 663 MWh/year and 29 799 MWh/year re-spectively.

Optimisation results show that it is more optimal for the system to import straw and also use it for heat and power production in the polygeneration production system. This explains the significant difference in heat and power production and the much lower biogas production in the polygeneration sys-tem.

Figure 7 graphically summarises the optimisation results for the changes in total costs of supplying passenger cars in the study region with transport fuel, ranked from largest to smallest.

Figure 7. Optimisation results for polygeneration system (Case 2)

In the case of the polygeneration system, the import of straw is motivated in all scenarios except where the amount of available straw in the region

in--10,0% -8,0% -6,0% -4,0% -2,0% 0,0% 2,0% 4,0% 6,0% 8,0% 10,0% ethanol production costs petrol fuel

price productionstraw costs

heat price imported ethanol

costs

imported

straw costs availablestraw powerprice

changes in

total

cost

cost drivers

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20

creases. Optimisation results show that exceptionally high levels of straw imports result in four scenarios: when petrol fuel prices increase, straw pro-duction costs decrease, imported straw costs decrease, or regional straw availability decreases. In the first three scenarios imported straw is used for biogas production, which dramatically increases from 519 to 67 232 MWh/year.

The lowest total costs are achieved when petrol fuel prices decrease. Im-port of ethanol is economically motivated only when the cost of imIm-ported ethanol decreases, which results in the second largest reduction of total costs among the analysed scenarios for the polygeneration system.

Similarly to the optimisation results for the standalone ethanol produc-tion, the regional transport fuel system becomes independent of petrol fuel imports in four scenarios: when costs for imported ethanol decrease, petrol fuel prices increase, straw production costs decrease, or the cost of imported straw decreases.

This thesis is a first step in evaluating the factors that play important roles when introducing local straw-to-ethanol production, although it is difficult for the production system to achieve high profitability when integrating small-scale ethanol production (10 MW) with an existing CHP.

The optimisation results show that in both cases (standalone ethanol pro-duction and polygeneration system) the changes in ethanol propro-duction costs have the biggest influence on the cost of supplying the regional passenger car fleet with transport fuel. Modelling results in both cases are also sensitive to changes in petrol fuel prices and straw production costs. In the course of optimisation, three less important drivers for both cases were identified as power price, regional straw availability and the cost of imported straw.

In this thesis, optimisation results show that by integrating the ethanol production process with a CHP plant, the cost of supplying the regional pas-senger car fleet with transport fuel can be reduced by up to one third.

4.3 CO

2

emissions mitigation from regional

road traffic

This thesis analyses CO2 eq. emissions savings from private road traffic by

replacing current petrol use with ethanol derived from regionally produced straw. The CO2 eq. emissions from passenger cars in the Sala-Heby region

are estimated using the same approach as for estimation of ethanol fuel de-mand (see Chapter 3.3). Table 5 presents the results on CO2 eq. emissions

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Table 5. Estimates of CO2 eq. emissions from passenger cars in the Sala-Heby

region

Parameter 2009 2020-D1 2020-D2 2020-D3

Total CO2 eq. emission from passenger cars fuelled by petrol and ethanol fuel, tonnes

45 446 43 930 38 938 23 591

If regional passenger cars run on ethanol produced from locally available straw, 3% CO2 eq. emissions reductions can be obtained, assuming that all

other parameters remain the same (e.g. the number of passenger cars in use continues to increase according to the current trend until 2020). If regional passenger cars start to use E10 instead of E5, CO2 eq. emissions can be

re-duced by 14% compared to 2009 levels. If all passenger cars run on E85, and the number of passenger cars in the region continues to increase according to the trend of the last 5 years, there will be a CO2 eq. emission reduction of

21 855 tonnes, or 48%. The latter change in fuel use requires engine modifi-cation.

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22

5 Conclusions

This thesis presents the results of a study on the potential use of regionally produced cellulosic biomass, straw and Salix for small-scale production of fuel for transportation. The study considers smaller regions with existing CHP plants and investigates possibilities for the regions to become self-sufficient in transport fuels by supplying regional passenger car fleets with ethanol and biogas that are produced locally from cellulosic biomass.

The thesis presents results on potential CO2 emissions minimisation from

road traffic when fossil fuels are substituted with ethanol produced locally from straw.

The version of the optimisation model presented in this thesis relies on several simplifications and assumptions. It is the first step in optimisation of the regional waste-to-energy system study that aims to increase the utilisa-tion of agricultural residues for energy recovery.

The most important outcomes from the present thesis are listed below: The available cellulosic biomass (cereals straw and Salix) in the studied

regions is sufficient to meet current regional ethanol demand. However, it is not sufficient for scenarios where all passenger cars are fuelled with E85 (Papers I–III).

The optimisation results show that the costs of supplying the regional passenger car fleet with transport fuel can be reduced by 31% by using a polygeneration system instead of standalone ethanol production. The higher profitability of the integrated system can be explained by in-creased process efficiency and revenues that can be generated by using residuals and/or by-products within the system.

The cost optimisation results show that for both standalone ethanol pro-duction and polygeneration systems, the three main cost drivers for

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sup-plying passenger cars in the study region with transport fuel are ethanol production costs, petrol prices and straw production costs. Three less important drivers in both cases are power price, regional straw availabil-ity and the cost of imported straw (Paper I).

Modelling results (Paper I) are sensitive to all input parameters, and to changes in ethanol production costs in particular. As the estimates of these latter costs are strongly based on scientific assumptions and labora-tory and pilot-plant results rather than on real-life data, it is worth inves-tigating these parameters more closely.

3% CO2 eq. emissions reductions can be achieved by using locally

pro-duced ethanol from cereals straw if passenger car numbers in the Sala-Heby region increase according to current trends until 2020. CO2 eq.

emissions can be reduced by 14% by replacing all petrol fuel with fuel containing 10% ethanol (E10 fuel), and by 48% if all passenger cars in the studied region use E85 fuel (Paper II).

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24

6 Future work

As this study is a starting point in evaluating the potential for the regional energy system to become self-sufficient in transport fuels and to reduce local GHG emissions from transportation, the results indicate a need for further research.

The next steps for this research are to improve the following aspects of the model for optimising the regional waste-to-energy system:

The dynamic model needs to be developed with respect to policies and national regulations in the fields of waste management and climate change mitigation, to consider several scenarios for waste generation and economic development in Sweden and the EU.

Since modelling results are particularly sensitive to input data on ethanol production costs, it is worth investigating this parameter more closely. The model can be improved to include other residual products and

wastes as feedstock. The model can also be developed to consider a larg-er geographical area.

Detailed economical evaluation of the polygeneration system should be performed to include potential conflicting interests for straw use.

CO2 eq. emission evaluation is to be performed to also consider land use

change (LUC) and indirect land use change (iLUC). The overall objec-tive will be to minimise CO2 eq. emissions along the whole chain from

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