Estimating Life Cycle Research Articles

Urban Site Development as Temporal Carbon Storage—A Case Study in Germany

Increasing the use of sustainably sourced wood in construction for temporal carbon storage could be one vital part in the transition towards reaching the sustainable development goals for climate action and sustainable cities and communities. This paper explains the detailed steps from the planning to the realization process and shows how building with wood could be linked to the entire process from the sales of building plots to the realization of projects. Additionally, based on EN 15978, life cycle assessment (LCA) results of the constructed buildings were conducted to calculate the realistic carbon storage and the global warming potential for all new erected buildings on the site. The case study area and living lab is a building site in Munich with 566 flats, which will be finished in 2020 and will be the largest urban timber neighborhood in Germany by then. All development activities are summarized under the concept of building an eco-city with low carbon emissions and a high standard for living for all groups of inhabitants. Eight buildings with different material selections ranging from wood-constructions to wood-concrete hybrid constructions and concrete constructions with different energy standards are environmentally assessed. Results show that about 12.5 million kg of CO2 are stored in the wooden structures over the estimated life cycle of 50 years within this neighborhood. This clearly demonstrates the potential that building with wood has for achieving climate targets. Further results show that heating energy demand and material choices have a significant influence on LCA results.

Design of Eco-Efficient Body Parts for Electric Vehicles Considering Life Cycle Environmental Information

The reduction of greenhouse gas (GHG) emissions over the entire life cycle of vehicles has become part of the strategic objectives in automotive industry. In this regard, the design of future body parts should be carried out based on information of life cycle GHG emissions. The substitution of steel towards lightweight materials is a major trend, with the industry undergoing a fundamental shift towards the introduction of electric vehicles (EV). The present research aims to support the conceptual design of body parts with a combined perspective on mechanical performance and life cycle GHG emissions. Particular attention is paid to the fact that the GHG impact of EV in the use phase depends on vehicle-specific factors that may not be specified at the conceptual design stage of components, such as the market-specific electricity mix used for vehicle charging. A methodology is proposed that combines a simplified numerical design of concept alternatives and an analytic approach estimating life cycle GHG emissions. It is applied to a case study in body part design based on a set of principal geometries and load cases, a range of materials (aluminum, glass and carbon fiber reinforced plastics (GFRP, CFRP) as substitution to a steel reference) and different use stage scenarios of EV. A new engineering chart was developed, which helps design engineers to compare life cycle GHG emissions of lightweight material concepts to the reference. For body shells, the replacement of the steel reference with aluminum or GFRP shows reduced lifecycle GHG emissions for most use phase scenarios. This holds as well for structural parts being designed on torsional stiffness. For structural parts designed on tension/compression or bending stiffness CFRP designs show lowest lifecycle GHG emissions. In all cases, a high share of renewable electricity mix and a short lifetime pose the steel reference in favor. It is argued that a further elaboration of the approach could substantially increase transparency between design choices and life cycle GHG emissions.

Life cycle environmental and cost evaluation of renewable diesel production

Computer simulations are used to study the production of renewable diesel through the biochemical transformation of biomass sorghum [Sorghum bicolor (L.) Moench] to free fatty acids using a genetically modified strain of Escherichia Coli. We evaluate select environmental and economic metrics using life cycle assessment (LCA) and techno-economic analysis (TEA). The biofuel supply chain includes feedstock production, handling, pretreatment and hydrolysis, fermentation to free fatty acids, saponification of the free fatty acids, wax production on an electrochemical synthesis reactor, and hydrocracking to convert the wax to renewable diesel. The TEA model developed uses experimental data from pretreatment to wax synthesis steps and literature for the conversion of wax to diesel. The TEA model is integrated into a life cycle inventory model to estimate life cycle greenhouse gas and non-renewable energy consumption. Considering both environmental and economic factors we find that the performance of this pathway to produce renewable diesel returns lower product yield, higher cost, and higher GHG and energy impacts compared to biomass-to-ethanol pathways, primarily due to poor process yields (mainly fermentation). This limitation in the metabolic pathway constrains the maximum yield potential of FFA and therefore renewable diesel and other potential co-products from biomass derived sugars.

Estimation of Life Cycle CO2 emissions using oyster shells and bottom ash as materials for soil-mixing and a drainage layer

In South Korea, oyster shells and bottom ash are generated at around 0.2 million tons and 1.1–1.8 million tons per year, respectively. Interest in recycling oyster shells/bottom ash is increasing because most of them are piled up or landfilled illegally, causing various environmental problems. On the other hand, ground composed of fine-grained soil has poor drainage and is not suitable for cultivation or construction. The possibility of using oyster shells/bottom ash as drainage materials has been continually suggested, and it is expected to have various effects such as waste treatment, naturalaggregates preservation, and multifaceted uses in poorly-drained ground. However, environmental stability has not been properly verified such as pollution by materials themselves, or pollutant discharge by processing, transportation, and construction. Therefore, prior to recycling oyster shells/bottom ash, it is important to assess whether these materials are suitable and environmentally stable for recycling. In this study, the recycling suitability and environmental stability of oyster shells/bottom ash were assessed, as drainage materials for improving poor drainage. The use of these materials was considered in two ways: materials for soil-mixing (case 1) and horizontal drainage layers (case 2). For the suitability evaluation of oyster shells/bottom ash, their physical and chemical properties were analyzed. The results showed that oyster shells/bottom ash can be used as materials for soil-mixing or a horizontal drainage layer in place of natural sand. However, the high Cu content of oyster shells and low CEC of bottom ash should be considered. The environmental assessment was performed by examining the recyclability of oyster shells/bottom ash through quantitatively estimated Life Cycle CO2 emissions. As a result, Life Cycle CO2 emissions were in the order of ‘sand > oyster shells > bottom ash’ in both cases. Compared to natural sand, Life Cycle CO2 emissions of oyster shells and bottom ash were as low as 19–47% and 17–34% in Case 1, and 34–47% and 24–34% in Case 2, respectively. In conclusion, oyster shells and bottom ash can be used as drainage materials with engineering performance. In 6–31% of South Korea in particular, they can be substituted environmentally for natural sand, showing a CO2 emissions reduction effect.

Prognozowanie niezawodności elementów sieci wodociągowej na podstawie rzadkich danych terenowych i modeli przestrzeni stanów

The elements of critical infrastructure have to meet demanding dependability, safety and security requirements. The article deals with the prognosis of water mains reliability while using sparse irregular filed data. The data are sparse because the only thing we know is the number of mains failures during a given month. Since it is possible to transform the data into a typical reliability measure (rate of failure occurrence – ROCOF), we can examine the course of this measure development in time. In order to model and predict the ROCOF development, we suggest novel single and multiple error state space models. The results can be used for i) optimizing mains operation and maintenance, ii) estimating life cycle cost, and iii) planning crisis management.

Probabilistic and Fuzzy Approaches for Estimating the Life Cycle Costs of Buildings under Conditions of Exposure to Risk

The paper discusses issues related to life cycle costs in construction. Life cycle cost is a key element in the assessment of environmental sustainability in construction and it provides a tool for the economic evaluation of alternative sustainability options exhibiting different capital, operating costs or resource usage. The authors reviewed selected models of estimating life cycle costs in construction, drew attention to the complex mathematical models developed so far, namely those which take into account only financial risks and those which involve the possibility of the influence of other risk factors and described the main assumptions accompanying the original model for estimating the whole life costs of buildings, including: reasons for choosing theory of possibility, division and parametrization of input data. The aim of this paper is to confirm the validity of the model structure assumptions adopted by the authors by comparing the originally selected fuzzy approach to calculating life cycle costs taking into account the risk with the probabilistic approach, as well as indicating the domain in which the probabilistic approach will complement the fuzzy approach chosen by the authors. The paper presents a comparison analysis of two approaches used in the authors’ model, a fuzzy and a probabilistic approach, recommended by the ISO standard 15686-5:2008. The authors used the Oracle Crystall Ball software in their simulations.

Adopsi Life Cycle Costing Untuk Bangunan Gedung Diklat Muara Enim

Both initial cost for construction and future costs for operation and maintenance of buildings are very important that must be considered by the building owner. Therefore, estimating Life Cycle Cost (LCC) in long term is a must in determining the amount of money spent for the building projects. The objective of this study is to apply a method for LCC to estimate overall costs starting from initial, maintenance, and operational costs. In this study, the LCC also incorporated inflation and bank interest rates in long-term perspective. In this study, LCC was implemented in a building that functioned as a training facility in a building complex in the Muara Enim District. Southern Sumatera. By using the LCC method for estimating cost for a period of 25 years, result shows that the proportion initial cost of construction is 39.12%, maintenance and replacement cost is 16.28%; and operational cost is 44.61%.

A methodology for integrating the biomass balance approach into life cycle assessment with an application in the chemicals sector

Driven by the need to reduce greenhouse gas emissions and dependence on fossil resources, the chemical and other industries are gradually starting to develop bio-based products. For the introduction of bio-feedstocks in existing production pathways in a cost-effective way, a simplified approach based on mass balance has been proposed. This concept is known as the biomass balance (BMB) approach and the resulting products are called BMB products. They do not necessarily contain biomass material but can contribute to sustainable sourcing and production of bio-based products in the supply chain without any performance loss in comparison to the same products derived from fossil resources. The aim of the study is to show how the BMB approach can be used in life cycle assessment (LCA) while following the requirements set out in the ISO 14040 and 14044 standards. To demonstrate that, the proposed BMB approach has been used to estimate life cycle environmental impacts of a polymer product, which can be produced using fossil or bio-feedstocks. For the polymer derived from bio-feedstocks, bio-naphtha and biogas are considered as replacement to naphtha and its impacts are compared with the fossil-based alternative. The paper demonstrates that the BMB approach provides a quick and pragmatic method for establishing the biomass content in chemical and related products while incentivising the industry to continue increasing the proportion of bio-based products in their product portfolio. It also shows that the environmental performance of BMB products is highly dependent on the particular bio-feedstock used, the way it is sourced and on key modelling assumptions, including the assumptions on biogenic carbon uptake in the bio-feedstocks.

Life Cycle Greenhouse Gas Impacts of Coal and Imported Gas-Based Power Generation in the Indian Context.

Few studies have evaluated the life cycle greenhouse gas (GHG) impacts associated with India's power sector, despite the expectation that it will dominate new thermal generation capacity additions over the coming decades. Here, we utilize India-specific supply chain data to estimate life cycle GHG emissions associated with power generated by combustion of Indian coal and liquefied natural gas (LNG) imported from the United States. Life cycle impacts of domestic coal power vary widely (80% confidence interval (CI): 951-1231 kg CO2eq/MWh) because of heterogeneity in existing power plant characteristics such as efficiency, age, and capacity. Less variability is observed for LNG sourced from northeast United States and used in the existing Indian combined cycle gas turbine (CCGT) fleet (80% CI: 523-648 kg CO2eq/MWh). On average, life cycle GHG emissions from LNG imported into India are ∼54% lower than those associated with Indian coal. However, the GHG intensity of the Indian coal-power sector may be reduced by 13% by retiring plants with the lowest efficiencies and replacing them with higher-efficiency supercritical plants. Improvement of the CCGT fleet efficiency from its current level (41%) to that of a new plant with an F-class turbine (50%) could reduce life cycle GHG emissions for LNG-sourced power by 19%.

Decentralized water reuse planning: Evaluation of life cycle costs and benefits

The objective of this paper is to comparatively evaluate the life cycle costs and expected monetary benefits of decentralized greywater reuse systems. Specifically, added life cycle costs and estimated life cycle monetary benefits of satellite and onsite greywater reuse systems are evaluated in comparison with the prevailing centralized systems. Centralized systems refer to the traditional form of water delivery where one centralized treatment plant treats and distributes potable water to a large service area through a water distribution network while a sewer network collects used water for treatment at a centralized wastewater treatment plant before the wastewater effluent is disposed into the environment. Satellite greywater reuse systems collect raw greywater at neighborhood or district level for treatment and re-distribution for non-potable uses within the same neighborhood or district. Onsite greywater reuse systems collect raw greywater for treatment on the premises of where it is produced after which it is re-distributed for permitted non-potable use on the same premises. Infrastructure needs and associated life cycle cost information for both types of greywater reuse systems are appropriately modeled or synthesized from literature. The skeletal layout of a real-world water distribution network is adapted for performing the cost-benefit analysis in this study. Finally, sensitivity of the cost-benefit tradeoff associated with satellite and onsite greywater reuse adoption scenarios is evaluated for various uncertainties associated with technological evolution, policy incentives, and planning schemes. Given that several states in the U.S. are expected to face water shortages in the near future, this paper will provide guidance to water utilities and policy makers in planning of future water supply alternatives.

Estimating life cycle emissions in managing practical sewer pipeline projects

The objectives of this paper are 1) to estimate emissions in managing a sewer pipeline project from a life cycle perspective; and 2) to develop methods that can be used to assist engineers and stakeholders in the estimation especially when data are limited. The motivation is to provide an approach that can be used readily in practice to evaluate emissions in managing a sewer pipeline or a general infrastructure system by using available data. The life cycle assessment tool is applied over the pipe material manufacturing, installation, and maintenance phases. In the material manufacturing and installation phase, this research routinely tends to collect and evaluate detailed inventories data. The results show that the manufacturing phase contributes the most emissions. Material transportation in the installation also generates great amounts which are highly impacted by the transportation distance of vehicles. Emissions from activities such as equipment use and architecture and engineering services are not negligible which need to be considered in practice. In the maintenance phase, the study develops methods to estimate emissions based on the Markov chains model. The developed methods make it possible to estimate emissions within a given duration conventionally and at a ‘steady state’ phase once a strategy is applied. The study also presents a method to conduct the model sensitivity analysis using simulating results from Matlab tools. The analysis shows that the model has decent robustness. In addition, the methodology proposed may be applied to estimate emissions in other infrastructure management as well.

Economic viability of UK shale gas and potential impacts on the energy market up to 2030

The UK is in the early stages of developing a shale gas industry and to date six test wells have been drilled but none yet exploited commercially. Some argue that shale gas could reduce energy prices and improve national energy security. However, the costs of bringing commercial-size wells into operation are uncertain and the impact shale gas could have on the UK energy market is currently unknown. Therefore, this paper evaluates the economic viability of developing a UK shale gas industry and the impacts it could have on the UK gas and electricity markets and consumer energy bills up to 2030. The estimated life cycle (levelised) costs of shale gas production range from 0.47 to 56.74 pence/MJ (0.61–73 US$ cents/MJ), with an average value of 4.64 pence/MJ. The break-even price at which shale gas can be sold varies between 0.95 and 114.44 pence/MJ, averaging at 9.47 pence/MJ, depending on the volume of gas produced by a shale gas well. The latter is two times higher than imported liquefied natural gas, around 30% more expensive than UK natural gas and three times greater than the price of US shale gas. Electricity from shale gas is on average 17% more expensive than from domestic conventional gas but still more competitive than most other electricity options, including coal and renewables. However, the impact of shale gas on the energy market would be limited across the expected range of shale gas penetration into the gas and electricity mixes, suggesting that it would have little effect on energy prices. This is reflected in an almost negligible impact on consumer energy bills. The potential of shale gas to boost the UK economy is also limited, contributing 0.017–0.033% to the GDP. This is an order of magnitude lower than the contribution of US shale gas to its GDP (0.2%), indicating that the economic success of shale gas in the US may not be replicated in the UK. These findings will be of interest to shale gas developers and policy makers not only in the UK but in other countries considering exploitation of shale gas resources.

Life cycle energy use and CO2 emissions of small-scale gold mining and refining processes in the Philippines

Gold is one of the most significant metals in the world, with use in various sectors including the electronic, health, and fashion industries. The Philippines has the world’s third largest known Au deposits and is ranked 20th in global gold production. Of the country’s annual production, about 80% is from the small-scale gold mining (SSGM) sector. This work estimates the first location-specific life cycle energy use and CO2 emissions of SSGM establishments in the Philippines. Process-based LCA was used with functional unit of 100 g Au and observed data from 2010 to 2011 for mining, comminution, recovery, and refining. Four gold production paths were observed in the provinces of Benguet and Camarines Norte, namely, amalgamation, cyanidation with carbon-in-leach (CIL), cyanidation with leaching with zinc, and combination of amalgamation and cyanidation with CIL. It was estimated that 3–18 g of Au was extracted for every ton of ore within 57–159 man-hours from mining to refining. Energy use estimates ranged from 3501 to 67,325 MJ/100 g Au, while CO2 emission estimates ranged from 398 to 5340 kg CO2/100 g Au. The combination of amalgamation and cyanidation with CIL processes was the least energy and carbon intensive, while cyanidation with CIL process was the most intensive. Electricity use accounted for 95–100% of total emissions, except in cyanidation with CIL where kerosene accounts for 77% of the total. Since SSGMs contributed 80% of the 40 tons of Au produced in the Philippines in 2014, the SSGM energy use was estimated to be between 1120 and 21,544 TJ and the CO2 emissions to be between 129 and 1726 ktons CO2. Energy estimates are most sensitive to refining process yield and electrical equipment efficiency. The estimated life cycle emissions rate for SSGM in the Philippines is lower than available estimates of large-scale mining. Notwithstanding, given the sector’s reliance on fossil fuels for its energy needs and the Philippines’ pledge to reduce its CO2 footprint by 70% in 2030, every effort to mitigate energy use and CO2 emission counts. Three main recommendations toward energy consumption and CO2 emissions reduction in SSGMs are proposed: (1) policy to promote technologies that are energy-efficient and processes that maximize gold process yield, (2) effective Minahang Bayan (SSGM mining zone mandated by law) implementation to ensure use of higher-grade ores, and (3) adoption of renewable energy in Minahang Bayans to promote energy independence and mitigate CO2 emissions.

Estimating life cycle cost for a product family design: The challenges

A cost estimation system is required to assist in designing a product family. The aim of this paper is to identify the requirements and the problems in estimating the life cycle cost of a product family. Then, this paper also presents the state-of-the-art and the research challenges in developing a life cycle cost estimation system for a product family design. As the conclusion, the life cycle cost estimation process for a product family still needs to face the challenges to determine the end of life strategy of each sub module of a product family, to integrate the end of life strategy to estimate the life cycle cost of a product family, to estimate the life cycle cost of each component level of a product family for design purposes and for different technologies and approaches, to reduce the required time and effort for updating process in estimating the life cycle cost for different structures of different product families, and to transform the available information into the required information in order to estimate the life cycle cost of a product family at the early stage of product development.

Estimating life cycle cost for a product family design: The challenges

A cost estimation system is required to assist in designing a product family. The aim of this paper is to identify the requirements and the problems in estimating the life cycle cost of a product family. Then, this paper also presents the state-of-the-art and the research challenges in developing a life cycle cost estimation system for a product family design. As the conclusion, the life cycle cost estimation process for a product family still needs to face the challenges to determine the end of life strategy of each sub module of a product family, to integrate the end of life strategy to estimate the life cycle cost of a product family, to estimate the life cycle cost of each component level of a product family for design purposes and for different technologies and approaches, to reduce the required time and effort for updating process in estimating the life cycle cost for different structures of different product families, and to transform the available information into the required information in order to estimate the life cycle cost of a product family at the early stage of product development.

Life cycle ownership cost and environmental externality of alternative fuel options for transit buses

This paper assesses alternative fuel options for transit buses. We consider the following options for a 40-foot and a 60-foot transit bus: a conventional bus powered by either diesel or a biodiesel blend (B20 or B100), a diesel hybrid-electric bus, a sparking-ignition bus powered by Compressed Natural Gas (CNG) or Liquefied Natural Gas (LNG), and a battery electric bus (BEB) (rapid or slow charging). We estimate life cycle ownership costs (for buses and infrastructure) and environmental externalities caused by greenhouse gases (GHGs) and criteria air pollutants (CAPs) emitted from the life cycle of bus operations. We find that all alternative fuel options lead to higher life cycle ownership and external costs than conventional diesel. When external funding is available to pay for 80% of vehicle purchase expenditures (which is usually the case for U.S. transit agencies), BEBs yield large reductions (17–23%) in terms of ownership and external costs compared to diesel. Furthermore, BEBs’ advantages are robust to changes in operation and economic assumptions when external funding is available. BEBs are able to reduce CAP emissions significantly in Pittsburgh’s hotspot areas, where existing bus fleets contribute to 1% of particulate matter emissions from mobile sources. We recognize that there are still practical barriers for BEBs, e.g. range limits, land to build the charging infrastructure, and coordination with utilities. However, favorable trends such as better battery performance and economics, cleaner electricity grid, improved technology maturity, and accumulated operation experience may favor use of BEBs where feasible.

Fit-for-purpose wastewater treatment: Testing to implementation of decision support tool (II)

This paper is the second in a series of two papers. In Paper I, a decision support tool (DST), FitWater, was developed for evaluating the potential of wastewater treatment (WWT) trains for various water reuse applications. In the present paper, the proposed DST has been tested and implemented. FitWater has been tested with several existing WWT plants in Canada and the USA, demonstrating FitWater's effectiveness in estimating life cycle cost (LCC), health risk, and energy use. FitWater has also been implemented in a newly planned neighbourhood in the Okanagan Valley (BC, Canada) by developing 12 alternative WWT trains for water reuse in lawn and public parks irrigation. The results show that FitWater can effectively rank WWT train alternatives based on LCC, health risk, amount of reclaimed water, energy use, and carbon emissions. Moreover, functions have been developed for the variation of unit annualized LCC and energy intensity per unit log removal of microorganisms in different treatment technologies with varying plant capacities. The functions have power relations, showing the economies of scale. FitWater can be applied to identify a cost-effective, risk-acceptable, and energy efficient wastewater treatment train with a plant capacity of 500m3/day or more. Furthermore, FitWater can be used to assess potential economic impacts of developing microbiologically stringent effluent standards. The capability of FitWater can be enhanced by including physio-chemical quality of wastewater, additional treatment technologies, and carbon emissions from wastewater decomposition processes.

Application of life cycle assessment approach to deliver low carbon houses at regional level in Western Australia

Australian building sector contributes 23% of the total greenhouse gas (GHG) emissions. This is particularly important for Western Australia (WA) as the houses here are made of energy- and carbon-intensive clay bricks. This research has utilized life cycle assessment (LCA) approach and cleaner production strategies (CPS) to design low-carbon houses in 18 locations in regional WA. An integrative LCA analysis of clay brick house has been conducted by incorporating energy efficiency rating tool (i.e., AccuRate) to capture the regional variation in thermal performance of houses in 18 locations in WA under five climatic zones. The data bank provided information on energy and materials for mining to material production, transportation of construction materials to the site of construction, and construction stages, while an energy rating tool has been utilized to generate location-specific information on energy consumption during use stage for developing a life cycle inventory for estimating life cycle GHG emissions and embodied energy consumption of a typical 4 × 2 × 2 detached house (i.e., 4 bed rooms, 2 bathrooms, and 2 cars/double garage). This approach has enabled us to determine the location-specific hotspot of a house in order to select suitable CPS for achieving reduced level of GHG emissions and embodied energy consumption. Except for two hottest locations, the average life cycle GHG emissions and embodied energy consumption of houses at 16 locations in regional WA have been estimated to be 469 t of CO2 equivalent (or CO2 e-) and 6.9 TJ, respectively. Home appliances and water heating have been found to be the top two hotspots. The CPS options, including rooftop solar photovoltaic panels (PV), solar water heaters (SWH) integrated with gas based water heaters, cast in situ concrete sandwich wall, fly ash as a partial replacement of cement in concrete, and polyethylene terephthalate (PET) foam made of post-consumed polyethylene terephthalate bottles, have been considered to reduce GHG emissions and embodied energy consumption of a typical house in18 locations in regional WA. Excluding above two hottest locations, these CPS provide an opportunity to reduce GHG emissions and embodied energy consumption per house by an average value of 320 t CO2 e- and 3.7 TJ, respectively. Considering the alarming growth rate of the housing industry in WA, the incorporation of optimum house orientation, rooftop solar PV, roof top SWH, cast in situ sandwich wall, partial replacement of cement in concrete with fly ash, and PET foam insulation core could reduce the overall GHG emissions and embodied energy consumption associated with the construction and use of clay brick wall house which in turn will assist in achieving Australia’s GHG emission reduction target by 2050. The findings provide useful data for architects, designers, developers, and policy makers to choose from these CPS options based on existing resource availability and cost constraints.

Assessing Urban Wastewater System Upgrades Using Integrated Modeling, Life Cycle Analysis, and Shadow Pricing.

This study assesses the environmental impacts of four measures proposed for upgrading of the urban wastewater system of Eindhoven and the Dommel River in The Netherlands, against the base case, "do-nothing" option. The measures aim to reduce the overall environmental impact of the Eindhoven urban wastewater system (UWS) by targeting river dissolved oxygen depletion and ammonia peaks, reducing combined sewer overflows, and enhancing nutrient removal. The measures are evaluated using a life cycle analysis with the boundaries including the receiving river section by means of an integrated model of the UWS. An uncertainty analysis of the estimated impacts has been performed to support the outcomes. The study also uses the economic concept of shadow prices to assign relative weights of socio-economic importance to the estimated life cycle impacts. This novel integration of tools complements the assessments of this UWS with the inclusion of long-term global environmental impacts and the investigation of trade-offs between different environmental impacts through a single monetary unit. The results support the selection of deeper clarifiers as the most environmentally beneficial measure for upgrade.

Impacts of flexible pavement design and management decisions on life cycle energy consumption and carbon footprint

Purpose The study aims to develop a methodological framework to estimate life cycle energy consumption and greenhouse gas (GHG) emissions related to pavement design and management decisions. Another objective is to apply the framework to the design and management of flexible highway pavement in Hong Kong. Traditionally, pavement design and management decisions are solely based on economic considerations. This study quantifies the relationships between such decisions and the environmental impacts, thereby helping highway agencies understand the environmental implications of their decisions and make more balanced decisions to improve highway sustainability.