Life Cycle Assessment (LCA)
Figure 1: Scheme of the LCA framework – life cycle of a product.
By including all relevant life cycle stages, LCA allows for an unbiased and comprehensive environmental assessment of products and services. LCA can be used for identification of environmental “hot-spots” in the life cycle of a product, and in a comparative way determining the ecologically beneficial option among several alternatives. LCA is more and more frequently used in industry, commerce, and politics for decision support and in sustainability assessment for covering the environmental perspective.
1) Goal and Scope definition: First step is the explicit specification of goal and scope of the LCA. It includes specification of the product system to be investigated, system boundaries, functional unit(s), reference flow(s), assumptions and limitations, procedures for allocation or system expansion, and impact categories chosen.
Figure 2: Product system for the LCA of battery electric vehicles. Functional unit: 1 vehicle-kilometer.
2) Inventory Analysis (LCI): This phase comprises the creation of inventories of flows from and to nature and the technosphere (i.e., the “man-made world”) for a product system. Inventory flows include inputs of water, land, energy, raw and processed materials, and releases to air, land, and water. The product system (i.e., all processes being part of a product life cycle) can be split into “foreground” and background” system. The distinction is often ambiguous, but in general, the foreground system represents those processes, which are directly part of a value chain of the product or services in focus of the LCA, while the background system represents all up- and downstream processes connected to the foreground system. The background system usually comprises thousands of processes and therefore, generic background LCI databases such as the ecoinvent database are used. Based on the inputs and outputs of all individual processes, cumulative LCI data can be calculated representing the life-cycle environmental burdens per functional unit of the reference product.
3) Impact Assessment (LCIA): This phase of LCA aims at evaluating the importance of potential environmental impacts based on the cumulative LCI results. Traditional LCIA consists of the following mandatory elements:
- selection of impact categories, category indicators, and characterization models;
- the classification stage, where the inventory flows are sorted and assigned to specific impact categories;
- quantification of impacts, where the LCI flows are characterized, using one of many possible LCIA methodologies, into common equivalence units.
These four phases are often interdependent, i.e. LCA is carried out in an iterative way. The scientific community distinguishes between “attributional” and “consequential” LCA. Attributional LCA (aLCA) seeks to attribute the burdens associated with the production and use of a product, or with a specific service or process, at a certain point in time (typically the recent past). LCA represents the average mix of market suppliers or supply technologies. Consequential LCA (cLCA) seeks to identify the environmental consequences of a decision or a proposed change in the system under study (oriented to the future). Therefore, market information and economic implications of a decision have to be taken into account. cLCA represents marginal markets suppliers with unconstrained supply technologies only.
Our focus in LCA
Figure 3: Global coverage of electricity production and supply in the ecoinvent database.
LCA of the complete transport sector is performed within the SCCER Mobility. Within the previous project THELMA, our LCA centered on current and future passenger vehicles with a focus on electric mobility, i.e. battery and fuel cell vehicles.
Figure 4: LCA results for passenger vehicles: impact on climate change. ICEV: internal combustion engine vehicle; HEV: hybrid electric vehicle; BEV: battery electric vehicle; FCV: fuel cell vehicle; -g: gasoline; -d: diesel; -cng: compressed natural gas; EU mix: BEV using the average EU electricity mix for charging; H2-SMR: hydrogen generation via steam methane reforming. Source: Bauer et al. (2015).
Within the SCCER heat and electricity storage, we investigate the environmental performance of energy storage including Power-to-Gas, batteries, and compressed air storage. We use LCA results within Multi-Criteria Decision Analysis (MCDA) for covering environmental aspects in sustainability assessment; recently e.g. in the research project CARMA evaluating Carbon Capture and Storage (CCS) and in the assessment of deep geothermal energy in Switzerland. Carbon Capture and Storage has been featured in a recent issue of Energie-Spiegel; our book on deep geothermal energy is available from here.
Figure 5: LCA results for deep geothermal power generation in Switzerland: impacts on climate change from three different potential plant capacities. Drilling of boreholes turns out to be the most important factor, even if it’s carried out with Swiss electricity supply with a low carbon intensity. Source: Hirschberg et al. (2015).
- Christian Bauer, J. Hofer, H.-J. Althaus, A. Del Duce, A. Simons (2015) The environmental performance of current and future passenger vehicles: Life cycle assessment based on a novel scenario analysis framework. Applied Energy, 157, 871–883, doi:10.1016/j.apenergy.2015.01.019.
- Andrew Simons, C. Bauer (2015) A life-cycle perspective on automotive fuel cells. Applied Energy, 157, 884–896, doi:10.1016/j.apenergy.2015.02.049.
- Karin Treyer, C. Bauer (2014) Life cycle inventories of electricity generation and power supply in version 3 of the ecoinvent database – part II: electricity markets. International Journal of Life Cycle Assessment, doi:10.1007/s11367-013-0694-x.
- Karin Treyer, C. Bauer, A. Simons (2014) Human health impacts in the life cycle of future European electricity generation. Energy Policy, 74, S31–S44, doi:10.1016/j.enpol.2014.03.034.
- Karin Treyer, C. Bauer (2013) Life cycle inventories of electricity generation and power supply in version 3 of the ecoinvent database – part I: electricity generation. International Journal of Life Cycle Assessment, doi:10.1007/s11367-013-0665-2.
- Kathrin Volkart, C. Bauer, C. Boulet (2013) Life cycle assessment of carbon capture and storage in power generation and industry in Europe. International Journal of Greenhouse Gas Control, 16, 91–106, doi:10.1016/j.ijggc.2013.03.003.