Life Cycle Environmental Performance Research Articles

Comparative Study of Life-Cycle Environmental and Cost Performance of Aluminium Alloy–Concrete Composite Columns

As is widely known, the construction industry is one of the sectors with a large contribution to global carbon emissions. Despite numerous efforts in the construction industry to develop low-carbon materials, there is a limited number of studies quantifying and presenting the overall environmental impact when these materials are applied in a construction project as structural members. To address this gap, this study focuses on assessing the life-cycle performance of novel structural aluminium alloy–concrete composite columns. In this paper, the environmental impacts and economic aspects of a concrete-filled aluminium alloy tubular (CFAT) column and a concrete-filled double-skin aluminium alloy tubular (CFDSAT) column were assessed using life-cycle assessment (LCA) and life-cycle cost analysis (LCCA) approaches, respectively. The cradle-to-grave system boundary is considered for these analyses to cover the entire life-cycle. A concrete-filled steel tubular (CFST) column is also assessed for reference. All columns are designed to have the same load-carrying capacity and, thus, are compared on a level-playing basis. A comparison is also made of the self-weight of these columns. In particular, the self-weight of the CFST column is reduced by around 17% when the steel tube is replaced by an aluminium alloy tube, and decreased by 47% when the double-skin technique is adopted in CFDSAT columns. The LCA results indicate that the CO2 emission of CFST and CFAT is almost the same, which is 21% less than the CFDSAT columns due to the use of high aluminium in the latter. The LCCA results show that the total life-cycle cost of CFAT and CFDSAT columns is around 29% and 14% lower, respectively, than that of the CFST column. Finally, a sensitivity analysis was carried out to evaluate the effects of data and assumptions on the life-cycle performance of the examined columns.

The risk of shifting environmental burdens in biobased construction - Life cycle assessment of a residential renovated building case study in Belgium

Abstract The construction industry is a major contributor to environmental degradation, resource depletion, and energy consumption. As global concerns about sustainability and environmental impact continue to rise, it becomes imperative to reassess the materials used in building construction. This research paper presents a comprehensive life cycle assessment (LCA) using the Belgian TOTEM tool according to EN15804+A2 for evaluating material choices in building construction with a focus on the renovation of residential buildings in Belgium. The study aims to provide a holistic understanding of the environmental implications associated with biobased construction materials enabling informed decision-making for sustainable building practices. To achieve this, we conducted an analysis of the life cycle environmental performance of biobased materials used in external walls of a renovation case study project and compared it to common built-up scenarios of conventional construction materials applied in the same case study. The research results show that using biobased materials for renovation can significantly reduce embodied GHG emissions but can lead to burden shifting such as resulting in an increased impact on land use, particulate matter emissions, depletion of abiotic resources and eco-toxicity. The study not only underscores the importance of comprehensive cradle-to-grave life cycle thinking but also provides valuable insights for stakeholders in the construction industry.

The environmental performance of zero-emission buildings in a fossil-free energy system

Buildings can play an important role in reducing GHG emissions through increased energy efficiency. The European Commission mandates that all new buildings should be “zero emission buildings” (ZEB), aiming at a zero GHG emission building stock by 2050. The extent to which ZEB can contribute to reduced GHG emissions, however, varies between countries, due to different energy systems. It is also important to consider other environmental effects to avoid that climate benefits come with unintended consequences. Here, we explore the life-cycle environmental performance for a ZEB in a case where electricity and heating are largely fossil-free. The assessment concentrates on i) environmental impact of the use stage in relation to the product stage, ii) the interrelation between different energy sources, with focus on household electricity, and iii) the performance for more impact categories than primary energy use and climate change. While our results generally support the use of ZEBs from an environmental perspective, they also show that the climate benefit in this setting is marginal. However, given that energy systems are connected and energy savings in one place can reduce the demand for fossil energy elsewhere, the climate benefit of ZEBs is likely underestimated. Besides methodological implications for future studies, this indicates that current EU policy is promising, as incentives for implementation of ZEBs are unaffected by domestic effects.

Life cycle-based multi-objective model for optimal gaseous fuel generation and portfolio allocation in gas grids: A strategic decarbonization

Biomethane and hydrogen are acknowledged as transformative opportunities for decarbonizing the conventional gas grid. Essential to this transformation is the modeling of the gaseous fuel supply chain, particularly with hydrogen and biomethane, offering crucial insights for decision-makers. This study introduces a life cycle thinking-based multi-objective optimization model for the integrated design of biomethane and hydrogen gaseous fuel supply chain networks. The model determines optimal resource allocation for the production of the two fuels, integrating them into the conventional gas network. Moreover, it allocates conventional natural gas, biomethane, and hydrogen optimally across building, industry, and transport sectors, considering the life cycle environmental and economic performance of fuel integration paths. Objective functions include minimization of life cycle emissions and levelized cost of energy while maximizing revenue from fuel sales. Integrating life cycle assessment and cost analysis tools, the optimization model quantifies emissions and life cycle costs for biomethane and hydrogen paths. Results identify Pareto-optimal fuel production paths and portfolios, revealing that integrating the alternative fuels into the current gas grid can significantly reduce emissions (up to 250 tonCO2eq/year) and generate substantial carbon tax savings (up to $16,250/year). This model is useful for gaseous fuel industry stakeholders, offering a comprehensive view of supply chain costs and detailed insights into emission benefits when integrating alternative fuels into existing gas networks.

Comparing the circularity and life cycle environmental performance of batteries for electric vehicles

Batteries account for a significant share of the life cycle impact of electric vehicles (EV). Nonetheless, the circularity and environmental performance of EV batteries remains underexplored in the literature. This paper compares the circularity (Circularity Index and Product Circularity Indicator) and environmental performance (Global Warming Potential (GWP) and Abiotic Depletion Potential of minerals (ADPm)) of lithium nickel manganese cobalt (NMC) and lithium iron phosphate (LFP) batteries subjected to pyrometallurgy and hydrometallurgy recycling. Lifetime extension, improved energy efficiency, and material recovery ratios were also calculated to identify the optimal battery design. The findings show that NMC batteries are 6–25% more circular and environmentally sustainable (<4–6% GWP and <13–16% ADPm) than LFP batteries, primarily due to better material recovery ratios. Moreover, the longer lifetime of LFP does not sufficiently offset resource and environmental impacts. Finally, the study discusses the results to support circular and environmental innovation in EV battery design.

Materials Challenges in the Electric Vehicle Transition.

The ongoing transition toward electric vehicles (EVs) is changing materials used for vehicle production, of which the consequences for the environmental performance of EVs are not well understood and managed. We demonstrate that electrification coupled with lightweighting of automobiles will lead to significant changes in the industry's demand not only for battery materials but also for other materials used throughout the entire vehicle. Given the automotive industry's substantial consumption of raw materials, changes in its material demands are expected to trigger volatilities in material prices, consequently impacting the material composition and attractiveness of EVs. In addition, the materials recovered during end-of-life recycling of EVs as the vehicle fleet turns over will impact recycled material supplies both positively and negatively, impacting material availabilities and the economic incentive to engage in recycling. These supply chain impacts will influence material usage and the associated environmental performance of not only the automotive sector but also other metal-heavy industries such as construction. In light of these challenges, we propose the need for new research to understand the dynamic materials impacts of the EV transition that encompasses its implications on EV adoption and fleet life cycle environmental performance. Effectively coordinating the coevolution of material supply chains is crucial for making the sustainable transition to EVs a reality.

Modelling environmental life cycle performance of alternative marine power configurations with an integrated experimental assessment approach: A case study of an inland passenger barge

There is pressure on the global shipping industry to move towards greener propulsion and fuel technologies to reduce greenhouse gas emissions. Hydrogen and electricity are both recognised as pathways to achieve a net-zero. However, in the evaluation of the environmental performance of these alternative marine power configurations, conventional life cycle assessment (LCA) methods have limitations reflecting the varied nature of ship design and operational modes. The integration of LCA with experimental assessment could remedy the shortcoming of conventional approaches to data generation. The system energy demand data in this study was generated based on specific ship design and directly fed into life cycle assessment. To demonstrate the effectiveness and potential the approach was applied to a case study of inland waterway vessel. Suitable hybrid PV/electricity/diesel and hydrogen powered fuel cell systems for the case vessel were modelled; and hydrodynamic testing and dynamic system simulation was undertaken to provide ship performance data under various operational/environmental profiles. Lifecycle assessment (LCA) indicated hydrogen and electrical propulsion technologies have the potential for 85.7 % and 56.2 % emissions reduction against an MGO base case, respectively. The results highlight that implementation of both technologies is highly dependent on energy production pathways. Hydrogen systems reliant on fossil feedstocks risk an increase in emissions of up to 6.3 % against the MGO base case. Sensitivity analysis indicated an electrical system with electricity production from 79.5 % renewables could achieve savings of 82.2 % in GHG emissions compared to the MGO base case. Crucially, the results demonstrate a further development of the LCA approach which can enable a more accurate environmental performance evaluation of alternative marine power configurations considering specific ship design and operational characteristics. Ultimately this addition makes the results more meaningful for commercial operations and decision making in the selection of alternative marine power systems to support the transition to net-zero.

Assessing the Impact of Recycled Building Materials on Environmental Sustainability and Energy Efficiency: A Comprehensive Framework for Reducing Greenhouse Gas Emissions

In this study, we critically examine the potential of recycled construction materials, focusing on how these materials can significantly reduce greenhouse gas (GHG) emissions and energy usage in the construction sector. By adopting an integrated approach that combines Life Cycle Assessment (LCA) and Material Flow Analysis (MFA) within the circular economy framework, we thoroughly examine the lifecycle environmental performance of these materials. Our findings reveal a promising future where incorporating recycled materials in construction can significantly lower GHG emissions and conserve energy. This underscores their crucial role in advancing sustainable construction practices. Moreover, our study emphasizes the need for robust regulatory frameworks and technological innovations to enhance the adoption of environmentally responsible practices. We encourage policymakers, industry stakeholders, and the academic community to collaborate and promote the adoption of a circular economy strategy in the building sector. Our research contributes to the ongoing discussion on sustainable construction, offering evidence-based insights that can inform future policies and initiatives to improve environmental stewardship in the construction industry. This study aligns with the European Union’s objectives of achieving climate-neutral cities by 2030 and the United Nations’ Sustainable Development Goals outlined for completion by 2030. Overall, this paper contributes to the ongoing dialogue on sustainable construction, providing a fact-driven basis for future policy and initiatives to enhance environmental stewardship in the industry.

The Circularity of Materials from the Perspective of the Product Life Cycle: A Case Study of Secondary Fence Board, Part 2 (Scenario Analysis)

Recycling strategies demonstrate different life cycle environmental performance. In order to assess this performance, a life cycle assessment may be used. In such studies, the recycling should be linked with multifunctionality and allocation. This requires it to be modelled accordingly, especially in terms of environmental burdens and credits. The paper presents a case study of open-loop recycling. A flow of mixed post-consumer multi-material waste was reprocessed into another product with a new application—a fence board made of recycled material (secondary fence board). Although many allocation-related case studies are provided in the literature, no example of a comparison between different substitution scenarios for open-loop recycling has been found. In order to fill the gap, various hypothetical market-mix-based alternatives related to the virgin production and durability of products have been examined. The goal of the study is to assess the potential environmental impact of 1 m2 of secondary fence board modelled in different substitution scenarios. The paper is the second part of a two-part study. In Part 1, life cycle assessment results were presented for a baseline scenario (1A). Part 2 focuses strongly on allocation considerations. In order to ensure a consistency between the results of Part 1 and Part 2, the entire life cycle of the fence board has been taken into account in both calculations. The case study has shown that the results may be highly sensitive to the choice of substitutes and the choice of quality attributes impacting the reference flows (in our example, the durability of products).

Environmental Performance of a Mixed Crop–Dairy Cattle Farm in Alexandria (Romania)

Agricultural specialization has increased considerably in Europe over the last decades, leading to the separation of crop and livestock production at both farm and regional levels. Such a transformation is often associated with higher environmental burdens due to excessive reliance on exogenous inputs and manure management issues. Reconnecting crop and livestock production via mixed farming systems (MFSs) could improve circularity and resilience, leading to reduced environmental impacts. The objective of this study was to evaluate the life cycle environmental performance of a commercial mixed crop–dairy cattle farm in Romania and to compare it against the corresponding specialized systems. The evaluation covered both dairy cattle production (milk and meat) and cash crops. Overall, the results show that the coupled system improves environmental performance by reducing the over-reliance on high-impact inputs like synthetic fertilizers and exogenous feed. The carbon footprint for the milk production of the studied system (1.17 kg CO2 eq.) per kg of fat- and protein-corrected milk (FPCM) was 10% lower than the mean value of common intensive milk production systems. The eutrophication impacts (2.52 × 10−4 kg P eq and 2.67 × 10−4 kg N eq./kg of FPCM) presented values of one order of magnitude less than their specialized counterparts. However, the impacts of the studied MFS, albeit lower than those for comparable specialized systems, still remain relatively high. In particular, methane emissions from enteric fermentation (0.54 kg CO2 eq./kg FPCM) were a major contributor to the carbon footprint. This highlighted the need to address the elevated emissions from enteric fermentation with better feed management, as well as improving and reinforcing the system’s self-sufficiency.

Comparative environmental life cycle assessment of partition walls: Innovative prefabricated systems vs conventional construction

Prefabrication is increasingly recognized as an alternative to conventional on-site construction, offering potential environmental benefits. However, these benefits are context-specific, requiring precise studies for optimal solutions. This paper presents the life-cycle environmental performance of an innovative prefabricated interior partition wall and benchmarks it against a conventional system, providing a replicable model for other novel partition walls. Detailed data collected directly from direct sources were utilized to conduct a cradle-to-gate with options Life Cycle Assessment (LCA), presenting a conveniently described method that can be widely replicated in the construction sector. The adapted LCA method presented in this study contributes to sustainable construction, providing a straightforward and robust approach to assessing the environmental impacts of innovative partition walls compared to conventional walls. For the specific scenario studied, the life-cycle impact assessment results generally indicate a superior environmental performance of the innovative prefabricated interior partition wall compared to the conventional system, resulting in impact reductions ranging from 10 to 60% across evaluated categories. For both systems, the production of materials plays a predominant role in the impact contributions. Furthermore, exploring alternative scenarios yielded significant environmental benefits, particularly in cases considering higher incorporation of recycled materials. Therefore, the direct comparison of the environmental performance of innovative partition walls against traditional solutions emerges as an environmentally sustainable path in the short and medium term. This aligns with the ongoing progress towards decarbonizing the building sector, not only in choosing more environmentally friendly solutions but also in improving the environmental performance of products through assertive changes.

Life cycle environmental performance of methanol production through photocatalytic dry methane reforming

Photocatalytic dry methane reforming uses light energy and a nanostructured photocatalyst to convert both carbon dioxide and methane gas to syngas for production of fuels and value-added chemicals. The conversion of these two greenhouse gases (GHG) makes photocatalytic dry methane reforming a potentially environmentally attractive process; however, little research has been done to assess its life cycle environmental impacts in comparison to conventional commodity chemical production methods. Further, practical research has been limited to lab scale studies, which do not fully reflect the technical and environmental performance of commercial scale systems. In this work, a simulation describing the production of methanol from a photocatalytic dry reforming process is used to inform a life cycle assessment to estimate its potential environmental impacts at scale. Results indicate that for methanol produced via photocatalytic dry methane reforming to have the same life cycle GHG intensity as methanol produced through conventional steam methane reforming, a combination of improved technological performance and process intensification is required. This includes increased chemical conversion, electricity grid decarbonization, and the use of low greenhouse gas intensive feedstocks. Promisingly, results indicate that methanol produced using a photocatalytic dry methane reforming process that employs landfill gas as a feedstock and 100% renewable electricity, could potentially produce methanol with a negative global warming potential. Opportunities to improve the environmental impact of a photocatalytic dry reforming process so as to widen its scenario applicability are also discussed.

EPiC grasshopper: A bottom-up parametric tool to quantify life cycle embodied environmental flows of buildings and infrastructure assets

Reducing the embodied environmental flows of built assets is becoming increasingly important and is a key priority for actors in the built environment to improve life cycle environmental performance. Policies and related targets for embodied environmental flow reductions are emerging. Despite this, tools for quantifying the life cycle embodied environmental flows of built assets are limited in variety and scope. Parametric life cycle assessment (LCA) tools have emerged to address some of these limitations. These tools can enhance decision making, be embedded directly into CAD programs, and offer real-time LCA calculations across multiple design variations. Yet, existing parametric tools for LCA rely on process-based material environmental flow data, limited geometries, limited real-time data visualisation capacity, and often require specialised technical expertise to use. These gaps limit their ability to provide transparent, robust, and rapid assessments. This paper introduces EPiC Grasshopper, an open-source, open-access, bottom-up, parametric tool that enables the quantification of life cycle embodied environmental flows at the early stages of built asset design, bridging the aforementioned gaps. The key characteristics and functionalities of the tool are described, followed by verification (checking that calculations are correct), validation (checking that results are representative of reality), and demonstration of its application to two built asset case studies, i.e. parametrically-defined Australian house and road. The paper shows how the tool can be used to generate designs to meet specific embodied environmental flow targets as well as streamline and increase the uptake of embodied environmental flow assessment and considerations in built asset design workflows.

Office to housing conversion: estimating life cycle environmental and financial performance

Renovating existing building is often touted as having an improved environmental performance as compared to demolition and construction. However, very few studies have quantified the life cycle environmental benefits resulting from such renovations. The aim of this research is to provide a benchmark based on a real and representative case study building to estimate life cycle greenhouse gas emissions and financial costs of redeveloping an office building by considering different scenarios: (1) renovation as an office building; (2) conversion as a residential building; (3) demolition and construction of an office building and (4): demolition and construction of a residential building. Results show that the demolition-construction scenarios are undoubtedly the most environmentally impactful, but the difference between offices and housing is less significant and depends greatly on the assumptions made. On the other hand, from a tax point of view, the demolition-construction scenario is favoured by the real estate industry because it allows for the recovery of VAT in the operation and thus maximizes the value of the real estate asset as well as the financial return. There is also a significant difference between the profitability of a housing and an office project. The latter is favoured by market values. The tendency to favour offices in the European district could be reversed in the current post covid situation and solutions exist to encourage the development of housing projects through office conversion.

Single-use plastic bag alternatives result in higher environmental impacts: Multi-regional analysis in country with uneven waste management

Single-use plastics (SUPs) have been the focus of plastic pollution control, and limiting their use while shifting to other alternatives have been widely promoted in various countries. This study tries to verify the life cycle environmental performances of single-use plastic bag and its alternatives under different scenarios in real world. China is chosen as case study, where provincial variability is prominent in waste disposal, and strictest plastics ban has issued lately in this worldwide biggest market. The study found that HDPE plastic bags have relatively lowest environmental footprints regarding to Acidification Potential, Global Warming Potential, Chemical Oxygen Demand, Eutrophication Potential, Fossil Fuel Depletion Potential and Water Use. Sticking to current waste treatment, large-scale promotion of degradable products will increase environmental impacts by 1.4–22.6 times nationwide. Xinjiang has highest impact of using plastic bag at household level, due to its long-distance transport and high landfill ratio. Henan and Hebei will trigger the most significant changes in Global Warming Potential of 4.6 and 4.4 times if single-use plastic bags are all replaced with other alternatives. Uncertainty and sensitivity test further prove the robustness of results, and extends geographical implications of the findings. These suggest that introduction of new alternatives requires systematic deployment with full life cycle thinking, and SUPs pollution control should be a holistic transformation. Reducing bag weight while ensuring carrying capacity, purchasing local products to shorten transportation distances and shifting towards cleaner energy sources are synergetic ways to reduce the environmental impact of single-use plastic products.

Improving mechanical and life cycle environmental performances of recycled CFRP automotive component by fibre architecture preservation

Recycled carbon fibre reinforced polymer (rCFRP) is attracting interest for automotive applications but has reduced mechanical properties due to a loss of intact fibre architecture. This study investigates the effects of fibre architecture preservation during recycling of carbon fibres on the mechanical and life cycle environmental performances of rCFRP applied to a vehicle roof panel. Results show that rCFRPs with preserved unidirectional and woven fibre architectures have average flexural properties at least 4 times higher than those of current rCFRP with unpreserved fibre architecture. A hypothetical rCFRP roof panel with preserved plain woven rCF reduces the life cycle greenhouse gas emissions by 11% and 23% compared to the current rCFRP, respectively, when used in gasoline vehicle and battery electric vehicle. This paper demonstrates that the recycling approach with fibre architecture preservation offers great opportunities to improve the mechanical and environmental performances of rCFRP for use in the automotive industry.

Sustainability performance of interior wall types used in Canada: a life cycle thinking-based comparison

The wall system constitutes a large portion of the material used in building construction. Although interior walls cover more surface area within a building, published literature has mainly focused on the performance assessment of exterior walls. The aim of this research is to examine the life cycle environmental, social, and economic performance of interior wall construction methods (i.e., concrete block masonry, wood stud gypsum, and steel stud gypsum) used for industrial, commercial, and institutional buildings. The findings indicated that the environmental, social, and economic performance of concrete block masonry wall is 49%, 23%, and 18% higher than the next best alternative. This research has generated important information that can be used in material specification for greener building design.

Effect of short-term perennial leys on life cycle environmental performance of cropping systems: An assessment based on data from a long-term field experiment

Modern agriculture’s dependence on the intensive use of inputs, such as chemical fertiliser and pesticides, leads to high environmental impacts and, possibly, vulnerability in food security, since most of these inputs are imported from other countries. This calls for more sustainable and resilient agricultural practices. Diversification of crop rotations, e.g. by including perennial leys, enhances provision of ecosystem services, leading to healthier crops and increased yields. Perennial crops also increase soil organic carbon (SOC) stocks, which is interesting from a global warming mitigation perspective. In addition, legume-rich leys can utilise atmospheric nitrogen (N) through symbiotic association with N2-fixing bacteria. However, few studies have evaluated the effects of short-term perennial leys in rotation on cropping system performance over long periods and under different conditions. In this study, we used data from three sites in a long-term experiment in Sweden (initiated in the 1960 s), in combination with Life Cycle Assessment methodology, to assess the environmental and yield effect of including ley in crop rotations. Two N fertiliser regimes (High, Low) in combination with three six-year crop rotations, consisting of either i) two-year mixed grass-legume ley, ii) two-year pure grass ley or iii) annual crops without ley, were compared. Environmental impacts (climate impact, energy resource depletion, eutrophication potential) of the different combinations were quantified per kg harvested crop (expressed in cereal units, CU) and per hectare. The lowest environmental impact, at all sites, was found for the crop rotation with two-year mixed ley under the Low N regime. On average, this combination resulted in 329 g lower GHG emissions per kg CU than the crop rotation without ley and Low N, primarily due to lower input of chemical N fertiliser, which reduced the impact from fertiliser production and soil N2O emissions. Comparison of mean SOC change over the study period revealed reduced SOC stocks for all rotations and all sites, especially in the rotation without ley. Therefore, including short-term perennial leys, especially leys containing legume species, in crop rotations can be a useful tool in meeting policy targets on reducing the environmental impacts of agriculture, and in reducing the dependence on purchased agricultural commodities. However, despite the potential benefits of rotational leys, the market demand for the produced ley biomass may be insufficient. Hence, incentives to increase demand are necessary to promote large-scale adoption, for example, for use in bioenergy production and feed.

Energy and greenhouse gases life cycle assessment of electric and hydrogen buses: A real-world case study in Bolzano Italy

The transportation sector plays an important role in the current effort towards the control of global warming. Against this backdrop, electrification is currently attracting attention as the life cycle environmental performance of different powertrain technologies is critically assessed. In this study, a life cycle analysis of the public transportation buses was performed. The scope of the analysis is to compare the energy and global warming performances of the different powertrain technologies in the city fleet: diesel, full electric and hydrogen buses. Real world monitored data were used in the analysis for the energy consumptions of the buses and to produce hydrogen in Bolzano. Compared to the traditional diesel buses, the electric vehicles showed a 43% reduction of the non-renewable primary energy demand and a 33% of the global warming potential even in the worst consequential scenario considered. The switch to hydrogen buses leads to very different environmental figures: from very positive if it contributes to a further penetration of renewable electricity, to hardly any difference if hydrogen from steam-methane reforming is used, to clearly negative ones (approximately doubling the impacts) if a predominantly fossil electricity mix is used in the electrolysis.

Assessing the Life Cycle Environmental Performance and Economic Costs of Composite Materials in Certain Aircraft Structure

The aviation sector is looking to replace conventional metals for aircraft doors with composite materials due to the latter’s potentially favorable combination of mechanical properties and low weight. However, little is known about the environmental impacts and economic costs associated with the production of such composite doors. This study conducts a Life Cycle Assessment and Life Cycle Costing on an example composite aircraft door to quantify its environmental and economic impacts. In addition, uncertainty analysis has been performed to enhance the quality of the assessment.