Uncertainty in LCA case study due to allocation approaches and life cycle impact assessment methods

Purpose

Uncertainty is present in many forms in life cycle assessment (LCA). However, little attention has been paid to analyze the variability that methodological choices have on LCA outcomes. To address this variability, common practice is to conduct a sensitivity analysis, which is sometimes treated only at a qualitative level. Hence, the purpose of this paper was to evaluate the uncertainty and the sensitivity in the LCA of swine production due to two methodological choices: the allocation approach and the life cycle impact assessment (LCIA) method.

Methods

We used a comparative case study of swine production to address uncertainty due to methodological choices. First, scenario variation through a sensitivity analysis of the approaches used to address the multi-functionality problem was conducted for the main processes of the system product, followed by an impact assessment using five LCIA methods at the midpoint level. The results from the sensitivity analysis were used to generate 10,000 independent simulations using the Monte Carlo method and then compared using comparison indicators in histogram graphics.

Results and discussion

Regardless of the differences between the absolute values of the LCA obtained due to the allocation approach and LCIA methods used, the overall ranking of scenarios did not change. The use of the substitution method to address the multi-functional processes in swine production showed the highest values for almost all of the impact categories, except for freshwater ecotoxicity; therefore, this method introduced the greater variations into our analysis. Regarding the variation of the LCIA method, for acidification, eutrophication, and freshwater ecotoxicity, the results were very sensitive. The uncertainty analysis with the Monte Carlo simulations showed a wide range of results and an almost equal probability of all the scenarios be the preferable option to decrease the impacts on acidification, eutrophication, and freshwater ecotoxicity. Considering the aggregate result variation across allocation approaches and LCIA methods, the uncertainty is too high to identify a statistically significant alternative.

Conclusions

The uncertainty analysis showed that performing only a sensitivity analysis could mislead the decision-maker with respect to LCA results; our analysis with the Monte Carlo simulation indicates no significant difference between the alternatives compared. Although the uncertainty in the LCA outcomes could not be decreased due to the wide range of possible results, to some extent, the uncertainty analysis can lead to a less uncertain decision-making by demonstrating the uncertainties between the compared alternatives.

     

Streamlining scenario analysis and optimization of key choices in value chains using a modular LCA approach

Purpose

The environmental performance of products or services is often a result of a number of key decisions that shape their life cycles (e.g., techology choices). This paper introduces a modular LCA approach that is capable of reducing the effort involved in performing scenario analyses and optimization when several key choices along a product’s value chain lead to many alternative life cycles.

Methods

The main idea is that the value chain of a product can be divided into interconnected but exchangeable modules, which together represent a full life cycle. A module is comprised of unit processes from the practitioner’s LCI database. The inputs, outputs, and system boundaries of each module can be tailored to the context of the studied system. Alternatives arise whenever multiple modules produce substitutable products. Unlike in conventional LCI databases, no copies are necessary to represent the same process with different inputs. A module-product matrix is used to store this information. It can be used as a basis for an automated scenario analysis of all alternatives or as an input to an optimization model.

Results and discussion

Our approach is illustrated in two case studies: (1) Passenger car fuel choices are modeled by 15 modules representing 33 alternative value chains for diesel, petrol, natural gas and electric cars. The automated comparison of LCA results indicates that electric mobility is often the preferable option from a climate perspective, but impacts depend strongly on the electricity source. (2) A dynamic optimization model including stocks is built from eight modules to analyze the optimal use of wood for material and energy applications. Results indicate that although direct substitution benefits are higher for energy applications, cascading use of wood can maximize environmental performance over the entire life cycle.

Conclusions

The modular LCA approach permits an efficient modeling and comparison of alternative product life cycles, enabling practitioners to focus on key decisions. It can be applied to exploit a potential that is hidden in LCI databases, which is that they contain many specific inventories but not all useful combinations in the context of scenario analyses. The user-defined level of abstraction that is introduced through modules can be helpful in the communication of LCA results. The modular approach also facilitates the integration of LCA and optimization as well as other industrial ecology methods. An open source software is provided to enable others to apply and further develop our implementation of a modular LCA approach.

     

Evidence-informed policy formulation and implementation: a comparative case study of two national policies for improving health and social care in Sweden

Background

Evidence has come to play a central role in health policymaking. However, policymakers tend to use other types of information besides research evidence. Most prior studies on evidence-informed policy have focused on the policy formulation phase without a systematic analysis of its implementation. It has been suggested that in order to fully understand the policy process, the analysis should include both policy formulation and implementation. The purpose of the study was to explore and compare two policies aiming to improve health and social care in Sweden and to empirically test a new conceptual model for evidence-informed policy formulation and implementation.

Methods

Two concurrent national policies were studied during the entire policy process using a longitudinal, comparative case study approach. Data was collected through interviews, observations, and documents. A Conceptual Model for Evidence-Informed Policy Formulation and Implementation was developed based on prior frameworks for evidence-informed policymaking and policy dissemination and implementation. The conceptual model was used to organize and analyze the data.

Results

The policies differed regarding the use of evidence in the policy formulation and the extent to which the policy formulation and implementation phases overlapped. Similarities between the cases were an emphasis on capacity assessment, modified activities based on the assessment, and a highly active implementation approach relying on networks of stakeholders. The Conceptual Model for Evidence-Informed Policy Formulation and Implementation was empirically useful to organize the data.

Conclusions

The policy actors’ roles and functions were found to have a great influence on the choices of strategies and collaborators in all policy phases. The Conceptual Model for Evidence-Informed Policy Formulation and Implementation was found to be useful. However, it provided insufficient guidance for analyzing actors involved in the policy process, capacity-building strategies, and overlapping policy phases. A revised version of the model that includes these aspects is suggested.

     

Influence of methodological choices on maintenance and replacement in building LCA

The International Journal of Life Cycle Assessment - Previous life cycle assessments (LCAs) of buildings and building components show a broad range of values for the impact of maintenance and...     

Energy-saving policies and low-energy residential buildings: an LCA case study to support decision makers in Piedmont (Italy)

Background, aim and scope  

A low-energy family house recently built in Northern Italy was selected by Regione Piemonte as an outstanding example of resource efficient building. An economic incentive was awarded to cover the extra costs of the thermal insulation, windows and equipment in order to decrease the yearly winter heat requirement from the legal standard of 109 to 10 kW h/m², while existing buildings in the study area typically require 200 kW h/m². As the building was claimed to be sustainable on the basis of its outstanding energy-saving performance, an ex post life cycle assessment (LCA) was set up to understand whether, and to what extent, the positive judgement could be confirmed in a life cycle perspective.     

Proposal of a method for allocation in building-related environmental LCA based on economic parameters

Application and development of the LCA methodology to the context of the building sector makes several building specific considerations necessary, as some key characteristics of products in the building sector differ considerably from those of other industrial sectors. The largest difference is that the service life of a building can stretch over centuries, rather than decades or years as seen for consumer products. The result of the long service life is that it is difficult to obtain accurate data and to make relevant assumptions about future conditions regarding, for example, recycling. These problems have implications on the issue of allocation in the building sector, in the way that several allocation procedures ascribe environmental loads to users of recycled or reused products and materials in the future which are unknown today. The long service life for buildings, building materials and building components, is associated with the introduced concept of a virtual parallel time perspective proposed here, which basically substitutes historical and future processes and values with current data. Further, the production and refining of raw material as a parallel to upgrading of recycled material, normally contains several intermediate products. A suggestion is given for how to determine the comparability of intermediate materials. The suggested method for allocation presented is based on three basic assumptions: (1) If environmental loads are to be allocated to a succeeding product life cycle, the studied actual life cycle has to take responsibility for upgrading of the residual material into secondary resources. (2) Material characteristics and design of products are important factors to estimate the recyclable amount of the material. Therefore, a design factor is suggested using information for inherent material properties combined with information of the product context at the building level. (3) The quality reduction between the materials in two following product life cycles is indicated as the ratio between the market value for the material in the products. The presented method can be a good alternative for handling the problem of open-loop recycling allocation in the context of the building sector if a consensus for the use of the fictive parallel time perspective and the use of the design factor can be established. This as the use of the time perspective and design factor is crucial to be able to deal with the problem of long service lives for buildings and building materials and the specific characteristics of the same building materials and components built into different building contexts.     

LCA of a newsprint paper machine: a case study of capital equipment

Purpose

The environmental aspects of paper as a consumer good have been extensively studied. However, the paper machine has been mostly neglected in the literature. The purpose of this article is to present a LCA case study that explicitly focuses on the system of a newsprint paper machine and its environmental impacts and not on the system of the consumer good paper. The relevance of the paper machine as capital equipment is analyzed, and conclusions for the environmental improvement of paper machines are drawn based on identified hotspots. The article hereby answers the more general research questions of whether capital equipment has rightly been neglected in other studies regarding pulp and paper and which impact categories are important for analyzing the environmental burdens of a paper machine.

Methods

The study has been executed in collaboration with Voith Paper, an original equipment manufacturer. Hence, in distinction to literature-based studies, primary data on the paper machine was available resulting in a high overall data quality. Based on the ISO 14040 (2006) and 14044 (2006) standards, this article pursues a cradle-to-grave approach for the paper machine. It assesses the environmental impacts in the impact categories defined by the ReCiPe impact assessment methodology. Different types of energy generation are examined in a scenario analysis with combined heat and power generation (CHP) as the baseline case. For interpretation, a normalization and a sectoral analysis are performed.

Results and discussion

The normalized results indicate fossil resource depletion and global warming as the most important impact categories. Global warming impacts are highly dependent on the energy processes and result to 432.7 kg CO2e per production of 1 t of paper for CHP and to 701.7 kg CO2e for EU25 grid mix. The sectoral analysis shows that the machinery's operations/use phase is clearly dominating most impact categories due to its long lifetime. An exception is the metal depletion, for which the materials and manufacturing processes are most important.

Conclusions

These findings prove that for most categories, the operations/use phase of the paper machine is the most important life cycle stage. In systems focusing on the consumer good paper, it is therefore sufficient to model the operation of the paper machine, whereas the manufacturing, transport, and end-of-life processes regarding the paper machine equipment can be neglected, unless metal depletion is important to the study.     

Environmental impact evaluation of co-products: decision-aid tool for allocation in LCA

The International Journal of Life Cycle Assessment - As sustainability has become an important asset for production systems, it is important to conduct life cycle assessment (LCA) studies. When...     

Allocation issues in LCA methodology: a case study of corn stover-based fuel ethanol

Background, aim, and scope

Facing the threat of oil depletion and climate change, a shift from fossil resources to renewables is ongoing to secure long-term low carbon energy supplies. In view of the carbon dioxide reduction targets agreed upon in the Kyoto protocol, bioethanol has become an attractive option for one energy application, as transport fuel. Many studies on the LCA of fuel ethanol have been conducted, and the results vary to a large extent. In most of these studies, only one type of allocation is applied. However, the effect of allocation on outcomes is of crucial importance to LCA as a decision supporting tool. This is only addressed in a few studies to a limited extent. Moreover, most of the studies mainly focus on fossil energy use and GHG emissions. In this paper, a case study is presented wherein a more complete set of impact categories is used. Land use has been left out of account as only hectare data would be given which is obviously dominated by agriculture. Moreover, different allocation methods are applied to assess the sensitivity of the outcomes for allocation choices.

Materials and methods

This study focuses on the comparison of LCA results from the application of different allocation methods by presenting an LCA of gasoline and ethanol as fuels and with two types of blends of gasoline with ethanol, all used in a midsize car. As a main second-generation application growing fast in the USA, corn stover-based ethanol is chosen as a case study. The life cycles of the fuels include gasoline production, corn and stover agriculture, cellulosic ethanol production, blending ethanol with gasoline to produce E10 (10% of ethanol) and E85 (85% of ethanol), and finally the use of gasoline, E10, E85, and ethanol. In this study, a substantially broader set of eight environmental impacts is covered.

Results

LCA results appear to be largely dependent on the allocation methods rendered. The level of abiotic depletion and ozone layer depletion decrease when replacing gasoline by ethanol fuels, irrespective of the allocation method applied, while the rest of the impacts except global warming potential are larger. The results show a reduction of global warming potential when mass/energy allocation is applied; in the case of economic allocation, it gives contrary results. In the expanded systems, global warming potential is significantly reduced comparing to the ones from the allocated systems. A contribution analysis shows that car driving, electricity use for cellulase enzyme production, and ethanol conversion contribute largely to global warming potential from the life cycle of ethanol fuels.

Discussion

The reason why the results of global warming potential show a reverse trend is that the corn/stover allocation ratio shifts from 7.5 to 1.7 when shifting from economic allocation to mass/energy allocation. When mass/energy allocation is applied, both more credits (CO₂ uptake) and more penalties (N₂O emission) in agriculture are allocated to stover compared to the case of economic allocation. However, more CO₂ is taken up than N₂O (in CO₂ eq.) emitted. Hence, the smaller the allocation ratio is between corn and stover, the lower the share of the overall global warming emissions being allocated to ethanol will be. In the system expansion approach, global warming potentials are significantly reduced, resulting in the negative values in all cases. This implies that the system expansion results are comparable to one another because they make the same cutoffs but not really to the results related to mass, energy, and economic value-based allocated systems.

Conclusions

The choice of the allocation methods is essential for the outcomes, especially for global warming potential in this case. The application of economic allocation leads to increased GWP when replacing gasoline by ethanol fuels, while reduction of GWP is achieved when mass/energy allocation is used as well as in the system where biogenic CO₂ is excluded. Ethanol fuels are better options than gasoline when abiotic depletion and ozone layer depletion are concerned. In terms of other environmental impacts, gasoline is a better option, mainly due to the emissions of nutrients and toxic substances connected with agriculture. A clear shift of problems can be detected: saving fossil fuels at the expense of emissions related to agriculture, with GHG benefits depending on allocation choices. The overall evaluation of these fuel options, therefore, depends very much on the importance attached to each impact category.

Recommendations and perspectives

This study focuses only on corn stover-based ethanol as one case. Further studies may include other types of cellulosic feedstocks (i.e., switchgrass or wood), which require less intensive agricultural practice and may lead to better environmental performance of fuel ethanol. Furthermore, this study shows that widely used but different allocation methods determine outcomes of LCA studies on biofuels. This is an unacceptable situation from a societal point of view and a challenge from a scientific point of view. The results from applying just one allocation method are not sufficient for decision making. Comparison of different allocation methods is certainly of crucial importance. A broader approach beyond LCA for the analysis of biorefinery systems with regard to energy conservation, environmental impact, and cost–benefit will provide general indications on the sustainability of bio-based productions.     

Developing characterisation factors for land fragmentation impacts on biodiversity in LCA: key learnings from a sugarcane case study

Purpose

Habitat change was identified by the Millennium Ecosystem Assessment as the main direct driver of biodiversity loss. However, while habitat loss is already implemented in Life Cycle Impact Assessment (LCIA) methods, the additional impact on biodiversity due to habitat fragmentation is not assessed yet. Thus, the goal of this study was to include fragmentation effects from land occupation and transformation at both midpoint and endpoint levels in LCIA.

Methods

One promising metric, combining the landscape spatial configuration with species characteristics, is the metapopulation capacity λ, which can be used to rank landscapes in terms of their capacity to support viable populations spatially structured. A methodology to derive worldwide regionalised fragmentation indexes based on λ was used and combined with the Species Fragmented-Area Relationship (SFAR), which relies on λ to assess a species loss due to fragmentation. We adapted both developments to assess fragmentation impacts due to land occupation and transformation at both midpoint and endpoint levels in LCIA. An application to sugarcane production occurring in different geographical areas, more or less sensitive to land fragmentation, was performed.

Results and discussion

The comparison to other existing LCIA indicators highlighted its great potential for complementing current assessments through fragmentation effect inclusion. Last, both models were discussed through the evaluation grid used by the UNEP-SETAC land use LCIA working group for biodiversity impact assessment models.

Conclusions

Midpoint and endpoint characterisation factors were successfully developed to include the impacts of habitat fragmentation on species in LCIA. For now, they are provided for bird species in all forest ecoregions belonging to the biodiversity hotspots. Further work is required to develop characterisation factors for all taxa and all terrestrial ecoregions.

     

Differences between maize and rice in N-use efficiency for photosynthesis and protein allocation

The N-use efficiency for photosynthesis was higher in a C(4) plant, maize, than in a C(3) plant, rice, including rbcS antisense rice with optimal ribulose-1,5-bisphosphate carboxylase (Rubisco) content for CO(2)-saturated photosynthesis, even when photosynthesis was measured under saturating CO(2) conditions. The N cost for the C(4) cycle enzymes in maize was not large, and the lower amount of Rubisco allowed a greater N investment in the thylakoid components. This greater content of the thylakoid components as well as the CO(2) concentrating mechanism may support higher N-use efficiency for photosynthesis in maize.     

Thermodynamic resource indicators in LCA: a case study on the titania produced in Panzhihua city, southwest China

Purpose

While life cycle assessment (LCA) has standardized methods for assessing emission impacts, some comparable methods for the accounting or impact assessment of resource use exist, but are not as mature or standardized. This study contributes to the existing research by offering a comprehensive comparison of the similarities and differences of different resource indicators, in particular those based on thermodynamics, and testing them in a case study on titania (titanium dioxide pigment) produced in Panzhihua city, southwest China.

Materials and methods

The system boundary for resource indicators is defined using a thermodynamic hierarchy at four levels, and the case data for titania also follow that hierarchy. Seven resource indicators are applied. Four are thermodynamics-based??cumulative energy demand (CED), solar energy demand (SED), cumulative exergy demand (CExD), and cumulative exergy extraction from the natural environment (CEENE)??and three have different backgrounds: abiotic resource depletion potential, environmental priority strategies, and eco-indicator 99. Inventory data for the foreground system has been collected through on-site interviews and visits. Background inventory data are from the database ecoinvent v2.2. Characterizations factors are based on the CML-IA database covering all major methods. Computations are with the CMLCA software.

Results and discussion

The scores of resource indicators of the chloride route for titania system are lower than that of the sulfate route by 10?C35?%, except in terms of SED. Within the four thermodynamic indicators for resources, CED, CExD, and CEENE have similar scores, while their scores are five orders of magnitude lower than the SED score. Atmospheric resources do not contribute to the SED or CEEND score. Land resources account for a negligible percentage to the SED score and a small percentage to the CEENE score. Non-renewable resources have a dominant contribution to all seven resource indicators. The global production of titania would account for 0.12 and 0.14?% of the total anthropogenic non-renewable resource demand in terms of energy and exergy, respectively.

Conclusions

First, we demonstrate the feasibility of thermodynamic resource indicators. We recommend CEENE as the most appropriate one within the four thermodynamic resource indicators for accounting and characterizing resource use. Regarding the case study on the titania produced in China, all the resource indicators except SED show that the sulfate route demands more resource use than the chloride route.     

LCA and ecodesign in the toy industry: case study of a teddy bear incorporating electric and electronic components

Background, aim, and scope  A cradle-to-grave life cycle assessment (LCA) of a toy incorporating electric and electronic components is carried out following the ISO 14044 standard, with the purpose of identifying the environmental hotspots and suggesting ecodesign measures to the manufacturer. Materials and methods  The product under study is a teddy bear which sings songs and tells stories while moving its body, using conventional alkaline batteries as a source of energy. This toy is designed by a Spanish company, but manufactured entirely in China, from where it is exported to Europe, America, and Africa. The LCA study includes production of all components in China, maritime and road distribution, use phase, and end-of-life. Life cycle impact assessment is focused on five standard impact categories from the CML 2001 method. Results  The use phase is identified as potentially the most important life cycle stage, due to the impact of battery production. It is responsible for 50% to 64% of the overall life cycle impact, depending on the impact category. Toy production is also an important stage, with 28% to 34% of the total contribution. Maritime distribution also involves relevant contributions in some impact categories. Based on the results of the study, a set of ecodesign measures were suggested to the manufacturer, with most of them being judged as feasible, and applied in a new product. Discussion  Important data gaps were encountered during the study, especially concerning the use phase, due to lack of data on consumer behavior, and background inventory data on alkaline battery production. A sensitivity analysis applied to the use phase showed that the relative importance of this life cycle stage is strongly affected by the assumptions made in this work. Conclusions  The LCA study was found as a very helpful tool to define ecodesign measures for this product. Several measures suggested have been actually implemented by the manufacturer in a similar product. Recommendations and perspectives  This case study, together with others, will help in the long run to define general ecodesign measures for the toy sector in Catalonia.

Data strategy for environmental assessment of agricultural regions via LCA: case study of a French catchment

Purpose

Various approaches have been carried out to extrapolate environmental assessments of farms to the regional level, some of them oversimplified and thus leading to high uncertainty. Key challenges include selection of a representative sample, construction of a farm/land use typology, the extrapolation strategy and dealing with data limitations. This work proposes a method for addressing these issues by means of statistically supported approaches.

Methods

We applied a novel approach combining a sampling strategy, estimation of farm-level environmental impacts via life cycle assessment (LCA), a farm typology based on principal component analysis, a statistical method for extending the farm sample given data constraints and finally linear extrapolation based on regional production and land use, taking into account the regional import–export balance. The approach was applied to a French case study, the Lieue de Grève catchment in the dairy-intensive Brittany region. A decision flowchart was developed to generalise the approach for similar applications dealing with farm and LCA data constraints. Additionally, innovative farm practices were modelled and their impacts propagated to the regional level.

Results and discussion

The typology developed identified “dairy”, “beef”, “dairy + beef” and “swine” farms as the dominant farm types in the region. While swine farms had the highest mean impacts per hectare, dairy and dairy + beef farms had impacts two to five times as high as those of beef and swine farms, when extrapolated to the entire catchment. Multiple linear regressions based on an extended farm and LCA dataset were used to predict environmental impacts of dairy farms lacking LCA results, thus increasing their sample size before extrapolation. The inclusion of farm and LCA data from a neighbouring region did not contribute to the accuracy of predicted impacts, as determined by comparing them to those of the farm closest to the dairy cluster’s centre, but rather produced significantly larger coefficients of variation. Results of tests of including two extra-regional farm and LCA datasets helped determine decision rules for the decision flowchart. Modelling of innovative agricultural practices yielded regional impacts consistent with previous estimates.

Conclusions

This approach provides a generalisable approach for farm typologies, data handling and regional extrapolation of farm-level LCAs, applicable to estimate environmental impacts of any agricultural area if requirements of a representative farm sample are met. We demonstrate the utility of the method for estimating effects of innovative agricultural practices on a region’s impacts by modelling practices on virtual farms and extrapolating their results.

     

LCA for assessing environmental benefit of eco-design strategies and forest wood short supply chain: a furniture case study

Purpose

Eco-innovation strategies are increasingly adopted to ensure the minimization of environmental impacts. Nonetheless, only a comprehensive integrated assessment along the life cycle stages of a product may ensure a robust analysis of the benefit of the innovation. The object of the present study is the environmental assessment of furniture prototypes produced using certified wood and integrating eco-design criteria in their conception. The aim of the study was twofold: firstly, to evaluate the environmental profile of the furniture, highlighting possible hot spots of impacts, and secondly, to evaluate the capability of life cycle assessment (LCA) to identify the environmental benefit associated to the adoption of eco-innovation strategies, such as the following: ensuring short supply chain from raw material to production; using wood coming from certified forests (according to PEFC scheme); and the implementation of eco-design principles, also associated with green public procurement requirements.

Methods

LCA has been applied in a case study related to the wood furniture sector in the alpine region of Northern Italy. Every activity was modeled using primary data, related to the inputs and outputs of the processes, provided directly by the designers and by woodworking firms. Input data related to forestry activities and wood extraction were collected and processed in a previous phase of the study. The life cycle of a prototype school desk from the cradle-to-gate perspective was analyzed. A woodworking plant was examined in detail, dividing the whole manufacturing process into four phases: panels production, woodworking, painting and steel parts processing. The system boundaries included all the activities which take place inside the plant as well as energy inputs, transports and ancillary products used.

Results and discussion

The results highlighted that the working phases showing the greatest environmental burdens were the production of solid wood panels and the processing of iron parts. No concerns about chemicals, glues and paints were raised, due to the eco-design principles implemented in the production of the furniture. The choice of a short supply chain allowed for drastic reductions in the impacts associated to long-distance transports. Three sensitivity analyses were carried out to test the robustness of results concerning the following: (1) glue options, (2) drying phase and VOC emissions, and (3) transport options.

Conclusions

This study proves to which extent eco-design criteria implemented in practice improve the environmental performance of products. All positive effects due to decisions taken in school desk design and conception were supported by evidence.