The ISO-standard for LCA distinguishes four phases, of which the last one, the interpretation, is the least elaborated. It
can be regarded as containing procedural steps (like a completeness check) as well as numerical steps (like a sensitivity
check). This paper provides five examples of techniques that can be used for the numerical steps. These are the contribution
analysis, the perturbation analysis, the uncertainty analysis, the comparative analysis, and the discernibility analysis.
All five techniques are described at a non-technical level with respect to basic concept, possibilities, tabular and graphical
representation, restriction and warnings, and all are illustrated with a simple example. 相似文献
The role and meaning of accounting for energy, including feedstock energy, is reviewed in connection to Einstein’s special
theory of relativity. It is argued that there is only one unambiguous interpretation of the term energy-content: The one that
corresponds tome The implications for life cycle inventories is that all discussions concerning upper heating value, lower heating value,
feedstock energy, etc. are pointless as long as the motivation for choosing one or the other is not specified in relation
to the safeguard subjects defined for a particular analysis (LCA or energy analysis). The subjective aspects of energy accounting
schemes, even though based on mere thermodynamics, are highlighted. In inventory analysis, it is recommended that energy carriers
should be accounted separately and in mass terms.
For illustrative purposes, energy statistics and energy assessment are discussed in view of the safeguard subjects underlying
the accounting procedures. Based on a set of theses, one possible energy accounting scheme as an indicator of the “consumption
of non-renewable energy resources” within the impact assessment of LCA is sketched. It is emphasised that energy accounting
schemes do not reflect environmental impacts caused by the energy sources, and the characteristics of the indicator “consumption
of non-renewable energy resources” introduced here are highlighted.
An erratum to this article is available at . 相似文献
Until now, impact assessment within LCA has mainly focussed on the substance hazard for some impacts, whereas, for other impacts, substance fate is included in the assessment as well. The main goal of this paper is to define the position of fate modelling in LCIA, and to specify the requirements for a general LCA fate model. A proposal is made to clearly distinguish an impact-category independent fate analysis from a separate exposure analysis and an impact-category related impact analysis, and to use a global multimedia model as a modelling basis. This modelling basis might be supplemented with substance-specific models for a number of substances. 相似文献
One of the remaining important problems of life cycle inventory analysis is the allocation problem. A proper solution of this problem calls for a proper understanding of the nature of the problem itself. This paper argues that the established definition of the allocation problem as the fact that one unit process produces more than one function, is not appropriate. That definition points to an important reason of the occurrence of the problem, but the situation of internal (closed-loop) recycling already indicates that there may be product systems which contain multifunction processes, but which nevertheless need not exhibit an allocation problem. The paper proceeds by examining a number of simple hypothetical cases, and proposes a precise and operational definition of the allocation problem. This enables a systematic categorization of approaches for dealing with the allocation problem. 相似文献
In 1995, the original method for assessing the impact category abiotic resource depletion using abiotic depletion potentials (ADPs) was published. The ADP of a resource was defined as the ratio of the annual production and the square of the ultimate (crustal content based) reserve for the resource divided by the same ratio for a reference resource (antimony (Sb)). In 2002, ADPs were updated based on the most recent USGS annual production data. In addition, the impact category was sub-divided into two categories, using two sets of ADPs: the ADP for fossil fuels and the ADP for elements; in this article, we focus on the ADP for elements. Since then, ADP values have not been updated anymore despite the availability of updates of annual production data and also updates of crustal content data that constitute the basis of the ultimate reserves. Moreover, it was known that the coverage of elements by ADPs was incomplete. These three aspects together can affect relative ranking of abiotic resources based on the ADP. Furthermore, dealing with annually changing production data might have to be revisited by proposing new calculation procedures. Finally, category totals to calculate normalized indicator results have to be updated as well, because incomplete coverage of elements can lead to biased results.
Methods
We used updated reserve estimates and time series of production data from authoritative sources to calculate ADPs for different years. We also explored the use of several variations: moving averages and cumulative production data. We analyzed the patterns in ADP over time and the contribution by different elements in the category total. Furthermore, two case studies are carried out applying two different normalization reference areas (the EU 27 as normalization reference area and the world) for 2010.
Results and discussion
We present the results of the data updates and improved coverage. On top of this, new calculation procedures are proposed for ADPs, dealing with the annually changing production data. The case studies show that the improvements of data and calculation procedures will change the normalized indicator results of many case studies considerably, making ADP less sensitive for fluctuating production data in the future.
Conclusions
The update of ultimate reserve and production data and the revision of calculation procedures of ADPs and category totals have resulted in an improved, up-to-date, and more complete set of ADPs and a category total that better reflects the total resource depletion magnitude than before. An ADP based on the cumulative production overall years is most in line with the intent of the original ADP method. We further recommend to only use category totals based on production data for the same year as is used for the other (emission-based) impact categories.
It is frequently mentioned in literature that LCA is linear, without a proof, or even without a clear definition of the criterion for linearity. Here we study the meaning of the term linear, and in relation to that, the question if LCA is indeed linear.
Methods
We explore the different meanings of the term linearity in the context of mathematical models. This leads to a distinction between linear functions, homogeneous functions, homogenous linear functions, bilinear functions, and multilinear functions. Each of them is defined in accessible terms and illustrated with examples.
Results
We analyze traditional, matrix-based, LCA, and conclude that LCA is not linear in any of the senses defined.
Discussion and conclusions
Despite the negative answer to the research question, there are many respects in which LCA can be regarded to be, at least to some extent, linear. We discuss a few of such cases. We also discuss a few practical implications for practitioners of LCA and for developers of new methods for LCI and LCIA.
