Parametric Life Cycle Assessment Research Articles

Life cycle assessment and generative design: development of a national LCA tool for exterior walls

PurposeThe promotion of sustainable design is demanded globally. The life cycle assessment (LCA) proved its reliability in this mission, but the difficulty and time required to apply it discouraged designers. This research aims to integrate LCA into the building design process through a software tool, taking advantage of generative design features. This will facilitate decision-making by architects and construction professionals.Design/methodology/approachThe study develops the EGY-LCA (http://egy-lca.com/). This prototype tool suggests exterior wall design alternatives for residential buildings in Egypt, using the environmental impact indicators of LCA data and other criteria related to national codes, materials, construction methods and required thermal resistance. Within a generative design process, the algorithm tests every possible wall method with materials and thickness combinations for each layer in compliance with inputs. The paper begins by explaining the tool’s working method. Afterward, different sets of inputs are examined and the values of the resultant environmental impacts of several suggested wall solutions are statistically analyzed. The application demonstrates the importance of the generative design tool. Proposing several solutions based on a set of inputs facilitates the selection of sustainable choices and allows comparisons between alternatives.FindingsThe prototype experiment confirms the research hypothesis. Unlike the available LCA tools, architects can make decisions with limited LCA experience if the data and equations are integrated into a generative design tool. The prototype proves its applicability for exterior wall alternatives.Research limitations/implicationsThe prototype is the initial step toward a whole-building LCA tool. It includes limited LCA stages and materials for the external wall. Future research is required to expand this parametric tool concept to include all the building components. The framework in Section 5 proposes a visualization.Practical implicationsThe prototype tool: EGY-LCA (http://egy-lca.com/). The value added to the design and construction sectors through the uncomplicated LCA application is fostering sustainable design, generative design tools can achieve this.Originality/valueThe novelty of this work is that it is the first initiative offering a parametric LCA tool. It promotes the application of LCA at the design stage using generative design, which contributes to sustainable development.

Combining parametric life cycle assessment (LCA) and multi-criteria decision making (MCDM) for developing sustainable residential neighborhoods

Combining parametric life cycle assessment (LCA) and multi-criteria decision making (MCDM) for developing sustainable residential neighborhoods

Environmental Assessment of Metal Chip Recycling – Quantification of Mechanical Processing's Global Warming Potential

Material recycling is an essential lever for improving the sustainability of production processes. One way of reusing metal chips that occur as waste in machining or other subtractive manufacturing processes is to mechanically pretreat and remelt them. In mechanical pretreatment, the chips are separated from the cutting fluid by a centrifuge and then briquetted directly on site. This simplifies the handling and makes the transport and subsequent remelting more efficient than in thermal processing alone. The main objective of this work is to quantitatively assess the environmental impacts of the described recycling process, focusing on the global warming potential. Furthermore, recycling by means of mechanical chip processing is compared with alternatives such as thermal drying and primary material extraction. A parametric life cycle assessment (LCA) model has been developed for this purpose. The model considers equipment, material, throughput and location variations to analyze different use cases. The results of the LCA of an exemplary use case show that environmental benefits result from a higher bulk density during transport and a lower energy input during remelting due to a lower liquid content.

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.

Optimizing building solutions in a changing climate: parameter-based analysis of embodied and operational environmental impacts

Abstract Buildings contribute significantly to global energy consumption and carbon dioxide emissions. Climate change affects building performance, particularly heating and cooling demands. While current policies focus on improving energy performance and reducing operational emissions, the embodied emissions from building materials become more significant in energy-efficient buildings. This study aims to investigate optimal building solutions considering both operational and embodied environmental impact in the context of climate change in the Belgian context. The research questions address the influence of building characteristics on environmental impact and the contribution of embodied and operational emissions to optimal design. The study employs parametric life cycle assessment and dynamic building energy simulation to explore design strategies for a medium-sized office building. The results reveal the trade-offs between operational and embodied impacts. Buildings with better energy performance exhibit higher embodied emissions, highlighting the importance of considering both aspects. Pareto optimal buildings are identified, minimizing total life cycle environmental cost and operational environmental cost. Insulation levels, solar shading, and orientation are key factors in achieving optimal design. HVAC systems and electricity mixes also significantly influence optimal solutions. Lightweight and heavyweight buildings have distinct characteristics affecting heating and cooling demands. Variations in electricity mixes impact energy consumption and environmental costs of different HVAC system scenarios. The study emphasizes the need for a holistic life cycle approach and considering both operational and embodied impacts in building design. It underscores the importance of optimizing building characteristics while addressing climate change challenges. Further research should explore additional factors such as night cooling, HVAC system performance under climate change, and the inclusion of financial costs and visual comfort in the analysis.

Parametric design, life cycle assessment, and optimization of a discrete product with application to an electric traction motor

Humans are surrounded and even dependent on discrete products for their daily activities. Product design processes have been vastly studied towards a healthy economic prosperity and other technical objectives (e.g., low risk). However, recent studies show that these methods have been lacking in terms of the environmental challenges humanity faces in the present and future. This study proposes a novel design framework that incorporates a parametric life cycle assessment (PLCA) as part of the optimization-based design model of a discrete product at early stage. Electric traction motor design applied to an electric vehicle is used as a case study. The results of performing a multi-objective design problem and an uncertainty analysis using Monte Carlo simulation show the usefulness of incorporating the PLCA in a transparent manner, as required by the International Standards Organization. Future work suggests investigating the expansion of this technique to support a broader range of objective functions.

Parametric Life Cycle Assessment of Nuclear Power for Simplified Models.

Electrifying the global economy is accepted as a main decarbonization lever to reach the Paris Agreement targets. The IEA's 2050 Net Zero transition pathways all involve some degree of nuclear power, highlighting its potential as a low-carbon electricity source. Greenhouse gas emissions of nuclear power reported in the life cycle assessment literature vary widely, from a few grams of CO2 equivalents to more than 100 g/kWh, globally. The reasons for such a variation are often misunderstood when reported and used by policymakers. To fill this gap, one can make LCA models explicit, exploring the role of the most significant parameters, and develop simplified models for the scientific community, policymakers, and the public. We developed a parametric cradle-to-grave life cycle model with 20 potentially significant variables: ore grade, extraction technique, enrichment technique, and power plant construction requirements, among others. Average GHG emissions of global nuclear power in 2020 are found to be 6.1 g CO2 equiv/kWh, whereas pessimistic and optimistic scenarios provide extreme values of 5.4-122 g CO2 equiv/kWh. We also provide simplified models, one per environmental impact indicator, which can be used to estimate environmental impacts of electricity generated by a pressurized water reactor without running the full-scale model.

Parametric life cycle assessment modeling of reusable and single-use restaurant food container systems

Single-use packaging generates millions of tonnes of plastic waste per year – a circular economy waste-reduction strategy is to implement reusable container systems for restaurant takeout. We developed a parametric life cycle assessment (LCA) and cost model and used scenario analysis to study customer behavior effects on greenhouse gas (GHG) emissions, primary energy, water use, and cost of a reusable container system in Ann Arbor, Michigan. Under our base case scenario, the primary reusable container has lower impacts across most metrics than comparable single use containers. Benefits are sensitive to excess customer transportation; if 5% of customers make trips solely to return used containers, the reusable system has higher life cycle GHG emissions and primary energy use than single-use. Additionally, if a large fraction (close to 100%) of customers practice excess at-home washing of containers, the life cycle primary energy impacts will be greater than those of most single-use containers.

A parametric life cycle assessment model for ductile cast iron components

Life cycle assessment (LCA) is widely used to evaluate product environmental impacts, while detailed LCAs are missing that model the effect of design and manufacturing decisions on U.S. ductile iron casting environmental impacts. We develop a parametric LCA model by collecting inventory data from 11 foundries (26% of U.S. production) and literature to quantify the impact of design and manufacturing decisions on the product's cumulative energy demand (CED) and global warming potential (GWP). The model reveals the cradle-to-gate CED and GWP of U.S. ductile iron products at 24–50 MJ/kgproduct (mean: 37 MJ/kgproduct) and 1.6–3.0 kg.CO2eq./kgproduct (mean: 2.2 kg.CO2eq./kgproduct). A Sobol-indices sensitivity analysis revealed the factors that have the greatest effect in reducing these environmental impacts: casting yield, electricity grid, recycled content, and furnace technology. A comparative whole life cycle analysis of automotive ductile iron applications versus forged steel, stamped steel and aluminum alternatives highlights the design and manufacturing conditions that minimize life cycle impacts.

Tool characterisation framework for parametric building LCA

Connecting Life Cycle Assessment (LCA) to parametric design has been suggested as a way of facilitating performing environmental assessments in early design stages. However, no overviews of potential approaches and tools are available within recent research. Also, no characterisation frameworks adapted for parametric LCA tools are present. In order to guide the development of workflows for environmental analysis aimed at the early design stage of buildings, the goal of this paper is to provide such a framework, and to demonstrate its use by characterising a number of available LCA plug-ins for the commonly used parametric design framework Grasshopper® (GH). First, a framework for classification and characterisation of tools based on workflow, adaptability, and required user knowledge was developed. Second, a tool inventory was performed, identifying 13 parametric LCA plug-ins for GH. Finally, four of these plug-ins were further investigated using the developed evaluation framework, a user persona approach, and a simplified test case. It was found that the characterisation framework was able to differentiate tools based on the level of LCA expertise integrated in the tools, and the allocation of responsibility for data entry and interpretation. A contrast was found between streamlined tools, and tools which provide more versatility. The characterisation framework, and the resulting overview of approaches can be used to guide the future development of parametric environmental analysis frameworks.

Toward a national life cycle assessment tool: Generative design for early decision support

The life cycle assessment (LCA) has proven to be a reliable methodology for achieving sustainable development. The number of studies and attempts of integration at the building design stage is increasing. This study is aimed at developing a framework for a national LCA tool that considers Egyptian constraints and strikes a balance between embodied and operational impacts to serve as a decision-support tool for early design. This is achieved by first reviewing and analyzing LCA integration methods during the early design stages, emphasizing parametric methods. Second, studying the situation of LCA and energy efficiency in Egypt through publications, building codes, and residential building construction specifications. As a result of these steps, a suggested implementation method based on the generative design was developed as a tool framework that mainly focuses on residential building exterior walls as the first step of the national LCA tool to aid the design process and promote sustainable development. In addition to being the first initiative for a national LCA tool, the novelty of this work is the method of integration compared to other parametric LCA, which aims at optimizing both embodied and operational impact with respect to the Egyptian conditions while offering multiple solutions.

Lca_algebraic: a library bringing symbolic calculus to LCA for comprehensive sensitivity analysis

PurposeIn this paper, we present new tools to ease the analysis of the effect of variability and uncertainty on life cycle assessment (LCA) results.MethodsThe tools consist of a standard protocol and an open-source library: lca_algebraic. This library, written in Python and based on the framework Brightway2 (Mutel in J Open Source Softw 2(12):236, 2017) provides functions to support sensitivity analysis by bringing symbolic calculus to LCA. The use of symbolic calculus eases the definition of parametric inventories and enables a very fast evaluation of impacts by factorizing the background activities. Thanks to this processing speed, a large number of Monte Carlo simulations can be generated to evaluate the variation of the impacts and apply advanced statistic tools such as Sobol indices to quantify the contribution of each parameter to the final variance (Sobol in Math Comput Simul 55(1–3):271–280, 2001). An additional algorithm uses the key parameters, identified from their high Sobol indices, to generate simplified arithmetic models for fast estimates of LCA results.Results and discussionThe protocol and library were validated through their application to the assessment of impacts of mono crystalline photovoltaic (PV) systems. A comprehensive sensitivity analysis was performed based on the protocol and the complementary functions provided by lca_algebraic. The proposed tools helped building a detailed parametric reference LCA model of the PV system to identify the range of variation of multi-criterion LCA results and the key foreground-related parameters explaining these variations. Based on these key parameters, we generated simplified arithmetic models for quick and simple multi-criteria environmental assessments to be used by non-expert LCA users. The resulting models are both compact and aligned with the reference parametric LCA model of crystalline silicon PV systems.ConclusionThis work brings powerful and practical tools to the LCA community to better understand, identify, and quantify the sources of variation of environmental impacts and produce simplified models to spread the use of LCA among non-experts. The library mainly explores the uncertainties of the foreground activities. Further work could also integrate the uncertainty of background activities, described, for example, by pedigree matrices.

Optimization of eco-design decisions using a parametric life cycle assessment

The manufacturing industry consumes an excessive amount of materials, mainly from virgin sources and energy streams, which contributes significantly to global environmental problems such as climate change. To achieve sustainable development, the creation of eco-designs and their implementation in the manufacturing sector is crucial. However, it is tedious for product designers to generate alternative eco-designs and iteratively evaluate the mitigation of environmental hotspots. Therefore, this study proposes a parametric life cycle assessment (PLCA) approach to eco-design optimization and decision making at the early design stage. This proposed PLCA model reflects the characteristics of the environmental performance of the entire product life cycle as an objective function at the early design stage. In particular, this model allows designers to optimize the design and to mitigate environmental impacts, without performing scenario analysis. To illustrate the applicability of this approach, two case studies are presented, and the effectiveness of the approach is demonstrated for eco-design optimization and eco-design decision making. The results of the two case studies reveal that the developed objective function, which is expressed as a multi-variable optimization problem with constraints, can be used to generate optimum values for the product and process parameters that will have minimal environmental impacts. Therefore, it can be concluded that the PLCA based optimization approach in the early design stage of the product supports designers in their attempts to achieve the eco-design effortlessly.

Parametric life cycle assessment for distributed combined cooling, heating and power integrated with solar energy and energy storage

In this research, we develop a parametric life cycle assessment framework and evaluate the environmental and economic trade-offs of a distributed combined cooling, heating, and power system integrated with renewable energy and energy storage system (CCHP-RE-ESS). Also, we compare this to centralized conventional energy generation. The CCHP-RE-ESS system consists of microturbines, solar PVs, lithium-ion batteries, and other auxiliary system components. Using a parametric life cycle assessment approach, we learn the trade-offs environmental and economic impacts for various sizes of solar PVs arrays and batteries. The emission impact result from the parametric life cycle assessment is more accurate than the conventional life cycle assessment due to hourly-based simulation and parametric models for different system components. Our simulations show that the proposed system that follows the thermal load can primarily reduce the overall environmental impact as compared to the centralized conventional energy production for most building types and climate zones we studied. For example, the system can help a medium office in Atlanta reduce 46% of global warming impact, 98% of water usage, 93% of acidification impact, etc. In terms of cost, the life cycle cost of the proposed system is often higher than conventional energy generation while it is more economical for the small and large office than the medium office.

Life cycle assessment for Zero Emission Buildings – A chronology of the development of a visual, dynamic and integrated approach

Current regulations to reduce energy consumption, and GHG emissions from buildings have focused on reducing operational impacts [1] This paper addresses the specific challenge of increasing complexity and decreasing usability when dealing with the level of detail required when modelling life cycle assessment (LCA) and integrating embodied emission calculations in the design process of a ZEB. It is well known that architectural design processes inherently have high degrees of complexity, and this paper investigates how the use of information and communication technology (ICT) in the design process can have a great impact on reducing GHG emissions and increasing sustainability in ZEBs. Visualisation is an invaluable tool to communicate complex data in an interactive way that makes it easier for non-expert users to integrate LCA thinking early and throughout the design process.The paper presents a chronology in the development of a more visual, integrated and dynamic approach involving the use of parametric LCA models for decision-support purposes. Such an approach provides the designer with a direct link between the 3D digital model and embodied emissions data contained in the ZEB Tool to perform life cycle GHG emission calculations of buildings. Integrating LCA in a more visual and easily understood way in the holistic design process can also influence more tangible material choices in terms of, for example, architectural tectonics or cultural heritage. This allows designers the possibility to choose, for example, durable or natural materials with the lowest environmental impact or innovative materials with high or low associated emissions and consider these holistically early in the design phase when the level of design freedom is greater. The extent to which existing ICT tools and User Interfaces (UI), such as dashboards, can provide dynamic visual feedback on selected parameters, including LCA, in the design process of zero emission buildings, is discussed. The paper presents two ‘proof of concept’ dashboards to visualise LCAs at the building (ZEB) and neighbourhood (ZEN) scale. Both approaches are currently being further developed in The ZEN research centre to visualise, analyse and model the data at different scales for different ZEN Key Performance Indicators (KPIs) using visualisation and immersive technologies, such as Extended Reality (XR) technologies including Virtual Reality (VR) and Augmented Reality (AR).

Parametric life cycle assessment of a reusable brick veneer

A possible design strategy to improve the sustainability of building products is facilitating their future reuse. This strategy inspires some manufacturers to design innovative products, such as reusable façade products. Although these products might have a higher environmental impact for production, their reusability could lead to an environmental saving from a life cycle perspective. A possible method to evaluate their environmental performance is life cycle assessment (LCA). Nevertheless, LCA studies of reusable products are still rare. Furthermore, although the general LCA frameworks is fixed by ISO and CEN standards, some methodological choices must still be made by LCA practitioners. This paper first presents a method (as four methodological choices) for a parametric life cycle assessment of reusable building elements. Then, this method is applied to a comparative LCA of reusable and brick-and-mortar veneers. With proposed method, the reusable brick veneer is environmentally advantageous if it is reused at least once and if it is properly recycled at its end-of-life. The parametric method also indicates the relative influence of various parameters such as reuse rate, number of interventions, transport distances and waste treatment. The manufacturers can use this LCA study as a retrospective assessment to validate the relevance of design choices, but also as target-driven product management support to know hot-spots in the product’ life cycle management. This study will hopefully inspire other designers and manufacturers and accelerate the transition towards a sustainable built environment.

A design integrated parametric tool for real-time Life Cycle Assessment – Bombyx project

Life Cycle Assessment (LCA) has become a widely accepted method for environmental assessment of buildings, but is still not commonly applied in design practice. The biggest potential for optimization and reduction of GHG emissions lies in the early stages of the design process. Therefore, a design-integrated approach for LCA is needed. The goal of this paper is to describe the development of a parametric LCA tool for application in early design stages in the Swiss context. The envisioned users of the tool are primarily architecture and engineering students, but also practitioners. The integration of LCA throughout the design process is solved through a modular strategy. In the early stage, pre-defined components are selected to model a complete LCA. In the following design steps when more information is available, individual materials can be input with higher level of detail. The Bombyx tool is developed as a plugin for Grasshopper based on Rhinoceros3D and includes an SQL material and component database. Users are able to choose different materials and building systems and quickly modify the building’s geometry while continuously receiving the calculated environmental impact in real-time. Visualization of the results, e.g. colour code indicate how the design performs in relation to a benchmark or optimization potential. The project is developed in open source to broaden the user and developer community and foster new ideas, designs and implementations in Bombyx.

Optimal design of flax fiber reinforced polymer composite as a lightweight component for automobiles from a life cycle assessment perspective

AbstractThe present study combines the generalized rule‐of‐mixture (ROM) model and the Ashby material selection method for the life cycle assessment (LCA) of flax fiber reinforced polymers (FRPs) and glass FRPs (GFRPs). The ROM model allows life cycle environmental impact predictions according to specific parameters of flax FRPs such as fiber format, volume fraction, manufacturing technique, and load‐bearing capacity. The comparisons applied in this study are constructed on two common composite structures: mat panels and injection molded struts with equal stiffness and strength as the design criteria. On the one hand, the parametric LCA predicts that the equal strength design criterion for flax FRPs contributes to consistent mass increases, subsequently resulting in higher life cycle environmental impacts compared to the reference GFRPs; on the other hand, under the equal stiffness criterion the flax mat polypropylene (flax mat‐PP) film helps with mass reduction in reference to the glass mat‐PP composite, leading to the 20–50% life cycle environmental impact reductions for most impact categories. The subsequent evaluation of the influences of the fiber volume fraction on flax FRPs shows different patterns. For the short flax fiber‐PP composite, a steady decrease of the life cycle CO2 emissions can be observed with the increasing fiber volume fraction. However, for the flax mat‐PP composite, depending on the tensile modulus of the flax fiber, the optimal volume fractions of the fiber change from 28 to 32% v/v, whereby the lowest life cycle greenhouse gas (GHG) emissions can be achieved.

From Zero Emission Buildings (ZEB) to Zero Emission Neighbourhoods (ZEN): A Mapping Review of Algorithm-Based LCA

The building industry is responsible for approximately 40% of energy consumption and 36% of greenhouse gas emissions in the European Union (EU). The most efficient way of reducing a building’s environmental impact is addressing it in the design stage. Here, design freedom is the greatest, but uncertainty is high and there is a nearly limitless number of design options. Based on experiences with zero emission buildings (ZEB) and zero emission neighbourhoods (ZEN), a mapping review has been conducted to analyse how parametric life cycle assessment (LCA) and algorithms have been used to address neighbourhoods, buildings, and construction materials. Results have identified a general gap of knowledge regarding the use of parametric LCA models for decision-support purposes, demonstrated by the substantial focus on analytical methods compared to procedural methods. Implications for the evolution from ZEB to ZEN are twofold: (i) an integrated approach with multiple tools and methods is required, and (ii) further development of algorithms in the tool are needed to address complexity, sensitivity, and uncertainty. This study is expected to foster the development of algorithmic approaches to improve the ZEB tool as a decision-support tool. Further research should address the key questions of when and how.

Assessment of greenhouse gas emissions of ventilated timber wall constructions based on parametric LCA

The increased use of multi-storey timber buildings can potentially create a significant reduction on the life cycle environmental impact of a building. However, with an increasing height of timber buildings the challenge is to maintain the same expected performance independent of the height; tall buildings are particularly exposed to high wind pressures combined with wind-driven rain. Additionally, tall buildings require longer construction times in which the structural elements are especially exposed to moisture. Furthermore, inspection, maintenance and repair possibilities are limited compared to low-rise buildings. This work develops a parametric life cycle assessment (LCA) methodology to evaluate the consequences (greenhouse gas (GHG) emissions) caused by a potential moisture damage of a failure event (considered as the mould and decay growth) in typical ventilated timber wall constructions from four countries: Germany (DE), France (FR), Norway (NO) and Sweden (SE). The environmental performance is evaluated throughout the life cycle of the wall construction in accordance with the modular system of life cycle stages as defined in EN 15978. Global warming potential (GWP) is used as a proxy for environmental impact. Product specific average environmental product declaration (EPD) is used as a main data source in GHG emission calculation. Three parameters; i) number of windows, ii) extent of damage around the window area and iii) the number of damaged layers; are used to evaluate the potential risk of GHG emission from moisture damage around window connections. A probabilistic-based design methodology is also applied to assess the mould and decay occurrence. The total GHG emission results from different scenarios considered in this study and the magnitude of environmental impact related to probabilistic damage are presented. The results show that GHG emissions increase with increase of the number of windows, the damaged area and the increase in the number of replaced layers. This is due to the additional GHG emissions from the materials used to replace the damaged layers. The probability of failure is sensitive to the defined unacceptable level of mould growth. This affects the risk assessment, where the perturbation derived from the different probabilities of failure for different layers are observed at the corresponding replacement interval. The results also show that the parametric results are sensitive to the variables used to estimate the area of replacement, the number of windows, the number of damaged layers and the considered failure event. This study can be used to evaluate and minimize the potential GHG emission of possible moisture damages scenarios on building envelopes. Furthermore, it can enable to consider various improvement measures that reduce the risk, resulting in a robust construction with good function, longer service life and lower embodied emissions during the building's life time. The study also highlights the need for further analysis of the assumptions and background data used when developing the parametric tool.