Purpose
The use of life cycle assessment (LCA) as a decision support tool can be hampered by the numerous uncertainties embedded in the calculation. The treatment of uncertainty is necessary to ...increase the reliability and credibility of LCA results. The objective is to provide an overview of the methods to identify, characterize, propagate (uncertainty analysis), understand the effects (sensitivity analysis), and communicate uncertainty in order to propose recommendations to a broad public of LCA practitioners.
Methods
This work was carried out via a literature review and an analysis of LCA tool functionalities. In order to facilitate the identification of uncertainty, its location within an LCA model was distinguished between quantity (any numerical data), model structure (relationships structure), and context (criteria chosen within the goal and scope of the study). The methods for uncertainty characterization, uncertainty analysis, and sensitivity analysis were classified according to the information provided, their implementation in LCA software, the time and effort required to apply them, and their reliability and validity. This review led to the definition of recommendations on three levels: basic (low efforts with LCA software), intermediate (significant efforts with LCA software), and advanced (significant efforts with non-LCA software).
Results and discussion
For the basic recommendations, minimum and maximum values (quantity uncertainty) and alternative scenarios (model structure/context uncertainty) are defined for critical elements in order to estimate the range of results. Result sensitivity is analyzed via one-at-a-time variations (with realistic ranges of quantities) and scenario analyses. Uncertainty should be discussed at least qualitatively in a dedicated paragraph. For the intermediate level, the characterization can be refined with probability distributions and an expert review for scenario definition. Uncertainty analysis can then be performed with the Monte Carlo method for the different scenarios. Quantitative information should appear in inventory tables and result figures. Finally, advanced practitioners can screen uncertainty sources more exhaustively, include correlations, estimate model error with validation data, and perform Latin hypercube sampling and global sensitivity analysis.
Conclusions
Through this pedagogic review of the methods and practical recommendations, the authors aim to increase the knowledge of LCA practitioners related to uncertainty and facilitate the application of treatment techniques. To continue in this direction, further research questions should be investigated (e.g., on the implementation of fuzzy logic and model uncertainty characterization) and the developers of databases, LCIA methods, and software tools should invest efforts in better implementing and treating uncertainty in LCA.
Functional sales is a business model that has steadily seen increased use. This article features, from a life cycle perspective and in a novel way, its legal, environmental, and economic ...implications. Functional sales has been highlighted to have the potential for promoting the use of more resource-efficient technologies, which may have a positive impact on the provided solution’s environmental and economic performance. However, there are, to our knowledge, few articles published regarding the legal aspects of functional sales and still no laws regulating this type of business model, which can pose barriers to implementing functional sales. Functional sales is in uncharted territory in the legal sphere, and the lack of legal regulation can only, to a certain extent, be overcome by a contract. A contract must consider the relationship to be long-term, and evaluation is important.
In this paper, two different techniques for acquiring lighting representing product sales and functional sales are compared. The case for functional sales is based on the legal foundation of an existing public procurement, while the case for product sales is a likely alternative for lighting purposes. The study shows that there is a trade-off between environmental consequence and economic benefit and that qualitative aspects can be difficult to include in the contract and evaluation.
The conclusion is that the ordinary purchase is supported by long-established rules and regulations so that such a legal transaction (acquisition) is quite conventional and uneventful. However, if the business model changes without a proper legal foundation, the parties of such contracts will find themselves in a legal wilderness, where the outcome of civil litigations is unpredictable. There are ways to circumvent these difficulties, which is demonstrated in this article, as well as the principal advantages of functional sales.
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•Functional sale business model is an uncharted territory of the legal sphere.•Lack of legal regulation can only to a certain extent be overcome by a contract.•The contract must consider long-term relationship, where evaluation is important.•There may be a trade-off between environmental consequence and economic benefit.•Qualitative aspects can be difficult to include in the contract and evaluation.
This research was motivated to address limitations in the current lifecycle assessment frameworks with the absence of proper guidelines for developing default lifecycle values of energies in ...consideration of supply chain activities and maritime transportation. Given this, it aims to evaluate the level of life cycle GHG emissions of heavy fuel oil, LNG, LPG and methanol as marine fuels produced and supplied in energy import-dependent countries, using South Korea as a case study. The analysis clearly shows that the impact of international shipping on Well-to-Tank (WtT) GHG emissions for energy carriers would be subject to several factors: propulsion system types, the quantify of energy transported, and the routes and distances of voyages. For instance, transportation emissions from LNG carriers for LNG fuel vary significantly depending on the country of import, ranging from 2.26 g CO2 eq./MJ (representing 12.2 % of Well-to-Tank (WtT) emissions for Malaysia) to 5.97 g CO2 eq./MJ (representing 33.3 % of WtT emissions for Qatar). As a preliminary study, an enhancement on the quality of the input/inventory data is imperative for obtaining a reliability of results. Nevertheless, the comparative analysis of different fuels and life stages provides valuable insights for stakeholders to develop effective policies and energy refueling plans for reducing life cycle GHG emissions from marine fuels. These findings could also enhance the current regulatory framework and provide meaningful lifecycle carbon footprints of marine fuels for energy importing countries. The study results also strongly suggest that default values of GHG emission for different countries relying on energy imports via international maritime transport should be further developed in consideration of the impact of regional differences, such as distance, from the importing country for successful arrival of LCA application on marine industry.
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•Developed framework for baseline of life cycle GHG emissions from marine fuels•Demystified the current LCA framework for highlighting the potential impact of WtT areas neglected in regulation•Compared the WtW emissions of selected marine fuels imported to South Korea•Provided insights for future policies to reduce life cycle GHG emissions
Land use competition between agricultural activities and ground-mounted solar photovoltaic (PV) deployment has increased worldwide attention to hybrid agriculture, and PV systems known as agrivoltaic ...systems (AVS) in efforts to increase the efficiency of energy and food production and minimize the land use competition. However, little is known about AVS's economic feasibility and environmental tradeoffs. Here we aim to evaluate the techno-economic and environmental impacts of four AVS configurations (full density, half density, mono-axial tracking, and bi-axial tracking) and compare their performance against PV-only systems. We used the life cycle revenue generated from a hectare of land area ($/ha) as a functional unit of our analysis. We found that all AVS configurations outperformed PV-only systems in the economic feasibility assessment, where bi-axial tracking was the best-performing AVS. Further, we developed a case scenario for agricultural farmers to determine the minimum selling price of electricity required for AVS to compete with the economic performance of crop-only farms. We found that the AVS designs require additional incentives (2¢ - 6¢ per kWh of electricity generation) to be as competitive as the crop-only farms. The life cycle environmental assessment demonstrated that the AVS has better environmental performance than PV-only systems, with ∼15–55 % less environmental impacts per functional unit. On average, electricity generation accounts for ∼80 % of AVS environmental impacts, while food production and water demand account for ∼20 %. Additionally, a sensitivity analysis conducted on various uncertain parameters, such as crop yield, water demand, electricity selling price, crop selling prices, discount, and inflation rates, while varying these parameters across broader ranges, indicates that AVS designs become a more economically and environmentally sustainable alternative over PV-only systems in the majority (>66 %) of the data analyzed.
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•Both life cycle economic and environmental impacts of agrivoltaics were analyzed.•Agrivoltaics have better economic performance compared to photovoltaic-only systems.•Agrivoltaics need 2–6¢ incentives to outperform crop-only farms.•Agrivoltaics have 15–55 % less environmental impact than photovoltaic-only systems.
•Life cycle assessment of a new nuclear power plant in Europe.•Three methods used: process-based, input-output, and hybrid life cycle assessment.•Results range from 8 to 64 gCO2e/kWhe.•Averages for ...the three methods are 16.97, 24.89 and 27.63 gCO2e/kWhe.•Results are higher than generally accepted figures for nuclear energy.
Nuclear energy contributes ~10% of the global electricity generation and different views exist on its carbon-intensity and sustainability. Context is crucial to determine the sustainability of new nuclear power generators, making the existence of a global answer to the unresolved question unlikely. This study aims to establish the life-cycle greenhouse gas emissions associated with nuclear energy in Europe given ongoing construction of nuclear generators. Due to the high uncertainty and complexity that characterise construction and operation of nuclear generators, we adopt a multi-method, scenario-based approach. The three methods used are: process-based, input-output, and hybrid life cycle assessment. Scenarios account for different total energy outputs over the life cycle of the nuclear generator, different end of life options, and different sectoral allocations of costs in the input-output calculus. Results for the process-based, input-output, and hybrid methods range between 16.55–17.69, 18.82–35.15, and 24.61–32.74 gCO2e/kWh, respectively. These are either well above or at the upper end of the range of possibilities (5 to 22 gCO2e/kWh) stated in a report for the UK’s Committee on Climate Change, and significantly higher than the median value of 12 gCO2e/kWh presented by the Intergovernmental Panel on Climate Change. They are also higher than the values acknowledged by the nuclear industry. Given the severe potential lock-in effects of today’s energy choices for future generations, this research questions the role of nuclear energy to meet the UN Sustainable Development Goals and calls for further scrutiny on its sustainability and environmental viability.
Previous research efforts have focused on developing prospective life cycle inventory databases that build upon projections from integrated assessment models but were limited to attributional system ...models. A novel approach is required to construct consequential LCI databases that can be applied consistently on a large scale. To this end, the heuristic approach from Bo Weidema was selected as a basis for this study. This approach has been validated with historical data and was adapted in this study to identify the marginal suppliers in a prospective context. The different steps within the approach were analyzed, and alternative techniques for each step within the heuristic method were proposed. The techniques were tested on the future electricity sector using projections from two integrated assessment models (IMAGE and REMIND). Results show the sensitivity of results on the modelling technique selected in each step. The most sensitive step is the selection of the time interval, with even small changes resulting in a noticeable difference. In addition, the results also showed a substantial difference between the projections of the two models. The relevance and goals of the alternative techniques for each step were discussed to guide users in forming the heuristic method for their study.
•Development of a prospective consequential database.•Review on consequential approaches for marginal changes.•Work builds upon the commonly used heuristic approach.•Prospective approach is applied to the electricity market using IAM projections.•Results are incorporated into premise.
Purpose
The conventional decision-making for bridges is mostly focusing on technical, economical, and safety perspectives. Nowadays, the society devotes an ever-increased effort to the construction ...sector regarding their environmental performance. However, considering the complexity of the environmental problems and the diverse character of bridges, the related research for bridge as a whole system is very rare. Most existing studies were only conducted for a single indicator, part of the structure components, or a specific life stage.
Methods
Life Cycle Assessment (LCA) is an internationally standardized method for quantifying the environmental impact of a product, asset, or service throughout its whole life cycle. However, in the construction sector, LCA is usually applied in the procurement of buildings, but not bridges as yet. This paper presents a comprehensive LCA framework for road bridges, complied with LCA ReCiPe (H) methodology. The framework enables identification of the key structural components and life cycle stages of bridges, followed by aggregation of the environmental impacts into monetary values. The utility of the framework is illustrated by a practical case study comparing five designs for the Karlsnäs Bridge in Sweden, which is currently under construction.
Results and discussion
This paper comprehensively analyzed 20 types of environmental indicators among five proposed bridge designs, which remedies the absence of full spectrum of environmental indicators in the current state of the art. The results show that the monetary weighting system and uncertainties in key variables such as the steel recycling rate and cement content may highly affect the LCA outcome. The materials, structural elements, and overall designs also have varying influences in different impact categories. The result can be largely affected by the system boundaries, surrounding environment, input uncertainties, considered impact indicators, and the weighting systems applied; thus, no general conclusions can be drawn without specifying such issues.
Conclusions
Robustly evaluating and ranking the environmental impact of various bridge designs is far from straightforward. This paper is an important attempt to evaluate various designs from full dimensions. The results show that the indicators and weighting systems must be clearly specified to be applicable in a transparent procurement. This paper provides vital knowledge guiding the decision maker to select the most LCA-feasible proposal and mitigate the environmental burden in the early stage.
Due to severe sustainability problems caused by the built environment, calls for adopting circular economy principles in building design, such as flexibility and reversibility, are increasing. ...However, there is still a lack of quantitative studies on the corresponding environmental benefits in this regard. In the present study, a life cycle assessment of a multi-storey residential reference building is carried out, comparing a flexible, reversible building design using a load-bearing steel structure and wooden ceiling elements to a conventional, monolithic design based on reinforced concrete. The assessment is carried out on a whole building level, including construction, operation, maintenance, and the end-of-life phase. Both building designs show similar results for a regular life cycle of 60 years without major refurbishment (13 and 14.5 kg CO2-eq/m2 per operational year). When longer building lifetimes are considered, the environmental impact of the reference building per operational year decreases significantly. In this context, flexible building design is advantageous as it facilitates the refurbishment of buildings, while monolithic building design often leads to premature demolition due to low adaptability. Further advantages of reversible building design include the increased potential of materials to be recirculated at the end-of-life stage of a building and in the potential reuse of structural elements. This study shows that 14% of the embodied greenhouse gas emissions of the flexible building can be avoided if the foundation, load-bearing structure and ceiling elements are kept in place for a subsequent building. Such direct reuse leads to a substantially higher environmental value retention than recycling of the same materials.
•In depth comparison of the environmental performance of flexible and monolithic building designs.•Whole building life cycle assessment (WBLCA) and material flow analysis for a specific case study.•Extending building lifetime from 60 to 100 years reduces total greenhouse gas emissions per operational year by 19%.•Flexible building design shows higher material recycling rate after dismantling than monolithic design.•Direct reuse of structural elements in the flexible building can save of up to 14% of embodied greenhouse gas emissions.
After the success of the reusable Falcon 9 rocket, space actors are pursuing competitive space access by developing Reusable Launch Vehicles (RLVs). While this initiative may enhance recycling rates, ...it may also trigger the Jevons’ paradox as it amplifies the overall environmental footprint due to increased launch frequencies. It is therefore essential to quantify RLVs’ impacts and identify key design drivers to enable efficient design choices while mitigating undesirable environmental effects.
Consequently, this article uses a space specific Life Cycle assessment (LCA) approach to evaluate the environmental footprint, in terms of climate impact, water depletion and land use, of different RLV fleets designed to serve a forecasted European space market. The results show that the LH2 fleet options have 2–8 times lower carbon footprint when compared to the LCH4 fleet as a result of lower propellant consumption and lack of black carbon emissions, suggesting that the environmental burdens are mostly driven by propellant choice. Moreover, the analysis reveals a potential underestimation of climate impacts in previous LCA’s by 2–3 orders of magnitude due to the absence of high altitude characterisation of rocket exhaust emissions and demised aluminium oxides. This increased forcing could lead to fleet choices surpassing the Earth’s carrying capacity given by its planetary boundaries.
The methodology and results within this study can support further integration of launch and reentry emissions within LCA by refining modelling techniques, improving impact characterisation and quantifying uncertainties. These advancements can ultimately enable robust eco-design strategies for launch vehicles.
•Life cycle assessment of launch vehicles including impacts from stratospheric radiative forcing.•Liquid hydrogen–oxygen fuelled fleets show lower impact than the liquid methane-oxygen fleet.•Global warming impacts in a 20 year horizon were 1.4–2.5× higher than in a 100 year horizon.•Climate impacts become up to 1000× higher when characterising high altitude emissions.•Impacts over the fleet lifetime comparable to annual emissions of global commercial aviation.
The construction and building sector is one of the largest contributors to the global carbon emissions. Therefore, it is imperative to accurately assess the carbon emissions of buildings throughout ...the life cycle. Many studies conducted life cycle assessment (LCA) of buildings to evaluate carbon emissions. However, due to the lack of dynamic data, most studies adopted the static LCA methodology, which neglected the dynamic variations during life cycle stages of a building. Unlike previous studies that collected static data from questionnaires and documents, the present study aims to establish a novel dynamic life cycle assessment (D-LCA) framework for buildings by incorporating the building information modeling (BIM) and the building energy modeling program (BEMP) into the static LCA. First, a static LCA is established as the baseline scenario that covers the “cradle-to-grave” life cycle stages. A BIM model is established using Revit to obtain the inventory of building materials. The Designer Simulation Toolkit (DeST) is used as a BEMP to simulate the operating energy consumption of the studied building, taking into account changes in energy mix, climate change, and occupant behavior. At the same time, the DeST results are further used as a data input for dynamic scenarios. The D-LCA framework is applied to a high-rise commercial building in China. This study found that the difference between static and dynamic scenarios was up to 66.7 %, mainly reflected in the dynamic energy consumption during the operation phase, indicating the inaccuracy of traditional static LCA. Therefore, a D-LCA by integrating BIM and BEMP can facilitate dynamic modeling and improve the accuracy and reliability of LCA for buildings.
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•The traditional static LCA fails to capture the temporal variation of buildings.•This study integrates BIM and DeST to establish a D-LCA framework of the whole life cycle of buildings.•Dynamic factors of whole life cycle buildings are summarized from existing literature.•Influences from climate change and renewable energy are incorporated into the D-LCA model.•Compared with the static scenario, the carbon emission of the dynamic scenarios can be reduced by 66.7 %.
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