On the use of weighting in LCA: translating decision makers’ preferences into weights via linear programming

Purpose

The main goal of any life cycle assessment (LCA) study is to identify solutions leading to environmental savings. In conventional LCA studies, practitioners select from some alternatives the one which better matches their preferences. This task is sometimes simplified by ranking these alternatives using an aggregated indicator defined by attaching weights to impacts. We address here the inverse problem. That is, given an alternative, we aim to determine the weights for which that solution becomes optimal.

Methods

We propose a method based on linear programming (LP) that determines, for a given alternative, the ranges within which the weights attached to a set of impact metrics must lie so that when a weighting combination of these impacts is optimized, the alternative can be optimal, while if the weights fall outside this range, it is guaranteed that the solution will be suboptimal. A large weight value implies that the corresponding LCA impact is given more importance, while a low value implies the converse. Furthermore, we provide a rigorous mathematical analysis on the implications of using weighting schemes in LCA, showing that this practice guides decision-making towards the adoption of some specific alternatives (those lying on the convex envelope of the resulting trade-off curve).

Results and discussion

A case study based on the design of hydrogen infrastructures is taken as a test bed to illustrate the capabilities of the approach presented. Given are a set of production and storage technologies available to produce and deliver hydrogen, a final demand, and cost and environmental data. A set of designs, each achieving a unique combination of cost and LCA impact, is considered. For each of them, we calculate the minimum and maximum weight to be given to every LCA impact so that the alternative can be optimal among all the candidate designs. Numerical results show that solutions with lower impact are selected when decision makers are willing to pay larger monetary penalties for the environmental damage caused.

Conclusions

LP can be used in LCA to translate the decision makers’ preferences into weights. This information is rather valuable, particularly when these weights represent economic penalties, as it allows screening and ranking alternatives on the basis of a common economic basis. Our framework is aimed at facilitating decision making in LCA studies and defines a general framework for comparing alternatives that show different performance in a wide variety of impact metrics.     

PIQET: the design and development of an online ‘streamlined’ LCA tool for sustainable packaging design decision support

Background, aim and scope  

‘Streamlined’ life cycle assessment (LCA) tools hold out the possibility of providing LCA information quickly and easily in order to support a variety of decision-making environments and situations. The utility of such tools is closely related to the accuracy needs and possibilities, and the particular decisions to be supported. In order to facilitate the provision and application of LCA information in decision making during packaging design, development and utilisation, there is a prima facia case for a ‘streamlined’ LCA tool, provided it meets a set of requirements, including functionality, accuracy, validity, reliability and usability.     

Development of livestock production in the tropics: farm and farmers’ perspectives

Because of an increasing demand for animal-source foods, an increasing desire to reduce poverty and an increasing need to reduce the environmental impact of livestock production, tropical farming systems with livestock must increase their productivity. An important share of the global human and livestock populations are found within smallholder mixed-crop–livestock systems, which should, therefore, contribute significantly towards this increase in livestock production. The present paper argues that increased livestock production in smallholder mixed-crop–livestock systems faces many constraints at the level of the farm and the value chain. The present paper aims to describe and explain the impact of increased production from the farm and farmers’ perspective, in order to understand the constraints for increased livestock production. A framework is presented that links farming systems to livestock value chains. It is concluded that farming systems that pass from subsistence to commercial livestock production will: (1) shift from rural to urban markets; (2) become part of a different value chain (with lower prices, higher demands for product quality and increased competition from peri-urban producers and imports); and (3) have to face changes in within-farm mechanisms and crop–livestock relationships. A model study showed that feed limitation, which is common in tropical farming systems with livestock, implies that maximum herd output is achieved with small herd sizes, leaving low-quality feeds unutilised. Maximal herd output is not achieved at maximal individual animal output. Having more animals than required for optimal production – which is often the case as a larger herd size supports non-production functions of livestock, such as manure production, draught, traction and capital storage – goes at the expense of animal-source food output. Improving low-quality feeds by treatment allows keeping more animals while maintaining the same level of production. Ruminant methane emission per kg of milk produced is mainly determined by the level of milk production per cow. Part of the methane emissions, however, should be attributed to the non-production functions of ruminants. It was concluded that understanding the farm and farmers’ perceptions of increased production helps with the understanding of productivity increase constraints and adds information to that reported in the literature at the level of technology, markets and institutions.     

Integrating topics of sex and gender into medical curricula—lessons from the international community

In the era of individualized medicine, training future scientists and health-care providers in the principles of sex- and gender-based differences in health and disease is critical in order to optimize patient care. International successes to incorporate these concepts into medical curricula can provide a template for others to follow. Methodologies and resources are provided that can be adopted and adapted to specific needs of other institutions and learning situations.     

LCA and decision making: when and how to use consequential LCA; 62nd LCA forum,Swiss Federal Institute of Technology,Zürich, 9 September 2016

The 62nd life cycle assessment (LCA) forum was held on 9 September 2016 to discuss the state of research and application with regard to consequential life cycle assessment. This conference report presents the highlights of the LCA forum. The state of the art of consequential LCA was presented from different viewpoints. It was pointed out that consequential LCA is more than marginal mixes and avoided burdens and involves causal modelling. It was also said that social responsibility calls for consequential LCA. Currently, different models are used to support decision making. It was suggested to make use of the variety of models to check the conclusiveness of their results and thus the reliability of the LCAs. Current and future implementations of consequential LCI models in background databases and linking algorithms were presented. Several speakers presented consequential LCA case studies covering the sectors energy, transport, housing and mining. Some of the LCA models used in the case studies are complemented with general and partial computable equilibrium models and agent-based models and use environmentally extended input-output data or process-based LCA data. Some of the presentations focused on elements such as constrained production, marginal market mixes and technologies or recycling and system expansion. In three parallel workshops, the needs, contents and methodology, and implementation of consequential LCA approaches were discussed. The participants seemed to generally agree on the basic goal that LCA should be able to reflect the consequences of decisions. The inquiry among the participants showed that the demand for consequential LCA studies is hardly existent. The appropriate implementation of consequential modelling in LCA databases and on the appropriate model to be used in consequential LCA case studies was debated. It revealed a need for further and extensive discussions to be able to reach (minimum) consensus.     

Marine plastics in LCA: current status and MarILCA’s contributions

The International Journal of Life Cycle Assessment -     

Integrating pathology into human disease modelling – how to eat the elephant

Mouse models are increasingly being used for the study of human disease, and the generation and functional characterisation of new models is underpinned by high-throughput phenotyping consortia such as the International Mouse Phenotyping Consortium. A new study by Adissu and colleagues, published in Disease Models & Mechanisms, demonstrates the usefulness of histopathology in providing corroborative information and uncovering novel phenotypes in genetically modified mice in a high-throughput screen. Although pathology is recognised as a valuable tool to enhance our understanding of animal disease models, it has also been systematically under-resourced. This Editorial aims to highlight ways in which the gap between the usefulness of pathology and its perceived inaccessibility can be addressed by considering pragmatic solutions for planning, resourcing and accessing pathology expertise. The role of funding agencies, academic centres and journals in ensuring that the value of pathology is fully recognised and is adequately supported and funded is also discussed.KEY WORDS: Pathology, Phenotyping, Mouse, IMPC

“When eating an elephant take one bite at a time” –Creighton Williams Abrams.

     

Integrating small-scale landscape elements into land use/cover: The impact on landscape metrics’ values

Over the last 30 years the use and misuse of landscape metrics has been widely studied. However, there has been less attention on incorporating small-scale landscape elements into landscape analysis. Data type used in the analysis can be either vector or raster, while the raster format is more widely used. However, using large-scale topographical vector databases has several advantages – they cover whole countries with very detailed and accurate topographical data. Despite the high level of detail, their amount in Mb is small, which allows simultaneously to analyse large areas. The peculiarity of vector data is that small-scale landscape elements are mapped as point elements or lines. For calculating landscape metrics, the integration of these features and LULC (land use/cover) polygons is needed. In the current study we investigated how integration of point and linear elements into polygon layers affects the values of landscape metrics. Adding line buffers influenced metrics’ values more than adding point elements. The ensemble of point and linear objects is similar to linear objects. Our study revealed that integrating small-scale landscape elements into land use/cover layers by using buffers gives more realistic values if the buffer size is in compliance with the size of the phenomena in the real world and suitable landscape metrics are chosen. However, the metrics that responded to adding small-scale landscape elements in correspondence with their real world impact on landscape metric values might not always be the best ecological indicators in terms of small-scale landscape elements. Another issue is that values of landscape metrics depend directly on the number of classes determined in the data specification, and on the data model. If the number of mappable point and linear objects changes, or the data model of the linear objects changes, the values of landscape metrics differ.     

Modelling perspectives on aging: can mathematics help us stay young?

We survey several types of mathematical models that keep track of age distributions in a population, or follow some aspects of aging, such as loss of replicative potential of stem cells. The properties of a class of linear models of this type are discussed and compared. We illustrate the applicability of such models with a simple example based on hypothetical stem cell dynamics developed to address age-related telomere loss in the human granulocyte pool. We then describe the contrasting behaviour of nonlinear systems. Examples are drawn from the class of "dynamical diseases" to illustrate some of the aspects of nonlinear systems. Applications of these, and other models to the problems of aging and replicative aging are discussed.     

The Fitness Check of the Birds and Habitats Directives: A discourse analysis of stakeholders’ perspectives

In 2015, the European Union’s Birds and Habitats Directives underwent an evaluation in which selected national stakeholders provided their perspectives on the directives’ implementation. Analyzing the views of different stakeholder groups from eight European member states, this study found that these views could be synthesized into three more general perspectives. The first perspective focuses on problems, indicating that these are caused by legislative drawbacks in the directives. The second perspective holds that problems are generated by improper implementation by member states. The third perspective commends the benefits of the directives in face of the existing implementation problems. Interest groups and to a minor extent governmental bodies espoused the first perspective, and environmental non-governmental organizations especially favored the third. The struggle between these three perspectives reflects ongoing debates regarding positive and negative aspects of the directives and possibilities for improving their implementation. We conclude that the relevance and impact of conservation policies should never be seen as self-evident. In order to reach the conservation goals envisaged, continuous efforts are needed to enforce and maintain environmental legislation.     

LCA and LCC of the world’s longest pier: a case study on nickel-containing stainless steel rebar

Purpose

Built in 1941, the Progreso Pier was the first concrete structure in the world built with nickel-containing stainless steel reinforcement. The Pier has been in service for over 70 years without any significant repair or maintenance activities. The aim of this study was to understand the environmental and economic implications of selecting nickel-containing stainless steel reinforcement using the Progreso Pier as the case study.

Methods

A combined environmental life cycle assessment (LCA) and life cycle costing (LCC) study was conducted. The analysis considered the potential environmental impacts and the net present cost of the stainless steel reinforced structure from cradle to grave and compared it to the same structure using conventional carbon steel.

Results and discussion

The results indicated that while using stainless steel reinforcement resulted in a marginally higher environmental impact after initial construction, this is offset by the increased service life and, hence, less frequent maintenance and reconstruction activities. Relative to the as-built stainless steel reinforcement design, the environmental impacts of the carbon steel reinforced design are between 69 and 79 % higher over the analysis period. Similar observations were made for the other investigated impact categories. The cost implications of using stainless steel reinforcement show economic benefits that are complementary to the environmental benefits. Similar to the LCA, the service life benefits outweigh the higher unit costs for stainless steel, assuming a discount rate of 0.01 % as the baseline scenario. The carbon steel reinforced design has a net present cost that is 44 % higher than the as-built stainless steel reinforcement design. The crossover point for the two designs occurs at year 50, which corresponds to the reconstruction activity. A sensitivity analysis shows that the results and conclusions are sensitive to the choice in discount rate: Rates 3 % and lower produce net present costs that are lower for the as-built design; rates 4 % and higher produce net present costs that are lower for the alternative design.

Conclusions

The study demonstrates how LCA and LCC are complementary tools that can be used in decision-making for sustainable construction. The Progreso Pier exemplifies the importance of considering the entire life cycle with service life and recycling as well as long-term life cycle impacts of infrastructure projects from an environmental and economic perspective.

     

Monkeys into Men and Men into Monkeys: Chance and Contingency in the Evolution of Man, Mind and Morals in Charles Kingsley’s Water Babies

The nineteenth century theologian, author and poet Charles Kingsley was a notable populariser of Darwinian evolution. He championed Darwin’s cause and that of honesty in science for more than a decade from 1859 to 1871. Kingsley’s interpretation of evolution shaped his theology, his politics and his views on race. The relationship between men and apes set the context for Kingsley’s consideration of these issues. Having defended Darwin for a decade in 1871 Kingsley was dismayed to read Darwin’s account of the evolution of morals in Descent of Man. He subsequently distanced himself from Darwin’s conclusions even though he remained an ardent evolutionist until his death in 1875.