Life Cycle Assessment (LCA)

Life Cycle Assessment (LCA, also known as life-cycle analysis, and cradle-to-grave analysis; in German “Ökobilanz” and “Lebenszyklusanalyse”) is a technique to assess environmental burdens and impacts associated with all the stages of a product's life from cradle to grave. I.e., the value chain is modeled using single processes from raw material extraction through material processing, manufacture, distribution, use, repair and maintenance, and disposal or recycling. This model is called “product system”.

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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.

Method

The procedures of life cycle assessment (LCA) are part of the ISO 14000 environmental management standards and specified in ISO 14040 and ISO 14044. Life Cycle Assessment is carried out in four distinct phases:

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.

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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.
4) Interpretation: The interpretation phase aims at formulating a set of conclusions and recommendations based on the LCA results. The level of confidence in the final results needs to be determined, uncertainties and limitations evaluated and explicitly stated.

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

We primarily use LCA for evaluation of the environmental performance of current and future electricity generation and heat supply technologies, energy storage as well transport technologies. The Technology Assessment group regularly provides LCI data for power generation and heating as well as passenger and freight transport technologies to the ecoinvent database. Since the power sector is very important from the LCA perspective of global supply chains of today’s economy, we aim at a complete coverage of global electricity supply with (at least) country-specific inventory data. Ecoinvent v3.2 contains inventory data for electricity production in 56 countries with 107 corresponding geographic regions resulting in 85% coverage of global power supply.

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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.

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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.

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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).

Selected Publications