Download
1 / 25
260 likes | 574 Views
UNIT 8 Impact Assessment 1.1 Objectives of lesson 8 The aim of this unit is to achieve the following points: understanding the general procedure of impact assessment, having a clear idea about an impact assessment method,
E N D
UNIT 8 • Impact Assessment
1.1 Objectives of lesson 8 • The aim of this unit is to achieve the following points: • understanding the general procedure of impact assessment, • having a clear idea about an impact assessment method, • learning about the framework for toxicity assessment (presential course). • What should be assimilated: • At the end of this lesson, you should be able to answer the following questions: • Why isn't it possible to determine the best scenario just after LCI? • What do you have to define if you want to compare a bicycle with a pair of jeans, for example? • What are the different steps of LCIA? Give a short description of them. • How can you value social Weighting factors?
Interpretation Goal definition Impact assessment Inventory of extractions and emissions 1.2 LCA Steps, where are we ? • We previously have looked at the goal definition, defined our system and its function. The elementary flows crossing the system boundaries have been determined. They enabled to get the emissions and extractions inventories thank to databases. Interpretations had to be performed all along these steps. • Let’s now focus on the third main step of the LCA : the impact assessment. This step is crucial since no assessment meansan implicit assessment ! • An example from the automobile industry - and adressed in lesson 5 - will be detailled to illustrate the theory developped in this lesson. We will compare three kind of front-end panel made of either steel or aluminium or composite material.
Front-end panel 1.3 The front-end panel Function: transport over the whole car life-cycle (200'000 km). Functional unit: 1 component of equivalent stiffness for a given service of 200'000 km. System boundaries: the whole life cycle from extraction of raw materials to recycling.
databases 1.4 Interpreting the raw inventory Studying and interpreting the inventory flows is necessary before performing any impact assessment. It avoids many mistakes! reference flows What can we conclude from this inventory? Can you determine the best scenario? Why? inventory We can't give a definite conclusion from this inventory. A scenario would be the best only if all its emissions were the lowest.
1.5a How to compare pollutants? Regarding the variety of impacts due to the inventory flows of the different scenarios, the comparison is not straightforward. It is like comparing apples and pears. And considering the wide range of pollutants, it can even be seen as putting apples and elephants side by side... By the way, can you compare an apple with an elephant? ? You cannot add an apple and an elephant, but you can actually compare them. To enable a comparison, it is necessary to define criterias. For example, for transport, the comparison has to consider the weight. Thus transporting one elephant is equivalent to transporting about 20'000 apples.
1.5b Safeguard subjects In our front-end panel example, as in any LCA example, answering the question of the best scenario requires to know the impact of each substances on determined areas. Those areas are defined as the safeguard subjects the society is willing to protect. As shown in this diagram, Life Cycle Inventory (LCI) data have to be related to indicators. Those indicators are representative of effects or damages classified in different categories. What would you suggest as safeguard subjects? Basically, there are four basic areas of protection: human health, natural environment, natural resources, man-made environment and life-support systems.
1.6 Life Cycle Inventory Analysis (LCIA)in practice • Impact assessment will allow us to aggregate all the inventory data in order to quantify the environmental load. The SETAC – Society of Environmental Toxicology And Chemistry – recommends to perform this aggregation in three steps : • Classification, organization of emissions in categories that represent given kind of problems . SETAC standards define fifteen areas to protect: Input related categories: abiotic resources; biotic resources; land; erosion. Output related categories: global warming; acidification; noise; depletion ozone layer; eutrophication; odours; human toxicology; ecotoxicology; radiation; photo oxidant formation; casualties. • Characterization, application of specific weighting factors to emissions in order to have a unique unit within each impact category (e.g. kgPb for human toxicity, …), • Normalisation + weighting, application of other weighting factors to theseimpact classes in order to gather them into damage classes or a single score.
2.1a Classification - Definition • During the former steps of LCA, the systems have been properly defined and their boundaries carefully set. This has allowed to get the inventory of the emissions and extractions that cross these boundaries. We are now facing a huge list of data… • How do you react in front of this new challenge ? The Classification step allows to dispatch the pollutants according to the area of protection they affect (ex: CO2, CH4 and N2O influence the Global warming). This step is required to carry on the LCA process.
2.2a Characterisation - Definition • Once the Classification is achieved, the problem is to find a common unit to aggregate the different emissions and perform comparisons. What is required is a category indicator representative of the considered area of protection. For example, a common indicator chosen for Global warming is the equivalent kg of CO2. Quantitative modelling enables to get the weighting factor that links each pollutant to the category indicator. Coming back to the Global warming example: *IPCC: International Panel on Climate Change (International organism)
2.2b Characterisation - Definition Next two slides present the characterisation step for our front-end panel example with ecoindicator99. The categories and their indicators are listed in the table below. Forsupplementary information on Ecoindicator99: http://www.pre.nl/eco-indicator99 DALY or "disability adjusted life years": the total amount of healthy life lost, to all causes, whether from premature mortality orfrom some degree of disability during a period of time. PDF*m2*years or "potentially of disappeared fraction": the percentage of species disappeared in a certain area due to the environmental load. MJsurplus: the energy requirements in mining and concentrating of ores with decreasing material content, based on present known technology.
2.2e Characterisation - Interpretation Which scenario turns out to be the best ? The recycled aluminium front-end panel is the best as it has the lowest scores in all impact categories. It is not possible to determine the worst scenario at this point, as none of them has the highest impacts in all categories. Further assessment is required… Indeed, at that stage, we can not compare the different impact classes with each other since they are not expressed in consistent units. To help to overcome this problem, we will begin with a normalisation step which answers the following question: Does our scenario induce an important effect compared to the overall worldwide effect ?
2.3a Normalisation - Definition • At this point, the idea is to analyse the respective share of each impact in the overall worldwide effect. This comparison between the scenarios’ and the average European impacts enables to evaluate the relative importance of the former. It does not give a damage oriented comparison but a better intuition of the impact of the scenarios. Normalisation enables you to see the relative contribution from the material production to each already existing effect. Next two slides come back to the front-end panel example to illustrate normalisation with Ecoindicator99.
2.3dNormalisation - Interpretation Which scenario turns out to be the best? The recycled aluminium front-end panel is the best as it has the lowest scores in all impact categories. It is not possible to determine the worst scenario at this point. On which impact categories do the scenarios have the greatest effects? For all scenarios, the impact on climate change, and to a lower extent, the impact caused by inorganic substances on respiration, are the most important. Why cannot we determine a worst scenario? What is requested? None of them shows the highest damages in all categories… Further assessment is required… Indeed, at that level, the different impact categories can be compared with each other since they are in the same unit. Nevertheless, no final judgment can be made as effects are not considered to be of equal importance. A further step, the Weighting, is necessary.
2.4a Weighting - Definition • The question we have to ask ourselves now is : « How to value these social weighting factors ? » • Three main assessment methods are currently used to value these factors : • Monetary methods (willingness to pay): here, the impacts are transformed into costs, the central point is how much money we are ready to pay to avoid an impact. One year of life lost is estimated to 300’000 € (dixit european insurance companies). • Consensual methods involving expert panels or stakeholders, who gather to determine the relative importance of the different safeguard subjects. Global warming is currently considered as a hotter topic than eutrophication. • Distance to target methods: the normalisation results are compared with political objectives. In Southern countries, Human Health has a higher priority than Ecosystem Quality. Next slides show the situation of Weighting in the LCA process and its application to our front-end panel example.
2.4d Weighting - Definition Ecoindicator 99 performs an evaluation based on a consensual method. Which scenario turns out to be the best ? (running gag…) Previous slide confirms that recycled aluminium turns out to be the best scenario. Moreover, we can now establish a ranking between our studied scenarios. The steel front-end panel is the worst, SMC and aluminium are more environmentally friendly, recycled aluminium is the best.
3. Questions of understanding • Why isn't it possible to determine the best scenario just after LCI? • What do you have to define if you want to compare a bicycle with a pair of jeans, for example? • What are the different steps of LCIA? Give a short description of them. • How can you value social Weighting factors?
