Environmental impacts of the national renewable energy targets – A case study from Finland

Environmental impacts of the national renewable energy targets – A case study from Finland

Renewable and Sustainable Energy Reviews 59 (2016) 1599–1610 Contents lists available at ScienceDirect Renewable and Sustainable Energy Reviews jour...

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Renewable and Sustainable Energy Reviews 59 (2016) 1599–1610

Contents lists available at ScienceDirect

Renewable and Sustainable Energy Reviews journal homepage: www.elsevier.com/locate/rser

Environmental impacts of the national renewable energy targets – A case study from Finland L. Sokka a,n, T. Sinkko b, A. Holma d, K. Manninen e, K. Pasanen c, M. Rantala c, P. Leskinen d a

VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044, Finland Natural Resources Institute Finland (Luke), Latokartanonkaari 9, FI-00790 Helsinki, Finland c Natural Resources Institute Finland (Luke), Box 68, FI-80101 Joensuu, Finland d Finnish Environment Institute (SYKE), Joensuu, Finland e Finnish Environment Institute (SYKE), Helsinki, Finland b

art ic l e i nf o

a b s t r a c t

Article history: Received 9 March 2015 Received in revised form 16 August 2015 Accepted 9 December 2015

Reduction of greenhouse gas emissions and mitigation of climate change are the main aims of the global climate policy. Increased use of renewable energy is a central measure in achieving these goals. However, mitigation of climate change through increased use of renewable energy also has negative environmental impacts. Focusing merely on greenhouse gas emissions may lead to overseeing these other negative environmental impacts and thereby in unwanted side-effects. The aim of this review was to assess the overall life cycle impacts related to the production and use of the different renewable energy sources. Impacts were assessed for unit processes and for the Finnish national renewable energy targets as a whole. The review points out that in order to comprehensively understand the overall environmental impacts of the different renewable energy sources, a thorough life cycle assessment with a unified framework would be needed. Presently there is only limited information available or the published results are not comparable with each another. However, assessment using the Finnish National Renewable Energy Targets for 2020 also indicates that under the present targets, the overall environmental impacts of the renewable energy use are likely to be low. Main impacts or risks of impacts relate to the use of forest energy. & 2016 Elsevier Ltd. All rights reserved.

Keywords: Renewable energy Life cycle assessment Environmental impacts Risks Environmental policy

Contents 1. 2. 3.

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Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1600 Material and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1600 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1601 3.1. Unit process impacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1601 3.1.1. Forest biomass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1601 3.2. Hydropower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1602 3.3. Wind power. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1602 3.4. Solar power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1602 3.5. Geothermal energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1602 3.6. Agricultural fuels and biogas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1602 3.7. Total environmental impacts related to the 2020 renewable energy targets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1603 Discussion and conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1605 4.1. Main environmental impacts of the renewable energy sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1605 4.2. Uncertainties and limitations of the study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1605 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1606

Corresponding author. Tel.: þ 358 40 187 9067. E-mail address: [email protected]fi (L. Sokka).

http://dx.doi.org/10.1016/j.rser.2015.12.005 1364-0321/& 2016 Elsevier Ltd. All rights reserved.

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Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1606 Appendix A. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1606 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1609

1. Introduction Reduction of greenhouse gas emissions and mitigation of climate change are the main aims of the global climate policy. Increased use of renewable energy is a central measure in achieving these goals. According to the latest report of the Intergovernmental Panel on Climate Change (IPCC), the share of low-carbon energy (incl. nuclear and CCS) is expected to increase by over 3-fold in the stringent mitigation scenarios [6].The EU is aiming to increase its use of renewable energy to 20% of total energy consumption by 2020. Furthermore, the EU has agreed to reduce greenhouse gas emissions by 40% of the 1990 level by 2030 [8]. According to the proposal, for renewable energy a common target on the Union level of 27% would be set but the member states would be allowed to set their own country-level targets. In the EU, targets have been set for the individual member countries on what their share of renewable energy should be in 2020. The target for Finland is 38%. Finnish national targets for renewable energy use in 2020 have been specified in the National Renewable Energy Action Plan ([24] and Table 1). They will primarily be achieved by increasing the use of forest biomass for energy but targets have also been set to increase the use of other renewable energy sources as well, such as wind and solar power and ground-source heat pumps. Mitigation of climate change through the use of renewable energy also has negative environmental impacts. Focusing merely on greenhouse gas emissions may lead to overseeing other negative environmental impacts. As shown by Laurent et al. [21], carbon footprint of a product often does not correlate well with other impact categories, due to the different origins of the impacts along the product life cycles. In order to ensure that mitigation of climate change through enhancement of renewable energy production does not lead to other environmental problems, it is therefore important to assess their environmental impacts comprehensively, taking into account all relevant impact categories. Life cycle assessment (LCA) is a tool for quantitatively and systematically evaluating the environmental aspects of a product or system throughout its whole life cycle (e.g., [33]). As LCA concentrates on all the inflows and outflows of substances, and the impacts of these, in a certain system, it provides means to identify effective policy options. Such knowledge also reduces the risk of simply shifting pollution from one environmental media to another. LCA has primarily been applied to assess the life cycle impacts of products but it can also be used for the assessment of services, technologies or regions. Up to now, there have only been a few attempts to comprehensively study the environmental impacts of renewable energy Table 1 Finnish targets for the use of renewable energy in 2020. Energy source

2010 (TWh) Target 2020 (TWh)

Forest residues in CHP and heat production Pellets Residential wood combustion Wind power Hydro power Biogas Liquid biofuels in transportation Agricultural biomass Heat pumps Waste fuels Other renewables including solar power

14 0.7 12 0.3 12.7 0.5 0.6 in total 3.1 1.7 0.4

25 2 12 6 14 0.7 7 Use is increased 8 2 0.4

sources (see e.g., Varun and Prakash [45,37]). Many studies have assessed a limited number of impact categories, such as greenhouse gas emissions and acidifying emissions (e.g., Turconi et al. [44]; [37]). There is a lack comprehensive overview of the environmental impacts and risks caused by the various renewable energy sources in relation to different life cycle phases on the one hand but also over the different energy sources on the other hand. Moreover, consideration of the whole life cycle is particularly relevant as for many renewable energy sources, such as wind or solar power, most of the environmental impacts are caused by the upstream processes. The aim of the present study was to assess the overall life cycle impacts related to the production and use of the different renewable energy sources through literature review. Following energy sources were included in the assessment: forest-based energy sources (incl. forest residues, stumps and small diameter wood from thinnings in power and heat production, wood pellets and residential wood combustion), domestic agricultural fuels (incl. biogas), hydropower, solar power, wind power and groundsource and air-source heat pumps. The study looked at impacts on both unit process level and in relation to the target use level in 2020. The study was conducted as a literature review with the aim of giving a comprehensive view with respect to multiple impact categories and production systems. The review was based on quantitative results available in the literature. Moreover, the purpose was to take into account also such impact categories that are typically not considered, for example toxicity, abiotic resource consumption, noise, odour and impacts on recreational use. The analysis of the present study was complemented with a qualitative assessment in a subsequent study (see [16]).

2. Material and methods The main approach used in this study was to collect comprehensive quantitative information on the different energy sources through literature review. Impacts were studied over the whole life cycle and the aim was also to specify the life cycle phase in which the adverse impacts were created. The life cycle phases studied were the following: 1. 2. 3. 4.

Raw material mining and acquisition Refining Energy production Disposal of the raw material or technology, waste treatment (recycling, deposition)

The following impact categories were included in the assessment 1. 2. 3. 4. 5.

Climate change Ozone depletion Acidification Tropospheric ozone formation Particulate matter formation: impacts on public health and short-term climate effects 6. Eutrophication 7. Toxicity 8. Impacts on biodiversity

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9. 10. 11. 12. 13. 14.

Soil depletion and soil quality Water use Land use Abiotic resource depletion Radiation Plant pests and diseases

In addition to environmental impact categories, the study looked at the following impacts, which may also affect the acceptability of renewable energy sources: 1. 2. 3. 4. 5. 6.

Noise Odour Shading and shadow flicker Aesthetic impacts and impacts on scenery Health impacts Impacts on recreational use

The environmental impacts of the different renewable energy sources were assessed using peer-reviewed scientific papers and other literature, and domestic reports. Peer-reviewed literature was preferred but due to limited availability of such literature, also nonpeer-reviewed reports and books were used. Peer-reviewed literature was mainly searched through common scientific reference databases, such as Scopus and Google Scholar. In some cases also environmental impact assessment reports of different production facilities were used. The literature searches were conducted applying appropriate keywords, such as “wind power”, “rape seed oil”, “environmental impact”, “LCA”. The literature review was mainly focused on studies that used LCA. However, as we aimed to also study impacts which are typically not included in an LCA, such as noise, odour or aesthetic impacts, other literature were used as well. All the reference sources are listed in Appendix A. The reviewed publications were reviewed and classified according to a set of pre-defined criteria: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

Type of publication Main scope of the study, Environmental impact categories covered Final product and by-products Region Allocation methods used Reference land use if relevant Characterisation methodology of N2O emissions if relevant LCIA methods used Energy sources used in the production Other remarks

Although the aim of the review was to get information on the environmental impacts based on LCA, it soon became clear that information was not available on all the energy sources or impact categories. Therefore also expert interviews were conducted to get information on missing impacts. Interviewed experts were chosen on the basis that they were the best available experts on the impact category or energy source at hand. There were several impact categories that were not covered by literature. In the case of agricultural fuels, these impacts included among others plant pests and diseases, soil depletion and soil quality, and toxicity of biogas production and digestion use. Interviews concerning agricultural fuels consisted of eight experts with different expertise in the field of agriculture. As a result of the interviews, several new articles were included to the literature review but also some qualitative estimates concerning different impacts were made on the basis of the interviews. In the case of wind power, one expert was interviewed who provided information on impacts of wind power on biodiversity, land use, noise, shading, recreational use, aesthetic aspects and scenery. However, for most of

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these impact categories also literature was used (see Appendix A). For ground-source and air-source heat pumps two experts were interviewed who commented on the noise impacts of heat pumps. For forest biomass, four experts were interviewed who gave information on the ecological impacts and impacts on scenery and recreational use of forest biomass removal. Results of the literature review and interviews were collected in two excel tables1. The other table contained detailed information for each reference source, while in the other table information was combined for each energy source, and the range of values presented in the literature for each impact category and energy source was presented. For forest biomass only the use of forest residues, small-diameter wood and stumps for heat and power production and liquid biofuel production were taken into account. However, a large part of the energy use of wood originates from the by-products of pulp and paper production in Finland. This use was left out of the scope of the present study. The studied agricultural fuels were rape seed diesel, barley and wheat ethanol and biogas. Altogether 36 articles and reports related to environmental impacts of agricultural fuels and biogas were reviewed. Most articles concerned rape methyl ester (RME) and rape diesel (20 articles), but also wheat ethanol and biogas were included to many articles (wheat ethanol in 12 articles and biogas in 13 articles). Most of the papers focused on climate impact, some had also included acidification and eutrophication. Also, the energy use along bioenergy chain was included in several papers. Other impact categories were present in only a few studies. Data on wind power mainly represents 1–2 MW wind mills. In addition, most of the data relates to on-shore wind power, which is the “traditional” form of producing wind power. However, offshore wind power is gaining popularity as the its potential is vast and it also lacks some of the problems related to onshore wind farms, such as noise and visual impacts [22]. Data includes environmental impacts from the building and use of the wind mills. The possible extension of the electricity production network was not included. This applies to the other energy sources as well. For solar power, methodological adjustments needed to be made in order to make the results comparable with one another. Since the amount of radiation varies according to latitudes, also the amount of energy received with the solar panels and solar collectors varies. Thus, the data concerning solar panels was transformed to represent the Finnish average radiation regime (1050 kWh/m2 [28]). Data concerning solar collectors was transformed to represent the average amount of heat obtained with 1 m2 solar collector per year (325 kWh/v [26]). Concentrated solar power was not assessed in this study. In addition, for many of the energy sources, unit conversions were conducted for example from MJ to kWh or from gram to kilogram in order to make the results from different publications comparable with one another.

3. Results 3.1. Unit process impacts 3.1.1. Forest biomass In the combined heat and power (CHP) production and heat (only) production, significant amounts of wood-based fuels are presently utilised in Finland. Most of the wood raw materials used are small diameter wood from thinnings and forest residues. As explained in Section 1, fairly high targets have also been set for 1 Excel table with the combined information can be found in http://www.syke. fi/fi-FI/Tutkimus__kehittaminen/Tutkimus_ja_kehittamishankkeet/Hankkeet/Selv itys_ja_arvio_uusiutuvan_energian_tuotannon_ja_kayton_ymparistovaikutuksista_ ja_riskeista_UUSRISKI (in Finnish).

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increasing their use. The large and medium sized CHP plants usually use multi-fuel technologies, in which wood is combusted along with other fuels, such as peat, heavy fuel oil or coal. On the basis of the review conducted in this study, assuming a 100 years rotation period, the greenhouse gas emissions related to forest residue utilisation in heat and power production were found to lie between 14 and 56 g CO2-eq/MJ. In order to conclude how efficiently biomass harvesting works in climate change mitigation, forest biomass harvesting must be compared to a reference situation where no additional biomass harvesting for energy production takes place. The so-called climate debt from the utilisation of forest biomass for energy stems is based on the following: when biomass is taken from the forest, an unavoidable reduction in forest carbon stock is caused compared to a situation where biomass is not taken [30]. Boreal forests have relatively long rotation periods (typically 80–100 years), and thus it takes decades after final felling for temporal carbon neutrality to be achieved [18]. The relative carbon loss of forest harvesting may last for decades compared to a scenario where additional forest biomass is not harvested for energy production. The other processes related to forest biomass utilisation (such as ploughing, fertilisation, harvesting, transportation, storage, fuel conversion and distribution etc.) cause emissions as well. The greenhouse gas emissions from these sources depend on many case-specific factors. Regardless of uncertainties and sensitivities involved, the magnitude of these emissions is mainly minor compared to changes in forest carbon balances (e.g., [39,38]). However, in some case these emissions may have a considerably contribution to the overall life cycle emissions of forest biomass utilisation. If storage times of forest chips increase due to logistical matters, emissions from chip storage resulting from material decomposition could be as high as 15–24% (Wihersaari [46], [35]). Small-scale wood combustion is a fairly important source of particulate, CO, VOC and PAH emissions in Finland. There are several different factors that affect the size of these emissions, particularly the quality and structure of the stove, the way it is used and the quality of the wood fuel. The main health risks of small-scale wood combustion are caused during the winter time when most heating takes place. At that time, particulate matter concentrations may increase even to dangerous levels in the densely populated areas. Emissions are the highest in fireplaces and sauna stoves (up to 200–300 mg/MJ) (e.g., [20,42,43]).

average water flow to 14 TWh in 2020.The increase comprises increased capacity at existing power plants and small hydro power (1–10 MW). The environmental effects of hydropower differ, if the capacity of existing power plants is increased or new power plants are constructed. The effects caused by the increased capacity are likely to be quite small. Local effects on the eutrophication, biodiversity and erosion can occur. The construction of new power plants causes significant effects on climate change and land use changes. Climate change effects are dependent on the soil drown under water. 3.3. Wind power The literature review indicates that the life cycle emissions related to the production of wind power are fairly small. The greenhouse gas emissions varied between 4 and 68 g CO2eq/kWh, NOX emissions between 0.01 and 0.02 g/kWh and SO2 emissions between 0.036 and 0.04 g/kWh (Fig. 1). Main environmental impacts were biodiversity, noise and landscape impacts related to the use phase. In addition, rare minerals (e.g., dysprosium and neodyme) are needed during the production of the wind mills. 3.4. Solar power According to the review, the life cycle greenhouse gas emissions were approximately 32–79 g CO2eq/kWh for solar panels and 11–68 g CO2eq/kWh for solar collectors. Also other emissions to air were small compared to fossil fuels. However, according to Evans et al. [11], toxic emissions from the production of certain chemicals used in the manufacturing of the panels may be high. On the basis of the review it can be concluded that the main risk related to large-scale production of solar panels is the availability of critical minerals needed in their production. According to Moss et al. [25], using the production capacity needed to fulfil the targets of the European Strategic Energy Technology Plan, in particularly the availability of tellurium, indium, tin, silver and gallium might be threatened. Target level for solar power in 2020 is very low. However, price of solar power panels has decreased considerably during the past years and installitations of solar power systems have increased in Finland. Thus, there are prospects for its use to increase more than the target level is. 3.5. Geothermal energy

3.2. Hydropower Environmental impacts of hydropower production depend greatly on the type and location of the plant. Reservoir type hydropower plants typically cause larger impacts than run-of-the river type plants. Especially the land use and biodiversity impacts, and greenhouse gas emissions can be high. GHG emissions are caused by methane emissions due to the decomposition of soil and organic plant waste, which in tropical climates can be significant (Fthenakis and Kim [13]; April [1]). However, it should be noted that the emissions presented for reservoir type hydropower plants may be misleading. Many LCAs report gross emissions of reservoirs but most natural lakes and rivers area also major sources of GHGs, and therefore reports on gross emissions often overestimate emissions related to reservoir plants [32]. Climate change impacts result also from the energy consumption of plant and the use of non-renewable natural resources as building material [17,32]. The building of hydropower plant can have impacts on biodiversity if the plant is built in the route of migrants, for instance. During the operation time, regulation of watercourse has effects on waterside vegetation, other population and spawning (Melin [23]). According to the Climate and Energy Strategy of Finland, hydro power production is to be increased by around 0.5 TWh per year of

The main environmental impacts related to ground-source and air-source heat pumps are dependent on the electricity used to operate the pumps. In the studies reviewed for this paper, the life cycle greenhouse gas emissions of ground-source and air-source heat pumps were 53–65 gCO2eq/MJ and 58–77 g CO2eq/MJ, respectively. In many pumps HFC-compounds have been used as circulating fluids. However, they are gradually being replaced by other substances. As is the case with GHG emissions, also other emissions to air related to heat pump use mainly relate to the electricity used during operation of the pumps. For example, according to Saner et al. [36], only about 10% of the life cycle acidifying emissions related to ground-source heat pumps originates from the production of the system components and transports, while the rest stems from electricity required for operating the pumps. 3.6. Agricultural fuels and biogas There was big variation between the LCA results for agricultural fuels. There were 13 studies containing climate impact for rape methyl ester (RME) of which some studies had several results with different allocation methods (total 40 results). In those studies, the

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Fig. 1. Emissions of NOX (a), PM (b), SO2 (c) and CO2 (d) to air for wind, hydro and solar power in comparison to hard coal. Data regarding hard coal has been taken from [37].

results varied between 21 and 154 g CO2eq/MJ. There was large variation also in the other impact categories and bioenergy forms (see Fig. 2). The results for biogas production varied the most as the raw materials in biogas production could range from cultivated crops to waste materials. When comparing agricultural fuels and biogas, rape diesel has the highest climate impact and biogas has the lowest (Fig. 2a). Also, wheat ethanol has significantly lower climate impact than rape diesel. In case of acidification, biogas production and use has the highest impact compared to other agricultural fuels, when wheat ethanol has the lowest impact. Barley ethanol, in turn, has the highest eutrophication impact, when wheat ethanol has again the lowest impact. Rape diesel needs the highest amount of energy along its production chain, it could be as high as 1.5 MJ/MJ rape diesel produced [4]. The variation between studies remained large even when comparing results with the same allocation method (Fig. 3). The variation between studies is biggest in case of no allocation, but there were also more studies where no allocation methods were used than studies that used some allocation method. This variation was mainly caused by different yields, fertilizer rates or emission factors for fertilizer production or for N2O emissions from cultivation. Also, the characterisation factors varied between studies. The climate impact would be highest when there is no allocation, i.e. all emissions are allocated to biofuel. In the case of RME, the climate impact would be lowest when system expansion is used (21–44 g CO2eq/MJ). Also wheat ethanol has lowest climate impact with system expansion, but it could also be higher compared to other allocation methods. In the case of biogas, the results vary between raw material used in biogas production (Fig. 4). Lowest climate impact was for biogas from manure, when almost all studies gave negative results, i.e. there is more emission savings compared to emissions from biogas chain, when emissions from manure management can be avoided due to closed tanks in biogas plant. Also, the biogas from biowaste has low

climate impact, but grass cultivation has more impacts. However, there was one study that took into account benefits of grassland as carbon sink [41], and had negative value also to biogas from grass silage. Biogas can also be used different purposes (e.g., only heat, combined heat and electricity production or for transportation fuel), but the end use way did not have clear effect to the results. Some studies also covered other impact categories, e.g., water and land use, but these studies were sparse. According to them studies, the biggest water consumption is in the RME chain, between 100 and 409 m3/MJ ([14], de Vries et al. [94]) while water consumption in biogas production is almost zero [31]. Land use is the highest for wheat ethanol, it could be as high as 0.067 ha/GJ (de Vries et al. [94]), but according to Börjesson and Tufvesson [7], the land use for wheat cultivation is only 0.0083 ha/GJ, which is lower than in case of other agricultural fuels. According to expert interviews, one-year plants (e.g., wheat and rape seed) have bigger negative impact to soil depletion and soil quality compared to perennial plants (e.g., grass). In addition, toxicity of biogas production was estimated to be low as production is in closed tanks. However, the toxicity of digestate use could be an issue, depending on raw materials used in biogas production. 3.7. Total environmental impacts related to the 2020 renewable energy targets When the impacts are studied on the basis of the target levels of 2020, the impacts that stand out are related to forest biomass use. Several studies indicate that the climate impacts related to boreal forest biomass use can substantial. However, according to availability studies of forest biomass for energy production, fulfilment of the 2020 targets can be achieved by harvesting small diameter wood from young forest silviculture and early thinnings, harvest residues and stumps from regeneration fellings and by

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Fig. 2. Impacts on (a) climate change; (b) acidification; (c) eutrophication; and (d) energy consumption of the different agricultural fuels. Data on fossil petrol and diesel taken from Eriksson and Ahlgren [10].

Fig. 3. The impact of different allocation methods on the climate impacts of rape methyl ester (RME) and wheat ethanol.

recovering industrial waste wood. Except for stumps, the climate impacts of these wood resources have been found to be fairly low within a 100 year time-frame. According to the values collected in this study, the total greenhouse gas emissions related to the Finnish national renewable energy targets would be 3.1–10.7 million tons/year in 2020 (Fig. 5). For biofuels the range given in the literature is very large and therefore also the potential GHG emissions related to their use stand out. The role of the other energy sources is more minor. Biodiversity impacts were not assessed to be considerable in comparison to other forestry operations. However, biodiversity should be monitored as the extraction of harvest residues, stumps and small-dimension wood increases. Moreover, more information

Fig. 4. Greenhouse gas emissions from biogas production with different raw materials.

is needed on the long-term effects of these actions. The influence of more intensive biomass harvesting and thus extraction of biomass and nutrients may also have an impact on forest soil physical properties, nutrient balance and fertility. However, the results from research are somewhat controversial and more information is still needed on long-term effects. Although the production of agricultural plants for energy use may lead to eutrophication impacts in a same way as any other agricultural activity, the produced amounts in 2020 will be so small that the overall eutrophication impacts related to them will not be large. Also, the greenhouse gas emissions per produced energy could be quite high when crop is cultivated for energy purpose, but the increase of agricultural biomass use for energy will be so small that also GHG emission impacts will be small. If

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Fig. 5. Total greenhouse gas impacts related to the national renewable energy targets of Finland (t CO2eq/year).

the target level for agricultural biomass would be higher, it could cause clearance of forests for arable land, which in turn could cause significant greenhouse gas emissions. According to the national renewable energy targets, the use of wind power will grow considerably. The main environmental impacts caused by wind mill are local, such as noise, shadowing and impacts on scenery. These impacts can be reduced through careful planning. The target level for hydropower production in 2020 would in principle imply building of new hydropower capacity. Nevertheless there are presently no plans for additional capacity. Environmental impacts related to the existing hydropower production are fairly small but the climate and biodiversity impacts related to new hydropower can be considerable. The use of ground-source and air-source heat pumps is also expected to increase by over two-fold. The environmental impacts of the heat pumps mainly stem from the electricity needed to operate them. It has been pointed out by many authors that systems relying on decentralised energy production (such as heat pumps) set challenges for the total energy system due to increased peak electricity demand. Furthermore [34] (2013) compared CO2 emissions from district heating and ground-source heat pumps and found that the latter resulted in higher emissions due to the high CO2 emissions of marginal electricity production. Thus, they point out that ground-source heat pumps may not be the best solution on areas where a district heating network is available.

4. Discussion and conclusions 4.1. Main environmental impacts of the renewable energy sources According to this study, most of the environmental impacts caused by the Finnish renewable energy targets result from the use of forest biomass. In addition to climate impacts, impacts on particulate matter formation and biodiversity stand out. Increased harvesting of wood residues may have adverse impacts on both biodiversity and the nutrient balance of the forests. However, these impacts can be reduced with the right practices. In the Finnish Silvicultural Guidelines [47] instructions are given on how to reduce the biodiversity impacts and nutrient losses related to residue harvesting. Still, more information is needed on the longterm impacts of forest residue harvesting. Although our original aim was to collect data separated for each life cycle phase, it was soon noticed that the availability of such data was very limited. On the other hand, some of the impacts can clearly be related to only

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one life cycle phase, such as noise of windmills to the use phase, and emissions from agricultural fuels to cultivation phase. On some of the impacts, such as climate change, acidification, eutrophication, there was fairly comprehensive data available while on others, such as impacts on biodiversity or toxicity, data availability was much more limited. Methods have been developed within LCA to assess these impacts but they are still often omitted from the studies. One reason for this, particularly in the case of toxicity emissions, is the lack of inventory data. Pang et al. [27] point out that studies on renewable energy mainly focus on climate issues while impacts on biodiversity and landscapes are largely neglected. Nevertheless ecological assessment models exist that could be further developed from LCA perspective. The authors thus conclude, that a higher-level integration between different assessment tools would be needed in order to comprehensively study the different impacts related to renewable energy production [27]. Some studies report the results directly as impact category indicators (e.g., [3,15]). When different impact assessment methods are being used the impacts are not really comparable to one another. Even though the environmental impacts of most of the renewable energy sources appear small they cannot be completely ignored. Like Leung and Yang [22] argue, the role of renewable energy may be considerable in the future, and some impacts that seem small today may be of greater importance in the future (see also [40]). Therefore it is important to further study the environmental impacts of renewable energy sources in order to improve understanding of them. Moreover, it is also essential that comprehensive evaluation methods for assessing all aspects of given energy production technologies are available [9]. There have been recent attempts to develop such evaluation methods, for example within the 6th framework program of the European Commission project NEEDS (see [12]). Use of natural resources is often poorly covered in LCA studies. Major risk related to wide-spread exploitation of wind and solar energy is the availability of natural resources, particularly certain rare-earth elements [25]. The global market of these resources is presently dominated by China with its share over 90% of the production, and this can be seen as threat to wide-spread use of these of technologies [9]. Moreover, the rare earth elements are almost always connected to radioactive heavy metals [9]. Their production may thus result in emissions of radioactive substances. It has been increasingly recognised that systems relying on decentralised or fluctuating energy production, such as solar or wind power and heat pumps, increase peak electricity demand and therefore set challenges for the functioning of the total energy system. Many renewable energy sources require increased reserve capacity due to intermittent production (e.g., Altmann et al. [2]). In the long run, the energy system needs to be developed to make it flexible in order to accommodate fluctuations in the production of these energy sources (e.g., [19]). 4.2. Uncertainties and limitations of the study The literature review indicated that on many renewable energy sources there is only limited information available or the published results are not comparable with each another. For many of the energy sources the published data is scattered, and different studies use differing assumptions, system boundaries and allocation methods. Moreover, results are not necessarily applicable in a given country, such as Finland. For example, for ground source heat pumps, a large part of the impacts is generated by the electricity production. Thus, results calculated using e.g., UK electricity production profile may not be applicable for the Finnish heat pumps. Also, the yields of agricultural biomasses are significantly lower in Finland compared to other European countries. This limits the possibilities to make reliable conclusions on the environmental impacts of the different energy

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sources. However, in many instances the environmental impacts were so much lower than those of the fossil comparators, such as hard coal, that fairly solid conclusions could still be drawn. Data regarding wind power in this study mainly represent 2– 2.5 MW plants. However, new plants are typically 3 MW or larger in size. This may have an impact on the environmental impacts per unit of electricity produced but there is not enough data available to conclude whether that impact would be positive or negative for the environmental impacts. Furthermore, efficiency of the solar panels in the reviewed studies was assumed to be approximately 12–13%. However, current technology typically has an efficiency of 15%. Thus, the results presented in this study slightly overestimate the impacts of solar power production. In the future environmental impact assessment should also increasingly take into account changes in the ecosystems as a result of climate change, and the need for climate adaptation [5]. This is particularly relevant when new energy investments are planned. Quantitative studies can be supplemented with qualitative methods, such as multi-criteria analysis tools (see [16]).

5. Conclusions The aim of this study was through literature review to comprehensively assess the environmental impacts related to the use of renewable energy in Finland in 2020. Environmental impacts of renewable energy have been studied by many authors during the past years. However, this study differed from most of them in that its scope was wider, aiming to take into account more impact categories that are typically considered. Moreover, the Finnish energy production structure differs from many others in that forest biomass has a prominent role in the energy mix. The review points out that in order to understand the overall environmental impacts of the different renewable energy sources,

a thorough life cycle assessment with a unified framework would be needed. However, assessment using the Finnish National Renewable Energy Targets for 2020 also indicates that under the present targets, the overall environmental impacts are likely to be low. Main impacts or risks of impacts relate to the use of forest energy. This is not surprising considering the high share of forest based energy in the Finnish energy mix. In addition to impacts on climate change, impacts on particulate matter formation originating from small-scale wood combustion, stand out. Increased harvesting of wood residues may also have adverse impacts on both biodiversity and the nutrient balance of the forests. Use of agricultural raw materials in energy production is very low with the present targets but in larger quantities it contributes to indirect land use change and eutrophication. Possible new hydropower plants would potentially have large impacts on climate change, land use and biodiversity. Regarding wind power the main concern has been related to noise, land use and aesthetic impacts. However, a potential concern in the future may be caused by the availability of metals and other resources needed for the mills. This same concern is also related to the manufacturing of solar panels.

Acknowledgements This study was conducted as part of the Evaluation of environmental effects and risks of renewable energy production and use (UUSRISKI) – project funded by the Finnish Ministry of the Environment, Ministry of Employment and the Economy and Ministry for Agriculture and Forestry. In addition, support by the Academy of Finland funded project ECOSUS (decision no. 257174) as a part of Sustainable Economy Programme is also gratefully acknowledged.

Appendix A Table. References used in the review. Energy source

Reference

Agricultural fuels RME, wheat etha[7] nol, biogas from grass RME, rape biodiesel, [93] wheat ethanol, barley ethanol RME, wheat ethanol [94]

Type of Impact categories covered publicationa

P

Climate change, eutrophication, land use, energy balance

R

RME

Bernesson et al. (2004)

P

RME, wheat ethanol RME, rape biodiesel, wheat ethanol, biogas from manure and biowaste Biogas from manure and grass silage Wheat ethanol Wheat ethanol

[62] [53]

P D

Climate change, acidification, trophospheric ozone formation, eutrophication, energy balance Climate change, water consumption, land use Climate change, acidification, trophospheric ozone formation, eutrophication Climate change, energy balance Climate change

[87]

R

Climate change

[70] [80]

P R

Climate change Climate change, energy balance

P

Other remarks

L. Sokka et al. / Renewable and Sustainable Energy Reviews 59 (2016) 1599–1610

RME, barley ethanol RME RME Biogas from manure and grass

[50] [54] [92] [49]

R P P R

Rape biodiesel

[4]

P

RME rape biodiesel, wheat ethanol, barley ethanol RME, biogas from grass RME, wheat ethanol

[76] [58]

P P

Climate change, energy balance Land use, energy balance Toxicity Climate change, acidification, trophospheric ozone formation, eutrophication, human toxicity, water consumption, energy balance Climate change, acidification, eutrophication, energy balance Climate change, toxicity, energy balance Water consumption

[41]

P

Climate change, energy balance

[52]

R

[65] RME, wheat ethanol, biogas from biowaste and manure Biogas from grass [69] Biogas from manure [82] and grass silage

R

Climate change, acidification, trophospheric ozone depletion, eutrophication Climate change, acidification, energy balance

[31]

P

RME, rape biodiesel [64] Bioethanol [48]

P R

Biogas from biowaste, manure and grass silage

P P

1607

Climate change, acidification Climate change, acidification, trophospheric ozone depletion, eutrophication, energy balance Climate change, ozone depletion, acidification, particulate matter formation, tropospheric ozone formation, eutrophication, toxicity, water consumption, land use, abiotic resource consumption Particulate matter formation Particulate matter formation, trophospheric ozone formation, toxicity

Wind power [11]

P

[29]

P

[37]

P

[3]

P

[13] [25] [96] [81] [44] [22] [79]

P R R R P P P

Solar panels and collectors [86]

P

Climate change, biodiversity, land use, water consumption and impact on scenery Climate change, acidification, particulate Assesses also matter formation, tropospheric ozone offshore formation, abiotic resource consumption plants Climate change, particulate matter formation, NMVOC emissions, biodiversity, water consumption, abiotic resource consumption Climate change, acidification, particulate matter formation, tropospheric ozone formation, abiotic resource (fossil fuels) consumption, toxicity Land use Abiotic resource consumption Impacts on scenery Biodiversity (impacts on birds) Climate change, acidification Biodiversity, impacts on scenery, noise Noise

Climate change, acidification, toxicity, biodiversity, abiotic resource consumption

Solar collectors

1608

L. Sokka et al. / Renewable and Sustainable Energy Reviews 59 (2016) 1599–1610

[51]

P

[37]

P

[29]

P

[63] [57] [89] [68] [11]

P P P P P

[13] [56] [25] [44]

P R R P

Ground source and air source heat pumps [36]

P

Climate change, acidification, particulate matter formation, tropospheric ozone formation, eutrophication Climate change, particulate matter formation, NMVOC emissions, biodiversity, water consumption, abiotic resource consumption Climate change, acidification, particulate matter formation, tropospheric ozone formation, abiotic resource consumption Climate change Climate change, acidification, toxicity Climate change Climate change Climate change, toxicity, land use, water consumption and impact on scenery Land use Abiotic resource consumption Abiotic resource consumption Climate change, acidification

Climate change, ozone depletion, acidification, particulate matter formation, tropospheric ozone formation, eutrophication, toxicity, water consumption, land use, abiotic resource consumption Climate change, ozone depletion, acidification, tropospheric ozone formation, eutrophication, toxicity, land use, abiotic resource consumption

[15]

P

[66]

P

Climate change

P P P P P P R R R

Climate change Climate change Climate change Climate change Climate change Climate change Climate change Climate change Climate change, Tropospheric ozone formation, particulate matter formation, toxicity Climate change, Tropospheric ozone formation, particulate matter formation, toxicity Climate change, ozone depletion, eutrophication, acidification, toxicity Climate change Climate change, biodiversity, land use and land use change Soil depletion and soil quality Climate change, biodiversity, land use and land use change Climate change, biodiversity, land use and land use change Soil depletion and soil quality Soil depletion and soil quality

Forest residues and other wood-based energy sources [83] [67] [84] [97] [55] [88] [60] [72] Tissari et al. (2011)

[42,90]

P

[59]

P

[44] [75]

R

[96] [50]

P

[25]

P

[61] [78]

R P

Solar collectors Both solar panels and collectors Both solar panels and collectors Solar panels Solar panels Solar panels Solar panels Solar panels Solar Solar Solar Solar

panels panels panels panels

Only groundsource heat pumps Both groundsource and air-source heat pumps Only airsource heat pumps

L. Sokka et al. / Renewable and Sustainable Energy Reviews 59 (2016) 1599–1610

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Hydro power [23]. P [79] Postnote October 2006 Number 268 O Carbon footprint of electricity generation http://www.parliament.uk/documents/ post/postpn268.pdf [11] P

a

[13] [29]

P P

[71]

P

Climate change

Climate change, toxicity, land use, water consumption and impact on scenery Land use Climate change, acidification, particulate matter formation, tropospheric ozone formation, abiotic resource consumption Climate change

P¼ Peer review, R¼ Report, D¼Database, O¼Other, I¼Interview.

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