Environmental Impacts and External Costs Assessment

The use of energy technologies is often associated with impacts on human health and environment. The goal of environmental impact assessment is the modeling and quantification of these effects. Not only the direct emissions from the operating system (e.g. the power plant, or the vehicle) have to be considered, but also impacts that arise from the life cycle of the system (e.g. the fuel production, the vehicle production, the impacts of roads and other infrastructure, etc.). The quantified impacts include damages on human health, impacts on crop yields, damages on ecosystems, and damages on materials. A method to aggregate different environmental impacts is the use of external costs.

The special focus of the LEA group is on the combination of environmental impact and external cost assessment with full-scope life cycle inventory analysis.


The basis of the environmental impact assessment method is the “impact pathway approach” including life cycle data. The assessment starts with the modeling of emissions of the systems under consideration. The contributions of the life cycle to emissions and other burdens (e.g. land-use) are considered as well. Based on the emission data, the changes of the environment are modeled (e.g. increased air pollutant concentrations). Exposure-response models are used to estimate the physical impacts on receptors. Impacts on human health include mortality (i.e. the loss of life expectancy) and a variety of morbidity impacts like chronic bronchitis, chronic cough in children, cough in asthmatics, lower respiratory symptoms, congestive heart failure, respiratory hospital admissions, and restricted activity days. In addition to health damages, impacts on ecosystems, agriculture, and materials are considered. The last step is the aggregation of different environmental impacts in terms of external costs. Figure 1 shows the structure of the impact pathway approach.

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Figure 1: The impact pathway approach including LCI (life cycle inventory).

Selected results

Project SCCER-mobility (Swiss Competence Center for Energy Research in Mobility)

The SCCER-mobility (Swiss Competence Center for Energy Research in Mobility) aims at developing the knowledge and technologies essential for the transition of the current transportation system to a sustainable one, featuring minimal CO2-output and Primary Energy Demand as well as minimal pollutant emissions and minimal externalities.

For the impact and external cost assessment, the direct emissions from the vehicle as well as the indirect emissions from the rest of the chain using LCA (Life Cycle Assessment) data have to be considered. For cars with internal combustion engine (fossil-based or biofuel-based), the exhaust emissions from the motor during the drive-cycle are essential. On the other hand, for electric cars, the direct emissions from the vehicle are small (although not zero because of e.g. particulate emissions due to abrasion from tires, brakes and road). Nevertheless, also in this case there are indirect emissions and associated damages from the rest of the chain. This includes in particular the production of electricity (leading to potential emissions from power plants or, e.g. in case of solar electricity, emissions during solar module production) and the production of the vehicle itself. Substantial additional contributions to the impacts compared to conventional vehicles arise in particular for the production of the battery or the fuel cells and other specific components. These contributions are investigated in the LCA part of the project and integrated into the environmental impact and external cost assessment. Figure 2 shows results for environmental external costs of different vehicle classes in Switzerland. Conventional petrol and diesel cars in compliance with the EURO I to VI emission norms are compared to electric cars. (The figure refers to environmental impacts i.e. accidents or noise exposure are not considered here. Furthermore, secondary organic aerosols and effects of aerosols on climate are not included).

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Figure 2: Estimated environmental external costs per vehicle-km for different passenger cars in Switzerland. Life-cycle contributions are included under rest of chain. PM = Particulate matter. GHG = Greenhouse gas emissions. CH mix = Electricity supply mix in Switzerland. Source: Heck (2014).

Previous project on electric mobility: THELMA (TecHnology-centered ELectric Mobility Assessment).

Project OPTIWARES (OPTImization of the use of Wood As a Renewable Energy Source)

The goal of the project OPTIWARES (OPTImization of the use of Wood As a Renewable Energy Source) is to improve the quantitative understanding of the impact of aerosols from wood combustion on air quality and climate and to develop improved strategies for encouraging the use of more appropriate wood combustion facilities.

The substitution of fossil fuels by biomass can reduce carbon dioxide emissions if the biomass is sustainably produced. However, emissions from biomass combustion have a variety of impacts on human health and environment. Especially, aerosol particles cause health damages and exert a climate forcing.

Figure 3 shows estimates of external costs for different classes of wood combustion systems in Switzerland. The assessment includes direct effects due to the emissions from the chimneys of the appliances as well as indirect effects due to the life cycle of fuel wood production, transports, materials etc. Primary PM (particulate matter) and secondary PM are major contributors to health damages. Primary particulates are formed during the combustion process and emitted from the chimneys. Secondary particles are formed in the atmosphere from gaseous precursor emissions. The assessment includes also health impacts due to other emissions like hazardous organic compounds and heavy metals, impacts on crop yields, risk of biodiversity losses, material damages, and climate change effects of greenhouse gases (GHG). Climate change refers to a 100-years time horizon. The contributions from the rest of chain have been calculated with life cycle inventory data from ecoinvent. (Secondary organic aerosols are not included.)

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Figure 3: External costs per MJ fuel wood for different classes of wood combustion systems currently operating in Switzerland (PM = Particulate matter. GHG = Greenhouse gas emissions. See text). Source: Heck & Meyer (2012).

Note that estimates of externalities are subject to high uncertainties which are discussed in the publications. Figure 4 shows an example of a cost-benefit comparison for adding a particulate filter (ESP, electrostatic precipitator) to a wood furnace.

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Figure 4: Cost-benefit comparison for 1 MW wood furnace without and with ESP (electrostatic precipitator). PPM: Primary particulate matter emissions. O&M: Operation & maintenance costs (Data for internal costs: Nussbaumer IEA 2007; External costs: own calculations). Source: Heck (2015).

Previous project on biomass: IMBALANCE (Impact of Biomass burning Aerosol on Air quality and Climate).

Selected Publications