Is the process of comparing a value to the endpoints of numerical ranges to find a category in which the value belongs?

Life Cycle Impact Assessment (LCIA)

LCIA is a step for evaluating the potential environmental impacts by converting the LCI results into specific impact indicators. Conducting LCIA has to follow several substeps: First is to select impact categories for analysis. The major impact categories are divided into three general groups in terms of impacting subjects (shown in Fig. 18.2). Second is to assign the LCI results to different impact categories (classification). Third, the potential impact indicators are calculated (characterization). These three steps are mandatory for LCIA. Also, there are optional steps for LCIA, including relating the impact indicators to reference conditions (normalization), grouping, and weighting impacts. Currently, most LCIAs only perform three mandatory steps [1].

When LCIA of microalgae bioenergy is carried out, environmental impact categories can be selected according to project requirements. Many studies include only the most important environmental impacts and ignore other impacts. Of many impacts for analysis, the fossil fuel use is always included in algal biofuel LCIA, because the purpose to produce algal biofuel is to replace fossil fuels. It is necessary to examine if fossil fuel use of algal biofuels is less than producing petroleum-based fuels. Similarly, using algal biofuels is expected to reduce GHGs in the atmosphere. It is also necessary to study the GHG emissions of algal biofuels in order to evaluate whether algae biofuel is superior to traditional fossil energy. Other impacts in conducting algal biofuel LCIA include eutrophication (N), ozone depletion (O3), acid rain (SO2), respiration (PM2.5), water use, and land use, etc.

4.1 Definition

Life cycle impact assessment (LCIA) is the phase of an LCA where the evaluation takes place of the potential environmental impacts stemming from the elementary flows (environmental resources and releases) obtained in the LCI. LCIA consists of the following steps:

Selecting the relevant impact categories

Classification: assigning the elementary flows to the impact categories

Characterization: modeling potential impacts using conversion factors obtaining an indicator for the impact category

Normalization (optional): expressing potential impacts relative to a reference

Grouping: sorting or ranking the impact indicators

Weighting: relative weighting of impact categories; and evaluation and reporting

Abstract

Life cycle impact assessment (LCIA) is the method for converting inventory data from a life cycle assessment into a set of potential impacts. This enables practitioners and decision makers to better understand the damage caused by resource use and emissions. Understanding that a process emits 10 g of carbon dioxide emissions and 1 g of methane emissions gives a partial understanding of climate change. Giving the methane emissions given a characterization factor of 28 kg CO2-eq [100 year impacts according to (IPCC, 2013)]. A robust LCA may assess thousands of resources and emissions. LCIA combines these emissions according to effect or damage to give a more manageable set of impacts.

7.2.5 Impact assessment phase

Life cycle impact assessment (LCIA) is a qualitative and quantitative assessment of the environmental impact of a product based on the resource, energy consumption data, and various emission data provided after the inventory analysis. LCIA transfers the corresponding materials and consumed energy into understandable impact indicators. These indicators express the severity of the contribution of the impact categories to the environmental load. As shown in Fig. 7.3, there are several steps in a LCIA. These indicators are concluded through a series of steps recommend by ISO 14040 and ISO 14044 (ISO, 2006a, 200b). For example, the impact on the ecological environment includes global warming, ozone layer depletion, eutrophication, acidification, and so on. In LCIA, such definitions are called the category indicators, numerical entities belonging to impact categories.

Once the indicator is defined, a model can be developed that predicts the indicator value as a function of an emission. Such models are normally simple linear models defined by characterization factors. If an emission is multiplied by a characterization factor, an indicator value is obtained.

The sum of indicator values obtained through multiplying all emissions assigned to that impact category by their respective characterization factors is called the category indicator result. The indicator “moles of H” may, for instance, be the sum of contributions from sulfur dioxide, nitrogen oxides, and hydrogen chloride, and there is a characterization factor for each of them relative to the indicator. The category indicator results may then be analyzed further by normalization, grouping, and weighting. These procedures are optional in the standard, as they are not as well-known as the preceding steps and contain more subjective elements. The aim of these steps is to clarify the results by comparing them to some references.

The LCIA method is the controversial research. Because of the complexity of the LCIA step, methodologies have been developed to simplify and optimize the LCIA process. Within the LCIA step, two characterization approaches can take place along the impact pathway of an impact indicator: the midpoint approach and the endpoint approach. Fig. 7.4 illustrates the framework of midpoint and endpoint categories for the impacts (Hauschild et al., 2013). Characterization at midpoint level models the impact using an indicator located somewhere along the methodology mechanism but before the endpoint categories; while characterization at the endpoint level requires modeling all the way until the endpoint categories described by the areas of protection (AoPs) (in most methodologies, the main AoPs are: ecosystem quality, human health, and resources).

The research and application greatly depend on the accumulation of evaluation data and results. Basic inventory analysis data, such as inventory data related to industrial processes, energy, resources, transport, basic materials, and waste disposal, are required in most current case studies of LCA. Because the LCA database is very regional, almost all countries and regions need to establish their own LCA database.

Effects

LCIA follows from RA concepts in incorporating hazard and dose-response into the effect factors. LCIA generally groups hazard into either carcinogenic and non-carcinogenic (Rosenbaum et al., 2008). The main difference in effects calculations between LCIA and RA is in the dose–response. LCIA generally applies linear dose–response for all chemicals irrespective of whether they are carcinogens or not. This is in contrast to RA, which generally classifies carcinogenic effects to follow linear dose–response and noncarcinogenic effects to follow threshold response (although this may be undergoing changes in RA). The premise of threshold-based response is that a chemical is not excepted to have adverse effects above a below a given dose (Csiszar et al., 2016). The limitation of this approach has been recognized in both LCA (Bare et al., 1999) and RA (National Research Council, 2009) approaches as not protective without knowledge of exposure to other chemicals or stressors with the same health endpoint and in LCA without knowledge of future scenarios (Bare et al., 1999). Within the context of FU-based exposure estimates, knowledge of aggregate exposure is not readily available in LCA to use as dose comparison due to reasons such as the normalization to the FU (as discussed above) and to lack of spatial specificity or population variability considerations. This is referred to as a lack of background exposure knowledge in LCA (Bare et al., 1999). As a result, nonthreshold-based dose–response has been used in LCIA of chemical toxicity for noncarcinogens and generally follows linear dose–response (Csiszar et al., 2016). This is one of the key differences identified by many comparisons between LCA and RA (Bare, 2006; Harder et al., 2015; Potting et al., 1999) and was also identified as an area where LCA is in contrast to RA during the development of the human toxicity impact category in LCA (Pennington et al., 2002). The use of linear dose–response has been discussed and undergone debate in the LCA literature (Potting et al., 1999; Bare et al., 1999). Additionally, the inclusion of threshold considerations has been used as a basis for combination of LCA and RA (Csiszar et al., 2016; Walser et al., 2014).

5.18.2.3 Life cycle impact assessment (LCIA)

LCIA is the process of assessing the environmental impacts attributable to a product under study using the input data from the LCI. It consists of mandatory and optional elements, 3 each. The mandatory elements are

selection i.e., selecting which characterization model(s), impact category (or categories), and category indicator(s) to be adopted in the study;

classification i.e., assigning LCI results to the chosen impact categories; and

characterization i.e., estimating the category indicator result (also referred to as LCIA result) for the chosen impact category. The category indicator result is the product of relevant LCI results and pre-defined characterization factors.

The optional LCIA elements include

normalization i.e., comparing the category indicator result to a reference, which supports consistency control;

grouping i.e., grouping and ranking impact categories based on indicator results and value choice; and

weighting i.e., converting normalized results or indicator results into an aggregated score based on weighting factors which are derived from value choice.

There is a range of software tools that can significantly assist with this task, including GaBi, SimaPro, OpenLCA and AMEE. LCIA methodologies include (but are not limited to) Anthropogenic stock extended Abiotic Depletion Potential (AADP), Centrum voor Millikunde Leiden (CML), Environmental Development of Industrial Products (EDIP), Impact 2002 +, ILCD Recommendation, ReCiPe, Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts (TRACI), UBP 2006, USEtox, Eco-Indicator 99 and PE LLCIA Survey 2012. The characterization models embedded in these LCIA methodologies convert relevant environmental interventions into category indicators at a point close to the middle or the end of the environmental mechanism defined for a particular impact category. As such, the LCIA methodologies are commonly referred to as midpoint or endpoint approaches. Midpoint approaches look at the result in the short term (e.g., climate change assesses the increase in radiative forcing in carbon dioxide (CO2) equivalent over a period of 100 years) whilst endpoint approaches estimate the eventual result of the environmental impact (e.g., human life lost and species extinct).

A list of impact categories and relevant indicators that could be assessed by individual LCIA methodologies is established during methodology development. For instance, the midpoint approach of ReCiPe covers the following impact categories with specific category indicators:

Climate change, kg CO2 equivalent

Ozone depletion, kg chlorofluorocarbon (CFC)-11 equivalent

Terrestrial acidification, kg sulfur dioxide (SO2) equivalent

Freshwater eutrophication, kg phosphorus (P) equivalent

Marine eutrophication, kg nitrogen (N) equivalent

Human toxicity, kg 1,4-dichlorobutane (C4H8Cl2) equivalent

Photochemical oxidant formation, kg non-methane volatile organic compound (NMVOC)

Particulate matter formation, kg particulate matter (PM10) equivalent

Terrestrial ecotoxicity, kg C4H8Cl2 equivalent

Freshwater ecotoxicity, kg C4H8Cl2 equivalent

Marine ecotoxicity, kg C4H8Cl2 equivalent

Ionizing radiation, kg 235-Uranium (U) equivalent

Agricultural land occupation, square meter years (m2a)

Urban land occupation, m2a

Natural land transformation, m2

Water depletion, m3

Fossil depletion, kg oil equivalent

As one or more impact categories could be assessed in a study, they should be chosen according to their relevance to a particular study. The impacts from the product can be normalized according to the impact categories, to show the impacts with respect to various methodologies.

Impact assessment

Life cycle impact assessment (LCIA) is the step in which the practitioner uses impact categories, category indicators, characterization models, equivalency factors, and weighing values to realize the potential impact of data that are obtained in LCI analysis as shown in Fig. 1.5. In practice, this step is usually carried out with LCA software, and the practitioner only chooses the method and some other details. The impact assessment may include a duplicate review of the purpose and scope of the study of life cycle assessment to determine whether the objectives of the study have been met, or if not, whether the purpose and scope of the application should be corrected.

14.3.3 Life Cycle Impact Assessment

LCIA studies the importance of environmental impacts on the LCI flow results. LCIA provides category indicators and selection of impact categories. LCIA evaluates the product life cycle by the functional unit. There are many impact assessment methods like TRACI, commonly used in the United States; Ecoindicator, ReCiPe, and ILCD, employed in Europe; and CML method [58–61]. CML is a procedure used to estimate the measure of environmental impact that is caused by the product. This method uses various impact categories such as eutrophication, ionization radiation, aquatic ecotoxicity, land use, and human toxicity [58]. In midpoint method, the characterization factors are directly applied to the LCI results. In Ecoindicator 99, three categories are used to evaluate the environmental impact of a product [62]. These three categories are ecosystem quality, depletion of nonrenewable resources, and human health. The total environmental impact score is obtained by quantifying the impact of three categories and then normalized and weighted. There are three different types of perspectives based on the weighting step. They are Individualist, Egalitarian, and Hierarchist. The Individualist neglects the hazard of a near fossil fuels depletion. They only consider the mineral extraction. The outlook of an average scientist can be represented using the Hierarchist perspective, whereas in the Egalitarian perspective, a long time duration into the future is considered and given more importance to the ecosystem quality.

Several indicators are discussed in perovskite LCA studies. Energy payback time (EPBT) and CO2 emission factor are two important sustainable indicators. EPBT gives the time taken by a photovoltaic device to generate equal energy that was used up during its production. Inorganic solar cells like crystalline silicon module have an EPBT of about 3–4 years. EPBT was reduced to 1.1 years using amorphous silicon thin-film solar cells. Another predominant impact indicator is the carbon footprint. It is a measure of greenhouse gas emission during the product’s life cycle [63]. The CO2 emission factor is obtained by dividing the carbon footprint by the electricity generated during the product’s life cycle. For calculating the electricity generated, we need the lifetime of the solar cell. But the exact lifetime of perovskite solar cells is not known as it is in the early stage of development. So there can be fluctuations in the carbon footprint results and primary energy consumption.

2.60.2.3 Impact Assessment

Life cycle impact assessment (LCIA) aims to understand and evaluate environmental impacts based on LCI data. In this phase, the inventory inputs and outputs are assigned to different impact categories (climate change, destruction of the ozone layer, toxicity, acidification, etc.). Only potential environmental impacts can be regarded, as real impacts are influenced by factors that usually are not included in the study. LCIA generally consists of four steps:

Classification. In this first step LCI data are assigned to the considered impact categories. The selection of these impact categories is based on the expected types of impacts.

Characterization. This second step involves the application of weighting factors or equivalence to unify all relevant substances within each impact category (e.g., all contributions to global warming are transformed into kilograms of equivalent CO2). This step provides a way to directly compare the LCI results within each category.

Normalization. The goal of this third step is to establish a common reference to enable comparison of different environmental impacts. To achieve this aim, a reference quantity is used to make the data ‘dimensionless’ (e.g., the value of the considered category for the total activity in the world, country, or region).

Valuation. The final step is the assessment of the relative importance of the potential environmental impacts identified in the previous steps by assigning them weightage. It consists in determining which impact category is the most damaging and in what intensity in relation with the others. The final aim is to obtain a unique result. Valuation is usually a controversial step, being based on subjective considerations.

14.1.4 Life Cycle Impact Assessment

Life cycle impact assessment (LCIA) refers to the steps that assess the type and extent of environmental impacts that may arise quantitatively based on data collected in the LCI. The LCIA procedure primarily consists of: (a) categorizing, (b) classifying, (c) characterizing, (d) normalizing, (e) grouping, and (f) integrating environmental impact (Itsubo et al., 2007). Figure 14.2 shows schematically how these steps are related.

Categorizing impacts determines which technique will be used to assess what kinds of environmental problems (impact categories) such as global warming, ozone layer depletion, and acidification (SETAC, 1996). Classifying impacts is the task of sorting inventory data into their related impact categories and results in several substances being grouped into one impact category. For example, CO2, CH4, and N2O are grouped into global warming, whereas NOx and SOx are grouped into acidification. Characterizing impacts involves assessing the environmental impacts of impact categories. Here, characterization factors that have been created for each environmental problem in the impact category are designated. For example, global warming potential (GWP; IPCC, 1995) is often used as the characterization factor for global warming so that the type of greenhouse gases contributing to global warming and to what extent can be analyzed. Normalizing impacts is a process that normalizes the assessment results obtained by characterizing each impact category in order to make relative comparisons. Grouping impacts typifies the impact categories resulting from characterization and normalization according to certain fixed conditions. Integrating impacts assigns weights to impact categories to achieve a single index weighting. Integration methods are now a subject of research under worldwide discussion. For example, one question is at which stage, e.g. from the emission of environmental burdens to the point where actual harm is done, is the integration performed? A method that directly integrates impact categories is called “midpoint assessment”, whereas “endpoint assessment” is another method that calculates the actual magnitude of harm for items in each impact category, and remakes them into safeguard subjects such as “human health” or “ecosystem conservation” to be integrated later. In this way, although converting a number of approaches and methodologies into a single index weighting has been proposed, the resulting single index is often an economic or dimensionless indicator. Either way, the integration process requires that the different components of the natural environment, such as human health, the ecosystem, or social assets be weighed. The fairness and transparency of judgment criteria must be guaranteed because subjective value judgments are sometimes unavoidable. One must also fully keep in mind that results may change depending on how the environmental planners are tackling the problems, and how they implement the aforementioned integration method.

The LCIA methodology and scientific framework are still in development, and no specific item has been widely adopted. For this reason, among the international standards being implemented currently, (a)–(c) above are mandatory whereas (d)–(f) are optional. In other words, when carrying out an LCIA, one must perform all tasks up to and including characterization. Whether to carry out normalization and integration depends on the final objective because the difficulties of comprehensively judging the importance of different impact categories and formulating a single index are recognized.