Characterization model to assess ocean acidification within life cycle assessment

Purpose

Ocean acidification due to the absorption of increasing amounts of atmospheric carbon dioxide has become a severe problem in the recent years as more and more marine species are influenced by the decreasing pH value as well as by the reduced carbonate ion concentration. So far, no characterization model exists for ocean acidification. This paper aims to establish such a characterization model to allow for the necessary future inclusion of ocean acidification in life cycle assessment (LCA) case studies.

Methods

Based on a cause-effect chain for ocean acidification, the substances carbon monoxide, carbon dioxide, and methane were identified as relevant for this impact category. In a next step, the fate factor representing the substances’ share absorbed by the ocean due to conversion, distribution, and dissolution is determined. Then, the fate sensitivity factor is established reflecting the changes in the marine environment due to the amount of released hydrogen ions per gram of substance (category indicator). Finally, fate and fate sensitivity factors of each substance are multiplied and set in relation to the reference substance, carbon dioxide, thereby delivering the respective characterization factors (in kg CO₂ eq) at midpoint level.

Results and discussion

Characterization factors are provided for carbon monoxide (0.87 kg CO₂ eq), carbon dioxide (1 kg CO₂ eq), and methane (0.84 kg CO₂ eq), which allow conversion of inventory results of these substances into category indicator results for ocean acidification. Inventory data of these substances is available in common LCA databases and software. Hence, the developed method is directly applicable. In a subsequent contribution analysis, the relative contribution of the three selected substances, along with other known acidifying substances, to the ocean acidification potential of 100 different materials was studied. The contribution analysis confirmed carbon dioxide as the predominant substance responsible for more than 97 % of the total ocean acidification potential. However, the influence of other acidifying substances, e.g., sulfur dioxide, should not be neglected.

Conclusions

Evaluation of substances contributing to ocean acidification is of growing importance since the acidity of oceans has been increasing steadily over the last decades. The introduced approach can be applied to evaluate product system related impacts of ocean acidification and include those into current LCA practice.

     

Including metal atmospheric fate and speciation in soils for terrestrial ecotoxicity in life cycle impact assessment

Purpose

The aim of the study is to calculate regionalized characterization factors for the atmospheric emissions of metals transferred to soil for zinc, copper, and nickel taking into account the atmospheric fate and speciation.

Methods

In order to calculate characterization factors for all possible atmospheric emission locations around the world, the link between atmospheric deposition with regionalized soil fate factors and bioavailability factors accounting for the metal’s speciation was established. The methodology to develop the regionalized fate factors and characterization factors is threefold. First, the emitted metal fraction that is deposited on soils is calculated from atmospheric source-receptor matrices providing for each emission location the fraction of an emission that is deposited on each worldwide receiving cell (2°?×?2.5° resolution). Second, the fraction of metal deposited in different soil types is determined by overlapping the deposition map with a soil map, based on the 4513 different soil types from the Harmonized World Soil Database. Third, bioavailability factors are calculated for each soil type, which allows determining the bioavailable fraction of the deposited metal depending on the soil properties. Combining these steps with the effect factors results in a series of terrestrial ecotoxicological characterization factors. These characterization factors are then applied in an illustrative example and compared to results obtained with generic characterization factors. The case study focuses on the electricity production process in Québec, whose ecosystem impacts are currently dominated by metal ecotoxicity impacts. The uncertainty due to the spatial variability of the impact is quantified.

Results and discussion

Our results show that regionalized characterization factors are over three orders of magnitude lower than generic characterization factors. They are presented on maps and their spatial variability was evaluated at different regional scales (region, country, world). The use of regionalized characterization factors with their spatial variability at different geographic resolution scales in the case study gives a result more or less precise depending on the level of resolution of the characterization factor applied (country or global-default). The impact scores of the three metals in the case study are three orders of magnitude lower when compared to the scores obtained with generic characterization factors.

Conclusions

The development of those regionalized characterization factors improves the terrestrial ecotoxicity assessment in life cycle impact assessment by taking into account the atmospheric fate and the speciation of the metal for new 3 metals for the different soil types in the world and by documenting their spatial variability.

     

Identifying best existing practice for characterization modeling in life cycle impact assessment

Purpose

Life cycle impact assessment (LCIA) is a field of active development. The last decade has seen prolific publication of new impact assessment methods covering many different impact categories and providing characterization factors that often deviate from each other for the same substance and impact. The LCA standard ISO 14044 is rather general and unspecific in its requirements and offers little help to the LCA practitioner who needs to make a choice. With the aim to identify the best among existing characterization models and provide recommendations to the LCA practitioner, a study was performed for the Joint Research Centre of the European Commission (JRC).

Methods

Existing LCIA methods were collected and their individual characterization models identified at both midpoint and endpoint levels and supplemented with other environmental models of potential use for LCIA. No new developments of characterization models or factors were done in the project. From a total of 156 models, 91 were short listed as possible candidates for a recommendation within their impact category. Criteria were developed for analyzing the models within each impact category. The criteria addressed both scientific qualities and stakeholder acceptance. The criteria were reviewed by external experts and stakeholders and applied in a comprehensive analysis of the short-listed characterization models (the total number of criteria varied between 35 and 50 per impact category). For each impact category, the analysis concluded with identification of the best among the existing characterization models. If the identified model was of sufficient quality, it was recommended by the JRC. Analysis and recommendation process involved hearing of both scientific experts and stakeholders.

Results and recommendations

Recommendations were developed for 14 impact categories at midpoint level, and among these recommendations, three were classified as “satisfactory” while ten were “in need of some improvements” and one was so weak that it has “to be applied with caution.” For some of the impact categories, the classification of the recommended model varied with the type of substance. At endpoint level, recommendations were only found relevant for three impact categories. For the rest, the quality of the existing methods was too weak, and the methods that came out best in the analysis were classified as “interim,” i.e., not recommended by the JRC but suitable to provide an initial basis for further development.

Discussion, conclusions, and outlook

The level of characterization modeling at midpoint level has improved considerably over the last decade and now also considers important aspects like geographical differentiation and combination of midpoint and endpoint characterization, although the latter is in clear need for further development. With the realization of the potential importance of geographical differentiation comes the need for characterization models that are able to produce characterization factors that are representative for different continents and still support aggregation of impact scores over the whole life cycle. For the impact categories human toxicity and ecotoxicity, we are now able to recommend a model, but the number of chemical substances in common use is so high that there is a need to address the substance data shortage and calculate characterization factors for many new substances. Another unresolved issue is the need for quantitative information about the uncertainties that accompany the characterization factors. This is still only adequately addressed for one or two impact categories at midpoint, and this should be a focus point in future research. The dynamic character of LCIA research means that what is best practice will change quickly in time. The characterization methods presented in this paper represent what was best practice in 2008–2009.     

Application of life cycle assessment to landfilling

A case study of a life-cycle assessment (LCA) is performed concerning the treatment of household solid wastes in a landfill. The stages considered in this LCA study are: goal and scope definition, inventory analysis and impact assessment. The data of the inventory include the consumption of raw materials and energy through the transport of wastes and the management of landfill, and the corresponding emissions to the environment. Abiotic resource depletion, global warming, acidification, eutrophication and human toxicological impacts have been considered as impact categories for the impact assessment phase of the LCA. A comparison of the environmental impact of the landfilling with and without energy recovery is carried out. Members of the Spanish Association for LCA Development (APRODACV)     

Application of life cycle assessment to footwear

Life Cycle Assessment (LCA) has been applied in the leather footwear industry. Due to the fact that the goal of the study is to point those steps in the footwear cycle which contribute most to the total environmental impact, only a simplified semi-quantitative methodology is used. Background-data of all the inputs and outputs from the system have been inventoried. Impact assessment has been restricted to classification and characterisation. From the results of this LCA it has been concluded that energy consumption is an important impact generator phase, due to the characteristics of the electricity production in the studied area (Catalonia and the rest of Spain). A remarkable impact is generated in the solid waste management phase, also due to its characteristics in the studied area. Another significant impact source is the cattle raising phase where great values of Global Warming, Acidification and Eurrophication Potentials are estimated. At the tannery, a great value of water eutrophication potential is observed and this phase is also important for its non-renewable resource consumption.     

Using GaBi 3 to perform life cycle assessment and life cycle engineering

The growing availability of software tools has increased the speed of generating LCA studies. Databases and visual tools for constructing material balance modules greatly facilitate the process of analyzing the environmental aspects of product systems over their life cycle. A robust software tool, containing a large LCI dataset and functions for performing LCIA and sensitivity analysis will allow companies and LCA practitioners to conduct systems analyses efficiently and reliably. This paper discusses how the GaBi 3 software tool can be used to perform LCA and Life Cycle Engineering (LCE), a methodology that combines life cycle economic, environmental, and technology assessment. The paper highlights important attributes of LCA software tools, including high quality, well-documented data, transparency in modeling, and data analysis functionality. An example of a regional power grid mix model is used to illustrate the versatility of GaBi 3.     

Application typologies for life cycle assessment

Different lists of application areas for life cycle assessment are reviewed together with some suggestions for a typology of these application areas. It is concluded that the scope of a life cycle assessment is determined by the area of validity of the decision with respect to time, space, and interest groups affected. On this basis, six application areas are distinguished. It is further concluded that the application area has limited influence on the inventory analysis and impact assessment phases, although these may be influenced significantly by the decision-maker and the complexity of the trade-offs between the involved environmental impacts. The reporting format for a life cycle assessment depends on the socio-economic importance of the decision, the intended audience, and the time available for decision making.     

Methodologies for social life cycle assessment

Goal, Scope and Background  

In recent years several different approaches towards Social Life Cycle Assessment (SLCA) have been developed. The purpose of this review is to compare these approaches in order to highlight methodological differences and general shortcomings. SLCA has several similarities with other social assessment tools, although, in order to limit the expanse of the review, only claims to address social impacts from an LCA-like framework are considered.     

Parameterised inventories for life cycle assessment

Background and Objective  

Life cycle assessment (LCA) is a highly data intensive undertaking, where collecting the life cycle inventory (LCI) data is the most labour intensive part. The aim of this paper is to show a method for representing the LCI in a simplified manner which not only allows an estimative, quantitative LCA, but also the application of advanced analysis methods to LCA.     

Application of probability distributions to the modeling of biogenic CO2 fluxes in life cycle assessment

In life cycle assessment (LCA), the same characterization factors are conventionally applied irrespective of when the emissions occur (the same importance is given to emissions in the past, present, and future). When the assessment is constrained by fixed timeframes, the appropriateness of this paradigm is questioned and the temporal distribution of emissions becomes of relevance. One typical example is the accounting for biogenic CO₂ emissions and removals. This article proposes a methodology for assessing the climate impact of time‐distributed CO₂ fluxes using probability distributions. Three selected wood applications, such as fuel, nonstructural panels, and housing construction materials are assessed. In all the cases, CO₂ sequestration in growing trees is modeled with an appropriate forest growth function, whereas CO₂ emissions from wood oxidation are modeled with different probability distributions, such as the delta function, the uniform distribution, the exponential distribution, and the chi‐square distribution. The combination of these CO₂ fluxes with the global carbon cycle provides the respective changes caused in CO₂ atmospheric concentration and hence in the radiative forcing. The latter is then used as basis for climate impact metrics. Results demonstrate the utility of using emission and removal functions rather than single pulses, which generally overestimate the climate impact of CO₂ emissions, especially in presence of short time horizons. Characterization factors for biogenic CO₂ are provided for selected combinations of biomass species, rotation periods, and probability distributions. The time discrepancy between biogenic CO₂ emissions and capture through regrowth results in a certain climate impact, even for a system that is carbon neutral over time. For the oxidation rate of wooden products, the use of a chi‐square distribution appears the most reliable and appropriate option under a methodological perspective. The feasibility of its adoption in LCA and emission accounting from harvested wood products deserves further scientific considerations.     

Environmental impacts of household goods in Europe: a process-based life cycle assessment model to assess consumption footprint

The International Journal of Life Cycle Assessment - Current patterns of household goods consumption generate relevant environmental pressures and impacts. Environmental impacts are not only...     

Moving from completing system boundaries to more realistic modeling of the economy in life cycle assessment

The International Journal of Life Cycle Assessment - Existing process-based life cycle assessment (LCA) models can be supplemented by input-output (IO) models to correct for the so-called...     

Environmental life cycle assessment for rapeseed-derived biodiesel

Purpose

Biofuels have received special research interest, driven by concerns over high fuel prices, security of energy supplies, global climate change as well as the search of opportunities for rural economic development. This work examines the production of biodiesel derived from the transesterification of crude rapeseed oil, one of the most important sources of biodiesel in Europe, paying special attention to the environmental profile-associated to the manufacture life cycle (i.e., cradle-to-gate perspective).

Methods

To do so, a Spanish company with an average annual biodiesel production of 300,000 t was assessed in detail. The Life Cycle Assessment (LCA) study covers the whole life cycle, from the production of the crude rapeseed oil to the biodiesel production and storage. The inventory data for the foreground system consisted of average annual data obtained by on-site measurements in the company, and background data were taken from databases. Seven impact categories have been assessed in detail: abiotic depletion, acidification, eutrophication, global warming, ozone layer depletion, land competition, and photochemical oxidant formation. An energy analysis was carried out based on the cumulative nonrenewable fossil and nuclear energy demand as an additional impact category. Furthermore, well-to-wheels environmental characterization results were estimated and compared per ton-kilometer for the biodiesel (B100) and the conventional diesel so as to point out the environmental drawbacks and strengths of using biodiesel as transport fuel in a 28 t lorry.

Results and discussion

The results showed that the cultivation of the rapeseed was the main key issue in environmental terms (68 %–100 % depending on the category) mainly because of fertilizer doses and intensive agricultural practices required. With regard to the biorefinery production process, pretreatment and transesterification sections considerably contribute to the environmental profile mostly due to electricity and chemical requirements. Concerning the well-to-wheels comparison, using B100 derived from rapeseed oil instead of petroleum-based diesel would reduce nonrenewable energy dependence (?20 %), GHG emissions (?74 %), and ozone layer depletion (?44 %) but would increase acidification (+59 %), eutrophication (+214 %), photochemical smog (+119 %), and land competition.

Conclusions

The information presented in this study could help to promote the use of renewable transport biofuels. However, the extensive implementation of biodiesel (particularly rapeseed oil-derived biodiesel) in our society is enormously complex with many issues involved not only from environmental but also economical and social points of view.     

Service life prediction of residential interior finishes for life cycle assessment

Purpose  

Service life of building products has an important influence on life cycle assessment (LCA) results of buildings. The goal of this study was to propose a systematic approach to estimate service life of building products by including both technical and social factors.     

Criteria for the evaluation of life cycle assessment software packages and life cycle inventory data with application to concrete

Purpose

Life cycle assessment (LCA) software packages have proliferated and evolved as LCA has developed and grown. There are now a multitude of LCA software packages that must be critically evaluated by users. Prior to conducting a comparative LCA study on different concrete materials, it is necessary to examine a variety of software packages for this specific purpose. The paper evaluates five LCA tools in the context of the LCA of seven concrete mix designs (conventional concrete, concrete with fly ash, slag, silica fume or limestone as cement replacement, recycled aggregate concrete, and photocatalytic concrete).

Methods

Three key evaluation criteria required to assess the quality of analysis are adequate flexibility, sophistication and complexity of analysis, and usefulness of outputs. The quality of life cycle inventory (LCI) data included in each software package is also assessed for its reliability, completeness, and correlation to the scope of LCA of concrete products in Canada. A questionnaire is developed for evaluating LCA software packages and is applied to five LCA tools.

Results and discussion

The result is the selection of a software package for the specific context of LCA of concrete materials in Canada, which will be used to complete a full LCA study. The software package with the highest score is software package C (SP-C), with 44 out of a possible 48 points. Its main advantage is that it allows for the user to have a high level of control over the system being modeled and the calculation methods used.

Conclusions

This comparative study highlights the importance of selecting a software package that is appropriate for a specific research project. The ability to accurately model the chosen functional unit and system boundary is an important selection criterion. This study demonstrates a method to enable a critical and rigorous comparison without excessive and redundant duplication of efforts.

     

Comparative life cycle assessment of metal arc welding technologies by using engineering design documentation

The International Journal of Life Cycle Assessment - The paper aims to analyze and compare the environmental performances of metal arc welding technologies: gas metal arc welding (GMAW), shielded...