Restrictions as to the interpretation of the results and the equivalence of the compared activities are to be carefully observed when doing so. However, it is argued that in this specific case the risk of being misleading is low: other than when comparing other types of products that differ in the qualitative aspects of their functional units, in this case it is obvious that they differ regarding the technical function they perform. It is argued to be fully within the judgement of the consumer to decide whether he or she considers one hour watching some entertainment program on TV is equivalent (in the view of the consumer!) as is one hour reading a book or one hour playing chess. The related issue of positioning principles has already been addressed. It is acknowledged also that further work on a more comprehensive guidance would be beneficial in this field of non-technical functions and related studies


It is acknowledged also that further work on a more comprehensive guidance would be beneficial in this field of non-technical functions and related studies. 6.4.7 Comparisons of systems and the functional unit (Refers to aspect of ISO 14044:2006 chapter 4.2.3.2) Special provisions on the functional unit apply to comparisons and especially comparative assertions disclosed to the public; details see chapter 6.10.3. In the case of only partial equivalence, mechanisms exist to render them comparable in many cases. The details depend on the applicable LCI modelling principle and approaches that are still to be identified; details on rendering systems comparable are addressed in chapter 7.9.3 for attributional modelling and chapter 7.2.4.6 for consequential modelling; the simplified provisions for Situation A, B and C are found in chapter 6.5.4.

European Commission – JRC, ILCD Handbook: General Guide for LCA (2010)


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how Provisions: 6.4 Function, functional unit, and reference flow Note that for further processes that were identified as part of the life cycle model beyond the central process(es) that can be identified in the initial scope phase, these provisions will be applied only in the later iterations and in the LCI phase. I) SHALL - Identify system or process: Identify in line with the goal and with the other scope settings the to-be-analysed system(s) or process(es)40 (e.g. good, service, technology, strategy, country, etc.) and describe it/them in an unambiguous way (6.4.1). II) MAY - Photos, specifications: Provide photos, and/or technical specifications, and/or descriptions of the system(s), if and as appropriate for the addressees (6.4.1)


II) MAY - Photos, specifications: Provide photos, and/or technical specifications, and/or descriptions of the system(s), if and as appropriate for the addressees (6.4.1). [ISO+] III) SHALL - Identify function(s) and functional unit(s): One or more function(s) and quantiative, measurable functional unit(s) of each of the system(s) shall be clearly identified, if applicable and appropriate for the type of system (for exceptions see the following provisions on subchapter 6.4.6) (6.4.2). IV) SHALL - Functional unit, details: The functional unit(s) shall be identified and specified in detail across all the following aspects (6.4.2, 6.4.3): IV.a) Function provided (what), IV.b) in which quantity (how much), Note that, even though the "how long" information is important, the use intensity and resulting overall quantity of the performed function is key to valid comparisons. IV.c) for what duration (how long), and IV.d) to what quality (in what way and how well is the function provided)


IV.c) for what duration (how long), and IV.d) to what quality (in what way and how well is the function provided). IV.e) Changes in the functional performance over time (e.g. due to ageing of the product) shall be explicitly considered and quantified, as far as possible. [ISO+] V) MAY - Obligatory and positioning properties: If product systems are analysed, it is recommended to use obligatory and positioning properties for the quantitative and qualitative aspects of their function, respectively (6.4.4). [ISO+] VI) SHALL - Measurement methods: ISO or national harmonised standards shall be used as measurement methods, as far as possible and wherever available and appropriate for use in an LCA context. Own measurement methods should only be used in case of unavailable or inappropriate harmonised standards only. They shall be clearly specified and documented and later be subject to critical review (6.4.5)


They shall be clearly specified and documented and later be subject to critical review (6.4.5). VII) SHOULD - Alternatives and complements to the functional unit: It is noted that a functional unit cannot always be given or is not appropriate / useful. In such cases, it should be replaced or complemented by another clearly defined, quantitative and measurable item as outlined below; deviations shall be concisely justified (6.4.6): [ISO!] VII.a) Materials and other application unspecific products: A functional unit cannot generally be given. Only the reference flow that includes the main technical specification of the product should be provided. In this case, the reference flow is 40 Plural in case of comparisons.


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how Provisions: 6.4 Function, functional unit, and reference flow also the declared unit, but not the functional unit. VII.b) Multifunctional processes: For each function one functional unit and/or reference flow should be given, as appropriate, depending on the kind of cofunction / co-product (see other items in this sub-list). Otherwise the technical specification of the process and functions should be provided in the accompanying documentation. VII.c) Monofunctional systems: For systems (e.g. products) with only one relevant function or combination of functions, the functional unit(s) should be specified. In addition, one reference flow with a clear and detailed system name should be provided. The functionally relevant technical specification should be provided as part of the reference flow name and/or in the accompanying documentation


The functionally relevant technical specification should be provided as part of the reference flow name and/or in the accompanying documentation. VII.d) Multifunctional systems: For multifunctional systems with multiple, parallel functions, the detailed technical specification should be provided. The corresponding functional units should be given in addition and when appropriate to the given case. One reference flow with a clear and detailed system name should be provided. (This one reference flow can be split up into each one reference flow for each function in case the data set is directly used in comparative studies. This to allow substitution of single functions to achieve equivalence of compared alternatives.) VII.e) Systems with alternative functions: For systems with alternative functions, the most relevant alternative functions and functional units should be specified. In addition, one reference flow with a clear and detailed system name shall be provided


In addition, one reference flow with a clear and detailed system name shall be provided. The functionally relevant technical specification should be provided as part of the reference flow name and/or in the accompanying documentation. VIII) SHOULD - Highly variable functions: For highly variable functions of processes and systems, the way that the variable and parameters relate to the system's performance and to its inventory should be documented. This should be in form of mathematical relations or in another suitable form. The use of parameterised data sets is recommended to support appropriate documentation and efficient use. IX) SHALL - Comparative studies: For comparative studies, see the additional special provisions in chapter 6.10.3 (6.4.7). Among others, they shall be compared based on their reference flow. Detailed recommendations on the use of flow properties and units for product and waste flows are given in the separate document 'Nomenclature and other conventions'.


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how 6.5 Life Cycle Inventory (LCI) modelling framework (No directly corresponding ISO 14044:2006 chapter41; subchapters relate to aspects of several ISO 14044:2006 chapters) 6.5.1 Introduction and overview (No corresponding ISO 14044:2006 chapter) Introduction Early in the scope definition an important decision must be made on the life cycle inventory modelling principles and method approaches that are to be applied in the modelling of the system: attributional or consequential modelling and allocation or system expansion / substitution approaches. This has implications for many of the later choices including on which inventory data are to be collected or obtained. This decision is to be made in accordance with the goal of the LCI/LCA study


This has implications for many of the later choices including on which inventory data are to be collected or obtained. This decision is to be made in accordance with the goal of the LCI/LCA study. Especially does it depend on the decision-context of the LCI/LCA study as well as a number of other criteria such as reproducibility and robustness, practical feasibility, stakeholder acceptance, and others. The choice of the LCI modelling framework and approaches is hence not an independent one but is to be derived individually for each study along the study's goal. Frequent errors: Subjective or unsystematic choice of LCI modelling principles and method approaches It is a frequent and severe error in LCA practice to “always perform attributional (or consequential) LCA” and to “always allocate” (or “do substitution”). Equally is it incorrect to unsystematically combine attributional and consequential modelling in the same system model on an ad hoc basis, e.g


Equally is it incorrect to unsystematically combine attributional and consequential modelling in the same system model on an ad hoc basis, e.g. allocating among the co-products of one multifunctional process and substituting the co-products of another. Instead a systematic approach needs to be followed; chapter 6.5.4 gives guidance on this. Overview After an introduction to the two main LCI modelling principles (attributional and consequential) and the related main LCI method approaches (allocation and system expansion / substitution), the LCI methodological provisions are detailed for the three earlier identified archetypal goal situations A, B, C into which the LCI/LCA study belongs. Guidance on how to in practice identify processes for attributional or for consequentially modelling is given in chapters 7.2.3 and 7.2.4


Guidance on how to in practice identify processes for attributional or for consequentially modelling is given in chapters 7.2.3 and 7.2.4. How to solve the specific multifunctionality of recycling / end-of-life treatment is explained in detail in the annexes 14.4 (attributional modelling) and 14.5 (consequential modelling). The simplified provisions for Situation A, B, and C are found in chapter 6.5.4. 6.5.2 The two main LCI modelling principles (No corresponding ISO 14044:2006 chapter) Two main LCI modelling principles are in use in LCA practice: attributional and consequential modelling, with the former being more widely used for historical and practical 41 While the issue of allocation/multifunctionality is well covered in ISO 14044, the initial and more fundamental issue of determining the appropriate LCI modelling framework is not addressed in any detail in ISO 14044 and hence has no corresponding chapter there.


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how reasons. They represent from their logic the two fundamentally different situations of modelling the analysed system (e.g. a product):  The attributional life cycle model depicts its actual or forecasted specific or average supply-chain plus its use and end-of-life value chain. The existing or forecasted system is embedded into a static technosphere.  The consequential life cycle model depicts the generic42 supply-chain as it is theoretically expected in consequence of the analysed decision. The system interacts with the markets and those changes are depicted that an additional demand for the analysed system is expected to have in a dynamic technosphere43 that is reacting to this additional demand


The following boxes explain and illustrate these two principles in a bit more detail: Terms and concepts: Attributional modelling The attributional life cycle inventory modelling principle is also referred to as "accounting”, “book-keeping”, “retrospective”, or “descriptive” (or sometimes and potentially confusing: “average” or “non-marginal”). It depicts the potential environmental impacts that can be attributed to a system (e.g. a product) over its life cycle, i.e. upstream along the supply-chain and downstream following the system's use and end-of-life value chain. Attributional modelling makes use of historical, fact-based, measureable data of known (or at least knowable) uncertainty, and includes all the processes that are identified to relevantly contribute to the system being studied. In attributional modelling the system is hence modelled as it is or was (or is forecasted to be)


In attributional modelling the system is hence modelled as it is or was (or is forecasted to be). This also applies to its background processes: As background data, producer-specific LCI data is ideally used where specific producers provide a background good or service (e.g. a single tier-two supplier is producing the required bricks for a large office building). Average or generic data is typically used where the goods and services stem from a wide mix of producers or technologies (e.g. for electricity consumed by a consumer product in Austria the Austrian consumption mix of electricity with the actual quantitative share of power plants using hydro-power, natural gas, hard coal, fuel-oil, nuclear power, biomass, etc. would be used, including the specific electricity imports and exports to/from the Austrian market)


would be used, including the specific electricity imports and exports to/from the Austrian market). The change from specific to average or generic data is only done for practicality reasons and is a simplification that is justified from the averaging effect that typically occurs several steps up and down the supply-chain and value chain. More details on how to model a system with the attributional modelling principle are given in chapters 7.2 and 7.8. Terms and concepts: Consequential modelling The consequential life cycle inventory modelling principle is also called “change-oriented”, "effect-oriented", "decision-based", “market-based” and (older and incompletely / misleadingly capturing the issue: “marginal” or “prospective”). It aims at identifying the consequences that a decision in the foreground system has for other processes and systems 42 These "generic" and "specific / average" supply-chains are not to be confused with generic and specific / average LCI data


43 Additionally also the interactions with the political system and society may be included by modelling possible public and private policy and behaviour consequences.


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how of the economy, both in the analysed system's background system and on other systems. It models the analysed system around these consequences. The consequential life cycle model is hence not reflecting the actual (or forecasted) specific or average supply-chain, but a hypothetic generic supply-chain is modelled that is prognostizised along marketmechanisms, and potentially including political interactions and consumer behaviour changes. To better reflect market constraints and supplier-related explicit decisions, some researchers constrain the market-mechanism models by explicitly considering existing supply-contracts and planned future suppliers. Other constraints in use are existing or expected policy measures such as e.g. green taxes / incentives and material bans


Other constraints in use are existing or expected policy measures such as e.g. green taxes / incentives and material bans. A key step in consequential modelling is the identification of the marginal processes, i.e. the generic supply-chain, starting from the decision and building the process chain life cycle model around it (details see chapter 7.2.4). Some experts identify each one single marginal process, others identify a combination of several of the most likely marginal processes to have a more robust estimate. A wide range of mechanisms is discussed among LCA practitioners, how a decision affects other processes and products, and which type of consequences follow: These mechanisms range from causing the need to build new production plants for additionally required materials, parts, etc. (or taking plants out of operation), to market displacement of competing products, consumer behaviour changes, and the like


(or taking plants out of operation), to market displacement of competing products, consumer behaviour changes, and the like. Secondary consequences may counteract the primary consequences (then called 'rebound effects') or further enhance the preceding consequence. Regarding modelling the main market consequences, components of general (and in some cases partial) equilibrium models are employed. Central in modelling market consequences is a quantitative understanding of the markets and how direct and indirect changes in supply and demand of the analysed good or service act in the markets to cause specific changes in demand and supply of other goods and services. More details on how to model a system with the consequential method principle are given in chapter 7.2.4 and 7.8. Closely related to the choice of the appropriate LCI modelling framework is the choice of how to solve multifunctionality of processes and products (grouped under the common heading “allocation” in ISO 14044:2006)


This issue is therefore explained and illustrated before detailing the provisions on the LCI modelling framework and how to deal with multifunctionality for the three distinct archetypal goal situations A, B, and C: 6.5.3 LCI method approaches for solving multifunctionality (Refers to ISO 14040 chapter 4.2.3.1) 6.5.3.1 Introduction Multifunctional processes If a process provides more than one function, i.e. delivering several goods and/or services (often also named simplified "co-products"), it is “multifunctional” (see Figure 6). A classical example is the electrolysis of sodium chloride solution, providing the coproduced goods sodium hydroxide solution, chlorine gas, and hydrogen gas. The cotreatment of different wastes in a waste incinerator is another example; in that case the process provides several co-services of treating distinct wastes.


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how In most LCI/LCA studies of simple goods and services, one is interested in the specific life cycle inventory of only one44 of the co-functions (e.g. only of the sodium hydroxide solution OR the chlorine gas, of the above example). To achieve this, only the appropriate inputs and outputs of the process (i.e. consumed materials, energy carriers and parts, resource flows, emissions, wastes, etc.) are to be counted for the analysed function. I.e. the inventory of the specific function is to be isolated. Figure 6 Multifunctional process with several input products and resources consumed and various wastes and emissions generated as well as providing the two co-products 1 and 2. Multifunctional processes with multiple sets of co-functions In rare cases, a multi-functional process may have more than one set of co-functions


Multifunctional processes with multiple sets of co-functions In rare cases, a multi-functional process may have more than one set of co-functions. An example is the incineration of different wastes that result in the production of electricity and steam as co-products. It depends on the perspective of the study, i.e. the question posed, which of the here two sets of co-functions is the set that will effectively be considered to be the relevant co-functions of the process: In the case the study aims at calculating an inventory for one of the wastes, the services of the treatment of the different wastes are the co-functions. If the study in contrast aims at calculating the inventory for the electricity or the steam, these two are the relevant co-functions. For the latter example and in case of allocation, the inventory would be allocated between these two only and all other flows including the waste treatment services would be considered non-functional product flows only


In the case of substitution only the not required co-function (i.e. steam or electricity, depending on which of the two is the required co-function) would be substituted. Multifunctional products A variant of multifunctional processes is the multifunctional product (e.g. a mobile phone), which is methodologically equal, but is modelled typically differently in LCI data sets: while each co-function of the before-mentioned multifunctional processes has a separate reference flow, in this case typically only one reference flow is used. This is justified not only as the 44 This holds true also when the whole technology (e.g. a waste incineration plant) is to be analysed and improved with help of the LCA results: it is necessary to get comparative values for the co-products/-functions and therefore one needs to single out the inventories of all the individual co-products. Product A Product B Emissions Wastes Input products (goods and services) Resources Process


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how user perceives e.g. the named mobile phone as one product, but also as it is further managed (e.g. packaged), transported, used and discarded as one item, i.e. different from the other cases that have physically distinct goods (or services). For LCI/LCA studies on complex goods and services (e.g. the mobile phone), that often combine several functions in one physical unit of a product, in contrast, the product as a whole with all its functions is of interest. However, when it comes to comparisons with similar products, the need comes up to make the alternatives fully comparable, e.g. the to-becompared mobile phone model may lack at least one the functions (e.g. MMS) or differs in quantitative aspects of at least one of the functions (e.g. storage space for pictures and music clips)


MMS) or differs in quantitative aspects of at least one of the functions (e.g. storage space for pictures and music clips). Solving multifunctionality Different approaches are used for solving multifunctionality. The choice of the most appropriate approach depends among others on the goal situation of the study, available data and information, and the characteristics of the multifunctional process or product. The most appropriate way how to solve this multifunctionality is to be identified already in the scope phase of the LCA (or at least in the inventory phase when planning data collection), as it affects which inventory data and other information is required. This topic and the related concepts are hence introduced in the remainder of this chapter; they serve also as basis for the later application of the approaches as part of the inventory work


This topic and the related concepts are hence introduced in the remainder of this chapter; they serve also as basis for the later application of the approaches as part of the inventory work. 6.5.3.2 The ISO hierarchy for solving multifunctionality Introduction Under the heading “Allocation”, ISO 14044:2006 presents a hierarchy of different approaches to this multifunctionality problem45. This hierarchy is the starting point for developing the ILCD guidance to this problem that is provided in detail for full attributional modelling in chapter 7.9 and for full consequential modelling in chapter 7.2.4.6. The systematic and somewhat simplified provisions for the main three goal situations A, B, and C that are encountered in LCA practice are given in chapter 6.5.4


The systematic and somewhat simplified provisions for the main three goal situations A, B, and C that are encountered in LCA practice are given in chapter 6.5.4. First approach: Subdivision of multifunctional processes The ISO hierarchy starts with the subdivision of multifunctional black box unit processes to mono-functional single operation unit processes46 and thereby cutting free the actually required processes, avoiding the need for allocation (see Figure 7 and Figure 8). 45 As the hierarchy covers other approaches than only allocation and also identified the first two approaches as "avoiding allocation", it is argued that clearer and more appropriate would be the encompassing title „Solving multifunctionality of processes“. 46 The two sub-terms of "unit process" are introduced here to be able to differentiate between a) "single operation unit processes" that can physically not be further subdivided and b) "black box unit processes" that can be further subdivided


Allocation of black-box unit processes can result in distortions of the results if they include multifunctional processes.


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how Figure 7 Black box unit process and single operation unit process. Both can have one or more (co-)functions (e.g. co-products as shown here). Terms and concepts: Subdivision of multifunctional processes “Subdivision” of multifunctional processes refers to the collection of data individually for those of the mono-functional processes that relate to the analysed system and that are contained in the multifunctional process. Subdivision is often but not always possible to avoid allocation for black box unit processes; see Figure 7. Thereby the actually required processes are cut free and the multifunctionality problem is solved. This is unless any of the included single-operation unit processes is still multifunctional. However, even then the data accuracy has been improved, often substantially


This is unless any of the included single-operation unit processes is still multifunctional. However, even then the data accuracy has been improved, often substantially. Note that subdivision is the only correct / exact solution under attributional modelling to solve multifunctionality of further sub-dividable processes; the 'short-cut' of allocation of black box unit processes will often result in distorted inventories, as explained in the text. Under consequential modelling subdivision is also applicable47. See also chapter 7.4.2.2 with more details on subdivision, partial subdivision, and virtual subdivision. 47 However, it could be argued that the logic of consequential modelling might request to account for synergies and other interrelations of processes that operate e.g. on the same site. This foreground-system internal interrelations and consequences needs still further methodological clarifications


on the same site. This foreground-system internal interrelations and consequences needs still further methodological clarifications. Similarly, the synergies on sitelevel might even need to be considered in attributional modelling by an allocation of synergies. E.g. on a site a small steam consuming process may benefit from a big steam consuming process that has lead to the installation of a very efficient steam generating process. Resources Input products (Co-)Products Waste Emissions (Co-)Products Waste Resources Input products Single operation unit process Black box unit process Emissions


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how Figure 8 Solving the multifunctionality problem (see Figure 6) by subdivision of the black box unit process. Subdivision yields exclusively the process-chain of mono-functional unit processes “P1” to “P3” that result in the analysed “Product 1”. Subdivision can serve this purpose only, if the separated unit processes are not also multifunctional (as the example in Figure 8). However, next to potentially solving the multifunctionality, singling out the 'true' unit processes has other advantages for quality control and review, as the inventories do not combine several processes or even a whole site in a 'black box'. It is also noted that in case allocation is done on black box unit processes, the results are regularly distorted / incorrect, as normally not all processes inside a black box unit process relate to all co-functions to the same extent (see e.g


Figure 7). In addition to what ISO says on the general case, it is noted that also under consequential modelling, substitution of co-functions of in principle subdividable unit processes will distort the results, hence, subdivision or virtual subdivision should be preferred. Black box unit processes should be subdivided also if this does not solve the multifunctionality problem, as it renders it smaller and often easier solvable and as it improves reviewability48. Otherwise, the potentially distorting effect shall be explicitly considered when stating accuracy of results and drawing conclusions and recommendations. Note that, while subdivision requires collecting more specific data, it often avoids the need for otherwise required data: in the illustrative Figure 8, this is data for the treatment of the wastes A and C and in case allocation would be chosen, this is the allocation criteria information (e.g. physical properties, market prices etc.)


physical properties, market prices etc.). Second approach: System expansion (including substitution) As second option for avoiding the need for allocation the ISO hierarchy names the approach of system expansion. This can mean to add another, not provided function to make to system comparable (i.e. system expansion in the stricter sense) or to subtract not required function(s) substituting them by the ones that are superseded / replaced (i.e. substitution by system expansion). 48 It is recognised that budget or time restrictions may often limit this possibility. Product A Product B Emissions iii Waste i Input products (goods and services) Resources Waste ii Waste iii P 1 P 2 P 3 P 4 P 5 Emissions i Emissions ii


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how Terms and concepts: System expansion / substitution “System expansion” and its variant “substitution” are also called “system enlargement” and “crediting" / "avoided burden approach”, respectively. This is a combined concept for ensuring the equality of multifunctional systems with each other. In practice two different situations can be encountered: The first one is to solve the multifunctionality by expanding the system boundaries and substituting the not required function with an alternative way of providing it, i.e. the process that the not required function supersedes (“substitution”). An example: Blast furnace slag is a joint co-product of steelmaking (typically in the range of 0.2 to 0.35 kg per kg hot metal)


An example: Blast furnace slag is a joint co-product of steelmaking (typically in the range of 0.2 to 0.35 kg per kg hot metal). It is mainly used in cement making (superseding Portland cement) and in road building (superseding primary aggregates), while a smaller part is not used, i.e. deposited. If we want to obtain exclusively the life cycle inventory of producing blast furnace steel, the inventory of the co-function blast furnace slag will be eliminated from the process by subtracting the inventory of the superseded processes / systems49. In this way, we can obtain an LCI data set exclusively for the production of the steel from this process/plant. Here we have expanded the system's perspective by subtracting the not wanted function(s) via the life cycle inventory of alternative means to provide it. See Figure 9 for a schematic representation. The other situation is when several multifunctional systems (e.g


See Figure 9 for a schematic representation. The other situation is when several multifunctional systems (e.g. different brands of a complex consumer product) are to be made comparable in a comparison study. This would be done by expanding the system boundaries and adding for the given case missing functions and the inventories of the respective mono-functional products: E.g. when comparing a combined copier, printer, scanner, fax machine with a combined copier, scanner, fax machine, the missing function "printer" would be added to the inventory of the second product system; see upper part of Figure 10 for the schematic representation. The term system expansion is more illustrative in the second situation where we add one or more missing function(s).50 Note that both uses are mathematically equivalent as Figure 10 demonstrates (while not necessarily in their meaning and interpretation)


System expansion and substitution are the corresponding method approaches under consequential modelling for solving multifunctionality. Substitution is also applicable for attributional modelling that is interested to include existing interactions with other systems (e.g. credits to existing / past recycling operations for avoided primary production), i.e. under Situation C1. Substitution means to subtract the inventory of another system from the analysed system. This often leads to negative inventory flows. It can even result in negative overall 49 Note that in full consequential modelling, any additional BOF slag would go to landfill, as the supply is already higher than the demand. In that case, nothing is superseded and landfilling would be modelled. Looking in contrast at the existing average situation, a high share of the already produced BOF slag is replacing e.g. Portland cement and avoids its production


Looking in contrast at the existing average situation, a high share of the already produced BOF slag is replacing e.g. Portland cement and avoids its production. In that perspective, it is appropriate to substitute the mix of alternative uses (and have only a share modelled as landfilled). As a second comment it is interesting to note that the modelling of "additional BOF slag" changes if the BOF slag would be already fully used e.g. in the named cement applications. In that case, also any additionally co-produced BOF slag would supersede Portland cement, since the market demand would be higher than the supply. 50 The case of substitution could actually also be called "system reduction".


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how environmental impacts for the analysed system. This means that there is a net benefit of producing the analysed system as the overall impact is more than compensated by the avoided impact the co-functions have elsewhere. This is the correct interpretation, if made within the assumptions of the study, including on the amount of co-functions produced. This has nevertheless often lead to communication problems, especially to non-experts, as negative emissions and negative impacts are not directly intuitive. If such occurs, this needs special attention, including already in the reporting of results. At the same time, such results can also be misleading, if wrongly interpreted that an unlimited production of the analysed system will lead to unlimited benefits


At the same time, such results can also be misleading, if wrongly interpreted that an unlimited production of the analysed system will lead to unlimited benefits. This however ignores that an ever-increased amount of production will produce very large amounts of the co-function, while the market for the superseded processes that was originally modelled might be much smaller. I.e. if the amount of the production is increased, the modelling would need to be changed to reflect whether the market can still take up the bigger amounts and these would still actually supersede any other process or system. This means that a study under Situation A can only be used to provide decision support under the original assumption that the not required co-functions are absorbed by the market and supersede the identified alternative processes / system and without large-scale consequences


Otherwise, for larger amounts, another mix of process / system might be superseded or the system would even need to be modelled under Situation B. Also a study under Situation B, e.g. on "10 % biofuels in China", cannot be used to support a decision on e.g. "50 % biofuels in China", as other large-scale consequences would likely occur in the rest of the society and industry that were not considered in the initial study but that would change the results. Figure 9 Solving the multifunctionality problem by substitution of the not required cofunctions, schematic. In practice, system expansion can lead to the need of further system expansion as the additionally included systems often are again multifunctional. This can be addressed in many cases via cut-off rules. There are however systems for which no alternative production / process for exactly the same function exists (e.g. rice grains and straw always grow together, i.e


There are however systems for which no alternative production / process for exactly the same function exists (e.g. rice grains and straw always grow together, i.e. there is no alternative production of rice grains to be substituted). A substitution of the function that the rice grains provides is however feasible, i.e. other grains and staple fruits can be assumed to be superseded. Depending on the specific situation this can however need to a large number of superseded systems, so that in the balance of effort and accuracy, pragmatic but systematic approaches are required. In other cases, the alternative processes exist only in theory or are of no quantitative relevance in practice (e.g. Sodium hydroxide is basically exclusively produced from sodium chloride electrolysis, hence there is no truly superseded process of industrial relevance)


Sodium hydroxide is basically exclusively produced from sodium chloride electrolysis, hence there is no truly superseded process of industrial relevance). Another challenge is that it is not straightforward to identify the one or more superseded Co-production of A + B ≈ X units of A Y units of B Y units of B X units of A Alternative production of B Alternative production of A –


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how processes that should be integrated into the expanded system; the necessarily complex approach is detailed in chapter 7.2.4. Figure 10 Equivalence of additive and subtractive ("substitution") system expansion: Achieving functional equivalence of compared systems by either adding functions (system expansion, top) or subtracting them (bottom) Third approach: Allocation As last step in the ISO hierarchy, allocation is named, partitioning the inputs and outputs between the co-functions according to some allocation criterion. ISO gives a preferred order of potential criteria; see box. Terms and concepts: Allocation “Allocation”, also called “partitioning”, solves the multifunctionality by splitting up the amounts of the individual inputs and outputs between the co-functions according to some allocation criterion, being a property of the co-functions (e.g


element content, energy content, mass, market price etc.); see Figure 11. If possible, according to ISO 14044:2006, allocation should be performed in accordance with the underlying causal physical - and implicitly also covered: chemical and biological - relationship between the different products or functions. This should reflect the way in which the individual inputs and outputs are quantitatively changed by quantitative changes in the multiple functions delivered by the process or system. When it is not possible to find clear common physical causal relationships between the co-functions, ISO 14044:2006 recommends performing the allocation according to another relationship between them. This may be an economic relationship or a relationship between some other (e.g


This may be an economic relationship or a relationship between some other (e.g. non-causal Co-production of A + B ≈ + X units of A Y units of B Y units of B X units of A Alternative production of B Alternative production of A Co-production of A + B ≈ X units of A Y units of B Y units of B X units of A Alternative production of B Alternative production of A –


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how physical) properties of the co-functions such as energy content that is often used in the allocation between different fuels co-produced in a refinery51. Note that if subdivision cannot provide exclusively mono-functional unit processes that can be attributed to the analysed function, allocation is the corresponding method approach under attributional modelling for solving multifunctionality of processes. Figure 11 Solving the multifunctionality problem by allocation of the inventory to the cofunctions (illustrative). The thickness of the lines inside the process indicates which share of each non-functional flow is allocated to each of the two co-functions (here: "Product A" and "Product B"). The flows can be quantitatively allocated to only one (blue, solid lines) or to several (red, dotted lines) of the co-functions


The flows can be quantitatively allocated to only one (blue, solid lines) or to several (red, dotted lines) of the co-functions. Different allocation criteria can be applied that need to be appropriately identified. The sum of the allocated amount of inventory flows shall be identical to the un-allocated inventory of the process. In practice there is often the difficulty to clearly identify the most appropriate allocation key, as the following examples illustrate. There is also often a lack of data (e.g. in the above example case data on how a varying amount of carbon and chlorine in the waste quantitatively changes effects the amount of dioxin formation), what renders the use of physical causality as solemn allocation criteria not always feasible or at least reduces the robustness. In chapter 7.9.3.2 some examples are given to illustrate this. On using the market price as allocation criterion The use of the market price as allocation criterion is hence often found in practice


In chapter 7.9.3.2 some examples are given to illustrate this. On using the market price as allocation criterion The use of the market price as allocation criterion is hence often found in practice. In many cases however the co-products are not directly traded but further processed internally e.g. compressed, purified, packaged etc. first. Hence the market price of the resulting product that is old is to be adjusted (i.e. reduced) for these additional steps, before using it as allocation key. Some interim co-products are not at all or at least seldom traded externally (e.g. refinery gas); market price information is to be approximated in such cases. Market 51 Note that the use of e.g. the lower calorific value for allocation across refinery products for the black-box unit process refinery is not a causal physical relationship, but a simplified allocation of a not causal physical relationship in the sense of ISO


Product A Product B Emissions Wastes Input products (goods and services) Resources Process


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how price based allocation on site level (i.e. of black box unit processes) disregards that emission abatement technologies often treat emissions that are related to only one of the co-products. A general disadvantage of using market prices in allocation is that this assumes a positive correlation of impacts with the market price, disregarding that environmental measures such as emission reduction technologies in fact increase the production cost while reducing the environmental burden. Using the market price for allocation also leads to some degree of correlation of the environmental impact with the price of the product, what limits the meaningfulness of such environmental impact data in eco-efficiency analysis


The ILCD provisions solving multifunctionality of processes How to identify the most appropriate, specific allocation and substitution approaches is detailed in the following subchapters for the general cases. 6.5.4 LCI modelling provisions for Situations A, B, and C (Refers to aspects of ISO 14044:2006 chapter 4.3.4 and 4.2.3.6.1) 6.5.4.1 Introduction and overview In preparation of identifying the most appropriate LCI modelling principles and method approaches oriented to the goal of the LCI/LCA study, in chapter 5.3 the LCA work to be performed has been classified as belonging to one of three distinct decision-context situations A, B, or C. In practice and next to the formal decision-context there is a wide range of other aspects that finally determine the most appropriate LCI modelling principles and method approaches to be applied


In practice and next to the formal decision-context there is a wide range of other aspects that finally determine the most appropriate LCI modelling principles and method approaches to be applied. These aspects comprise among others reproducibility, information and data availability, precision and robustness, practicality, communicatability, cost-effectiveness, coherence with other instruments, and stakeholder acceptance. Taking into account all these aspects, the modelling provisions for Situations A, B, and C are derived, as follows: 6.5.4.2 Situation A: "Micro-level decision support" (Refers to aspects of ISO 14044:2006 chapter 4.3.4 and 4.2.3.6.1) 6.5.4.2.1 Overview Situation A relates to a life cycle based decision support on micro-level (e.g. for productrelated questions). It is typically, but not necessarily referring to the short-term (up to 5 years from present) or mid-term (5 to 10 years from present) future. I.e


for productrelated questions). It is typically, but not necessarily referring to the short-term (up to 5 years from present) or mid-term (5 to 10 years from present) future. I.e. the analysed changes directly or indirectly relate to inform the purchase of products that are already offered in the market or the design / development of products that are foreseen to entering the market typically. Key criteria is that the analysed e.g. product has a limited share of the total production of its sector, so that its production, use and end-of-life can be reasonably expected to have no large-scale consequences in terms of additionally installed or reduced capacity in the background system or other systems, i.e. not structurally change it52. 1. 52 Sometimes it is theoretically assumed that any small-scale decision would have long-term consequences on installed capacity (e.g


not structurally change it52. 1. 52 Sometimes it is theoretically assumed that any small-scale decision would have long-term consequences on installed capacity (e.g. the purchase of 500 polypropylene-based ball pens would result in marginally increased capacity of polypropylen production by resulting in a marginal extra of newly installed polypropylene plants). This is understood to need further research before it can be considered for inclusion under Situation A, as a valid, efficiently applicable and robust guidance is required. Especially investment decisions under market, policy and other constraints as well as the specific effect of secondary consequences that counteract or block any such large-scale consequences need to be better understood.


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how In condensed form and for orientation only, the following guidance is given: The most appropriate LCI model for Situation A shall represent the supply-chain of the analysed system, applying attributional modelling. For cases of system-system relationship and multifunctionality of processes and products that cannot be solved by subdivision or virtual subdivision, the system expansion approach shall be adopted, substituting the avoided process as its market mix (excluding the to-be-substituted function/route). Value-correction may be needed to adjust for differences in performance. In the case of large complexity, allocation is the next option to solve multifunctionality. The following paragraphs provide further details. Details on modelling are given in the respective Life Cycle Inventory chapters


The following paragraphs provide further details. Details on modelling are given in the respective Life Cycle Inventory chapters. 6.5.4.2.2 LCI modelling provisions General life cycle model The following general guidance shall be applied:  attributional modelling shall be used for the general system LCI modelling, i.e. depicting the existing supply-chain, use and end-of-life downstream chain, as for the given to be included in the model. Multifunctionality For solving multifunctionality, subdivision or virtual subdivision shall be aimed at, cutting free non-multifunctional processes (see chapter 6.5.3)


Multifunctionality For solving multifunctionality, subdivision or virtual subdivision shall be aimed at, cutting free non-multifunctional processes (see chapter 6.5.3). For system-system relationships and for solving multifunctionality where this is principally not possible OR where other reasons such as data availability or cost considerations hamper this, the appropriate LCI method approaches shall be:  Cases of system-system relationship (see box in chapter 7.2.2): if the secondary function acts within another system where it only affects the existing processes‟ operation (and potentially also the installed capacity, e.g. because this secondary function had been considered when planning the affected system), system expansion shall be done via substitution of the short-term marginal. In more detail: the systemsystem relationship related multifunctionality does not lead to installation of new processes or their taking out of operation, but only to changes in their operation (i.e


In more detail: the systemsystem relationship related multifunctionality does not lead to installation of new processes or their taking out of operation, but only to changes in their operation (i.e. 'short-term marginal' consequences). This is given for those cases where the secondary function of the analysed product acts directly in context of another system, the 'context system'. An example is a coffee-machine that generates heat as co-function that lowers the heating demand for the building in which it is operated (and/or increases the cooling demand, depending on the region and season) (details see box of system-system relationships in chapter 7.2.2). The superseded process is hence directly the one affected in its operation (e.g. in case of the above example the average house heating and cooling systems in the analysed country)


The superseded process is hence directly the one affected in its operation (e.g. in case of the above example the average house heating and cooling systems in the analysed country). Note that in case the existence of the coffee-machine was anticipated in the building design and the installation of heating/cooling capacity, the same applies, just that in that case other heating/cooling systems are in use and to be modelled.  Cases of multifunctionality - general: - If for the not required co-function functionally equivalent alternative processes / products are operated / produced in a suffient58 extent, the not required co-function shall be substituted with the average market59 consumption mix of the processes or products that are superseded, excluding the to-be-substituted process-route/product from this mix. The reasoning for this simplification compared to a full consequential


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how modelling is that a high effort is required to identify among the potential processes those that are most likely superseded and calculate the superseded mix: In full consequential modelling the mix of the most likely superseded processes would need to be identified. The limited benefit of a potentially more accurate, but also less certain selection of processes is not found justified for Situation A studies. The market mix is used as a realistic and robust approximation that additionally considers the existence of various secondary consequences and constraints that can be assumed to often reduce or fully compensate/avoid the theoretical primary consequences


- If such alternative processes / systems do not exist or are not operated to a sufficient extent, alternative processes / systems of the not required co-function in a wider sense should be used for substitution, along the same provisions as set in the preceding sub-provision. - If also such alternative processes / systems for the wider function do not exist or do not meet the named requirements, the study is in fact a Situation B type study, as this implies large-scale consequences on other systems: the amount of not required co-function is more than the market can easily absorb without structural changes - It can be that modelling of substitution is not feasible. This can be e.g. as very many alternative processes / systems or alternatives for the function in a wider sense exist (e.g. over 10 alternative processes / systems make up over 80 % of the market for the to-be-substituted function and/or the superseded processes / systems themselves have a number of co-functions))


over 10 alternative processes / systems make up over 80 % of the market for the to-be-substituted function and/or the superseded processes / systems themselves have a number of co-functions)). The effort for modelling and qualitycontrolling this system would counteract applicability and practicality for Situation A studies. For this reason a simplification is applicable, compared to the theoretical full consequential model: In such cases and also if otherwise usable generic data is not sufficiently accurate to represent the superseded processes / systems, the two-step allocation procedure of chapter 7.9.3 can be applied instead. This shall however not be done if it would relevantly favour the analysed process / system; this should be argued or approximated. Note that if allocation is done, the resulting lack of accuracy shall be reported and later be considered in the interpretation


Note that if allocation is done, the resulting lack of accuracy shall be reported and later be considered in the interpretation. - Another simplification applies compared to the theoretical full consequential model: Substitution of the determining co-function(s) shall not be done. If they cannot be identified, the determining co-function(s) should be assumed to be those that jointly contribute more than 50 % to the combined market value of all co-functions of the analysed multifunctional process or system. That implies that in fact the main, determining co-function(s) of the process would be substituted. In this case, the twostep allocation procedure shall be applied (see chapter 7.9.3). - Differences in functionality between substituted and superseded function shall be considered either and preferably by substituting the actually superseded amounts (e.g. the amount of Portland cement that the steel making co-product BOF slag actually replaces in cement)


the amount of Portland cement that the steel making co-product BOF slag actually replaces in cement). Or, as second priority, these differences shall be considered by market value correction of the amount of the substituted function and its inventory, i.e. the ratio of market price between the co-function and the ones it is supposed to supersede. - As special case of the above, for waste and end-of-life treatment (for all cases, i.e. "closed loop", "open loop - same primary route", and "open loop - different primary route"): system expansion shall be done, substituting the avoided primary production using the recyclability substitution with the average primary route market mix of the


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how market where the secondary good is produced; differences in functionality shall be considered by substituting the actually superseded amounts or by market value correction (details see annex 14). An example: recycled, untreated wood from construction waste53 might be chipped and used in particleboard production in Europe. Primary produced wood chips (European market consumption mix) would be superseded and their inventory used in substitution. If the secondary wood chips would have a lower functionality than the primary wood chips (e.g. more would be needed for a particleboard of the same performance specifications), the respectively reduced amounts of superseded primary wood-chips is substituted


more would be needed for a particleboard of the same performance specifications), the respectively reduced amounts of superseded primary wood-chips is substituted. Or, if this is not identifiably and quantifiable, but the market value of primary wood chips would differ to the secondary ones, the substituted inventory is corrected by their market price ratio. Any efforts of sorting, transport, chipping, etc. of the construction wood waste would be part of the building inventory from which the construction wood waste stems. The simplified substitution of the market mix of primary production is reasoned the same way as the use of the market mix for the general case of multifunctionality, as explained more above. An example is the electricity produced from production waste or end-of-life product incineration with energy recovery. The superseded and to be substituted process is the electricity mix of the market (e.g


The superseded and to be substituted process is the electricity mix of the market (e.g. country, region, sub-grid) where the waste / end-of-life treatment takes place, excluding the to-be-substituted electricity source - Especially for the case of "open loop - different primary route" in addition it shall be checked whether for the reused part, recycled material, or recovered energy functionally equivalent, alternative processes / systems, or functional equivalents in a wider sense exist and are operated to a sufficient extent (as detailed above for the general cases of multifunctionality). Otherwise, the study is in fact a Situation B type study, as this implies large-scale consequences on other systems. Analogously to the general case of multifunctionality, the amount of secondary good provided is so high that the market cannot absorb it without structural changes. Note that this usually does not apply to closed-loop cases, as the secondary good enters the same kind of system, i.e


Note that this usually does not apply to closed-loop cases, as the secondary good enters the same kind of system, i.e. the market can always absorb the secondary good. This is unless the quality is too low and it cannot replace the functions of the primary good. - Similarly as for the general case, very complex and expanded substitution systems can render the study impractical, as data is not available or accessible for all parts, or lead to inappropriately high costs. In that case (see above), allocation can be done, applying the procedure for waste / end-of-life treatment multifunctionality; this is detailed in annex 14.4 and chapter 7.9.3. Allocation shall however not be done if it would relevantly favour the analysed process / system. This can be analysed qualitatively or semi-quantitatively argued or approximated. If allocation is done, the resulting lack of accuracy shall be reported and later be considered in the interpretation


If allocation is done, the resulting lack of accuracy shall be reported and later be considered in the interpretation. Comparative studies For comparative studies of Situation A the main model for each of the compared alternatives shall be complemented with assumption scenarios of reasonably best and reasonably worst cases and (optionally) further assumption scenarios within the reasonably best and worst cases. Uncertainty calculation shall be performed, unless it has already been 53 Methodologically identically for wood waste collected during production of a building and from decommissioning of an old building.


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how used to derive the reasonably best and worst case scenarios. The interested parties shall be involved towards a best attainable consensus on the definition of the reasonably best and reasonably worst assumption scenarios that can in principle vary all data and method provisions and assumptions for Situation A, except for the "shall" provisions and assumptions. Note that the comparative case under Situation A (e.g. procurement of cleaning services) in most cases assumes that one of the compared alternatives will be procured. The LCAbased decision support hence only compares the alternatives. There is hence usually no 'zero' option. If among the to-be-compared systems, one or more systems have additional functional units, comparability shall be achieved by system expansion


There is hence usually no 'zero' option. If among the to-be-compared systems, one or more systems have additional functional units, comparability shall be achieved by system expansion. 6.5.4.3 Situation B: "Meso/macro-level decision support" (Refers to aspects of ISO 14044:2006 chapter 4.3.4 and 4.2.3.6.1) 6.5.4.3.1 Overview Situation B refers to life cycle based decision support on a meso or macro-level, such as for strategies (e.g. raw materials strategies, technology scenarios, policy options, etc.). It typically refers to the mid-term (5 to 10 years from present) or long-term (beyond 10 years from present) future, given the nature of the study. Key criterion is that the analysed decision has consequences on changes in production, use and end-of-life activities that will directly or indirectly change relevant parts of the economy by having large-scale structural effects


In condensed form and for orientation only, the following guidance is given: The analysed systems or alternative scenarios shall be modelled, applying the modelling guidance of Situation A (see chapter 6.5.4.2). Those processes that have been identified as being affected by "big" large-scale changes as consequence of the analysed decision shall be modelled as the market mix of the long-term marginal processes (details see chapter 7.2.4). This shall be complemented with assumption scenarios of reasonably best and reasonably worst cases. Also uncertainty calculation can support the analysis


This shall be complemented with assumption scenarios of reasonably best and reasonably worst cases. Also uncertainty calculation can support the analysis. The following paragraphs provide further details with the full details are given in the respective chapters: 6.5.4.3.2 LCI modelling provisions General life cycle model and multifunctionality Situation B shall apply the LCI modelling guidance of Situation A, with one exception: processes that have been identified as being affected by big54 changes as consequence of the analysed decision shall be modelled as mix of the long-term marginal processes. Comparative studies Comparisons of alternatives would then be made among the various alternatives, considering the assumption scenarios and uncertainty analysis (unless such has already been used to derive the reasonably best and worst case scenarios). Note that in contrast to Situation A, the comparative case (e.g


Note that in contrast to Situation A, the comparative case (e.g. options for recycling policies) in most cases also has a 'zero' option of 'business as usual', i.e. that a new policy 54 Definition and guidance see chapter 7.2.4.


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how would not be put in place (or that no change would be made to an existing policy). The LCAbased decision support hence usually also has one scenario of 'no action'. For comparative studies the systems or alternative scenarios shall be complemented each with further scenarios (here called "assumption scenarios") to improve the robustness of the analysis, by varying the key data related assumptions (e.g. recycling rates, use intensity, life times, etc.) and potentially the relevant method assumptions. The assumption scenarios shall combine variations of the most influencing assumptions aiming at representing reasonable worst and reasonable best cases around the system(s)


The assumption scenarios shall combine variations of the most influencing assumptions aiming at representing reasonable worst and reasonable best cases around the system(s). These reasonable worst and reasonable best cases should be derived by expert judgement aiming at capturing the upper and lower 90 % percentile of error around the system / alternative scenario (including accounting for co-variance among assumptions). This scenario analysis shall be combined or integrated with stochastic uncertainty calculation e.g. applying Monte-Carlo Simulation, unless such has already been used to derive the reasonably best and worst case scenarios. The assumption scenarios may deviate from all LCI modelling requirements of Situation B, including the "shall". The necessary reasonable worst and reasonable best scenarios shall be agreed among the involved interested parties of a public stakeholder hearing aiming at the best attainable consensus55. These scenarios can hence include e.g


These scenarios can hence include e.g. full consequential scenarios for the entire system life cycle and attributional (allocation) for cases of multifunctionality. Details on which consequences should be included by default in case consequential modelling is done and guidance on determination of the marginal processes is found briefly in chapter 7.2.4. If an LCI data set is the deliverable of the study, the modelling of assumption scenarios is recommended, only. If performed, the outcome may be documented together with the data set. Note that this is a "shall" requirement if the data set is intended to be used in subsequent comparisons. 6.5.4.4 Situation C: “Accounting” (Refers to aspects of ISO 14044:2006 chapter 4.3.4 and 4.2.3.6.1) Overview Situation C relates to studies that require a entirely descriptive, accounting-type of life cycle model, typically referring to the past or present (while individually also to the future via extrapolation)


The object of the analysis can be both on a micro-level and on a meso or macro-level; the amount of production or consumption and of co-functions does not change the modelling. Key difference from Situations A and B is that the study is interested in documenting what has happened (or will happen) based on decisions that have already been taken; there is hence no small-scale or large-scale consequences on the background system or other systems in the rest of the society that would be in the interest of the analysis. However, existing benefits and negative interactions with other systems (e.g. recycling credits) may be included. This leads to the two differentiated cases C1 and C2. For the two sub-types of Situation C, the key difference is whether existing benefits outside the analysed system are considered or not: In Situation C1, this is the case (e.g


For the two sub-types of Situation C, the key difference is whether existing benefits outside the analysed system are considered or not: In Situation C1, this is the case (e.g. the 55 As the review requirements for such Situation B studies foresee an external review (for the exact type of review see the review guidance document), it is one possibility to fulfil this hearing requirement by joining it with the stakeholder involvement in this review: the reviewer / review chair can invite affected stakeholders and steer a process towards the best attainable consensus on the primary and secondary consequences that are to be included into the scenarios of the respective study.


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how benefit of a process of the analysed system is producing a co-product that actually supersedes another product). This is hence to be credited. Note that in difference to Situation A (or B), here this benefit is already existing (as an existing system is described). In Situation A (or B) this benefit is assumed to occur only in consequence of the decision that is supported with the study, i.e. in addition. This "addition" is the key: only if the additional amount of co-product can be used in the market, only then the crediting is appropriate in Situation A, otherwise the structural consequences are to be modelled (Situation B). For that reason in Situation A, the credit is only given if it can be shown that the superseding actually takes place (or is likely to take place as the amount is relatively small)


For that reason in Situation A, the credit is only given if it can be shown that the superseding actually takes place (or is likely to take place as the amount is relatively small). In Situation C1, the fact of superseding can actually be measured by inventorying how much of the co-product is actually used and for which purposes and how much may be deposited. This results in the following, general modelling provision: LCI modelling provisions For both Situation C1 and C2 the life cycle of the analysed system(s) shall be modelled as attributional model of the supply-chain, i.e. as in Situation A (details see chapter 7.2.3; see also again 6.5.2). Multifunctionality For solving multifunctionality, subdivision or virtual subdivision shall be aimed at, cutting free non-multifunctional processes (see chapter 6.5.3)


Multifunctionality For solving multifunctionality, subdivision or virtual subdivision shall be aimed at, cutting free non-multifunctional processes (see chapter 6.5.3). For system-system relationships and for solving multifunctionality where this is principally not possible OR where other reasons such as data availability or cost considerations hamper this, the appropriate LCI method approaches shall be:  For Situation C1 multifunctionality of processes and systems should be solved with substitution via system expansion, similarly as in Situation A but independently of the amount of secondary function. That means hat studies done under Situation A are identical to studies done under Situation C1 (while not vice versa).  For Situation C2, multifunctionality of processes and systems shall be solved with allocation. This also applies to all end-of-life product and waste management including material recycling, energy recovery, part reuse, product further use, etc


This also applies to all end-of-life product and waste management including material recycling, energy recovery, part reuse, product further use, etc. The guidance on the two-step procedure for applying allocation is provided in chapter 7.9.3. Details on modelling recycling are provided in annex 14.4. Note that given the purely descriptive character of the model, the resulting accountingtype data of Situation C1 – while informing decision makers about developments and hot spots – cannot DIRECTLY be used for decision support or comparisons of alternative measures: this requires the subsequent use of the modelling under Situation A or B. Provisions: 6.5.4 LCI modelling provisions for Situations A, B, and C The following modelling provisions can be applied only in the Life Cycle Inventory phase. However, because the step of determining the LCI modelling and method approaches is part of the scope definition, the provisions are given here


However, because the step of determining the LCI modelling and method approaches is part of the scope definition, the provisions are given here. They are also required to provide orientation to some of the remaining steps of the scope phase. Note that the inventory of a unit process is basically identical for Situation A, B, and C, although some differences apply e.g. for required additional information, e.g. market size. What differs is which processes are within the system boundary, especially in the background system (what is addressed in chapter 7.2), and how the processes are combined to represent the life cycle model and how multifunctionality is solved; both are addressed in this chapter. The following provisions draw on the provisions in the referenced LCI chapters. They are partly simplified compared to the 'full' consequential and attributional modelling provisions to improve practicality and applicability;


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how Provisions: 6.5.4 LCI modelling provisions for Situations A, B, and C this is highlighted in the respective provision. I) SHALL - LCI modelling provisions to be applied: A specific combination of LCI modelling framework (attributional or consequential) and LCI method approaches (allocation or system expansion / substitution) is identified for each of the goal situations A, B, C1, and C2. The provisions cover scenario and uncertainty calculation. The provisions shall be applied as follows (6.5.4.1): [ISO!] I.a) Situation A - "Micro-level decision support": (6.5.4.2) I.a.i) Life cycle model: The life cycle model of the analysed system(s)56 shall be modelled as an attributional model, i.e. depicting the existing supplychain processes (for details see chapter 7.2.3)


depicting the existing supplychain processes (for details see chapter 7.2.3). I.a.ii) Subdivision and virtual subdivision for black box unit processes and multifunctionality: It shall be aimed at avoiding black box unit processes and solving multifunctionality by subdivision or virtual subdivision (see chapter 7.4.2.2), as far as possible. The following applies for cases of system-system relationships and cases of multifunctionality, if subdivision / virtual subdivision is not possible or not feasible: I.a.iii) Cases of system-system relationship: if the analysed system's secondary function acts within a context system, where it only affects the existing processes‟ operation, system expansion shall be performed via substitution with the short-term marginal (for terms, concepts, and details see boxes in chapter 7.2.2 and chapter 7.2.3)


Note that the analysed system may also have influenced the installed capacity of the context system, if it had been considered when planning the context system. For example the heat generated by office equipment may have been considered when dimensioning the heating and cooling system of an office building. Part-system relationships require no specific modelling provision, but the correct identification of the processes within the system boundary; see boxes in chapter 7.2.2. I.a.iv) Cases of multifunctionality - general: (For terms, concepts, and details see chapter 7.2.4.6, but note the simplifications given here for Situation A): I.a.iv.1) Substitution of market mix of specific alternatives: (Simplification compared to full consequential model): If for the not required57 specific co-function, functionally equivalent alternative processes / systems are operated / produced to a 56 Plural in case of comparisons. 57 I.e


57 I.e. in contrast to the one that is analysed or within the system boundary in the background system.


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how Provisions: 6.5.4 LCI modelling provisions for Situations A, B, and C sufficient58 extent: the not required co-function shall, as far as possible, be substituted with the average market59 consumption mix of the processes or systems that it supersedes, excluding the to-be-substituted function from this mix. If the to-besubstituted function has a small share in the overall environmental impact of the market mix, the market mix can be used instead, if the results are not relevantly changed. I.a.iv.2) Substitution of market mix of general, wider alternatives: If such alternative processes / systems do not exist60 or are not operated to a sufficient extent, alternative processes / systems of the not required co-function in a wider sense should be used for substitution61, applying the same provisions as set out in the preceding sub-provision


I.a.iv.3) Situation B?: If also such alternative processes / systems for the wider function do not exist or do not meet the named requirements, the study is in fact a Situation B type study, as this implies large-scale consequences on other systems. I.a.iv.4) Allocation: (Simplification compared to full consequential model): if modelling of substitution is not feasible62 and generic data is not sufficiently accurate to represent the superseded processes / systems: the two-step allocation procedure of 58 "Sufficient" means that the not required co-function can quantitatively be absorbed by the market. That shall be assumed to be the case, if the annually available amount of the to-be-substituted co-function is not more than the annual amount produced by the annually replaced installed capacity of the superseded alternative process(es) or system(s) (see also paragraph on "Guidance for differentiating between Situation A and B" in chapter 5.3.6)


! Note that this refers to the amount of co-function provided by the analysed process. E.g. if the study refers to a specific producer that contributes only a small share to the total production of the co-function, only this small amount counts. I.e. it is very likely that it can be absorbed by the market. If the study refers to the total production of a certain product that has the not required co-products, there is the chance that this much larger amount of coproducts cannot be absorbed by the market. 59 This "market" is the market where the secondary function is provided. E.g. for products produced from end-oflife and waste management this is the market of the primary production at the time and the location (e.g. country, region or global etc. market) where the end-of-life product or waste is known or forecasted to undergo recycling, reuse, or energy-recovery


country, region or global etc. market) where the end-of-life product or waste is known or forecasted to undergo recycling, reuse, or energy-recovery. If this market cannot be clearly determined, the most likely market shall be assumed and well justified; this most likely market shall be on a continental scale or at least cover a group of countries / markets. For explanation of the "market" concept see chapter 6.8.3. 60 As is the case e.g. for wheat grain and straw production, many oil refinery products, etc. 61 E.g. for NaOH, as co-product of Chlorine production, apart from NaCl electrolysis no alternative route is operated to the sufficient extent. However, NaOH provides in a wider sense the function of neutralising agent (next to some other, quantitatively less relevant functions) and hence other, technically equivalent and competing neutralising agents such as KOH, Ca(OH)2, Na2CO3, etc. can be assumed to be superseded; their mix would be used to substitute the not required NaOH


can be assumed to be superseded; their mix would be used to substitute the not required NaOH. For the example of a wheat grain study and the not required co-product straw: instead of straw, other dry biomass (e.g. Miscanthus grass, wood for heating, etc.) provides equivalent functions and its market mix can be assumed to be superseded. 62 "not feasible" refers to cases where many alternative processes / systems or alternatives for the function in a wider sense exist (e.g. where over 10 alternative processes / systems make up over 80 % of the market for the tobe-substituted function, and/or where the superseded processes / systems themselves have a number of cofunctions.


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how Provisions: 6.5.4 LCI modelling provisions for Situations A, B, and C chapter 7.9.3 can be applied instead. Allocation shall however not be performed if it would relevantly favour the analysed process / system. This fact shall be argued or approximated. If allocation is performed, the resulting lack of accuracy shall be reported and explicitly be considered later in the results interpretation. For multifunctional products and the alternative second step in allocation, Quality Function Deployment (QFD) is the preferred alternative to market price allocation. I.a.iv.5) No substitution of main function(s): (Simplification compared to full consequential model): The determining co-function(s) shall not be substituted (for term and concept see chapter 7.2.4.3)


In the case the determining and dependent cofunctions cannot be clearly identified, the determining cofunction(s) should be assumed to be those that jointly contribute more than 50 % to the combined market value of all co-functions of the analysed multifunctional process or system63. (The market value is for this purpose the value of the co-functions as provided by the multifunctional process, i.e. without any further processing). In this case, the two-step allocation procedure shall be applied (see chapter 7.9.3). I.a.iv.6) Considering functional differences: Differences in functionality between substituted and superseded function shall be considered either preferably by substituting the actually superseded amounts, or by substituting the market value corrected amount of the function (details see chapter 7.2.4.6)


I.a.v) Cases of multifunctionality - waste and end-of-life treatment: (For terms, concepts, and details see chapter 7.2.4.6 and annex 14.5, but note the simplifications given here for Situation A): I.a.v.1) Recyclability substitution of primary route market mix: (Simplification compared to full consequential model): For waste and end-of-life treatment as cases of multifunctionality: system expansion shall be performed in accordance with the provisions for the cases of general multifunctionality. The avoided primary production of the reused part, recycled good, or recovered energy shall be substituted. This shall apply the recyclability substitution approach, with the simplification of substituting the average primary route market consumption mix of the market where the secondary good is produced


This shall apply the recyclability substitution approach, with the simplification of substituting the average primary route market consumption mix of the market where the secondary good is produced. I.a.v.2) Recyclability substitution of general, wider alternatives: For "open loop - different primary route" cases, the market consumption mix of alternative goods in a wider sense should be used for substitution, along the same provisions as set out in the preceding sub-provision. 63 The reasoning is that in that case it is likely that the determining co-functions would be substituted.


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how Provisions: 6.5.4 LCI modelling provisions for Situations A, B, and C I.a.v.3) Situation B?: Especially for the case of "open loop - different primary route" and for secondary goods with relevantly changed / downcycled properties, in addition verification is needed on whether for the reused part, recycled material, or recovered energy, functionally equivalent, alternative processes or systems, or functional equivalents in a wider sense exist. If this is the case it needs additional verification whether these are operated to a sufficient extent (as detailed above for the general cases of multifunctionality, see also footnote 58). Otherwise, the study is in fact a Situation B type study, as this implies large-scale consequences on other systems


Otherwise, the study is in fact a Situation B type study, as this implies large-scale consequences on other systems. I.a.v.4) Allocation: (Simplification compared to full consequential model): if modelling the substitution is not feasible (see footnote 62) and generic data is not sufficiently accurate to represent the superseded processes / systems, then the two-step allocation procedure applied to waste/end-of-life given in annex 14.5 and chapter 7.9.3 can be applied instead. This shall not be done if it would relevantly favour the analysed process / system; this fact shall be argued or approximated. If allocation is performed, the resulting lack of accuracy shall be reported and explicitly be considered later in the results interpretation. I.a.v.5) Considering functional differences: Differences in functionality between substituted and superseded function shall be considered either and preferably by substituting the actually superseded amounts


As second priority and if the superseded amounts are not known, market value correction of the amount of the substituted function shall be performed. Note that this applies to all cases of waste and end-of-life treatment that generate any valuable secondary good, i.e. "closed loop", "open loop - same primary route", and "open loop - different primary route" (concepts see 14.3). I.a.vi) Comparative studies, scenarios, uncertainty calculation: I.a.vi.1) If among the to-be-compared systems, one or more systems have additional functional units, comparability shall be achieved by system expansion. I.a.vi.2) For comparative studies of Situation A, the main model for each of the compared alternatives shall each be complemented with assumption scenarios of reasonably best and reasonably worst cases. Optionally further assumption scenarios can be defined. Uncertainty calculation shall be performed, unless it has already been used to derive the reasonably best and worst case scenarios


Optionally further assumption scenarios can be defined. Uncertainty calculation shall be performed, unless it has already been used to derive the reasonably best and worst case scenarios. These scenarios serve to later perform the sensitivity check (see chapter 9.3.3). The interested parties shall be involved towards a best attainable consensus on the definition of the reasonably best and reasonably worst case assumption scenarios (and uncertainty calculation) that can in principle vary all data and method provisions and assumptions


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how Provisions: 6.5.4 LCI modelling provisions for Situations A, B, and C for Situation A except for the "shall" provisions and assumptions / conventions. It is recommended to also perform and report such assumption scenarios and uncertainty calculations for non-comparative LCI and LCA studies. Note that for LCI data sets that are intended to support comparative studies, the reasonsbaly best and worst case scenarios may be included within these data sets or be provided as complement


Note that for LCI data sets that are intended to support comparative studies, the reasonsbaly best and worst case scenarios may be included within these data sets or be provided as complement. I.b) Situation B "Meso/macro-level decision support" (6.5.4.3): I.b.i) Provisions as for Situation A with two differences: The above provisions for Situation A shall also be applied for Situation B, with two differences: I.b.i.1) Large-scale consequences: Processes that have been identified as being affected by "big"64 large-scale changes as a consequence of the analysed decision shall be modelled as the expected mix of the long-term marginal processes (for details see chapter 7.2.4)


I.b.i.2) Comparative studies, scenarios, uncertainty calculation: (Additional flexibility for assumption scenarios), for comparative studies of Situation B: The assumption scenarios and uncertainty calculation can in principle vary all data and method provisions and assumptions for Situation B including the "shall" provisions and assumptions / conventions of the ILCD Handbook, while not those of ISO 14040 and 1404465. Note that comparative Situation B studies often include a "zero" option, i.e. include a scenario of "no action" (e.g. "no change in existing policy Y", or "no strategic measure on raw material X security of supply"). I.c) Situation C - "Accounting" (6.5.4.4): I.c.i) Provisions as for Situation A with two differences: The provisions for Situation A shall also be applied for Situation C


I.c) Situation C - "Accounting" (6.5.4.4): I.c.i) Provisions as for Situation A with two differences: The provisions for Situation A shall also be applied for Situation C. With two differences: I.c.ii) Remaining cases of multifunctionality: These shall be solved as follows: I.c.ii.1) Situation C1: Multifunctionality of processes and systems shall be solved with substitution via system expansion, as in Situation A, but independently of the absolute amount of the not 64 Large-scale ("big") consequences shall generally be assumed if the annual additional demand or supply that is triggered by the analysed decision exceeds the capacity of the annually replaced installed capacity of the additionally demanded or supplied process, product, or broader function, as applicable (see also chapter 5.3.6, under the paragraph heading "Guidance for clearly differentiating between Situation A and B"). 65 I.e


65 I.e. these scenarios and uncertainty calculation aloow to apply the full range of method and modelling options of of ISO 14044.


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how Provisions: 6.5.4 LCI modelling provisions for Situations A, B, and C required co-function(s) that will be substituted66. The other provisions apply analogously. I.c.ii.2) Situation C2: General cases of multifunctionality of processes and systems shall be solved with allocation (i.e. applying the two-step allocation procedure; for details see chapter 7.9.3). Cases of waste and end-of-life treatment shall be solved via allocation, as described in annex 14.4.1 (with the provisions being included in the 'Provisions' of chapter 7.9.3). I.c.iii) Comparative studies: Note the restrictions for direct comparative decision support of accounting data (see chapter 5.3.7). Note that Situation C1 is thereby modelled identically to Situation A, while independently of the size of the system or processes


Note that Situation C1 is thereby modelled identically to Situation A, while independently of the size of the system or processes. Note that substitution can lead to negative elementary flows or in rare cases even negative overall environmental impacts of the analysed systems. This must be explicitly addressed in reporting, explaining all implications and helping to avoid misinterpretation and misleading conclusions. The main guidance on attributional LCI modelling is given in chapter 7.2.3. Guidance on the two-step procedure for applying allocation is provided in chapter 7.9.3. Main guidance on consequential LCI modelling is given in chapter 7.2.4. Details on LCI modelling of reuse/recycling/recovery are provided in annex 14.4 (attributional) and annex 14.5 (consequential)


Main guidance on consequential LCI modelling is given in chapter 7.2.4. Details on LCI modelling of reuse/recycling/recovery are provided in annex 14.4 (attributional) and annex 14.5 (consequential). 6.6 Deriving system boundaries and cut-off criteria (completeness) (Refers to ISO 14044:2006 chapters 4.2.3.3.1, 4.2.3.3.2, AND 4.2.3.3.3) 6.6.1 Introduction and overview (Refers to ISO 14044:2006 chapter 4.2.3.3.1) Overview The system boundaries define which parts of the life cycle and which processes belong to the analysed system, i.e. are required for providing its function as defined by its functional unit. They hence separate the analysed system from the rest of the technosphere. At the same time, the system boundaries also define the boundary between the analysed system and the ecosphere, i.e. define across which boundary the exchange of elementary flows with nature takes place67


define across which boundary the exchange of elementary flows with nature takes place67. 66 The reasoning is that the effect of superseding alternative processes / systems is existing, other than in Situation A where an additional amount of co-function is pushed into the market. I.e. in Situation C1, the check whether alternative processes / systems are operated or produced to a sufficient extent is unnecessary, as the superseding factually already occurs. 67 This is not always straightforward, e.g. for agricultural systems that need a clear definition where the technosphere (i.e. the managed field) ends and nature begins. See chapter 7.4.4.1.


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how Terms and concepts: Technosphere and ecosphere – clearer defining the boundary The terms technosphere and ecosphere are central and it can often be observed that these two terms are interpreted differently by different practitioners: in ISO 14044:2006 the ecosphere is referred to as “environment” what can be confusing as in LCA practice e.g. also buildings and dams are referred to as “man-made environment”. In addition, the elementary flows that cross the system boundary are defined as “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” . This brings ambiguity in cases such as e.g


This brings ambiguity in cases such as e.g. tailings from ore mining, fertiliser applied in agriculture, but also non-managed waste land-filling in general as such 'materials' are sometimes wrongly interpreted as being an elementary flow to the environment. The difficulty of impact assessment of complex flows such as land-filled end-of-life products or tailings is that LCIA relates to single substances and energy flows. In order to ensure reproducibility and an appropriate and working link with impact assessment it is necessary to completely model the named cases until emissions of single substances enter the natural environment. I.e. instead of inventorying “tailings” (which moreover can mean very different things in practice and for which no impact factors exist) the leaching of e.g. sulphuric acid and specific metals from the tailings is to be modelled and inventoried as "Emissions to water"


sulphuric acid and specific metals from the tailings is to be modelled and inventoried as "Emissions to water". The same applies to land-filled waste with both the emissions accounted for and the resources/products to operate the land-fill (if any). The boundary technosphere / ecosphere can hence be more suitably be defined by defining the elementary flow as “single substance68 or energy entering the system being studied that has been drawn from the ecosphere without previous human transformation, or single substance or energy leaving the system being studied that is released into the ecosphere without subsequent human transformation”. A precise definition of the system boundaries is important to ensure that all attributable or consequential processes are actually included in the modelled system and that all relevant potential impacts on the environment are appropriately covered


The levels of cut-off criteria and the maximum permissible uncertainty are - together with the achieved technical, geographical and time-related representativeness as well as method consistency - the key measure for the overall quality (i.e. accuracy, completeness, and precision) of the outcomes of the LCI/LCA study. 68 Note that while not being single substances, sum indicators such as VOC, COD can be addressed in LCIA by assuming a breakdown list of single substances. While the inventorying of actual single substances is to be preferred, LCIA can be operationalised also with such sum indicators (as long as they are sufficiently homogenous). Analogous considerations apply for energy resources such as e.g. hard coal. See however also chapter 7.4.3 on this and other overarching LCI modelling and inventorying issues.


ILCD Handbook: General guide for Life Cycle Assessment - Detailed guidance First edition 6 Scope definition - what to analyse and how Limitations of the system scope of the LCA approach (Accidents and other non-LCA impacts) Note that LCA only accounts for impacts related to normal and abnormal operation of processes and products, but not covering e.g. impacts from accidents, spills, and similar69. The health impact (or improvement) that products may directly exert on humans is equally not covered by LCA. This is because these impacts (or beneficial effects) occur within the technosphere and are not subject to any environmental fate and exposure chain. This applies to the use stage of a range of products such as food and drink, personal hygiene, healthcare products, tobacco products, etc. Use-phase related impacts that these products exert via an emission to the ecosphere (e.g. smoke emissions to the environment, wastewater-discharge) are however to be included