From "Life Cycle Assesment - Theory and Practice" (H2018) Flashcards
LCA characteristics can be grouped into four headlines. Which?
(1) takes a life cycle perspective,
(2) covers a broad range of environmental issues, (3) is quantitative,
(4) is based on science.
Why are LCA considering multiple environmental issues?
To avoid burden-shifting between impacts.
Describe the strengths of LCA
The LCA is comprehensive in terms of its life cycle perspective and coverage of environmental issues. It allows comparison of environmental impacts of product systems that are made up of hundreds of processes, accounting for thousands of resource uses and emissions that are taking place in different places at different times.
What are the limitations about an LCA being comprehensive?
The modelling of the product systems requires simplifications and generalisations and this result in the LCA calculating potential (not acutal) environmental impacts.
What can an LCA conducted on two product systems tell you and what can it not tell you?
It can tell which product system is better for the environment.
It cannot tell if “better” is good enough. It is wrong to conclude that a product is environmentally sustainable in absolute terms.
In 1997 the first version of ISO 14040 standard was published. What was the attempt by this publishing?
Harmonize the framework and principles of LCA and to increase transparency and comparability of LCA studies.
From an government perspective, what can the application of LCA support?
Policy formulation, policy implementation and regulation imposed by policies, and can be used to perform evaluation of policies.
The application of LCA in enterprises can be classified into five main purposes. Which?
(i) decision support in product and process development.
(ii) marketing purposes (e.g. Eco-labelling).
(iii) development and selection of indicators used in monitoring of environmental performance of products or plants.
(iv) selection of suppliers or subcontractors.
(v) strategic planning.
What is LCA often used for at the product level?
Product development and for identifying environmental hotspots of a product or process either within the organization or in its supply chain.
How are consumers exposed to LCA results?
Through ecolabels or other consumer information from producers.
Through the media reporting academic findings.
The LCA framework operates with four separate phases. Which?
1) Goal and scope definition
2) Inventory analysis
3) Impact assessment
4) Interpretation
Which questions should be answered in the goal definition?
Why is this study performed?
Which question(s) is it intended to answer and for whom is it performed?
The goal definition sets the context of the LCA study and is the basis of the scope definition where the assessment is framed and outlined in accordance with the goal definition
What should be included in the scope definition?
- Defining the functional unit and reference flow
- Scoping the product system, deciding which activities and processes belong to the life cycle of the product that is studied.
- Selecting the assessment parameters, i.e. the impacts that shall be assessed in the study.
- Selecting the geographical and temporal boundaries and settings of the study and the level of technology that is relevant for the processes in the product system.
- Deciding the relevant perspective to apply in the study: should it be a consequential study assessing the impacts that can be expected as a consequence of choosing one alternative over another, or should it be an attributional study assessing the impacts that are associated with the studied activity?
- Identifying the need to perform critical review, in particular if the study is a comparative assertion intended to be disclosed to the public.
What is done in an inventory analysis?
It collects information about the physical flows for the product system.
The physical flows are:
Input of resources, materials, semi-products and products and the output of emissions, waste and valuable products
What is the outcome of the inventory analysis?
The life cycle inventory, a list of quantified physical elementary flows for the product system that is associated with the provision of the service or function described by the functional unit.
What is done in life cycle impact assessment (LCIA)?
The impact assessment translates the physical flows and interventions of the product system into impacts on the environment using knowledge and models from environmental science.
Which 5 elements does the impact assessment consists of? Give a short explantion for all 5 elements.
1) Selection of impact categories representative of the assessment parameters that were chosen as part of the scope definition.
2) Classification of elementary flows from the inventory by assigning them to impact categories.
3) Characterisation using environmental models for the impact category to quantify the ability of each of the assigned elementary flows to impact the indicator of the category.
4) Normalisation is used to inform about the relative magnitude of each of the characterised scores for the different impact categories by expressing them relative to a common set of reference impacts—one reference impact per impact category.
5) Grouping or weighting supports comparison across the impact categories by grouping and possibly ranking them according to their perceived severity, or by weighting them using weighting factors that for each impact category gives a quantitative expression of how severe it is relative to the other impact categories.
What does the interpretation consider?
The interpretation considers both results of the inventory analysis and the impact assessment elements characterisation and, possibly, normalisation and weighting. The interpretation must be done with the goal and scope definition in mind.
What is a sensitivity analysis and uncertainty analysis used for in the interpretation phase?
To guide the development of conclusions from the results, to appraise the robustness of the conclusions, and to identify the focus points for further work in order to further strengthen the conclusions.
Mention the six aspects of goal definition
- Intended applications of the results,
- Limitations due to methodological choices
- Decision context and reasons for carrying out the study,
- Target audience
- Comparative studies to be disclosed to the public
- Commissioner of the study and other influential actors.
All LCAs involve studying one or more product systems and this can be used in several applications. Mention some of these applications.
- Comparing environmental impacts of specific goods or services.
- Identifying the parts of a product system that contribute most to its environmental impact (i.e. “hot spot identification”, focusing in product development).
- Evaluating improvement potentials from changes in product designs (analysis and ‘what-if’ scenarios in eco-design).
- Documenting the environmental performance of products (e.g. in marketing using environmental product declarations or other types of product environmental footprints).
- Developing criteria for an eco-label.
- Developing policies that consider environmental aspects.
Mention the three different types of decision contexts:
Situation A (Micro-level decision support) Situation B (Meso/macro-level decision support) Situation C (Accounting)
Explain decision context: Situation A
The study results are intended used to support a decision, but the small scale of the studied product system means that regardless the decision made, it will not cause structural changes in the systems that the studied product system interacts with.
Explain decision context: Situation B
The study results are intended used to support a decision, and the scale of the studied product system is such that the decisions that are made are expected to cause structural changes in one or more processes of the systems that the studied product system interacts with.
Give examples on studies that use the decision context of situation A
Studies that intend to compare individual product systems, identify hotspots within these or document the environmental performance of a product in the form of an environmental product declaration fall into this decision context.
Give examples on studies using the decision context of situation B
A study intended as decision support for policy development on potential nationwide substitution of diesel derived from oil with biodiesel for private cars. Such a decision will lead to structural changes in the biodiesel industry in the form of new equipment being installed to respond to the substantially increased demand for biofuels.
The LCIA transforms an elementary flow from the inventory into its potential impacts on the environment. Why isn’t it possible to just compare the different elementary flows to each other in terms of the importance of their impact? Explain it by using CO2 and methane contribution to climate change.
The characterisation factor of methane and CO2 isn’t the same.
1 kg of methane emitted into air does not have the same impact on climate change as 1 kg of CO2, even though their emitted quantities are the same (1 kg) since methane is a much stronger greenhouse gas (GHG).
Are the calculated impacts in the LCIA actual impacts or potential impacts?
Explain your reasoning.
Potential impacts
Because:
• Relative expressions of potential impacts associated with the life cycle of a reference flow needed to support a unit of function (=functional unit)
• Based on inventory data that are integrated over space and time, and thus often occurring at different locations and over different time horizons.
• Based on impact assessment data which lack information about the specific conditions of the exposed environment (e.g. the concomitant exposure to substances from other product systems).
What is a category indicator?
A quantifiable representation of an impact category
What is a characterization model?
The model reflect the environmental mechanism by describing the relationship between the LCI results, category indicators and, in some cases, category endpoint(s). The characterisation model is used to derive the characterisation factors (could be the characterization factor of methane that makes us able to estimate the contribution of a elementary flows methane emission to the impact category of global warming)
What is a characterisation factor?
Factor derived from a characterisation model which is applied to convert an assigned life cycle inventory analysis result to the common unit of the category indicator.
What is a elementary flow?
Material or energy entering the system being studied that has been drawn from the environment without previous human transformation, or material or energy leaving the system being studied that is released into the environment without subsequent human transformation. The elementary flow can be emission to air water or soil and extraction of resources.
What is an environmental impact?
Potential impact on the natural environment, human health or the depletion of natural resources, caused by the interventions between the technosphere and the ecosphere as covered by LCA (e.g. emissions, resource extraction, land use).
What is an environmental mechanism?
System of physical, chemical and biological processes for a given impact category, linking the life cycle inventory analysis results to category indicators and to category endpoints.
What is an impact category?
Class representing environmental issues of concern to which life cycle inventory analysis results may be assigned.
What is an impact pathway?
Cause–effect chain of an environmental mechanism.
What is an midpoint indicator?
Impact category indicator located somewhere along the impact pathway between emission and category endpoint.
What is an LCIA method?
Collection of individual characterisation models (each addressing their separate impact category). Fx ReCiPe.
The methods have to meet the requirements of ISO 14044.
When choosing an LCIA method several questions should be addressed in terms of choosing the right method. Mention some of these questions.
- Which impact categories (or environmental problems) do I need to cover and can I justify those that I am excluding?
- In which region does my life cycle (or its most contributing processes) take place?
- Do I need midpoint or endpoint assessment, or both?
- Which elementary flows do I need to characterise?
- Are there any recommendations from relevant organisations that can help me choose?
- How easily can the units of the impact categories be interpreted (e.g. absolute units, equivalents, monetary terms, etc.)?
- How well is the method documented?
- How easily can the results (units, aggregation into specific indicator groups, etc.) be communicated?
- Do I need to apply normalisation and if yes for which reference system (in most cases it is not recommendable to mix characterisation and normalisation factors from different LCIA methods due to the difference in characterisation modelling, units, numerical values, etc..)?
- When was the method published and have there been important scientific advances in the meantime?
- Do I have the resources/data availability to apply a regionalised methodology (providing more precise results)?
- Do I need to quantify the uncertainty of both LCI and LCIA and does the LCIA method support that?
Does ISO 14040/14044 provide any recommendations about which LCIA method to choose?
No
How is a characterisation factor calculated?
It is calculated using (scientifically valid and quantitative) characterisation models of the environmental mechanism representing as realistically as possible the cause–effect chain of events leading to effects (impacts) on the environment for all elementary flows which contribute to this impact.
In general there are two types of elementary flows. Which?
An emission into the environment (=elementary flow from the technosphere to the ecosphere). This leads to emission-related impacts
A resource extraction from the environment (=elementary flow from the ecosphere to the technosphere). This leads to extraction-related impacts.
For the emission-related impacts there are 5 main steps. Together these steps constitute the environmental mechanism of the specific impact category. Mention the 5 steps
Emission, Fate, Exposure, Effects and Damage.
For the extraction-related impacts there are 5 main steps. Together these steps constitute the environmental mechanism of the specific impact category. Mention the 5 steps
Extraction or use, Fate, Exposure, Effects and Damage.
Which kinds of indicators is found along the cause-effect chain
Midpoint impact indicators and endpoint impact indicators
What is characteristic for the indicators placed early in the cause-effect chain (midpoint indicators) regarding environmental relevance?
They are giving a more measurable result but with less environmental relevance because they are more remote from the concerns directly observable in the environment (damage to human health and ecosystems and resource availability)
What is characteristic for the indicators placed further downstream early in the cause-effect chain (endpoint indicators) regarding environmental relevance?
Relative higher environmental relevance compared to the midpoint indicators but the uncertainty on emissions is higher.
Which factor is used when going from midpoint to endpoint?
midpoint-to-endpoint characterisation factor also called severity or damage characterisation factors.
What are the main topic for the three types of endpoint indicators that are typically used? and what are the three types of endpoint indicators?
Areas of protection
- Human health
- Ecosystem quality or natural environment
- Natural resources and ecosystem services
Give examples on global, regional and local impacts
Global: Global warming and stratospheric ozone depletion
Regional: acidification, eutrophication, toxicity
Local: water use, land use
Is it alright to neglect an impact category in the LCIA due to uncertainty of the elementary flows contributing to the specific impact category?
It is not allowed to neglect any impact categories in the LCIA. But in the interpretation the focus can be on specific impact categories.
How can uncertainty be reduced in the LCIA?
Uncertainty in LCIA can only be reduced by improved data or model quality, essentially coming from updated LCIA methods.
What does it mean that we in the LCIA assume linearity?
Linear relationship is assumed between the increase in an elementary flow and the consequent increase in its potential environmental impact. In other words, e.g. doubling the amount of an elementary flow doubles its potential impact.
What does it mean that the LCIA assumes steady-state?
Most LCIA models are not dynamic but represent the environment as a system in steady state, meaning that all parameters which define its behaviour are not changing over time.
What does it mean that parsimony is assumed in the LCIA?
This refers to the basic modelling principle of “as simple as possible and as complex as necessary”, an ideal balance that applies to LCIA characterization models as well as to the entire LCA approach.
What can normalisation be useful for?
- Providing an impression of the relative magnitudes of the environmental impact potentials
- Presenting the results in a form suitable for a subsequent weighting
- Controlling consistency and reliability
- Communicating results
For external normalisation, where do the normalisation factors come from?
From the used LCIA method (eg. ReCiPe)
Can normalisation factors from a specific LCIA method be combined/mixed with characterisation factors from other LCIA methods?
No. The normalisation factors should be calculated using the same characterisation factors for the reference inventory as used for the inventory of the product system.
Which unit does normalisation factors have?
A unit expressing an impact per person and year, also referred to as person equivalent (PE)
What does external normalisation helps to identify?
It helps to identify the impacts from the product system that are large compared to the chosen reference system, but large is not necessary the same as important.
The size of the normalized results cannot be compared between impact categories but only within a impact category (in case of several product systems) or to a reference system.
Why can the interpretation of normalised impacts as contributions to or fractions of the reference system be misleading?
Because the environmental interventions of the product system takes place in different regions that maybe aren’t included in the reference system.
To get around this issue the reference system should be global.
Can normalisation scores both be used for midpoint and endpoints? If yes, are the normalisation factors the same?
Yes normalisation can be done on both mid- and endpoints.
No the normalisation factors are not the same for mid- and endpoints.
Are the weighting based on scienific or objective basis or on subjective choices?
Subjective choices
What can weighting be useful for?
- Aggregating impact scores into several or one single indicator
- Comparing across impact categories
- Communicating results applying an underlying prioritisation of ethical values
Which different principles can be applied to derive weighting factors?
- Social assessment of the damages (expressed in financial terms like willingness to pay), e.g. impact on human health based on the cost that society is prepared to pay for healthcare
- Prevention costs (to prevent or remedy the impact through technical means), e.g. the higher the costs, the higher the weighting of the impact
- Energy consumption (to prevent or remedy the impact through technical means), e.g. the higher the energy consumption, the higher the weighting of the impact
How is footprint different from LCA?
It focuses on one impact category / environmental issue.
Footprints are not suitable to support decisions regarding environmental sustainability (meaning that no product labels, ecodesign or policy-support can be based on a footprint).
Footprints are life cycle-based, narrow-scoped, environmental metrics focusing on an area of concern.
What are the 7 steps in the cause-effect chain of climate change?
- GHG emissions
- Transport, transformation and distribution of GHG in the atmosphere
- Disturbance of the radiation balance—radiative forcing (primary effect, midpoint)
- Increase in global temperatures of atmosphere and surface
- Increase in sea level due to heat expansion and the melting of land-based ice
- Increased water vapour content of the atmosphere causing more extreme weather
- Negative effects on the ecosystems and human health (endpoint)
Which characterisation factor is commonly used for the climate change impact category?
GWP100-year (global warming potential).
It is the ratio of the cumulated radiative forcing over 100 years of a given GHG and that of CO2, with the unit of kg CO2-eq/kg GHG.
What is the GWP100 for CO2 and methane, respectively?
1 kg CO2eq/kg CO2 and 28 kg CO2eq/kg methane
Is the GWP for methane lower or higher, when integration over 20 years instead of 100 years?
Higher. It is 84 kg CO2eq/kg methane.
The difference in GWP20 and GWP100 for methane is due to the fact that methane has a relatively short atmospheric lifetime of 12 years compared to CO2’s lifetime which is at least one order of magnitude higher, which means that methane’s GWP gets lower the longer the time horizon over which it is integrated.
Which mispoint indicator is used in all LCIA method to calculate the characterisation factor for the stratospheric ozone depletion impact category?
Ozone Depletion Potential (ODP).
And ozone depleting substances is expressed in CFC-11 equivalents.
All endpoint LCIA methods characterise one of the three endpoint impact categories. Which one?
Damage to human health
Which capacity of a system can be reduced in the acidification impact category?
The system’s acid neutralising capacity (ANC), i.e. a reduction in the quantity of substances in the system which are able to neutralise hydrogen ions added to the system.
What are the most important acidifying man-made compounds?
Sulphur oxides, nitrogen oxides, ammonia, strong acids.
Is acidification global, regional or local?
Because of their high water solubility, the atmospheric residence time of acidifying substances is limited to a few days, and therefore acidification is a regional effect with its extent limited to the region around the point of emission.
The acidification potential depends on two main factors. Which?
1) Potency of the emitted gas
2) Sensitivity of the receiving environment
Explain the 7 main steps of the cause-effect chain of eutrophication
- Emission of N or P containing substances
- Growth and blooming of algae and higher plants increases
- Sunlight no longer reaches lower water layers, which creates a temperature gradient with increasing depth
- This supports a stable stratification of water layers reducing the transport of fresh oxygen-rich surface water to deeper layers.
- Oxygen is steadily depleted in bottom layers, which leads to suffocation of bottom-dwelling species and fish
- This is additionally accelerated by the oxygen consuming decomposition of the dead species and sedimented dead algae
- The aquatic medium becomes hypoxic and finally anoxic, favouring the formation of reducing compounds and noxious gases (mercaptans, methane)
Which nutrients enrichment equivalents is used in the eutrophication impact category?
kg N-equivalents and kg P-equivalents
Often an aggregation of N and P potentials are made, which requires an assumption concerning the magnitude of the N/P ratio between these two elements in living organisms. The often used ratio is 16.
One mole of phosphorus (in an area where the availability of phosphorus limits growth) therefore contributes as much to eutrophication as 16 mol of nitrogen (in an area where the availability of nitrogen limits growth). The aggregate nutrient enrichment potential for nitrogenous substances is then calculated as the emission’s N potential multiplied by the gram/mol molecular weight of the reference substance (e.g. NO3- of 62 g/mol). The P potential for phosphorous-containing substances is multiplied by 16 times the gram/mol molecular weight of the reference substance.
What does the photochemical ozone formation impact category address?
Address the impacts from ozone and other reactive oxygen compounds formed as secondary contaminants in the troposphere by the oxidation of the primary contaminants volatile organic compounds (VOC).
Mention the 5 driving factors for the impact of ecotoxicity
(1) emitted quantity (determined in the LCI),
(2) mobility,
(3) persistence,
(4) exposure patterns and bioavailability and
(5) toxicity, with the latter four considered by the characterisation factor.
The environmental mechanism of ecotoxicity can be devided in four (modelling) steps. Which?
- The fate model (estimates the increase in concentration in a given environmental medium due to an emission quantified in the life cycle inventory)
- The exposure model (quantifies the chemical’s bioavailability in the different media by determining the bioavailable fraction out of the total concentration)
- The effect model (relates the amount available to an effect on the ecosystem.)
- The severity/damge model (translates the effects on the ecosystem into an ecosystem population (i.e. biodiversity) change integrated over time and space.)
What is the name of the widely used global scientific consensus model for characterisation modelling of human and ecotoxic impacts in LCA?
USEtox
Which 5 driving factors are human toxicity based on in LCA?
(1) emitted quantity (determined in the LCI),
(2) mobility,
(3) persistence,
(4) exposure patterns
(5) human toxicity, with the latter four considered by the characterisation factor.
The characterisation model of human health is expressed by 4 factors. Which ones?
fate, exposure, effects and severity
In the impact category of particulate matter formation, the exposure to particulate matter (PM) is considered. PM can be distinguished by the use of two parameters. Which ones?
Formation type (primary and secondary) and aerodynamic diameter (respirable, coarse, fine and ultrafine).
What does primary PM refer to?
Particles that are directly emitted, e.g. from road transport, power plants or farming activities.
What does secondary PM refer to?
Organic and inorganic particles formed through reactions of precursor substances including nitrogen oxides (NOx), sulphur oxides (SOx), ammonia (NH3), semivolatile and volatile organic compounds (VOC).
The characterisation model for particulate matter formation is expressed by four factors. Which ones?
Fate factor
Exposure factor
Effect factor
Severity factor
Why doesn’t the land use impact category assess the emission of nutrients, pesticides etc. to the ecosphere?
This would lead to double counting of the same impact category. Nutrients and pesticides are coupled to the emission-based categories as eutrophication and ecotoxicology.
The same type of human activity may cause different land-use related impacts depending on the region of the world where the activity takes place. This variation is due to the strong influence of climate, soil quality, topography and ecological quality on the magnitude of the impact.
Would deforestation has the greatest impact in Brazil or Denmark in terms of number of species affected?
In Brazil, because the species diversity is a lot higher in Brazil compared to DK.
Is the land use impact category considered global, regional or local?
Local.
As a consequence, methods that focus on land-use
impacts should include geospatial data both in the LCI and the LCIA phases. The inventory must contain information on the geographic location of the human intervention, with a level of detail that may vary from the exact coordinates to coarser scales (e.g. biome, country, continent).
In the water use impact category one distinguishes between different types of water use. Which ones?
o Water withdrawal: “anthropogenic removal of water from any water body or from any drainage basin either permanently or temporarily” (ISO 2014)
o Consumptive use/water consumption: water use where water is evaporated, integrated in a product or released in a different location then the source
o Degradative use/water degradation: Water that is withdrawn and released in the same location, but with a degraded quality. This includes all forms of pollution: organic, inorganic, thermal, etc. (ISO 2014)
Within the abiotic resource use, resources are classified into three different categories. Which ones?
