Transportation fuels from Swedish biomass — environmental and cost aspects

Pergamon

Transpn. Rex-D, Vol. I, No. I, PP. 47-62, 1996 Copyright 0 1996 Elsevier Science Ltd

Printed in Great Britain. All rights reserved 1361-9209/96 $15.00 + 0.00

PII: S1361-9209(%)00005-3

TRANSPORTATION FUELS FROM SWEDISH BIOMASS - ENVIRONMENTAL AND COST ASPECTS

BENGT JOHANSSON Department of Environmental and Energy Systems Studies, University of Lund, Gerdagatan 13,

S-223 62 Lund, Sweden

(Received 7 March 1996; in revised form 8 May 1996)

Abstract--In this paper, technical and economic prerequisites to attain reduced carbon dioxide (CO,) emissions through the use of biomass-based energy carriers in the transportation sector are studied. COz emission reduction per unit of land used for biomass production as well as costs for CO, emission reduction arc estimated when substituting rape methyl ester, biogas from luceme, ethanol from wheat and ethanol, methanol and hydrogen from Salix (willow) and logging residues for petrol and diesel. Other environmental impacts resulting from an increased use of biomass-based energy carriers are briefly discussed. The study shows that the transportation fuels based on Sulix will provide the largest CO2 reduction per hectare. For the technologies assumed to be available in 5-10 yr time, the costs for CO, reduction will be lowest for methanol from Salix and logging residues; USD 23@430/tonne C at current biomass costs and USD 18@-340itonne C at estimated biomass costs around 2015, when used instead of petrol in internal combustion engine vehicles (ICEVs). Using biomass-based methanol in ICEVs will, at current biomass costs, result in 5-10% higher kilometre costs than for petrol-fuelled vehicles, and at estimated biomass costs around 2015, 48% higher costs, excluding fuel taxes. If on-going development is successful, ethanol from cellulosic feedstocks might achieve costs for CO* reduction that are similar or lower than for methanol when the fuels are used in ICEVs, but the uncertainties are large. Ethanol is, however, in contrast to methanol, not a suitable fuel for fuel-cell electric vehicles. Biomass-based energy carriers used in battery or fuel-cell powered electric vehicles would provide twice the amount of transportation work per unit of biomass than if used in ICEVs. Copyright 0 1996 Elsevier Science Ltd

INTRODUCTION

In 1992 mobile sources produced 46% of total Swedish carbon dioxide (CO,) emissions, 80% of total Swedish nitrogen oxides (NO,r) emissions, 40% of total emissions of volatile organic compounds (VOCs), and 23% of total sulphur dioxide (SO,) emissions (Statistics Sweden, 1993a, 1994a). High urban concentrations of particulates are, too, mainly the result of vehicle energy use (Swedish Environmental Protection Agency, 1993a). Petroleum fuels accounted for 97% of the transportation energy in 1992 (NUTEK, 1995). An increased use of alternative fuels, both fossil and renewable, can reduce the dependence on petroleum fuels, and may also result in lower emissions of NO,, VOCs, particulates and SO;, (OECD, 1993). Several studies (e.g. Swedish Transport Research Board, 1990; IEA, 1993a; OECD, 1993; Johansson, 1995a) have found that the use of renewable energy carriers can contribute to significant reductions of transportation CO, emissions. Such renewable energy carriers can be produced from biomass, wind, sun and hydro.

Using sustainably grown biomass will not result in net CO2 emissions, as the same amount of carbon released in combustion has been recovered from the atmosphere during biomass growth. The utilization of biomass-based transportation fuels might, however, result in CO, emissions from fossil fuels used for biomass production, transportation, conversion and distribution of final energy carriers. Biomass-based energy carriers may, however, be used also in these operations.

In this paper, the efficiencies of reducing CO* emissions from the transportation sector by using different biomass-based energy carriers are compared. The effect of an increased use of biomass-based energy carriers on other emissions, and the environmental

41

48 Bengt Johansson

impact from new land-use patterns resulting from biomass production are briefly discussed. Kilometre costs for vehicles using biomass-based energy carriers are compared with the costs for petrol-fuelled vehicles.

METHODOLOGY

The following measures were used for comparing the efficiency of reducing CO, emissions: (i) CO* emission reduction per unit of arable or forest land used for biomass production; and (ii) costs for CO2 emission reduction.

A fraction of produced biomass is assumed to be used for energy inputs in biomass production, transportation, conversion and fuel distribution, resulting in zero net emissions of CO, from the use of biomass-based energy carriers. The net production of biomass- based energy carriers is calculated as the gross production of transportation fuel and by-products, minus the transportation fuels needed for the inputs of such fuels, and by the by-products and, if not sufficient, part of the main biomass feedstock (e.g. S&x, wheat grain) needed for the inputs of heat and electricity. Estimated CO* emissions from fossil fuels include emissions from fuel extraction, conversion, distribution and end-use, and are taken to be 0.085 and 0.083 tonne/MWh for petrol and diesel, respectively (Ecotraffic, 1992, Ribacke, 1994). Energy by-products not needed for energy inputs are assumed to replace fossil fuels used for heat production, resulting in an assumed CO2 emission reduction of 0.077 tonne per MWh of by-product. This is equal to the reduction that would have been achieved if fuel oils were replaced.

In the calculations of CO* reduction costs for transportation fuel substitution, the by-products are valued according to how other biomass fuels with similar performance are valued when used for producing electricity or heat. This method enables a separation of the generally higher CO* reduction costs for replacing fossil transportation fuels, from the lower CO, reduction costs of replacing fossil fuels used for heat or electricity production. A method comparing average reduction costs for the substitution of fossil fuels with the produced biomass-based transportation fuels and by-products would have favoured technologies producing large shares of by-products compared to technologies producing larger shares of the more refined transportation fuels in an unfair way. (The by-products are mainly used for heat production where low CO* reduction costs could be achieved by using wood fuels directly instead.)

Yearly driving distances, D, which can be obtained by using biomass from one unit of land (km/ha, yr) are calculated as:

D = FIE,, (1)

where F is the net production of the biomass-based transportation fuel from one unit of land (MWh/ha, yr), and E,, is the specific energy use for vehicles using the biomass based fuels (MWh/km).

Reduced CO, emissions per unit of land, COZred, used for biomass production (tonne C/ha, yr) are calculated as:

CO,,,, = F X EflEb X e,, + B X 0.077, (2)

where Ef is the specific energy use for vehicles using fossil fuels (MWh/km), e,, is specific CO, emissions for the substituted fossil transportation fuel (tonne C/MWh), and B is the net production of by-products which can be used for heat and electricity production (MWh/ha, yr).

Costs of CO, reduction, Cred, for using biomass-based transportation fuels as substitutes for petrol or diesel (USD/tonne C) are calculated as:

C,, = (G + G/J% - EFI& X Cr - GJ&,)l(Elj& X e,J. (3)

where C, is the costs for biomass-based transportation fuel production and distribution where by-products have been credited for their value for use in heat production, as fertilizers or as fodder (USD/MWh), C,, is the capital costs for vehicles using biomass-based fuels

Transportation fuels from Swedish biomass 49

(USD/km), C, is the costs for the fossil fuel being replaced by the biomass-based fuel (USD/MWh) and C,, is the capital costs for vehicles using fossil fuels (USD/km). Service, maintenance costs and insurance, etc. are not assumed to differ between internal combustion engine vehicles (ICEVs) using biomass-based transportation fuels and ICEVs using fossil fuels, and are excluded here.

Kilometre costs, C,,, for vehicles (USD/km) are calculated as:

where E is vehicle specific energy use (MWh/km), C,,, is fuel costs excluding taxes (USD/MWh), C,,, is fuel taxes (USD/MWh), and C, is vehicle capital, service, maintenance costs, insurance and yearly vehicle taxes (USD/km).

All energy amounts are expressed in lower heating values (LHV). Large scale production and use of biomass-based transportation fuels are assumed, taking into account large- scale production advantages for both fuel plants and vehicles. The costs for CO, reduction are calculated excluding domestic fuel taxes and subsidies. Kilometre costs are, however, calculated both excluding and including fuel taxes. Swedish fuel taxes include a carbon tax of USD 160/tonne C. Investment costs are annualized using a 6% real discount rate. All costs and prices refer to June 1993, when the average exchange rate was USD 1 = 7.4 SEK. Fossil-fuel costs are taken as delivery prices in the second quarter of 1993 and are 39 and 36 USD/MWh for petrol and diesel, respectively (IEA, 1993b).

BIOMASS FROM FOREST AND AGRICULTURAL RESOURCES IN SWEDEN

Sweden is a sparsely-populated country (19 inhabitants/km2) with forest and agricultural land covering 59% and 9% of the land area, respectively (Statistics Sweden, 1994b). Current Swedish forest harvest corresponds to some 150 TWh/yr, of which 50% is used for energy purposes (Eriksson, 1991; National Board of Forestry, 1995; NUTEK, 1995). In 1994, 65% of the biomass energy was used in the industrial sector, mainly in the paper and pulp industry (NUTEK, 1995). The crop production from Swedish arable land corresponds to 80 TWh/yr, but less than 0.5 TWh is used for energy (Gustavsson et al., 1995).

Both roundwood and logging residues can be used for energy purposes. Only industrial by-products and logging residues are included in the estimated biomass potential (Table 1).

Extensive logging-residue extraction requires compensation for nutrient losses to ensure the long-term productivity of the forest soil (Lundborg, 1994; Gustavsson et al., 1995). Extraction of logging residues will reduce the nitrogen load, and would, combined with ash recirculation, counteract nutrient imbalances and acidification in areas with high nitrogen deposition. Stumps should be left at the site to minimize nutrient leaching and preserve the organic content of the soil (Lundborg, 1994). To preserve biodiversity in forests, it is important to increase the share of broad-leaf trees, old trees, and dead wood as well as to preserve areas with a great variety of species. Compared to these measures, the utilization of logging residues, leaving a minor fraction of the residues on the site, and ash circulation all have much less impact on the biodiversity in the forests (Rosen, 199 1; Lundborg, 1994).

Existing investment in agricultural machinery could be used for growing conventional crops, like rape and wheat for energy. Both rape and wheat have, however, lower productivity, and require larger energy inputs than do perennial crops, like lucerne and Salk (short rotation forest) (Bbrjesson, 1994). Other Swedish cereals have a lower productivity than wheat (Statistics Sweden, 1993b). The potential for growing rape for energy is restricted, due to the risk of crop rotation diseases (Noren, 1990).

Sugar beet is a suitable crop for ethanol production, and has a high productivity in southern Sweden (Swedish University of Agricultural Sciences, 1986; Borjesson, 1994). Ethanol produced from sugar beets in Sweden is, however, expected to be more expensive than ethanol from wheat (Swedish University of Agricultural Sciences, 1986).

Ley crops and Salix have a higher productivity and lower production costs than annual crops (Borjesson, 1994; Gustavsson et al., 1995). The cultivation of such perennial crops

50 Bengt Johansson

Table 1. Estimated potential in Sweden around the year 2015 for energy crops, logging residues and industrial by-products

Biomass potential* Production conditions 2015

Biomass resource (TWwyr)

Energy crop alternatives+ Rape, seed and straw 4 Winter wheat, grain and straw 29 Reed canary-grass 36 Lucerne 45 Sdix 59

Straw from food $P

reduction: I1 Logging residues 53-65 Industrial by-productl 47-5 1 Total” 170-186 1994 Swedish use of biomass for energy 61* Potential increase in use of biomass for energy 109-125

*The estimates exclude small-scale wood burning which, in 1993, was 12 TWh (NUTEK, 1995). ‘Potential ahernative production on 800,000 ha of arable land for the respective crops, except for rape, where a

maximum of 150,000 ha can be= used for energy purposes, due to the risk of crop rotation diseases. Based on Gustavsson et al. (1995).

:The land needed for grain production is estimated to be I. 1 Mha. Based on Gustavsson et al. (I 995). §Based on Gustavsson er al. (1995). Potential with recirculation of ashes, changed harvest of pulp wood in

thinnings, changed quality restrictions, and estimated annual fellings in 2015. The fellings here are calculated to be 10% higher than estimated annual fellings in 2005 according to the Official Report of the Swedish Government (1992).

nThe amount is equal to estimates for 2005 by the Official Report of the Swedish Government (1992). “Assuming that S&x is grown on the assumed available arable land (800,000 ha).

is expected to result in less nutrient leaching and soil erosion than with annual crops, and is expected to maintain or increase the organic matter in soils (Thyselius et al., 1991; Makeschin, 1994; Ritjema & de Vries, 1994). The biodiversity is expected to improve slightly with a shift from annual food crops to Salix and ley crops, due to a higher content of organic matter in the topsoil, reduced soil tillage and reduced use of chemical pesticides and, in open farmlands, greater ecosystem variety (Makeschin, 1994; Sage & Robertson, 1994; Gijransson, 1994).

Improved productivity in agriculture results in less land requirements for food production, and also increases the production of biomass for energy per unit of land. It has been estimated that 800,000 hectares can be used for purposes other than food production for domestic consumption in the future (Official Report of the Swedish Government, 1992). An estimate of the potential for biomass production from forest and arable land around 2015 is shown in Table 1.

There is a potential to increase the use of biomass for energy from Swedish forestry and agricultural land by 110-125 TWh/yr, compared to 1994. In 1994, Swedish fossil fuel use was some 240 TWh, of which 82 TWh was petrol and diesel (NUTEK, 1995).

PRODUCTION AND USE OF BIOMASS-BASED ENERGY CARRIERS FOR TRANSPORTATION

In this study, the uses of the following biomass-based energy carriers in ICEVs are studied: (i) rape methyl ester (RME) produced from rape seed oil and biomass-based methanol (MeOH), (ii) biogas from lucerne, (iii) ethanol (EtOH) from wheat, (iv) ethanol from Salix and logging residues produced using acid hydrolysis (acid), (v) ethanol from Salix and logging residues produced using enzymatic hydrolysis (enzym), (vi) methanol from Salix and logging residues, and (vii) hydrogen from Salix and logging residues. The use in both passenger cars and heavy-duty buses is studied, except for hydrogen, where only use in passenger cars is studied. The effect of using methanol and hydrogen in fuel cell electric vehicles (FCEVs) and biomass-based electricity in battery-powered electric vehicles (BPEVs) is studied in less detail.

RME is produced by a simple small-scale process consisting of two main steps: (i) pressing the rape seed to rape seed oil, and (ii) transesterification of the oil with


methanol. In the process, by-products, suitable for use as fodder, are produced. These by-products can also be used for energy purposes (Nor&n, 1990). RME can be used in standard diesel engines without any alteration of the engine or fuel supply system (Devitt et al., 1993). In Swedish tests, the fuel consumption of RME buses has been similar to that of diesel buses (Amten, 1993).

Biogas, a methane-rich gas, is produced through decomposition of biological material under anaerobic conditions. Most biological feedstocks, except for those with a high lignin content, are suitable for biogas production. Lucerne has been found to be a prefer- able crop for biogas production in Sweden due to low feedstock costs (Brolin et al., 1988). The biogas process yields by-products suitable as fertilizers. To obtain a more suitable and less corrosive motor fuel, the biogas has to undergo a process in which particulates, hydrogen sulphide, and CO, are removed. The use of biogas in Otto engines will probably result in l&15% higher end-use energy efficiency (krn/MWh) than the use of petrol (Sperling and Deluchi, 1989; Victor, 1992; Eriksson, 1992b). The use of biogas in heavy-duty vehicles will, however, decrease the energy efficiency by 15-20% compared to diesel, as biogas cannot currently be used in diesel engines (Eriksson, 1992b; Brolin et al., 1995).

Ethanol can be produced by biologically catalysed reactions from sugar-rich, starch-rich and cellulosic feedstocks. Whereas sugars extracted from sugar-rich crops can be directly fermented to ethanol, starch, cellulose and hemicellulose must be broken down to fer- mentable sugars. Difficulties in fermenting sugars from hemicellulose have been an obstacle to achieving high ethanol yields from low-cost cellulosic feedstocks. New processes, using enzymatic hydrolysis, capable of converting both cellulose and hemicellulose to ethanol are, however, under development (Wyman et al., 1993). Commercial by-products from ethanol production are, for example, fodder, CO, and, from cellulosic feedstocks, lignin fuels.

Methanol can be produced from biomass using a thermochemical process in which the main steps are (i) biomass gasification producing a gas consisting mainly of carbon monoxide (CO) and hydrogen (H,), (ii) adjustment of the carbon-to-hydrogen ratio to the level needed for effective conversion to methanol, and (iii) methanol synthesis, in which CO and H, are catalytically combined to methanol (Katofsky, 1993).

Ethanol and methanol vehicles with dedicated Otto-engines are expected to have lO-30% higher energy efficiency than current petrol-fuelled vehicles, and with diesel engines, equal energy efficiency as with diesel (Mills & Ecklund, 1987; Sharpe, 1991; Eriksson, 1992a; Kowalewicz, 1993; Wyman et al., 1993). The use of alcohol fuels in Otto and diesel engines requires minor changes of the engines due to, for example, the higher corrosivity of the alcohol fuels.

Hydrogen can be produced from biomass using the same gasifier technologies used for methanol production. After gasification, the hydrogen content of the product gas is max- imized in a shift reaction and the hydrogen is separated. Otto-engines, fuelled with hydrogen, are expected to have 1550% higher energy efficiency than petrol-fuelled engines. The main problems with hydrogen vehicles are the bulky and costly fuel storage (DeLuchi, 1989; De Luchi & Ogden, 1993).

The emissions from biomass-based fuels used in ICEVs equipped with catalytic converters are not well known, and potential emission reductions compared to petrol will start at relatively low levels. Biogas and alcohol-fuelled light-duty vehicles are expected to have similar levels of NO, and CO emissions as petrol-fuelled vehicles, whereas the emissions of non-methane VOCs, as well as the ozone forming potential of the emissions, are expected to be 50% lower than for petrol (Martin & Michaelis, 1992; OECD, 1993). Biogas and alcohol combustion will not result in any emissions of benzene or other aro- matic hydrocarbons, but the emissions of aldehydes are expected to be higher for alcohol fuels than for petrol. Hydrogen will emit essentially no other emissions than NO,Y, and will probably be able to meet any NO,Y standard that a petrol-fuelled vehicle can meet (Ogden et al., 1994).

Sulphur and particulate emissions will be reduced significantly compared to current diesel vehicles using RME, alcohols or biogas (Hardenberg, 1991; Stephenson, 1991;

52 Bengt Johansson

Eriksson, 1992a; OECD, 1993; DeVitt et al., 1993). NO, emissions from alcohol- and biogas-fuelled heavy-duty vehicles are expected to be less than 50% and 25%, respectively, of the emissions from average new diesel-fuelled heavy vehicles in Sweden (Eriksson, 1992a). RME-fuelled vehicles are, however, expected to produce 5-10% higher NO, emissions than diesel (Devitt et al., 1993; Amten, 1993). The emissions from diesel vehicles of VOCs and CO are relatively low, less than 15% (calculated as g/MJ,,,) of the emissions from petrol-fuelled vehicles with catalytic converters (Ecotraffic, 1992) and they are expected to remain at low levels with biomass-based fuels as well (Eriksson, 1992a; Devitt et al., 1993).

If fossil fuels are used for biomass production, conversion and distribution, the emissions of NO,r from these operations can be much higher than from the production of petrol, and can be as high as the end-use emissions from a car with a catalytic converter (Ecotraffic, 1992). If biomass-based fuels are used for biomass production, conversion and distribution, the fuel-cycle NO, emissions will be reduced to the same level as for petrol (1.5 times the end-use emissions) (Johansson, 1995a,b). In heavy-duty vehicles, more than 70% of the fuel-cycle NO, emissions, both for diesel and the biomass-based fuels, are end-use emissions (Johansson, 1995a,b). For both CO and VOCs, end-use emissions dominate the fuel-cycle emissions (Ecotraffic, 1992).

Electric vehicles have high end-use efficiencies and zero or very low end-use emissions. Energy efficiencies for future BPEVs are expected to be more than three times as high as in current petrol-fuelled vehicles (Wang & DeLuchi, 1992; Ogden & Nitsch, 1993). Electricity can be produced from biomass using conventional steam turbines. Combined cycles technologies using gasified biomass are, however, under development, and they are expected to have both higher efficiencies and lower costs than conventional steam turbines (Gustavsson & Johansson, 1994). The main problems of BPEVs are short driving-range and costly energy storage in batteries (IEA, 1993~).

In FCEVs, the electricity is produced by a fuel-cell in the vehicle, preferably from hydrogen. End-use efficiencies in future FCEVs are expected to be two or three times higher than in current petrol-fuelled vehicles (Ogden & Nitsch, 1993). Methanol is a suitable energy carrier in FCEVs since it can be reformed to hydrogen in the vehicle. The use of methanol instead of hydrogen is expected to result in lower mileage costs (Ogden & Nitsch, 1993).

The use of BPEVs will almost eliminate fuel-cycle CO and HC emissions, and can, if using electricity from modern biomass power plants, result in 70% lower NO, emissions, compared to an average petrol-fuelled vehicle equipped with a catalytic converter (Ogden et

al. 1994; Johansson, 1995a). FCEVs will emit no air pollutants, except for small amounts of CO and NO,X, from the reforming of methanol to hydrogen (Ogden et al., 1994).

Table 2. Biomass yields and energy use for biomass production and transportation per unit of land. Values without brackets are current yields and energy use, and values within brackets, estimated yields and energy use

around the year 2015 (Sundell & Ekborg, 1992; Borjesson, 1994)

Biomass yield* (MWh/ha,yr)

Motor fuel use Other energy use for biomass for biomass production production

(MWh/ha.yr) (MWh/ha,yr)

Motor fuel use for biomass

transportation+ (MWh/ha,yr)

Logging residues 1.1 (4.1) 0.03 (0.09) 0.004 (0.01) 0.01 (0.037) Salix 42 (75) 0.49 (0.59) 1.1 (0.73) 0.34 (0.60) Wheat (grain) 21 (31) 1.0 (0.80) 3.0 (2.3) 0.084 (0.124) Rape (seed) 18 (22) 1.2 (0.93) 2.4 (1.6) 0.013 (0.015) Straw (wheat, rape) 2.0 (8.0) 0.05 (0.14) 0.12 (0.08) 0.016 (0.064) Lucerne 32 (58) 1.3 (1.7) 0.52 (0.37) 0.077 (0.14)

*Lower heating values at assumed moisture content are (MWh/tonne dry-matter): for logging residues 5.1, for Salk 4.5, wheat 4. I, rape seed 7.3, straw, lucerne 4.0.

‘The data are based on Sundell and Ekborg (1992). adapted here for estimated transport distances. Lucerne and rape seed are expected to be used in small-scale plants with average transport distances of 10 km, whereas wheat, Salix and straw are expected to be transported 50 km, and logging residues 75 km.


Table 3. Costs for biomass production and transportation. Values without brackets give costs for current production conditions, and values, within brackets estimated costs for around the year 2015 (Axenbom et al,,

1992; Gustavsson et al., 1995)

Production costs Transportation costs* (USD/MWh) (USD/MWh)

Total costs (USD/MWh)

Logging residues Salk Wheat Rape seed Lucerne

I2 (9.2) 3.4 (3.0) I5 (12) I6 (IO) 2.1 (2.4) I9 (13) 50 (30) 2.0 (1.8) 52 (32) 61 (45) 1.4 (1.4) 62 (46) I5 (IO) 2.1 (2.7) 18 (13)

*Based on Gustavsson ef al. (1995), but adapted for the transport distances used in this paper, Table 2.

COMPARISON OF DIFFERENT BIOMASS-BASED TRANSPORTATION FUELS

Assumptions Energy balances for biomass production and transportation, and biomass production

costs, are shown in Tables 2 and 3. The calculations are based on biomass production conditions in central Sweden (between 58”N and 60”N).

Energy balances for biomass conversion technologies are shown in Table 4, and total costs of produced energy carriers, in Table 5. Efficiencies and costs for the production of ethanol from cellulosic feedstocks with enzymatic hydrolysis, methanol and hydrogen are expressed as an interval starting at lower limits, denoted ‘low efficiency’ (LE). These quantities represent conservative estimates of efficiencies and investment, operating and maintenance costs of the plants. The upper limits, denoted ‘high efficiency’ (HE), represent

Table 4. Energy balances for transportation fuel production and distribution

Rape methyl ester+ Biogas, lucerne: EtOH, wheats EtOH (acid) cellulosic’l.” EtOH (enzyme, LE) cellulosicn~” EtOH (enzyme, HE) cellulosicn~** MeOH (LE) cellulosicn.tt MeOH (HE;, cellulosicn.tt Hydrogen (LE), cellulosicn.zz Hydrogen (HE), cellulosicn.:: Electricity, ccllulosicn~~

Transportation fuel production*

SUPPlY Production

Process Transportation Feedstock energy fuel By-product

I 0.035 0.45 0.5 1 0.09 0.63 0.03 1 0.26 0.50 0.10 I 0.0910.08 0.3bO.27 0.4410.39 I 0.14/0.12 0.40/0.36 0.3110.28 I 0.6410.56 0.0510.04 I 0.04/0.03 0.5910.52 1 0.03/0.03 0.70/0.62 1 0.18/0.16 0.68/0.60 1 0.15/0.13 0.8210.72 1 0.45io.45

Energy use for

fuel distribution

=O 0.10 0.001

0.0006/0.0005 0.0008/0.0007 0.0013/0.001 I 0.0015/0.0013 0.0018/0.0015

0.07/0.06 0.0810.07 0.03/0.03

*As energy contents of biomass are shown as LHVs at the assumed actual moisture, the energy output/input ratios are higher here than in those of the referred studies, where the energy content of biomass is expressed as higher heating values, or as LHV at 0% moisture.

‘Including energy needed for rape-seed oil and methanol production and transesterlication (Noren, 1990; Ecotraffic, 1992).

:Based on Dalemo et al. (1993). Axenbom ef al. (1992) and Sundell and Ekeborg (1992). Energy for distribution includes energy for gas purification and compression (Ecotraffic, 1992).

DProcess Biostil based on Sundell and Ekeborg (1992). By-product is 0.2 MWh methane per MWh ethanol. Energy for distribution is based on Sundell and Ekeborg (1992) and a distance of 100 km.

lValues to the left of the slash are with Salk as feedstock, to the right, for logging residues. Differences in the energy flows are mainly the result of different LHVs/dry-tonne at assumed actual moisture.

“Based on von Sivers and Zacchi (1993). Acid hydrolysis according to the CASH-process. By-product is lignin fuel. Distribution, see note 0.

**Based on Wyman et al. (1993). The by-product is electricity, which is recalculated to fuel equivalent by using electric efficiency of 0.45. Distribution, see note 5.

‘+Based on Katofsky (1993). LE is an estimate for a plant using a directly heated gasifier studied at Institute of Gas Technology. HE is an estimate for a plant using an indirectly heated gasifier studied at Battelle- Columbus Laboratory. Distribution see note 5.

t:Production, see note tt. Energy for distribution includes pipeline distribution and high pressure compression based on Plass et al. (1990) and DeLuchi and Ogden (1993).

BBioflow-technology. Efficiency and distribution losses based on Gustavsson and Johansson (1994).

54 Bengt Johansson

Table 5. Costs for transportation fuels, including distribution costs. Values without brackets are based on current biomass costs, values within brackets on estimated costs around the year 2015 (Table 2)

Fuel costs. No credit for by-products

(USDIMWh)

Fuel costs.* Fuel costs.+ Credit for Credit for by- Time until energy by- products used as technology products fodder or fertilizer commercialization

(USDIMWh) (USD/MWh) (yr)

Agricultural feedstocks Rape methyl ester: Biogas, lucerne$

180 (147) 155 (126) 116 (84) 81 (72) 74 (65)

EtOH, wheatn 168 (127) 120 (81) EtOH (acid), cellulosi&** EtOH(enzyme LE) cellulosi&**

1361131 (120/120) 105199 (92/92) 5-10 1161111 (103/103) 99193 (88/88) 5-10

EtOH(enzyme HE) cellulosic”.:: MeOH (LE) cellulosic”.ZZ

59/54 (51151) 58153 (50/50) >15 5-10

MeOH (HE) cellulosic”.:: 81/77 (72/72) 64161 (55155) 5-10

Hydrogen (LE) cellulosici’.ZZ 5-10 Hydrogen (HE) cellular&

78174 (70170) 62159 (55155) 5-10

Electricity, cellulosic++.W 1181109 (1051103) 5-10

*Energy by-products from RME are valued as logging residues (USD lS/MWh today, USD lZ/MWh 2015), lignin fuel, as wood pellets, USD 7/MWh higher than logging residues (Elam ef al., 1994), and electricity, as USD 40IMWh.

‘Fodder by-products from production of RME and ethanol are valued to USD 290itonne and USD 250/tonne, respectively (Axenbom et al., 1992), and fertilizers from biogas production, to USD 7IMWh biogas produced (Dalemo ef al.. 1993).

:Based on Axenbom et al. (1992), NorCn (1990), and Dalemo (1991). Distribution costs are USD 5.4/MWh. $Based on Dalemo et al. (1993). Costs for gas cleaning included. Distribution costs are USD 14/MWh nBased on Axenbom ef (11. (1992). Distribution costs are USD 15IMWh (Ekstriim et ul., 1991). “Values to the left of the slash are calculated with &Z&Y as feedstock, to the right, with logging residues. **Based on von Sivers and Zacchi (1993). Distribution costs, see Q. ‘+Based on Wyman e/ u/. (1993). The technology for achieving these low-cost projections has only been demon-

strated in laboratories; thus a considerable effort is required for commercial readiness (Ogden et al., 1994). Distribution costs, see Q.

::Based on Svenningsson (1994) and Katofsky (1993). Biomass-to-methanol technology could according to Ogden et al. (1994) be commercially ready about the year 2000. The development of indirectly-heated gasifier units (technology HE) is, however, assumed to require somewhat more than 5 y. Distribution costs for methanol are USD 16IMWh. and, for hydrogen, USD 22iMWh (Ekstriim et ul., 1991; Ogden and Nitsch, 1993).

%Based on Gustavsson and Johansson (1994b). Distribution costs are USD 29iMWh.

estimates with relatively higher efficiencies and lower costs. Energy balances and costs for both LE and HE technologies are shown in Tables 4 and 5. Some of the studied technologies are not yet commercially available. When the technologies will be commercialized depends both on the current status and on the effort and resources allocated to the technology development. Very rough estimates by the author of when the technologies with given performances could be commercialized are shown in Table 5.

Assumed vehicle energy efficiencies, and added investment costs for vehicles using biomass-based fuels compared to vehicles using fossil fuels are shown in Table 6. Also for large-scale production, vehicle investment costs are assumed to be somewhat higher

for vehicles using biomass-based fuels than for petrol or diesel fuelled vehicles, resulting from, for example, higher corrosivity and more expensive storage of gaseous fuels. Service and maintenance costs, insurance and yearly vehicle taxes are not assumed to differ among vehicles with different fuels.

When average life-cycle kilometre costs for using passenger cars fuelled with petrol and biomass-based fuels are calculated; data in Table 6 are used, assuming a sale price for a petrol-fuelled vehicle of USD 16,000. Costs for insurance, service and maintenance and yearly vehicle taxes are assumed to be USD 1350/yr for all passenger cars studied (Swedish Motor Vehicle Inspection Company and National Swedish Board of Consumer Policies, 1994). Fuel taxes for petrol are taken as 1993 Swedish taxes for unleaded petrol, USD 84/MWh. Fuel taxes on biomass-based fuels are assumed to be equal to petrol taxes calculated per vehicle-kilometre, excluding 1993 carbon taxes (USD 160/tonne C).


Table 6. Assumed vehicle energy efficiencies and added investment costs for vehicles using biomass-based fuels compared with vehicles using fossil fuels

Fuel

Energy efficiency* Added investment costs*+

Passenger car Heavy-duty bus Passenger car Heavy-duty bus (kWh/km) (kWh/km) (USD/vehicle) (USD/vehicle)

ICEV Fossil Fuels: RME Biogas Ethanol Methanol Hydrogen Electric vehicles BPEV, electricity FCEV, hydrogen FCEV, methanol

0.72 3.6 0.65$ 3.6 0.63 4.2 0.63 3.6 0.63 3.6 0.55 n.s.

0.209 0.311 0.36n

n.s. n.s. n.s.

Iooo~ 0 1300 7800 500 1900 500 1900

6500 n.s.

ns. n.s. n.s. t-is. n.s. n.s.

*The assumptions are based on large-scale production vehicles optimized for the fuels and are based on Mills and Ecklund (1987) Eriksson (1992a,b), Swedish Environmental Protection Agency (1993b) and Ogden and Nitsch (1993).

‘Costs are transformed into km costs by assuming a vehicle lifetime of 15 years and a yearly driving distance of 13,000 km for passenger cars and a vehicle lifetime of 12 years and a yearly driving distance of 48,000 km for heavy-duty buses.

:Reference vehicles based on Average Sold Technology (AST) in Johansson (1995a). $RME is assumed to be used in diesel engines in passenger cars as well. Differences in efficiency and costs for

RME are differences between a diesel- and a petrol-fuelled passenger car. nThe relation between energy efficiencies of BPEVs, FCEVs and ICEVs recalculated from Ogden and Nitsch

(1993) assuming the same power-to-weight ratios and vehicle weights (excluding drive systems) in BPEVs, FCEVs and ICEVs.

n.s.: not studied.

This assumption is based on current Swedish Policy, in which marginal external costs of vehicle use should be included in the fuel prices (Swedish Government, 1988). Costs for infrastructure maintenance, traffic supervision and traffic accidents are a major percent- age (70-80%) in the current estimates of marginal external costs for Swedish passenger cars equipped with catalytic converters (Swedish Ministry of Communications, 1992). These costs cannot be expected to diminish when substituting biomass-based fuels for petrol. Current Swedish taxes on methanol and ethanol are USD 25/MWh and USD OlMWh, respectively.

Results The net production of biomass-based transportation fuel from 1 ha of arable land can,

with current cultivation conditions, be enough for more than 40,000 km of yearly driving with passenger cars (ICEVs), provided that Sulix is grown (Table 7). Transportation fuels from wheat or rape seed will only be sufficient for 25% of the driving that can be

Table 7. Driving distances obtainable for passenger cars using biomass-based energy carriers from I ha of arable land

Fuel, feedstock (vehicle-type)

Current cultivation Cultivation conditions conditions around 20 I5

(1000 km/ha, yr) (1000 km/ha. yr)

RME, rape seed (ICEV) II I4 Biogas, lucerne (ICEV) 26 48 Ethanol wheat (ICEV) 12 23 Ethanol with acid hydrolysis. S&u (ICEV) 20 36 Ethanol with enzyme hydrolysis, S&x (ICEV) 2542 45-75 Methanol, Suliu (ICEV) 3643 6679 Hydrogen, Sdix (ICEV) 3948 71-88 Methanol, Salir (FCEV) 62-75 114-137 Hydrogen, Salk (FCEV) 69-85 126155 Electricity, Salix (BPEV) 83 I51

56 Bengt Johansson

Current cultivation conditions

61

Cultivation conditions around 2015

6

Fig. I. Reduction of CO, emissions per hectare of arable land when petrol is replaced in passenger cars by biomass-based transportation fuels, and oil is rep aced by straw and other produced by-products. Lower limits

of intervals represent technologies LE, upper limits technologies HE (Tables 4 and 5).

achieved by using fuels from S&x. Around the year 2015, biomass from 1 ha Salix can yearly, at assumed cultivation conditions, be enough for 150,000 km of driving, equal to the current average annual driving distance of more than 10 Swedish passenger cars, provided that the biomass is used in electric vehicles.

The reduction of CO? emissions per hectare arable land is highest for the fuels produced from Safix (Fig. 1). The lowest emission reduction is achieved when ethanol from

wheat is used. The CO, emission reduction is some lo-15”/0 lower when the fuels replace diesel in heavy-duty buses than if the fuels replace petrol in light-duty vehicles. The rea- son is that, in contrast to when petrol is replaced, no advantages in end-use efficiency are assumed for the biomass-based fuels (see Table 6). For RME and ethanol from Mix produced with acid or enzymatic hydrolysis (LE), large shares, 50-60%, 50% and 20% respectively, of the CO? reductions are from substituting by-products for light fuel oils.

The costs for CO? reduction using biomass from agriculture land are lowest for methanol and ethanol produced with enzymatic hydrolysis (HE) produced from Salix

(Fig. 2). The use of ethanol, methanol and hydrogen produced from logging residues will, at current biomass costs, result in 5-10% lower reduction costs, than if Salix is

Current cultivation conditions

15001

Cultivation conditions around 2015

1500

Fig. 2. Costs of CO, reduction when petrol is replaced in passenger cars by biomass-based transportation fuels. Lower limits of interval represent technologies HE, upper limits technologies LE (Tables 4 and 5).


Table 8. Emission factors, and CO, reduction costs for heavy-duty buses, excluding and including an economic valuation of nitrogen oxides emissions. Values without brackets are based on current biomass costs, values

within brackets on estimated biomass costs around 2015

Costs of co, costs of co, costs of coz reduction reduction reduction

Emission factors NO,Y = NO, = NO, = nitrogen oxides* USD O/kg NO, USD 54/kg NO, USD 45 kg NO,

(gNO,/kWh) USDitonne C USDitonne C USD/tonne C

Diesel 7.0 Biogas, lucerne 2.0 670 (540) 560 (430) -230 (-360) Ethanol, enzyme, LE. Salix 4.2 770 (630) 710 (570) 270 (130) Ethanol, enzyme, HE, Salix 4.2 290 (190) 230 (130) -210 (-310) Methanol, LE, Sa1i.v 4.2 540 (440) 480 (380) 40 (-60) Methanol, HE, Sa1i.v 4.2 340 (250) 280 (190) -160 (-250)

*Emissions per unit of engine output measured using ECE R49 test-cycle. The values are based on Swedish Environmental Protection Agency (1993b). The value for diesel is the standard for Swedish environmental classes I and 2. This standard is about equal to the lowest emissions currently obtainable using diesel fuels. The use of methanol is assumed to result in as low emissions as does the use of ethanol.

used. Around 2015, this cost difference is expected to disappear. The costs for CO, emission reduction, when methanol is used instead of diesel, are USD 85-l 1Mtonne C higher at current biomass costs, and USD 70-851tonne C higher at estimated 2015 biomass costs, than if it is used instead of petrol. The high costs for RME and ethanol from wheat result mainly from costly feedstocks and the high costs for hydrogen, mainly from high fuel storage costs.

The estimates in Figs 1 and 2 are based on large-scale fuel production (>1.5 TWh transportation fuel/yr), where the production of fodder by-products from RME and ethanol production exceeds the demand (Noren, 1990; Axenbom et al., 1992) and the by-products are used for energy. If by-products can be sold as fodder, the RME and ethanol costs can be reduced by 2540% (Table 5). Consequently, the cost for CO, reduction will be reduced to USD 850/tonne C at current biomass costs and USD 450/tonne C at estimated biomass costs around 2015 for both RME and ethanol from wheat. The CO, reduction per hectare will, however, not increase.

The use of both biogas and alcohol fuels would result in lower emissions of particulates and nitrogen oxides than diesel. In Sweden, an environmental tax for NO, of USD 5.4/kg NO* is applied on large-scale heat and power plants. The local damage of NO, emissions on a central street in Gothenburg, Sweden, under mean weather conditions has been estimated by Leksell and Lijfgren (1995) to USD 45/kg NO,.

If these valuations of NO, emissions were applied to heavy-duty buses, the CO2 reduction costs for using biogas, ethanol or methanol instead of diesel could be reduced significantly (Table 8). If NO, emissions were economically valued to USD 45/kg NO?, negative CO? reduction costs would be achieved. The benefits for the local environment achieved by using biomass-based fuels, instead of diesel can, however, also be gained by using other fossil fuels, such as natural gas and methanol produced from natural gas.

Using biomass-based methanol in an internal combustion engine passenger car would, at current biomass costs, result in 5-10% higher kilometre costs, compared to those for a petrol-fuelled car, excluding fuel taxes (Fig. 3). At estimated biomass costs around 2015, the costs would be 48% higher than for petrol. Including fuel taxes, kilometre costs would be 04% higher for biomass-based methanol than for petrol, at biomass costs around 2015. The kilometre costs for the fuels not shown in Fig. 3 vary between 29 and 34 cents/km, excluding fuel taxes, at current biomass costs.

Kilometre costs for future battery-powered or fuel-cell powered electric vehicles have not been calculated in this study since major uncertainties exist about future vehicle costs, vehicle life length and service costs. For example, estimates on how much more BPEV are going to cost compared to a petrol fuelled vehicle vary between USD 2500 and 13,00O/vehicle (DeLuchi et al., 1989; Martin & Michaelis, 1992; Ogden & Nitsch, 1993; DeLuchi & Ogden, 1993). If optimistic development goals are met, however,

58 Bengt Johansson

40 1 I

0 Taxes

q Fuel costs excluding taxes

q Vehicle, service insurance etc

Petrol EtOH MeOH MeOH EtOH MeOH MeOH

ewm \ ewm

Current biomass costs 4.

Biomass costs 20 15 >

Fig. 3. Average life-cycle kilometre costs for using petrol-, ethanol- or methanol-fuelled passenger cars. Taxes are 1993 Swedish petrol taxes adapted for biomass-based fuels by eliminating the carbon tax.

kilometre costs for fuel-cell powered electric vehicles might, in the future, be as low as for current petrol-fuelled vehicles (Ogden & Nitsch, 1993; Ogden et al., 1994).

Sensitivity analysis CO? reduction costs are calculated, varying the assumptions of biomass production

costs, costs for fuel production technologies, fuel distribution costs, and extra investment costs for vehicles using biomass-based fuels (Table 9). For RME and ethanol from wheat, changed assumptions of feedstock costs by 30X, and for hydrogen, changed assumptions of vehicle investment costs by 30X, result in changes in the costs of CO, emission reduction by more than USD 200/tonne C.

In Table 10, the costs of CO? reduction are estimated, assuming no energy efficiency gains for vehicles using biomass-based transportation fuels compared to petrol-fuelled vehicles.

With increasing petrol prices, the costs of CO, reduction would be reduced (Fig. 4). Zero costs for CO> reduction may be achieved with a 50% increase in petrol price excluding taxes at current biomass costs, and with a 3&40% increase in petrol price, at estimated biomass costs around 2015. With current Swedish carbon taxes, methanol and ethanol from cellulosic biomass may be cost-competitive if the petrol price is increased by 15-30% at current biomass costs, and at current petrol prices at estimated biomass costs in 2015.

Table 9. Changes in costs of CO, emission reduction in passenger cars resulting from varied assumptions of feedstock costs, fuel production plant costs, distribution costs and added vehicle investment costs

costs of co2 Changes of costs of CO, emissions reduction as a result of reduction varied assumptions of different cost factors

USDitonne C (USD/tonne C)

Base-case Feedstock Fuel Distribution Added vehicle costs* production costs investment

Current (?30’%,) plant costs (+30’%,) costs Fuel biomass costs (*30X) (+30X)

RME 1260 *440 +I20 ?20 *40 Biogas, lucerne 470 flO0 *loo *40 PlO EtOH, wheat 1320 +300 &I50 fS0 *20 EtOH, S&u, acid 680 fl80 k80 *50 *20 EtOH, .Suli.u, enzyme (LE) 620 *140 ?I60 *50 +20 EtOH, Sulix, enzyme (HE) 220 *80 *40 +50 *20 MeOH, Sdix, (LE) 430 *90 flO0 *50 *20 MeOH, S&c. (HE) 260 +80 f50 f50 f20 Hydrogen, Sub, (LE) I090 +70 +70 +_60 f250 Hydrogen, Sulk, (HE) 940 k60 +50 *60 *250

*The feedstock cost changes are relative to current biomass costs.


Table 10. Costs for CO1 reduction when biomass-based fuels are used in passenger cars instead of petrol, assuming energy efficiencies according to Table 6 or equal efficiency in vehicles using biomass-based fuels as in

vehicles using petrol

Current biomass costs Biomass costs around 20 15

Efficiency Efficiency Efficiency Efficiency according to as for petrol according to as for petrol

Table 6 Table 6 (USD/tonne C) (USD/tonne C) (USD/tonne C) (USD/tonne C)

RME Biogas, Lucerne EtOH, wheat EtOH, Sulk, acid hydrolysis EtOH, .Su/iv enzymatic hydrolysis (LE) EtOH, S&v enzymatic hydrolysis (HE) MeOH, Saliv (LE) MeOH, Salk (HE) Hydrogen, S&v (LE) Hydrogen, Suli.v (HE)

1290 1440 950 1090 410 590 380 500

1370 1590 910 1110 690 840 550 690 640 790 505 650 220 320 130 220 430 550 330 460 260 370 180 280

1090 1540 1000 1450 940 1390 880 1280

C-t biomass costs

-200 ; , I %

i u 30 40 50 60 30 40 50 60

Petrol price. excluding taxes ($/MWh) Peti price. excluding raxes ($/MWh)

___ U-- EtOH. enzym, LE ---o-- EtOH, enzyrn, HE ---m-- M&H,LE ---a-- M&H, HE

Fig. 4. Costs for CO1 reduction when methanol or ethanol from Sukv are used instead of petrol as a function of petrol prices, excluding taxes. Swedish petrol prices 1993, excluding taxes, and current Swedish carbon tax

are given in the figure.

3 Biomass costs around 2015

CONCLUSIONS AND DISCUSSION

There is a potential in Sweden to increase the utilization of biomass from forest and agricultural land by 1 lo-130 TWh/yr. From this amount of biomass, some 70-80 TWh/yr of transportation fuels can be produced. Furthermore, some 6-8 TWh/yr of biogas can be produced from sewage, manure and other organic wastes (Brolin et al., 1995). In 1994, total Swedish petrol and diesel use was 82 TWh (NUTEK, 1995). Larger emission reductions per hectare and lower costs for CO1 emission reductions can, however, be achieved if fossil fuels, used for heat and electricity production, are replaced by biomass than if petrol or diesel is substituted (Gustavsson et al., 1995).

Using transportation fuels produced from Salix will result in the largest CO2 reduction per hectare of arable land of the fuels studied. Of the technologies assumed to be available in a 5-10 year perspective, methanol from Safix and logging residues has the lowest costs for CO1 reduction, USD 230-430 /tonne C at current biomass costs and USD 180-340/tonne C at estimated biomass costs around 2015, when used in ICEVs instead of petrol. In the longer perspective, ethanol from cellulosic materials used in ICEVs might, if on-going development is successful, achieve similar or lower costs for CO1

60 Bengt Johansson

reduction than the methanol technologies studied, but the uncertainties are large. Growing annual crops like cereals and rape is more costly, and the CO2 reduction per unit arable land is less compared to Salix and lucerne. Growing perennial crops like Salk and lucerne would also improve the local environment in areas dominated by agriculture. Increased use of logging residues will have to be combined with measures to maintain long-term productivity and minimize the negative impact on the local environment.

The costs for feedstocks are based on production costs. Subsidies to farmers may result in lower prices for the transportation fuels and may also change the competitiveness among the biomass-based fuels.

Estimated productivity and costs for biomass in 2015 are based on anticipated improvements in cultivation practices and breeding efforts increasing the potential feedstock available for producing biomass-based energy carriers and reducing the costs. Only methods for improving productivities which do not threaten long-term productivities in agriculture and forestry have been regarded.

The results may not be directly transferred to other countries since, for example, biomass yields and costs can differ among countries. Estimated current Swedish yearly yields of Salix of about 9 dry-tonne/ha are lower than the estimated yearly yields of eucalyptus in southern Europe and Brazil of 12 dry-tonne/ha and of poplar in eastern U.S.A. of 11 dry tonne/ha (Thurhollow & Perlack, 1991; Grassi & Bridgwater, 1992; Hall et al., 1992). Yearly Salk yields in Sweden around the year 2015 are estimated to be 17 dry-tonne/ha, which is about 10% lower than estimated poplar yields in the U.S. in 2010 (Thurhollow & Perlack, 1991). Current production costs for hybrid poplar vary in the U.S., depending on location, from USD 45 to USD 65/dry-tonne. Increased productivity and lower harvesting costs in the future are expected to reduce these costs to USD 38-55/dry-tonne (Perlack & Wright, 1995). Current and estimated 2015 costs for Safix in Sweden are USD 85/dry-tonne, and USD 60/dry-tonne, respectively.

The results are based on assumptions of performances and costs of some technologies, producing energy carriers from cellulosic biomass not yet commercially available. Continued research and development work will be required to reach the assumed performances and costs for those technologies.

The calculations have been made assuming 1993 fossil fuel prices. If fossil fuel prices increase, so will the competitiveness of the biomass-based fuels. With a 30400/o increase of petrol prices, excluding taxes, the use of methanol and ethanol instead of petrol might result in negative CO* reduction costs around 2015. An economic valuation of, for example COz, NO, and particulate emissions, makes the biomass-based fuels competitive at lower increases in fossil prices. For example, with current Swedish CO1 taxes ($160/tonne C), methanol and ethanol from cellulosic biomass might be cost-competitive with petrol around 2015, also at the current petrol prices.

The use of both BPEVs and FCEVs would enable twice the driving distance from the same amount of biomass than does the use of ICEVs. The further development of such vehicles would, therefore, be an important step towards efficient use of biomass resources for transportation. Hydrogen and methanol are, in contrast to ethanol, suitable energy carriers for FCEVs. Methanol, used in ICEVs, could thus be an important step towards a transportation system with large-scale use of FCEVs.

The cost of replacing fossil fuels with biomass during the transition period might be higher than the cost calculated in this paper, as the transition costs from diesel and gaso- line to large-scale production and use of biomass-based transportation fuels are not con- sidered here. This implies that stronger economic incentives for biomass-based technologies would be required during the transition period than for maintaining a biomass-based energy system.

Acknolr,ledge~enrs~l wish to thank P. Bbrjesson, 1. Gustavsson, 1. J. Nilsson and P. Svenningsson for review comments. 1 also gratefully acknowledge the economic support for is research provided from the Swedish Transport and Communications Research Board.


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Documents

Transportation fuels from Swedish biomass — environmental and cost aspects