The Potential for Electrofuels Production in Sweden Utilizing Fossil and Biogenic CO2 Point Sources

Highlights

• Sweden emits 50 million metric tons of CO₂ per year from different types of point sources, the vast majority of which is emitted at low concentrations.

• Of this, 65% is from biogenic sources, most of which are located in southern Sweden.

• Currently, the high-concentration sources of CO₂ in Sweden can provide a potential 1.5–2 TWh electrofuels/year (2% of current transportation demand).

• The Swedish potential for electrofuels is currently limited by the electricity required and production costs rather than the amount of recoverable CO₂.

Introduction

Anthropogenic greenhouse gas (GHG) emissions need to be reduced in order to limit global climate change and reach ambitious climate targets (Pachauri et al., 2014). Carbon dioxide (CO₂) emissions can be reduced by using less fossil fuels or by using fossil fuels in combination with carbon capture and storage (CCS) or carbon capture and utilization (CCU) [e.g., Cuéllar-Franca and Azapagic (2015), Wismans et al. (2016)]. In Sweden, the overall national vision is for zero net emissions of GHG to the atmosphere by 2050 (likely to be changed to 2045), along with a fossil fuel-independent vehicle fleet by 2030 (Government offices of Sweden, 2009; Swedish Government Official Reports, 2016). An extensive official investigation commissioned by the Swedish government has concluded that a range of options are needed to reduce CO₂ emissions from the transport sector, including biomass-based liquid and gaseous fuels (biofuels) along with hydrogen and electricity produced from renewable energy sources (Swedish Government Official Reports, 2013).

However, neither government nor academia have explored electrofuels (i.e., power-to-gas/fuels or synthetic hydrocarbons produced from CO₂ and water using electricity), extensively. Interest in electrofuels is on the rise, both in the literature (Graves et al., 2011; Mohseni, 2012; Nikoleris and Nilsson, 2013; Taljegård et al., 2015)¹ and in terms of demonstration plants in the EU, in some cases, including CO₂ capture (Gahleitner, 2013). Studies mainly investigate electrofuels as a (i) technology for storing intermittent electricity [e.g., Streibel et al. (2013), de Boer et al. (2014), Vandewalle et al. (2014), König et al. (2015), Qadrdan et al. (2015), Varone and Ferrari (2015), Zakeri and Syri (2015), Zhang et al. (2015), and Kötter et al. (2016)], (ii) fuel for transport [e.g., Connolly et al. (2014), Ridjan et al. (2014), Larsson et al. (2015)], or (iii) means of producing chemicals [e.g., Ganesh (2013), Perathoner and Centi (2014), and Chen et al. (2016)]. Different types of energy carriers [e.g., methane, methanol, DME (dimethyl ether), gasoline, and diesel] can be produced, which makes electrofuels a potentially interesting option for all transport modes, especially shipping, aviation, and long distance road transport, where the potential for other renewable fuel options, such as electricity and hydrogen, may be limited. Electrofuels may allow increased use of biofuels, if the CO₂ associated with their production is used for production of electrofuels instead of being emitted to the atmosphere (Mignard and Pritchard, 2008; Mohseni, 2012; Hannula, 2015, 2016).

CO₂ emissions can be captured from various point sources, including industrial processes that produce CO₂, such as biofuel production (including anaerobic digestion and fermentation), natural gas processing, steel plants, and oil refineries, fossil and biomass combustion in heat and power plants, or directly from the air.

Many studies have estimated CO₂ emissions from point sources in China [e.g., Chen and Chen (2010), Liu et al. (2010), Zhang and Chen (2014)]. Zhang and Chen (2014) used a bottom-up approach to estimate CO₂ emissions from fuel combustion and the main industrial processes at 7.7 Gt CO₂ per year in 2008, with coal as the main source. The potential global supply of CO₂ from point sources is estimated in Naims (2016). The total estimated global capturable CO₂ supply from point sources amount to approximately 12.7 Gton of CO₂ (Naims, 2016). High purity point sources (e.g., fermentation of biomass and ammonia production) and other low cost sources (e.g., bioenergy, natural gas, and hydrogen production) represent in total approximately 0.3 Gton of CO₂. Naims (2016) further indicates that there is enough CO₂ to meet the estimated global CO₂ demand in the near and long term.

In Austria, the iron and steel, cement industry, and power and heat industries are the largest point sources of CO₂ emissions (Reiter and Lindorfer, 2015). Biofuel production, a relatively modest point source at about 113 kton in 2013, is considered the most suitable Austrian source for power-to-gas application by Reiter and Lindorfer (2015). A German feasibility study by Trost et al. (2012) identifies a large potential for biogenic CO₂ sources, including biogas upgrading, bioethanol plants, and sewage treatment plants. Trost et al. (2012) also found a substantial electrofuels potential of over 130 TWh fuel per year in the form of methane produced using CO₂ from industrial processes and biogenic sources. Reiter and Lindorfer (2015) and Trost et al. (2012), both conclude that availability of CO₂ will not be a limiting factor for using power-to-gas as a balancing strategy for intermittent renewable power sources (wind power and photovoltaics) in Austria or Germany.

In Sweden, carbon capture is currently implemented at, for instance, Agroetanol in Norrköping. Agroetanol produces grain-based ethanol; the resulting CO₂ is purified and sold to the AGA Gas AB. Detailed quantification of current and/or future Swedish CO₂ emissions from point sources is, however, lacking in the scientific literature, and there are no assessments of the technical potential for Swedish production of electrofuels. Electrofuels may represent an interesting option in Sweden, that is a forest-rich country, due to the ambitious GHG emission reduction targets in general and specifically in the transport sector. Assessing the Swedish potential for CCS and CCU requires detailed knowledge of the stationary CO₂ emissions. The overall impact on CO₂ emissions of the production and use of electrofuels mainly depends on the electricity-related CO₂ emissions. The Swedish electricity production consists mainly of hydro power and nuclear power implying relatively low GHG emissions.

The overall aim of this paper is to map and quantify stationary Swedish CO₂ emissions by concentration, origin, and geographical distribution, as well as investigate the potential for CCU. Specifically, we aim to (i) map and quantify the major point sources of CO₂ emissions from industrial and combustion processes in Sweden with a bottom-up approach and estimate the technical potential for CO₂ capture or recovery and (ii) estimate the technical potential for production of electrofuels in Sweden, as an example of CCU. We analyze the potential for biofuels-related CO₂ in the future (a 2030 scenario), since the use of biomass and biofuels is expected to increase and use of fossil fuels decrease. Additionally, we estimate the potential demand for CO₂ and electricity corresponding to the use of electrofuels for road transport, heavy trucks, and shipping, at scale, in order to give a first indication of the potential role for electrofuels in transportation in Sweden.

Materials and Methods

This section describes the methodology for estimating both CO₂ emissions from major point sources and the potential for capturing and using the emissions.

Assumptions about the CO₂ Sources Included

CO₂ emission sources can be divided into diffuse sources (e.g., transport and agriculture) and point sources (e.g., factories and power production). This study uses a bottom-up approach to estimate CO₂ emissions from the following point sources in Sweden:

• Industrial process plants (including iron and steel, non-ferrous metal, oil and gas refineries, lime and cement, pulp and paper, chemical, metal, and other similar plants)

• Heat and power production (including biomass, waste, and fossil fuel-fired plants)

• Biofuels production facilities (including ethanol, biogas, and more advanced biofuels).

Emissions data for year 2013 from the European Environment Agency’s “European Pollutant Release and Transfer Register” (European Environment Agency, 2015) was used to estimate (i) the available amount of CO₂ and (ii) the share of fossil and biogenic CO₂, for Swedish point sources, including all sources emitting 0.1 million metric tons of CO₂ per year or more. Other CO₂ sources are assumed to be negligible (except in the case of biofuels production). The concentration of CO₂ for each type of sources was estimated using (Chapel et al., 1999; Bosoaga et al., 2009) (see Table 1). For the purposes of analysis, the concentrations were divided in three ranges: low (<15 vol%), medium (15–90 vol%), and high (>90 vol%).

TABLE 1

Table 1. The type of CO₂ stream, CO₂-concentration range, range of CO₂ emissions per unit, and share of recoverable CO₂, for different point sources in Sweden based on European Environment Agency (2015).

For biofuels plants, the CO₂ estimates are based on data gathered by Swedish Energy Agency and Energigas Sverige (2015) and Grahn and Hansson (2015) in 2012–2013. Also, the sources emitting less than 0.1 million metric tons of CO₂ per year are included in the case of biofuels since these are relatively pure and, therefore, well suited for electrofuels production. In most biofuels production processes, there is a surplus of CO₂ and the CO₂ is of high purity (Xu et al., 2010). When biogas is upgraded to transport fuel quality, a cleaning step to remove CO₂ is included, resulting in a relatively pure stream of CO₂. The CO₂ emissions from domestic biofuel production in a 2030 scenario are estimated based on biofuels production scenarios from Grahn and Hansson (2015) and on scenarios for anaerobic digestion and gasification-based biogas production from Dahlgren et al. (2013). Grahn and Hansson (2015) assessed the potential contribution of domestically produced biofuels for transport in Sweden in 2030 based on a mapping of the prospects for current and potential Swedish biofuel producers. Some of the planned biofuels production plants included in the scenario for 2030 have been canceled or put on hold and are, therefore, excluded in this study.

The 2030 scenario was constructed exclusively for biofuel plants because these represent a relatively pure stream of CO₂ of particular interest in electrofuels production, and because the use of biofuels is expected to increase in the future. For many biofuels, no extra major purification step is needed in the capture process, which leads to a relatively low capture cost. This can also be assumed for the case of biogas since CO₂ is already removed when biogas is upgraded to transport fuel quality. This can be compared to the CO₂ capture cost linked to processes requiring an extra purification step like steel and iron, ammonia, refinery, cement, and fossil or biomass combustion plants estimated at 20€₂₀₁₅–170€₂₀₁₅/ton CO₂ in the short term (10–15 years) and 10€₂₀₁₅–100€₂₀₁₅/ton CO₂ in the more long term (Damen et al., 2007; Finkenrath, 2011; Kuramochi et al., 2012, 2013; IEA, 2013). Even though it has been indicated that the cost for carbon capture represents a relatively modest share (a few percent) of the total electrofuel-production cost unless air capture is assumed (Graves et al., 2011; Tremel et al., 2015; Varone and Ferrari, 2015; see text footnote 1), using CO₂ from biofuel production represent an attractive source for electrofuel production since more pure streams will likely be used first for economic reasons and the domestic biofuel actors, representing a considerable biofuel production capacity, in order to comply with sustainability requirements need to improve their production processes in terms of CO₂ emissions.

Table 1 presents the type of CO₂ stream, typical concentration of CO₂, the range of CO₂ emissions per unit, and the amount of recoverable CO₂, for different point sources. Table 2 includes a list of all the biofuel production facilities in operation in 2015, their production capacity and associated CO₂ emissions, and the corresponding information for the biofuels plants planned by 2030. Table 3 summarizes the main assumptions used in estimating the amount of CO₂ that is available for recovery from current and future biofuels plants.

TABLE 2

Table 2. Biofuels production facilities and associated CO₂ emissions.

TABLE 3

Table 3. Main assumptions for assessing CO₂ availability from current and future biofuels plants in Sweden.

Availability of CO₂ for CCU

In order for CO₂ to be used to produce electrofuels, the gas needs to be separated from other substances in emissions from industrial and combustion processes, such as sulfur dioxide. The concentration of CO₂ in power plant flue gases is relatively low (<15 vol%) (Chapel et al., 1999); for process-related emissions, e.g., in the lime and cement industry, CO₂ concentrations are somewhat higher (14–33 vol%) (Bosoaga et al., 2009) (see Table 1). In this study, we assume that 90% of the CO₂ from medium- (15–90 vol%) and low- (<15 vol%) concentration CO₂ sources is recoverable (Chapel et al., 1999). Current CO₂ capture technologies do not usually capture all the CO₂ as this is too expensive and requires too much energy.

In biofuels production processes (fermentation, anaerobic digestion, gasification), relatively pure streams (>90 vol%) of CO₂ are available in latter cases due to the demand for high fuel purity in the transport sector. We assume that 100% of the CO₂ from biofuel plants is recoverable and could be converted into fuel. Approximately 54% of the biogas produced in Sweden is upgraded for the transportation sector (Swedish Energy Agency and Energigas Sverige, 2016), which means that CO₂ capturing technology already exist on several Swedish anaerobic digestion facilities. Another opportunity for anaerobic digestion-based biogas plants is to feed raw biogas to a methanation reactor, thereby combining biogas upgrading and electrofuels production (Johannesson, 2016). Biogas plants that currently do not upgrade their gas are generally small implying high costs for upgrading and currently supplying other markets than the transport sector, making them less suitable as a source of CO₂ for electrofuels production. Therefore, only CO₂ from biogas-upgrading plants is considered in this study. For simplicity, we assume that the share of upgraded biogas of total biogas production by 2030 remains at 54%.

Geographic Distribution of CO₂ Emissions

The CO₂ emission sources have been mapped and categorized by concentration and geographical area. The geographical areas are those used for the Swedish electricity market, i.e., four price areas (SE1, SE2, SE3, and SE4) (Swedish Energy Markets Inspectorate, 2014) (see Figure 1). The electricity price areas were implemented in Sweden in order to control the transmission of electricity between regions and to promote the construction of power generation and transmission capacity in and to areas with electricity deficits. On average, the northern parts of the country (SE1 and SE2) are characterized by an excess of electricity production due to the available hydropower resources and relatively low overall power consumption. In the southern parts (SE3 and SE4), electricity consumption often exceeds production, which leads to relatively higher electricity prices in these areas (Nord Pool, 2016).

FIGURE 1

Figure 1. The electricity price areas (SE1, SE2, SE3, and SE4) in Sweden, which are used to illustrate the geographic distribution of the CO₂ emissions. Figure based on SCB (2015).

Electrofuel-Production Efficiency and Cost

The focus in this study is on electrofuels in the form of methane, methanol, and DME since these are the most discussed electrofuels in the literature (see text footnote 1), are of interest for the relevant transport sector (shipping and trucks), and include fuels in liquid and gaseous form. The amounts of CO₂ and electricity necessary for the types of electrofuels included in this study are given in Table 4 and are based on lower heating value (LHV).

TABLE 4

Table 4. Estimated values for CO₂ and electricity demand per unit of electrofuel and production cost for 2015 and 2030 (based on literature review and base case reference scenario by Brynolf et al. (see text footnote 1) representing average data and based on lower heating value, for assumptions see the text).

Table 4 also presents cost ranges for 2015 and 2030 estimated in the base case reference scenario in Brynolf et al. (see text footnote 1). The electricity-to-fuel efficiency of the electrofuel-production process strongly depends on the type of electrolyzer and the future development of production technologies. Alkaline electrolysers have efficiencies in the range of 43–69% today, while the most efficient electrolysers are expected to reach efficiencies above 80% based on LHV (Smolinka et al., 2011; Benjaminsson et al., 2013; Grond et al., 2013; Mathiesen et al., 2013; Bertuccioli et al., 2014; Hannula, 2015; Schiebahn et al., 2015). Combining this with the efficiency for fuel synthesis yields electricity-to-fuel efficiencies in the 30–75% range for methane, methanol, and DME, this corresponds to an electricity demand of 1.33–3.33 MWh electricity/MWh electrofuel.

Brynolf et al. (see text footnote 1) suggest costs for different electrofuels (methane, methanol, DME, gasoline, and diesel) in the span of 120€₂₀₁₅–1,050€₂₀₁₅/MWh_fuel and 100€₂₀₁₅–430€₂₀₁₅/MWh_fuel in 2015 and 2030, respectively. However, in the base case of the reference scenario representing average data, the same costs are 200€₂₀₁₅–280€₂₀₁₅/MWh_fuel and 160€₂₀₁₅–210€₂₀₁₅/MWh_fuel in 2015 and 2030, respectively. The most important factors affecting the production cost of electrofuels are the capital cost of the electrolyzer, the electricity price, the capacity factor of the unit, and the lifetime of the electrolyzer. The base case reference scenario assumes alkaline electrolyzer with a capital cost of 600€₂₀₁₅/kW_el, capacity factor of 80%, lifetime of the electrolyzer at 25 years, carbon capture cost at 30€₂₀₁₅/ton, and electricity price of 50€₂₀₁₅/MWh. A capacity factor at 80% implies that the plant is run the major part of the year. However, if electrofuels are used to balance intermittent renewable power production (i.e., there is production only when there is a surplus of power from these sources), the capacity factor will be reduced. This will not influence the estimated technical potential for production of electrofuels in Sweden in this study, but it will lead to increased electrofuel-production costs [which is further assessed in Brynolf et al. (see text footnote 1)]. In the case of a carbon capture cost at 10€₂₀₁₅/ton representing more pure streams like biofuels operation, the production cost of electrofuels is reduced by approximately 3%. In their review of the literature, Brynolf et al. (see text footnote 1) also found that the cost of capturing CO₂ generally is a minor factor in the total production cost of electrofuels representing less than 10% (when not considering CO₂ capturing from air). CO₂ can be captured from various industrial sources with costs ranging from about 10€₂₀₁₅ to 170€₂₀₁₅/ton CO₂, depending on the CO₂ concentration (Damen et al., 2006, 2007; Finkenrath, 2011; Goeppert et al., 2012; Kuramochi et al., 2012, 2013; IEA, 2013; see text footnote 1). This indicates that from an economic point of view, all CO₂ sources (except from pure air) might be of interest for electrofuel production in the future.

Results

CO₂ Emissions in Sweden

In Sweden, major stationary point sources currently emit approximately 50 Mton CO₂ per year. Of this, about 45 Mton CO₂ is recoverable (see Figure 2). Our analysis includes 148 facilities, with 14 U emitting more than 1 Mton CO₂/year, 88 U emitting between 1 Mton and 100 kton CO₂/year, and 47 U emitting less than 100 kton/year.

FIGURE 2

Figure 2. Current recoverable CO₂ from major point sources in Sweden, based on European Environment Agency (2015), Grahn and Hansson (2015), and Dahlgren et al. (2013). In total, 149 point sources are included; the number of plants in each category is given in parenthesis.

Figure 2 shows the distribution of CO₂ emissions among different types of point sources. Pulp and paper plants and heat and power plants are the two major types of point sources, corresponding to 23 Mton CO₂ (45% of the total) and 11.5 Mton CO₂ (23% of the total) per year, respectively. In total, biogenic sources account for 65% or 32 Mton of CO₂ emissions per year. The high share of biogenic CO₂ is mainly due to the extensive use of biomass in producing pulp, paper, heat, and power and from waste treatment and incineration. Emissions from biofuel production represent a small share of the current total amount of available CO₂, with approximately 0.5 Mton of recoverable CO₂ per year. According to Andreas Gundberg, Innovation manager at Lantmännen Agroetanol, CCU has already been implemented at the main Swedish ethanol producer representing approximately 90% of the total Swedish ethanol production capacity. The emissions from this ethanol production (about 100 kton/year) are included in the analysis.

Figure 3 shows the amount of CO₂ available and the corresponding potential production of electrofuels in the form of methanol at different CO₂ concentrations in Sweden in 2013 and in 2030. The majority of the CO₂ is available at low and medium concentrations, equally spread between the categories low and medium but mainly below 20 vol%. A small share of the CO₂, mainly from the biofuels industry, is available at higher, significantly more accessible, concentrations.

FIGURE 3

Figure 3. Recoverable CO₂ and potential for production of electrofuels in the form of methanol at three different concentration levels (low: <15 vol%, medium: 15–90 vol% and, high: >90 vol%) in 2013 and at high concentration in 2030.

About 90% of the high-concentration emissions come from sources in geographic region SE3, along with about 60% of the rest of the CO₂ emission sources (see Figure 4). Anaerobic digestion and ethanol production from agricultural crops currently dominate biofuels production, and these are mostly located in densely populated areas (producing biogas from digestion of sewage sludge and food waste) or in proximity to agricultural operations (farm-based ethanol and biogas production), which are mainly found in southern Sweden. However, electricity prices in the southern parts are currently less favorable than further north where hydropower resources and lower demand create an excess of electricity while the transmission capacity to the southern industrial and population centers is limited.

FIGURE 4

Figure 4. CO₂ point sources by region and concentration level. (A) Low, (B) medium, and (C) high.

The projected large-scale introduction of biofuels based on lignocellulosic feedstocks should entail higher shares of high-concentration CO₂ emissions in the northern regions, SE1 and SE2, if plants are located near feedstock resources.

The biofuels sector is expected to grow significantly in Sweden during the coming years in order to achieve national climate and transport targets. Figure 5 illustrates the current and estimated amount of CO₂ available for electrofuels production from different biofuel production technologies and a minor share of others sources available by 2030 in Sweden based on Dahlgren et al. (2013) and Hansson and Grahn (2013). Only CO₂ from the production of upgraded biogas is included. In 2030, the CO₂ originates mainly from gasification, anaerobic digestion, and fermentation-based biofuels production (utilizing both cereals and lignocellulosic biomass and considering recent implementation plans). In 2030, these sources could potentially yield 2.2 Mton CO₂ for electrofuels production (approximately 5.5 times the amount currently available). The largest increase in production capacity is expected with the large-scale implementation of a variety of biomass-gasification-based biofuels, such as synthetic natural gas, DME, or methanol from lignocellulosic biomass. Ethanol produced from lignocellulosic feedstocks could also potentially generate large amounts of highly concentrated biogenic CO₂.

FIGURE 5

Figure 5. CO₂ from high CO₂ concentration sources (>90 vol-%) today and in 2030.

Swedish Production Potential for Electrofuels

Using all the currently recoverable CO₂ from the point sources identified in this study to produce electrofuel in the form of methane would yield approximately 224 TWh per year. This corresponds to approximately 2.5 times the current Swedish demand for transportation fuels [approximately 85 TWh per year in 2014 (Swedish Energy Agency, 2015b)]. For electrofuels with lower conversion efficiencies (e.g., methanol and DME), production could instead cover about twice the current demand. Producing 224 TWh per year of electro-methane requires about 448 TWh of electricity (assuming 2 MWh_el/MWh_fuel), which corresponds to three times the current Swedish electricity generation [149 TWh (Swedish Energy Agency, 2015a)].

The high-concentration sources, represented mainly by biofuel plants, suffice to provide only about 2% of the current demand for transportation fuels (corresponding to 1.5–2/year, see Figure 6). Converting the high-concentration emissions to electrofuels would require about 3–4 TWh of electricity (2–3% of the current national production). In 2030, the potential production of electrofuels in the form of methane, methanol, and DME from high-CO₂ sources is 8–11 TWh (see Figure 6). This corresponds to approximately 9–13% of the current demand for transportation fuels and would require about 15–21 TWh of electricity (10–14% of current electricity production).

FIGURE 6

Figure 6. Production potential for electrofuels in the form of methane, methanol and DME from current and future biofuel plants with high CO₂ concentrations.

Table 5 shows the requirements for meeting the current Swedish fuel demand for (non-air) transport with electrofuels in the form of methanol. As seen in Table 5, about half of the recoverable CO₂ (23 Mton) would be needed to supply the entire current Swedish road transport demand with electrofuels in the form of methanol (assuming a conversion factor of 0.275 ton CO₂/MWh methanol). The corresponding amount of CO₂ needed to satisfy the entire fuel demand from heavy trucks and all domestic and international shipping currently bunkering in Sweden is estimated to be about 5 and 6 Mton CO₂, respectively. This implies that in the case of large-scale introduction of electrofuels for road transport (including heavy trucks), heavy trucks only, or shipping in Sweden, the supply of CO₂ is not a limiting factor.

TABLE 5

Table 5. Outputs and inputs to electrofuels production if fulfilling the fuel demand with electrofuels in the form of methanol in three different transport modes.

However, meeting the entire current road transport demand with electrofuels would require about 164 TWh_el of electricity (with methanol at 1.93 MWh_el/MWh_fuel). This would more than double the current demand for electricity. To meet the current Swedish fuel demand for passenger cars (at about 41 TWh) (Swedish Government Official Reports, 2013) with electrofuels in the form of methanol would require approximately 11 ton CO₂ and 79 TWh_el of electricity. For comparison, if the entire passenger car fleet were replaced by electric vehicles, the increased demand for electricity would be approximately 10 TWh (based on Swedish Government Official Reports, 2013).

Using electrofuels for the heavy truck sector and for shipping bunker fuel sold in Sweden would require about 35 and 41 TWh_el, respectively. For comparison, in 2014, domestic power generation was 150 TWh (SCB, 2016). Further, the goal is to increase domestic generation from renewable sources by about 30 TWh by 2020, compared to 2002 figures and current production of renewable electricity is approximately 85 TWh (SCB, 2016). Large-scale introduction of electrofuels would require a major increase in the supply of electricity from renewable energy sources.

Discussion and Conclusion

This study shows that Swedish point sources emit approximately 50 million metric tons of CO₂ per year, 65% of which is biogenic in origin. The potentially recoverable emissions amount to 45 Mton. The main point sources are in the pulp and paper industry along with heat and power, while emissions from biofuel production (with relatively high concentrations of recoverable CO₂) amounted to 0.5 Mton CO₂ in 2015, with an estimated potential for 2.2 Mton CO₂ in 2030. Thus, the potential streams of relatively pure CO₂ are modest, at least in the near term. Currently, the potential yield from these sources is 1.5–2 TWh of electrofuels per year, corresponding to approximately 2% of the current Swedish demand for transportation fuels.

However, in Sweden, all types of CO₂ emissions, whether fossil or biogenic, and whether low-concentration or high, are of interest in terms of CCU (although carbon capture can be expected to first be applied to systems with higher concentrations of CO₂ because capture costs are somewhat lower for these, generally speaking). In the case of electrofuels, as mentioned earlier, it has been indicated that the cost for carbon capture represents a relatively modest share of the total electrofuel-production cost which makes the purity of the CO₂ sources less important. However, CO₂ from biofuel operations seem like an attractive source since biofuel actors strive to reduce their CO₂ emissions due to sustainability requirements. Further, biomass-related CO₂ emissions are expected to increase in the future, since the use of biomass for energy is expected to increase while fossil CO₂ emissions are expected to decrease.

We conclude that the Swedish supply of CO₂ does not have to be a limiting factor for the potential future production of electrofuels for the Swedish transport sector, even if the current supply of pure CO₂ streams is limited. However, there might be other limiting factors such as the associated electricity demand.

As indicated in the introduction, electrofuels represent a potential long-term energy storage option and could, therefore, be of interest in terms of managing grid-integration of more intermittent renewable energy sources (e.g., wind and solar power). But large-scale introduction of electrofuels in the transport sector would in turn represent a huge new demand for electricity. The direct use of electricity needed to supply the entire current transport demand for passenger cars would increase current electricity demand by 10%, while using electrofuels would require increasing the Swedish electricity generation by about 60% to meet the same transport demand (Swedish Energy Agency, 2015b). The electrofuels production process and combustion engine are simply that much less efficient than electric motors. Therefore, large-scale introduction of electrofuels might potentially increase the challenge of balancing intermittent renewable generation, rather than help solve it with long-term energy storage, since an increased demand for power would most likely be met with new wind power installations in Sweden. Producing electrofuels only part of the year is one option to limit this problem. However, according to Brynolf et al. (see text footnote 1), the production cost of electrofuels increases drastically per megawatt hours fuel when the capacity factor (i.e., actual production as share of total production capacity) of the wind turbines is decreased. Thus, the benefit of using electrofuels for balancing renewable energy need to be further assessed.

The production cost of different electrofuels is also a limiting factor for the potential future production of electrofuels in Sweden. The literature contains a fairly broad range of estimates, but the most important factors in the production cost of electrofuels are the capital cost of the electrolyzer, the electricity price, the capacity factor of the unit, and the lifetime of the electrolyzer (see text footnote 1).

The majority of the current CO₂ sources are located in southern Sweden, which is also the case for the current CO₂ sources with relatively pure CO₂ emissions. However, from the perspective of the electric-grid, electrofuels production may be more suitable in the northern parts of Sweden where there is generally a surplus of power generation and lower electricity prices. An increasing demand for electricity in southern Sweden might put additional pressure on the transmission capacity from north to south. Future biofuel plants based on forest biomass (as included in the 2030 scenario) are expected to be located mostly in northern Sweden and, therefore, represent an interesting source of CO₂ for production of electrofuels.

From a climate perspective, it might be preferable to capture and store CO₂ underground, using CCS technology, and not convert CO₂ into a fuel that after combustion will be released to the atmosphere again (van der Giesen et al., 2014; Sternberg and Bardow, 2015). If the CO₂ has been captured from burning fossil fuels, CCS will avoid increased CO₂ concentration, and if the CO₂ is captured from burning biomass (or from air), CCS will decrease the atmospheric CO₂ concentration, ceteris paribus. Today, however, there are several obstacles that have to be overcome before CCS could be available at a large scale, including public acceptance (Oltra et al., 2010; Dütschke, 2011). CCS is also only applicable for relatively large CO₂ sources and storage possibilities depend on geological prerequisites.

The overall impact on CO₂ emissions of the production and use of electrofuels mainly depends on the electricity-related CO₂ emissions and what the fuels replace (van der Giesen et al., 2014; Sternberg and Bardow, 2015). van der Giesen et al. (2014) conclude that for some production paths, the climate impact is worse than for fossil fuels, and achieving a net climate benefit requires using renewable electricity and renewable CO₂ sources. Sternberg and Bardow (2015) evaluate electrofuels relative to the case in which the same amount of CO₂ is instead either emitted or stored. They find that electrofuels can at best only make a small contribution to mitigation compared to other available solutions and that using CO₂ emissions for electrofuels is worse from a climate perspective compared to storing them. It would be interesting to more thoroughly study the environmental impact of electrofuels compared to other CCU technologies with a lifecycle perspective. For example, the amount of CO₂ emissions from electricity production will depend on (i) the time perspective (for example using a marginal or average electricity mix) and (ii) the geographical boundaries of the electricity supply. However, GHG emissions from electricity production are expected to decrease significantly as a consequence of stringent energy and climate policies changing the mix of energy sources.

To summarize, electrofuels are limited by electricity demand rather than the demand for CO₂ and, at scale, require a substantial amount of renewable electricity at relatively low cost. The GHG impact of electrofuels compared to other options, in particular CCS, needs to be further assessed.

Author Contributions

JH is the main author; planned the work and led the writing. RH was responsible for the mapping and quantification of the major Swedish point sources of CO₂ emissions and contributed to further assessments and paper writing. SB, MT, and MG contributed with the electrofuel-production characteristics, participated in the assessment, and contributed to paper writing.

Conflict of Interest Statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Acknowledgments

Financial support from the Swedish Research Council Formas, Nordic Energy Research through the Nordic flagship project Shift (Sustainable Horizons for Transport), the Swedish Energy Agency, and the Swedish Knowledge Centre for Renewable Transportation Fuels (f3) is acknowledged. This publication is partly the result of a project within the Renewable Fuels and Systems Program (Samverkansprogrammet Förnybara drivmedel och system), financed by the Swedish Energy Agency and the Swedish Knowledge Centre for Renewable Transportation Fuels (f3). The f3 Centre contributes, through knowledge based on science, to the development of environmentally, economically, and socially sustainable and renewable transportation fuels, as part of a future sustainable society (see www.f3centre.se). The authors also thank Magnus Fröberg, Scania CV AB, and Paulina Essunger for valuable input.

Funding

This work has received financial support from (i) the Swedish Research Council Formas via the project titled “Cost-effective choices of marine fuels under stringent carbon dioxide reduction targets,” (ii) Nordic Energy Research through the Nordic flagship project Shift (Sustainable Horizons for Transport), and (iii) the Swedish Knowledge Centre for Renewable Transportation Fuels and the Swedish Energy Agency via the project titled “The role of electrofuels: a cost-effective solution for future transport?”

Footnote

1. ^Brynolf, S., Taljegård, M., Grahn, M., and Hansson, J. (2017). Electrofuels for the transport sector: a review of production costs. Renew. Sust. Energ. Rev. (Submitted).

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