Stages Of Life Cycle Assessment Research Articles

The cost of sustainability in the construction sector – The case of family houses in Belgium

As the housing sector is a major contributor to greenhouse gas emissions a large body of literature has focused on measuring the environmental impact of houses, using the Life Cycle Assessment (LCA) methodology. This literature reaches the conclusion that alternative construction materials should be used to reduce the environmental impact of buildings. While such research provides essential knowledge on the carbon footprint of the housing sector, few studies take into account the economic side of the issue. This paper addresses this gap by calculating the Life Cycle Cost (LCC) of houses and matching the results with the LCA stages. The methodology is developed for two reference houses in Belgium. Considering all elements and materials used in the construction process, this approach allows a comparison of each house's elements based on the required investment to abate their carbon footprint. The most striking results are that (1) the operational stage (i.e., the use of houses) accounts for about 65% of the total carbon impact of a house; (2) a 1€ investment in sustainable materials induces a drop of 1–1.3 kgCO2eq; (3) this effect is heterogeneous across materials, with the highest returns obtained for external walls (−6 KgCO2eq) and windows (−3 to −6 kgCO2eq) and the lowest returns obtained for ground floor (−0.3 kgCO2eq).

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.

Carbon Footprint in Bovine Fat Biodiesel Synthesis - Comparison Using Methanol or Ethanol

Climate change makes the comparison of strategies to mitigate environmental impacts in the production of catalyzed biodiesel derived from animal fat waste a necessity. Transesterification of Bovine Kidney Fat (BKF) into biodiesel is feasible, but the utilized inputs can incur a substantial environmental cost, such as Carbon Footprint (CF). The utilization of Ethanol as a reagent for the transesterification of BKF presents a viable alternative that could influence the Life Cycle Assessment (LCA) of Biodiesel and reduce its CF. This study compares the CF for the LCA of producing 1 kg of Biodiesel for a 1-6 Methanol-BKF and 1-9 Ethanol-BKF ratio, catalyzed by Sodium Hydroxide (NaOH) and Potassium Hydroxide (KOH) at 0.35% at 60°C. The LCA was initially defined following ISO 14067:2018 standards, and subsequently, the Greenhouse Gas (GHG) Emission Inventory was conducted for each stage of Biodiesel manufacturing. Ultimately, CF was calculated using CCalC2 software for the two examined conditions. Five processes were identified in the manufacturing of Biodiesel from BKF in the LCA stages. The CF for Biodiesel derived from BKF with Methanol is 4.36 kg CO2eq/FU, whereas the CF for Biodiesel derived from BKF with Ethanol + 5mol H2O is 0.246 kg CO2eq/FU. Enhanced environmental performance was evidenced using Ethanol + 5mol H2O for the LCA in BKF Biodiesel manufacturing, exhibiting a 1772.35% improvement over Methanol.

A comparative analysis of recent life cycle assessment guidelines and frameworks: Methodological evidence from the packaging industry

In recent years, a number of new guidelines and frameworks for Life Cycle Assessment (LCA) have emerged, trying to support analysts in dealing with certain methodological issues and “gaps” of the ISO 14040-44, that are still the main LCA reference standards. This trend can be considered as positive, because the lack of shared, standardised and more detailed rules regarding LCA has affected for years the consistency of LCA analyses and their potential comparisons. However, the proliferation of guidelines and frameworks can also have negative consequences, first of all related to the potential resulting confusion and the lack of a clear reference for LCA analysts. These potential risks are particularly accentuated for multinational companies, which deal with many clients, in different markets, countries and sectors, and have to conform their analyses to different requirements each time.Focusing on the plastic packaging industry, this study compares six LCA guidelines and frameworks to highlight their similarities and differences. The documents selected to be analysed were: three documents applicable to products in general (ILCD, PAS 2050 and PEF), two packaging-specific guidelines (Pathfinder Framework and SPICE Methodological Guidelines) and a product specific standard for the packaging industry (PCR 2013:19). The methodological aspects analysed and compared, grouped according to the LCA stages, are: units of analysis; system boundaries; allocation methods; cut-off criteria; end-of-life; packaging; storage; biogenic CO2 emissions; carbon removals and carbon content; land use; offsets; impact categories and indicators; LCA methods and models; normalisation and weighting; data quality; sensitivity analysis. The aim is to understand to what extent potential differences may impact on companies and LCA analysts who conduct the assessments. Results highlight that the six guidelines and frameworks analysed are not always aligned and that, although some misalignments can be easily addressed, others could negatively affect the reliability of the analyses conducted.

Mechanistic-empirical pavement design to include mechanical performance of rubberized asphalt pavements in the use stage of life cycle assessment

The use phase of road pavements includes fuel consumption, urban heat island, and leaching. Life cycle assessment (LCA) often omits the use phase for its complexity. The use phase should also consider the durability of the asphalt mixtures. This study used the Mechanistic-Empirical Pavement Design to include the durability of five asphalt mixtures (control, styrene-butadiene-styrene - SBS, polymer coated rubber - PCR dry and wet, and devulcanized rubber - DVR) in the LCA of 1-mile road pavement over 50 years. Considering only the impact of the mixture production, the control mix had a carbon footprint 12.9 % lower than the other mixtures. When including the durability, the control mixture's carbon footprint was 69 % and 84 % higher than SBS and PCR dry mix, respectively. This study showed the importance of including the mechanical performance of the asphalt mixtures to better evaluate the environmental impact of road pavements over the service life.

Methodology of Eco-Design and Software Development for Sustainable Product Design

In the face of the growing social recognition of environmental awareness and emerging regulations in countries where targets include the reduction of the CO2 footprint in the industrial sector, several companies are facing the challenge of introducing environmental impacts as new key design criteria. To successfully launch new products with optimized environmental impact, it is crucial to apply Life Cycle Assessment (LCA) during the design phase. However, the design process of any product is a process where materials, production processes, concepts, and various design factors are constantly changing, which requires an agile LCA calculation for its effective inclusion during the iterative design process. This paper presents an eco-design methodology, based on the adaptation of the LCA method to the changing design environment, through the adaptation of LCA stages to the design process, the customization of environmental databases to the product of the company, and the development of a software tool for its application during the earlier design phases. This methodology assists designers to save efforts during the calculation process, with different integration levels of environmental data, according to LCA phases established by ISO 14040 and ISO 14044. The effectiveness of this methodology will be shown with a real case study.

Engaging Preuniversity Students in Sustainability and Life Cycle Assessment in Upper-Secondary Chemistry Education: The Case of Polylactic Acid (PLA)

This article reports about a lesson series that focuses on engaging students in sustainability, plastics, and life cycle assessment (LCA). The purpose of the lesson series is to give students insights into sustainability in the context of plastics and to foster awareness of and insights into the benefits of the LCA method. The lesson series introduces students to sustainability by enabling them to watch a video, answer questions, read articles, conduct laboratory experiments, and experience the four stages of LCA. In general, the findings reveal that the lesson series evoked in students a more critical view of the life cycle of plastics. The students showed increasing awareness of the complexity of the sustainability issue at hand. In addition, students used their acquired knowledge about LCA and mentioned impact categories in their argumentation. The lesson series evoked predominantly life cycle thinking, and the qualitative part of an LCA, and might thus serve as a stepping stone toward the quantitative assessment. The preliminary results show that the lesson series is effective for evoking life cycle thinking among students and serves as a stepping stone towards life cycle assessment. Future research could focus on setting the goal and scope of the process to be assessed, with emphasis on the functional unit in the context of plastics, and providing students a complete and coherent understanding of the entire cycle of production, use and recycling of plastics.

Study of Life Cycle Assessment of Bricks and the Impacts to the Environment in Malaysia

Life cycle assessment (LCA) is conducted in order to evaluate the environmental impacts of products chosen from the manufacturing phase and the end-of life cycle of the material and in clay brick and concrete were chose as the observed products. Brick is one of the important construction materials that can be seen at the surrounding. Main objective for this study is to investigate the impact of production of different types of brick to the level of emissions of carbon dioxide to the environment. Four stages of life cycle assessment were conducted before the result for the study analysis can be obtained and that stages including goal and scope definition, life cycle inventory (LCI), life cycle impact assessment (LCIA) and the interpretation part. The results obtained from the simulation of the Simapro shown that the concrete contributes more negative impact compared production of clay brick in terms of global warming, ozone depletion, formation of fine particulate matter and ozone formation. Manufacture of clay brick contributes more negative impact to the ionizing radiation, freshwater eutrophication and mineral resource scarcity.

Environmental Impact Evaluation of a Fresh Milk Production

The study aimed to evaluate the waste impact on the environment in fresh milk production activities from the dairy cows rearing on farms to the distribution process of fresh milk to a milk processing factory and fresh milk selling agents, identify the most significant potential for contamination from fresh milk production activities on the environment, and provide alternative improvements based on the most significant environmental impact caused by fresh milk production activities. This research was conducted in a dairy farmer cooperative which is an organization that produces fresh milk. The Life Cycle Assessment (LCA) method was used to evaluate the environmental impact of fresh milk production activities. The analysis was carried out using SimaPro 9.0.0.47 software. The LCA stages carried out were Goal and Scope Definition, Life Cycle Inventory, Life Cycle Impact Assessment (LCIA), and Life Cycle Interpretation. The assessment of improvement alternatives was then analyzed using the pairwise comparison method to determine the highest weight. The results showed that the three most significant impact categories, namely eutrophication, human toxicity soil, and acidification. The biggest contamination from fresh milk production activities occurs in the fresh milk extraction process. Processing dairy cow dung into manure was the prioritized recommendation to reduce the impact.

Spatial and territorial developments for life cycle assessment applied to urban mobility—case study on Lyon area in France

Purpose The environmental assessment of urban mobility, defined as the movement of people in an urban area, exceeds the scope of transportation life cycle assessment (LCA) with spatial, territorial and even social considerations. The objective of this study is to develop an original interdisciplinary method based on LCA coupled with a land use and transport interaction (LUTI) model to better consider spatial and territorial dimensions in an environmental assessment of urban mobility. Methods Spatial and territorial issues emerge in all LCA stages for urban mobility, and this study illustrates them with an application on the Lyon urban area. To consider most individual daily trips, the geographical boundary is related to the area of influence of the city and the functional boundary includes all transportation modes, with motorized, public and non-motorized transports. The life cycle inventories (LCIs) combined EcoInvent 3.2 inventories with a specific LUTI model, named SIMBAD, local mobility surveys and an emissions and consumptions model (COPERT5). These refinements allow a spatial environmental impacts assessment of urban mobility, expressed per inhabitant per day, at different residential locations and open opportunities to develop precise assessment methods for local air pollutants with detailed description on both population and pollution concentrations. Results and discussion At territorial scale, this study highlights the major contribution to environmental impacts from private cars (around 90%) and the relevance to consider fuel, vehicle, and infrastructure life cycles in a mobility assessment. Spatial interpretations show important variability in function of residential locations and urban form characteristics related to different mobility behaviours, distance travelled and transport technologies used. Through the proposed assessment method for local air pollution impacts on human health, hotspots are revealed in the urban area, especially in the urban centre or along main road axes. In order to test our methodology and open discussions on mobility solutions, two contrasted scenarios are explored on compact city and vehicle electrification both presenting impact transfers between global indicators or with the air pollution exposure indicator. Conclusions Urban mobility and its related environmental burden are not only related to technological choices but are also related to spatial characteristics and territorial context. The combination of urban and spatial tools and data, such as LUTI model, with the LCA methodology improves the local representativeness of environmental assessment of mobility and enlarges the ranges of analysis and perspective. Nonetheless, improvements remain to be made in relation to ongoing developments on spatialized and territorial LCA.

Analyzing Temporal Variability in Inventory Data for Life Cycle Assessment: Implications in the Context of Circular Economy

Life cycle assessment (LCA) is used frequently as a decision support tool for evaluating different design choices for products based on their environmental impacts. A life cycle usually comprises several phases of varying timespans. The amount of emissions generated from different life cycle phases of a product could be significantly different from one another. In conventional LCA, the emissions generated from the life cycle phases of a product are aggregated at the inventory analysis stage, which is then used as an input for life cycle impact assessment. However, when the emissions are aggregated, the temporal variability of inventory data is ignored, which may result in inaccurate environmental impact assessment. Besides, the conventional LCA does not consider the environmental impact of circular products with multiple use cycles. It poses difficulties in identifying the hotspots of emission-intensive activities with the potential to mislead conclusions and implications for both practice and policy. To address this issue and to analyze the embedded temporal variations in inventory data in a CE context, the paper proposes calculating the emission intensity for each life cycle phase. It is argued that calculating and comparing emission intensity, based on the timespan and amount of emissions for individual life cycle phases, at the inventory analysis stage of LCA offers a complementary approach to the traditional aggregate emission-based LCA approach. In a circular scenario, it helps to identify significant issues during different life cycle phases and the relevant environmental performance improvement opportunities through product, business model, and supply chain design.

Investigation of Implementation Stages and Boundaries of Life Cycle Assessment Method

With the massive growth in the population of the world, the rapid consumption of natural resources and unorganized urbanization causes an impact of air pollution, water pollution, environmental destruction, and global warming to increase. With these factors threatening human health, the term sustainability gained popularity for restoring the deteriorating ecological balance. This awareness is called green buildings in the construction sector. The purpose of sustainable green buildings is the restoration of corrupted order and utilization of energy effectively. The Life Cycle Assessment method is one of the assessment systems developed for reducing the environmental impacts of products/services in evolving green buildings. Life Cycle Assessment determines the environmental impacts of the process that studies the extraction, use and disposal of the material by taking the life long evaluation of any product. As a result of this study and the in depth review of the literature portrayed the pros and cons, and the applications of the terms sustainability, green buildings and life cycle. The application stages of Life Cycle Assessment are defining the purpose and concept, stock analysis, analysis of effectiveness, evaluation of subfields with a determination of the boundaries as initial, intermediate and final. With the final analysis, the aim is to produce environmentally friendly products/services. Keywords: Sustainability, Green Building, Life Cycle Assessment, LCA Application Steps, Construction Materials DOI: 10.7176/JSTR/6-13-01

Biodiversity Assessment of Value Chains: State of the Art and Emerging Challenges.

The consumption of materials and products is one of the drivers of biodiversity loss, which in turn affects ecosystem functioning and has socio-economic consequences worldwide. Life cycle assessment (LCA) is a reference methodology for appraising the environmental impacts of products along their value chains. Currently, a generally accepted life cycle impact assessment (LCIA) framework for assessing biodiversity impacts is lacking. The existing LCIA models present weaknesses in terms of the impact drivers considered, geographical coverage, as well as the indicators and metrics adopted. Sound ecological indicators and metrics need to be integrated in order to better assess the impacts of value chains on biodiversity on a global, regional, and local scale. This review analyses studies which, using a life cycle perspective, assess the impacts of products' and services' value chains on biodiversity. We identify and discuss promising synergies between the studies which look beyond the life cycle context, and apply other biodiversity metrics. Our results highlight that the existing metrics of biodiversity impact assessment in LCA are poor at capturing the complexities of biodiversity. There are operational models at the midpoint level that expand on the assessed dimensions of biodiversity (e.g., ecosystem structure), and the drivers of biodiversity loss (e.g., assessment of species exploitation), but efforts are required to fully include these models in the LCA framework. In the business domain, many initiatives are developing frameworks to assess impacts on biodiversity. Many approaches make use of LCIA methods and input-output databases. However, these are generally coupled with other biodiversity metrics. This shows that the current LCA framework is not yet sufficient to support decision-making based on different sets of biodiversity indicators. Ecosystem accounting may provide important ecological information for both the inventory and the impact assessment stages of LCA, helping to disentangle the relationship between biodiversity and ecosystem services. Looking beyond the LCA domain can lead us to new ways of advancing the coverage of biodiversity impacts, in a way that increases the relevance of LCA across a wider range of areas. Future work should assess the indicators provided in various policy contexts.

Environmental Pollution Impact Analysis on Faecal Sludge Process Using Life Cycle Assessment and Analytic Hierarchy Process

The processing of fecal sludge in the IPLT is an advanced processing activity because the sludge in the septic tank has not been properly disposed of into the environment. After all, it still contains high organic loads. IPLT Kota Batu is the object of research. It aims to determine the environmental impact caused by the treatment of sludge in the IPLT Kota Batu with the Life Cycle Assessment Method then provide an alternative in reducing the impact with the Analytic Hierarchy Process Method. Life Cycle Assessment is a method for analyzing the environmental impact of a product throughout the life cycle. Stages of life cycle assessment (LCA) are goals and scope, life cycle inventory, life cycle impact assessment, and interpretation data. An alternative selection is then made to reduce the environmental impact using the Analytic Hierarchy Process (AHP) Method. AHP is describing a complex problem into a result that is represented in a multi-level structure. AHP stages are input goals, criteria, alternatives, weighting, and priority scale, producing the recommended answer or decision. From the LCA method, it was found that the emission load released into the environment in the treatment of sludge was in the form of CO2 emissions, energy emissions, and potentially disappearing species fractions of 3.948,935 kg CO2/year, 1.100.334,84 MJ, and 3.624,647 PDF.m2.y. The use of this method can find out that the treatment of sludge in the IPLT Kota Batu has an environmental burden and impacts the phenomenon of global warming, non-renewable energy, and aquatic eutrophication. The best alternative to reduce emissions in the treatment process of sludge in the IPLT Kota Batu is to perform maintenance treatment on a scheduled basis.

Life cycle assessment analysis of kenaf cultivation in bonorowo land, laren, lamongan

The largest kenaf culture in Indonesia is in Laren, Lamongan. Kenaf plants are suitable to be planted in the Bonorowo field. The less potential land conditions make the cultivation of kenaf plants must use chemicals. The use of chemicals has the potential to harm the environment. The approach to identifying and analyzing environmental impacts is the Life Cycle Assessment (LCA). LCA is one method to find out the life cycle of agriculture. LCA stages are Goal and Scope Definition, Life Cycle Inventory, Life Cycle Impact Assessment, and Interpretation. Environmental impact measurement is based on fifteen categories grouped into four categories. LCA processing results show the use of urea fertilizer has the most significant negative impact on the environment. The biggest impact category due to the use of urea fertilizer is aquatic ecotoxicity. The use of urea fertilizer affects the types of resources, climate change, ecosystem quality, and human health. Of the four groups, which have the highest value, are the resource group. The use of urea fertilizer has the most significant role in the success of kenaf cultivation because kenaf cultivation requires more N elements to improve the quality of kenaf stems. The use of organic fertilizer can be an option to reduce the use of urea fertilizer.

Life Cycle Assessment of Low-Rank Coal Utilization for Power Generation and Energy Transportation

In China, the electricity load is concentrated in the east, but low-rank coal resources are concentrated in the west. To solve this contradiction, in this study, three cases for energy transmission about power system with and without solar energy were studied by life cycle assessment (LCA). Case 1 directly combusts low-rank coal to generate electricity in western China and transmits it to eastern China by grid. Cases 2 and 3 upgrade low-rank coal and transport it to eastern China for power generation. With the evaluating indicators and various stages of LCA, the impact of each case on the environment was compared clearly. The results show that over 90% of the pollutant emission comes from coal combustion throughout the life cycle. The pollutant emission of upgraded coal transportation is less than 5%. With low-rank coal upgrading then combusting, the total emission is less than that of direct combustion. In particular, with solar energy added, the emission of combustion can be further reduced. On the bases of LCA, analytic hierarchy process (AHP) was used to establish the connection of these four evaluation indicators to comprehensively evaluate the performance of the three cases through the objective function of AHP, which provided guidance for the energy transmission and utilization in the eastern and western China. Finally, sensitive analysis shows the main major factors affecting system performance on the system. The results show that the Case 3, which integrates with solar energy, performs best in the whole life scale.

REBUILD: Regenerative Buildings and Construction systems for a Circular Economy

Buildings and construction have been identified as having one of the greatest potential for value creation and capture from the application of circular economy principles. To achieve this requires a fundamental transformation in the recovery, remanufacture and re-use of end of service life structural products such as steel, bricks, concrete which make up the largest proportion of materials. At the same time these products must be re-used in new buildings and infrastructure designed for subsequent deconstruction and disassembly. REBUILD is a 3 year way UK research project to address this challenge. Initial findings on quantifying the material intensity of buildings (stock and flow assessment) are presented based on one of our case study cities. Results from new techniques to separate and reclaim bricks from cement mortar shows technical feasibility and ability to retain structural performance. Details on the next stage of scaling this work and techniques for separating and reclaiming steel and concrete are briefly described. Subsequent stage of life cycle assessment, value stream mapping and creating products for new forms of circular building and construction systems are also described. The paper concludes that whilst there are considerable challenges in reclaiming structural products that re-designed circular building and construction system could transform the value of end of service life buildings and the offers new opportunities for circular innovation and the circulation of materials and products at their highest value for the longest period.

Freshwater ecotoxicity assessment of pesticide use in crop production: Testing the influence of modeling choices

Pesticides help to control weeds, pests, and diseases contributing, therefore, to food availability. However, pesticide fractions not reaching the intended target may have adverse effects on the environment and the field ecosystems. Modeling pesticide emissions and the link with characterizing associated impacts is currently one of the main challenges in Life Cycle Assessment (LCA) of agricultural systems. To address this challenge, this study takes advantage of the latest recommendations for pesticide emission inventory and impact assessment and frames a suitable interface for those LCA stages and the related mass distribution of pesticide avoiding a temporal overlapping. Here, freshwater ecotoxicity impacts of the production of feed crops (maize, grass, winter wheat, spring barley, rapeseed, and peas) in Denmark were evaluated during a 3-year period, testing the effects of inventory modeling and the recent updates of the characterization method (USEtox). Potential freshwater ecotoxicity impacts were calculated in two functional units reflecting crop impact profiles per ha and extent of cultivation, respectively. Ecotoxicity impacts decreased over the period, mainly because of the reduction of insecticides use (e.g., cypermethrin). Three different emission modeling scenarios were tested; they differ on the underlining assumptions and data requirements. The main aspects influencing impact results are the interface between inventory estimates and impact assessment, and the consideration of intermedia processes, such as crop growth development and pesticide application method. Impact scores for AS2 were higher than RS and AS1, but the differences in the crops ranking was less apparent. On the other hand, the influence on the estimation of impacts for individual AIs was considerable and statistical differences were found in the impact results modeled in scenarios RS and AS2. Thereby indicating the effect of inventory models on ecotoxicity impact assessment.

Life cycle assessment of geopolymer concrete: A Malaysian context

The production of Portland cement is well acknowledged as having as significant impact on the environment, accounting for 8% of global CO2 emissions (4bn tonnes per annum). Concrete is the most widely used material in the world and therefore has vast potential to absorb high volumes of waste and by-product materials. These materials can act as partial replacements as supplementary cementitious materials or total replacements and perform as binders in geopolymer concretes. The use of Pulverised Fuel Ash (PFA) from coal-fired electricity generating stations to substitute Ordinary Portland Cement (OPC) is well established. Quantifying the potential environmental benefit of using such materials can be difficult. The life cycle assessment (LCA) methodology, internationally standardised through ISO14040 series, may be used to quantify the environmental impact of products and processes. This paper outlines the use of the LCA methodology to compare the environmental impact of OPC precast concrete products to PFA precast concrete products in a Malaysian context. The four stages of LCA are detailed and consequences of designating materials as a by-product or waste are discussed. A review of other LCA studies completed in Malaysia for the built environment are also presented so as to identify which impact assessment methods are most frequently used.

Model uncertainty analysis using data analytics for life-cycle assessment (LCA) applications

Objective uncertainty quantification (UQ) of a product life-cycle assessment (LCA) is a critical step for decision-making. Environmental impacts can be measured directly or by using models. Underlying mathematical functions describe a model that approximate the environmental impacts during various LCA stages. In this study, three possible uncertainty sources of a mathematical model, i.e., input variability, model parameter (differentiate from input in this study), and model-form uncertainties, were investigated. A simple and easy to implement method is proposed to quantify each source. Various data analytics methods were used to conduct a thorough model uncertainty analysis; (1) Interval analysis was used for input uncertainty quantification. A direct sampling using Monte Carlo (MC) simulation was used for interval analysis, and results were compared to that of indirect nonlinear optimization as an alternative approach. A machine learning surrogate model was developed to perform direct MC sampling as well as indirect nonlinear optimization. (2) A Bayesian inference was adopted to quantify parameter uncertainty. (3) A recently introduced model correction method based on orthogonal polynomial basis functions was used to evaluate the model-form uncertainty. The methods are applied to a pavement LCA to propagate uncertainties throughout an energy and global warming potential (GWP) estimation model; a case of a pavement section in Chicago metropolitan area was used. Results indicate that each uncertainty source contributes to the overall energy and GWP output of the LCA. Input uncertainty was shown to have significant impact on overall GWP output; for the example case study, GWP interval was around 50%. Parameter uncertainty results showed that an assumption of ± 10% uniform variation in the model parameter priors resulted in 28% variation in the GWP output. Model-form uncertainty had the lowest impact (less than 10% variation in the GWP). This is because the original energy model is relatively accurate in estimating the energy. However, sensitivity of the model-form uncertainty showed that even up to 180% variation in the results can be achieved due to lower original model accuracies. Investigating each uncertainty source of the model indicated the importance of the accurate characterization, propagation, and quantification of uncertainty. The outcome of this study proposed independent and relatively easy to implement methods that provide robust grounds for objective model uncertainty analysis for LCA applications. Assumptions on inputs, parameter distributions, and model form need to be justified. Input uncertainty plays a key role in overall pavement LCA output. The proposed model correction method as well as interval analysis were relatively easy to implement. Research is still needed to develop a more generic and simplified MCMC simulation procedure that is fast to implement.