Emnet for denne vejledning er nogle af de første elementer i en livscyklusvurdering, efter at man har defineret undersøgelsens mål (se også Figur 2), nemlig:
Disse elementer kan ofte være afgørende for resultatet af en konkret livscyklusvurdering. Derfor er det vigtigt at disse elementer udføres med omhu.
Formålet med denne vejledning er at tilvejebringe en entydig procedure for disse elementer i en livscyklusvurdering.
De omtalte elementer tjener tre formål:
En livscyklusvurdering undersøger miljøpåvirkningerne ved en mulig pro- duktsubstitution, dvs. et valg af ét produkt frem for et andet, eller et valg af et bestemt produkt i forhold til et fravalg af dette produkt.
Den funktionelle enhed beskriver og kvantificerer de egenskaber ved produktet, der skal være til stede, for at den undersøgte substitution kan finde sted. Disse egenskaber (funktionalitet, udseende, stabilitet, holdbarhed, osv.) bestemmes igen af kravene på det marked, hvor produktet skal sælges.
Referencestrømmene omsætter den abstrakte funktionelle enhed til konkrete produktstrømme for hvert af de systemer der sammenlignes, således at produktalternativerne sammenlignes på et ækvivalent grundlag, der afspejler de faktiske konsekvenser af den mulige produktsubstitution. Referencestrømmene er udgangspunkt for at opbygge de nødvendige modeller af produktsystemerne.
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”Livscyklusvurderinger – en kommenteret oversættelse af ISO 14040 og 14044” indeholder DS/EN ISO 14040:2008 og DS/EN ISO 14044:2008 på både danske og engelsk sammen med en vejledning til krav og anbefalinger til LCA. De mange råd gives ud fra de danske erfaringer med at lave livscyklusvurderinger og det teoretiske arbejde lavet af LCA-instituttet. Bogen henvender sig til personer, som skal udføre eller læse livscyklusvurderinger, hvor de skal leve op til ISO-standardernes krav, fx. miljø-og indkøbsansvarlige.
Denne rapport er et led i CONCITOs strategi om at få større fokus på produkters rolle i udledningen af drivhusgasser. Dette fokus finder CONCITO nødvendigt, da vi mener, at det er en forudsætning for at skabe en generel bæredygtig udvikling i såvel Danmark som i resten af verden. Rapporten er tredje led i en rapportrække om emnet, hvor de tidligere rapporter er ”Forbrugerens klimapåvirkning” (CONCITO (2010)) og ”Reducerer brug af biomasse atmosfærens indhold af CO2?” (CONCITO (2011)).
Rapporten går i dybden med metoder til og udfordringer i at beregne Carbon Footprint, hvilke standarder og metoder, der findes samt deres fordele, ulemper og mangler. Den kommer også med anbefalinger til, hvordan vi i Danmark kan implementere en mere generel anvendelse af Carbon Footprint, som både er administrativt og teknisk overkommelig. De første dele af rapporten, der går i dybden med standarder og metoder, kan være teknisk komplicerede, og kræver et vist kendskab til LCA-metoder og tankegange.
Rapporten er skrevet af CONCITO med bidrag fra Jannick H. Schmidt fra 2.-0 LCA consultants”. Udsagn og konklusioner i rapporten er dog alene CONCITOs.
While the PEF Guide intends to provide a “harmonised European methodology” and “to provide detailed and comprehensive technical guidance on how to conduct a PEF study” it contains requirements that may be difficult to interpret for LCA practitioners. This guide is our contribution to clarify the context and meaning of some of the requirements that may otherwise cause problems.
In general, a normal consequential LCA performed according to ISO 14040/44/49 will fulfil the requirements of the PEF guideline. However, some specific points to be aware of are outlined in this guide:
We analyse a number of different externalities to identify conceptual challenges for the practical implementation of their internalisation. Three issues were identified: i) The balance between compensation and technology change and the respective effects on the nominal and real GDP; ii) The relevance and efficiency of different instruments for internalisation and compensation; and iii) Implementing internalisation over large geographical and temporal distances. We find taxation to be a more relevant and efficient tool for internalisation than insurance and litigation. With increasing geographical and especially temporal distance between the benefitting actor and the victim of the external cost, the involvement of a non-governmental intermediate actor becomes increasingly necessary to provide the short-term capital required to ensure a successful implementation.
A design strategy for LCI databases was proposed by Weidema (2003), containing three elements: 1) Database completeness 2) Unlinked and unallocated unit processes 3) Markets as separate unit processes.
Database completeness is required to ensure that different kind of models can be applied without being hampered by lacking data availability. Data completeness of course also ensures that comparisons are not biased by differences in completeness of the compared systems.
Having datasets available as unlinked, unallocated unit processes is a requirement for allowing different models to apply different algorithms for linking the datasets. The difference in linking algorithms is what distinguishes attributional and consequential models. Linking algorithms differ in the extent to which they take into account constraints (thus excluding specific unit processes from the supply chain), and in the way they deal with by-products (by substitution or allocation; the latter with many different allocation keys). This also provides a clear distinction between the verifiable, unlinked, unallocated process models that can be checked directly against their real life counterparts, and the linked, mono-product systems that necessarily require the introduction of assumptions, either on how markets react to changes in demand and supply (the economic assumptions of consequential models) or on what constitutes a fair attribution of the exchanges of unit processes to their products (the normative assumptions of attributional models).
Modelling markets as separate unit processes provides a simple way of combining the same (non-market) unit processes in many different ways depending on the system model applied, without changing the flows in each of the processes supplying and being supplied by the market. Furthermore, this makes it possible to document different market conditions using the same data format as for all other unit processes.
While Weidema (2003) reported two examples of databases that had applied this design strategy, the full potential of the strategy was not realised at the time, partly because the market activities were not systematically implemented as separate unit processes, partly because of technical limitations in the LCI data formats and LCA softwares available (e.g. inability to assign more than one property to a flow, inability to handle negative product flows, lack of machine-interpretable technological and geographical identifiers to delimit markets and locations of unit processes).
With the implementation of the ecoSpold 2 data format in the context of the ecoinvent database version 3, these identified limitations have been removed.
This paper discusses the identification of the environmental consequences of marginal electricity supplies in consequential life cycle assessments (LCA). According to the methodology, environmental characteristics can be examined by identifying affected activities, i.e. often the marginal technology. The present ‘state-of the-art’ method is to identify the long-term change in power plant capacity, known as the long-term marginal technology, and assume that the marginal supply will be fully produced at such capacity. However, the marginal change in capacity will have to operate as an integrated part of the total energy system. Consequently, it does not necessarily represent the marginal change in electricity supply, which is likely to involve a mixture of different production technologies. Especially when planning future sustainable energy systems involving combined heat and power (CHP) and fluctuating renewable energy sources, such issue becomes very important.
This paper identifies a business-as-usual (BAU) 2030 projection of the Danish energy system. With a high share of both CHP and wind power, such system can be regarded a front-runner in the development of future sustainable energy systems in general. A strict distinction is made between, on the one hand, marginal capacities, i.e. the long-term change in power plant capacities, and on the other, marginal supply, i.e. the changes in production given the combination of power plants and their individual marginal production costs. Detailed energy system analysis (ESA) simulation is used to identify the affected technologies, considering the fact that the marginal technology will change from one hour to another, depending on the size of electricity demand compared to, among others, wind power and CHP productions. On the basis of such input, a long-term yearly average marginal (YAM) technology is identified and the environmental impacts are calculated using data from ecoinvent.
The results show how the marginal electricity production is not based solely on the marginal change in capacity but can be characterised as a complex set of affected electricity and heat supply technologies. A long-term YAM technology is identified for the Danish BAU2030 system in the case of three different long-term marginal changes in capacity, namely coal, natural gas or wind power.
Four analyses and examples of YAMs have been used in order to present examples of the cause–effect chain between a change in demand for electricity and the installation of new capacity. In order to keep open the possibilities for further analysis of what can be considered the marginal technology, the results of four different situations are provided. We suggest that the technology mix with the installation of natural gas or coal power plant is applied as the marginal capacity.
The environmental consequences of marginal changes in electricity supply cannot always be represented solely by long-term change in power plant capacity, known as the long-term marginal technology. The marginal change in capacity will have to operate as an integrated part of the total energy system and, consequently, in most energy systems, one will have to identify the long-term YAM technology in order to make an accurate evaluation of the environmental consequences.
This paper recommends a combination of LCA and ESA as a methodology for identifying a complex set of marginal technologies. The paper also establishes values for Danish marginal electricity production as a yearly average (YAM) that can be used in future LCA studies involving Danish electricity.
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Allocation in life cycle inventory (LCI) analysis is one of the long-standing methodological issues in life cycle assessment (LCA). Discussion on allocation among LCA researchers has taken place almost in complete isolation from the series of closely related discussions from the 1960s in the field of input−output economics, regarding the supply and use framework. This article aims at developing a coherent mathematical framework for allocation in LCA by connecting the parallel developments of the LCA and the input−output communities. In doing so, the article shows that the partitioning method in LCA is equivalent to the industry-technology model in input−output economics, and system expansion in LCA is equivalent to the by-product-technology model in input−output output economics. Furthermore, we argue that the commodity-technology model and the by-product-technology model, which have been considered as two different models in input−output economics for more than 40 years, are essentially equivalent when it comes to practical applications. It is shown that the matrix-based approach used for system expansion successfully solves the endless regression problem that has been raised in LCA literature. A numerical example is introduced to demonstrate the use of allocation models. The relationship of these approaches with consequential and attributional LCA models is also discussed.
