Life Cycle Carbon Footprint Research Articles

Research on Optimizing the Carbon Footprint of Products Based on Identifier Resolution

Abstract: This article takes a certain refrigerator of Haier Company as the research object and conducts an in-depth discussion on its carbon footprint throughout the full lifecycle. To achieve accurate tracking and calculation of the carbon footprint of the refrigerator's full lifecycle, this article adopts Handle and Ecode identification and resolution technologies. It establishes corresponding identification coding rules for key points throughout the lifecycle of refrigerator production, transportation, usage, and recycling, and designs a set of identification coding schemes for each stage of the refrigerator from raw material acquisition to recycling. Based on this identification coding scheme, this article calculates in detail the carbon footprint of the refrigerator at each stage of its full lifecycle. Based on the calculated carbon footprint data, it gains a deep understanding of the distribution of the carbon footprint of the refrigerator product and proposes a series of targeted optimization strategies. This research provides a powerful reference for the green development of the home appliance industry and promotes its development towards a more environmentally friendly and sustainable direction.

Life cycle assessment and design of LignoBlock: A lignin bound block on the path towards a green transition of the construction industry

Lignin-based biopolymer-bound soil composites (BSCs) are a new class of sustainable construction materials that utilize a bio-based biopolymer — lignin — as a binder. Prior use of lignin suggests that lignin is a promising candidate for the development of bio-based construction materials. Inspired by these applications, lignin-based BSCs were developed using lignoboost lignin, lignoforce lignin, alkali lignin, and hydrolysis lignin. Uni-axial compressive testing of lignin-based BSC shows that the compressive strength for these BSCs range from 1.6–8.1 MPa, which makes them appropriate for low compressive strength construction applications. We performed a life cycle assessment (LCA) of lignin-based BSC, with the functional unit being a CMU-sized block (V=6423cm3). The major advantage of BSC lies in the elimination of ordinary portland cement, which is common to many construction materials, including many forms of concrete. Furthermore, the use of lignin in lignin-based BSC results in carbon sequestration (lignin ≈ 60 wt% carbon), potentially making construction materials made from lignin-based BSC carbon negative. Additionally, a design guide for estimating the life cycle carbon footprint of lignin-based BSC for a required compressive strength was developed. By utilizing the results from material tests and the LCA, designers are now able to use lignin effectively in construction applications, as they can now design lignin-based BSC for a target compressive strength with a full understanding of the life cycle carbon footprint implications.

Environmental footprint and material composition comparison of single-use and reusable duodenoscopes.

Infection outbreaks associated with contaminated reusable duodenoscopes (RUDs) have induced the development of novel single-use duodenoscopes (SUDs). This study aimed to analyze the material composition and life cycle assessment (LCA) of RUDs and SUDs to assess the sustainability of global and partial SUD implementation. A single-center study evaluated material composition analysis and LCA of one RUD and two SUDs from different manufacturers (A/B). Material composition analysis was performed to evaluate the thermochemical properties of the duodenoscope components. The carbon footprint was calculated using environmental software. We compared the sustainability strategies of universal use of RUDs, frequent use of RUDs with occasional SUDs, and universal use of SUDs over the lifetime of one RUD. RUDs were substantially heavier (3489 g) than both SUD-A (943 g) and SUD-B (716 g). RUDs were mainly metal alloys (95%), whereas SUDs were mainly plastic polymers and resins (70%-81%). The LCA demonstrated the sustainability of RUDs, with a life cycle carbon footprint 62-82 times lower than universal use of SUDs (152 vs. 10 512-12 640 kg CO2eq) and 10 times lower than occasional use of SUDs (152 vs. 1417-1677 kg CO2eq). Differences were observed between SUD-A and SUD-B (7.9 vs. 6.6 kg CO2eq per endoscope). End-of-life incineration emissions for SUDs were the greatest environmental contributors. Widespread adoption of SUDs has greater environmental challenges; it requires a balance between infection control and environmental responsibility. Carbon footprint labelling can help healthcare institutions make sustainable choices and promote environmentally responsible healthcare practices.

Life cycle carbon footprints of alternative sludge pretreatment technologies to recover carbon sources for denitrification

Excess sludge from wastewater treatment holds promise as a carbon source for denitrification. While there have been attempts at technological breakthroughs for carbon recovery from sludge through pretreatment and hydrolysis, a low-carbon footprint solution remains elusive. In this study, we evaluated seven pretreatment technologies for carbon recovery from sludge using life cycle assessment (LCA) modeling. The carbon footprints of technological configurations involving alkaline, ultrasound, thermal, oxidation, mechanical, microwave, and alkali/thermal treatments were quantified based on 123 consistent datasets, and compared by incorporating probability and uncertainty analyses with Monte Carlo and global sensitivity methods. Alkaline treatment achieved carbon footprint savings with a median of −128.71 kg CO2-eq/t TS, and the other technological configurations all show loads in median values. Significant variations in carbon footprints were observed both within and across different technological configurations. Probability distributions reveal overlaps among these configurations. Alkaline treatment has a high probability of obtaining carbon footprints ranging from −300 to 300 kg CO2-eq/t TS, while those for the other configurations showed various distribution with modes ranging from 0 to 3000 kg CO2-eq/t TS. Energy and chemical consumptions during pretreatment emerging were identified as key factors influencing the carbon footprint, with contributing 95–99% of the result uncertainty. Recommendations based on the top 15% probability indicate that technological configurations involving alkali/thermal and alkaline treatments offer a good balance of carbon source quality (180.12 kg/t TS and 142.39 kg/t TS, respectively) and relatively low carbon footprints (517.29 ± 80.06 kg CO2-eq/t TS and 136.99 ± 648.64 kg CO2-eq/t TS, respectively). These findings help identify the most sustainable technologies for carbon recovery from sludge and their potential improvements from a carbon footprint perspective. This study thus underscores the need for further research and technological advancements in sludge treatment to facilitate carbon recovery through denitrification.

Study on Life-Cycle Carbon Footprints and an Uncertainty Analysis of Mega Sporting Events: An Analysis in China

This study proposes a model for the quantitative evaluation of the life-cycle carbon footprints of large sporting events and the uncertainties related to them. The model was used to analyze the case of a mega sporting event in Beijing, China. First, the quantitative model for the evaluation of the carbon footprints of mega sporting events includes a preparation stage, a holding stage, and an end stage. These stages consider the energy and resources used for construction, operation, transportation, catering, and accommodation. Second, this study proposes a prediction model using model-based and simulation-based methods to address the difficulty of obtaining traffic activity. Third, a semi-quantitative method that combines a data quality indicator and stochastic simulation is adopted for the uncertainty analysis of mega sporting events. Finally, a case study is used to indicate that the preparation stage of a mega sporting event accounts for the highest CO2 emissions at 92.1%, followed by 7.5% in the holding stage and 0.4% in the end stage. The total life-cycle CO2 emissions of a sustainable scenario of a mega sporting event in Beijing amount to 205,080.3 t CO2e, and the per capita CO2 emissions during the event’s holding stage amount to 0.26 t CO2e/person. The uncertainty in the input parameters is 0.0617, indicating that the uncertainty of the model is low, and the reliability of the results is high.

Optimization strategies for carbon neutrality in a maize-soybean rotation production system from farm to gate

Agricultural food production stands as a primary source of global greenhouse gas emissions, with residue management widely acknowledged as an effective avenue to achieve carbon neutrality. However, there is a lack of comprehensive assessment of the carbon footprint of agricultural residue production, processing, and recycling from farm to gate. Here we conducted a hybrid approach that integrated the DeNitrification-DeComposition (DNDC) model and life cycle carbon footprint to co-optimize water and residue management, targeting carbon neutrality and yield increase. The results revealed that controlled drainage with sub-irrigation (CDSI) served as a potent water management strategy to mitigate greenhouse gas emissions (15.65 %) while increasing yield (24.34 %) compared to free drainage. Regardless of the type of bioproduct, incorporating CDSI with downstream residue utilization exhibited substantial potential for carbon-negative emissions, reducing the average farm carbon footprint to −1538.15 kg CO2 eq yr−1. Among those scenarios, the CDSI with bioethanol scenario particularly stands out with its robust carbon mitigation capability (−1994.94 kg CO2 eq yr−1), driven by the enormous energy demand throughout the agricultural production process and the environmental friendliness of bioethanol, which substantially exceeds that of gasoline. However, challenges such as high plant construction costs and extended investment payback periods associated with residue conversion underscore the need for the urgent establishment of national subsidies and market mechanisms to foster carbon neutrality in agricultural production.

An electricity-driven mobility circular economy with lifecycle carbon footprints for climate-adaptive carbon neutrality transformation

Under the carbon neutrality targets and sustainable development goals, emergingly increasing needs for batteries are in buildings and electric vehicles. However, embodied carbon emissions impose dialectical viewpoints on whether the electrochemical battery is environmentally friendly or not. In this research, a community with energy paradigm shifting towards decentralization, renewable and sustainability is studied, with multi-directional Vehicle-to-Everything (V2X) and lifecycle battery circular economy. Approaches are proposed to quantify the lifecycle carbon intensity of batteries. Afterwards, pathways for zero-carbon transformation are proposed to guide the economic feasibility of energy, social and governance investment behaviors. Results show that lifecycle zero-carbon battery can be achieved under energy paradigm shifting to positive, V2X interaction, battery cascade utilization and battery circular economy in various climate regions. This study proposes an approach for lifecycle battery carbon intensity quantification for sustainable pathways transition on zero-carbon batteries and carbon-neutral communities.

Using miscanthus and biochar as sustainable substrates in horticulture: An economic and carbon footprint assessment of their primary and cascading value chains

Conventional substrates like peat, stone wool and coconut coir are responsible for high greenhouse gas emissions in the horticultural sector, necessitating low-emission and cost-efficient alternatives. Herein, using miscanthus and biochar as substrate components as well as in cascading substrate application can be alternative practices in a sustainable bioeconomy. However, the carbon footprint and economic impacts of these practices in relation to crop yields have not yet been investigated. Hence, we combined life cycle carbon footprint assessment and costing to analyze the Global Warming Potential and value chain costs of horticultural substrates in tomato cultivation in North-Rhine Westphalia. We conducted a comparison between conventional substrates (peat, stone wool, and coconut coir) and single use and cascading miscanthus-based substrates with and without 1–2 % biochar addition of the miscanthus mass. Also, a subsequent scenario analysis was carried out to examine alterations in inputs and costs.Our results demonstrate that miscanthus-based substrates are climate-friendly and low-cost alternatives to the conventional practices. Switching to miscanthus-based substrates results in more emission savings than other input scenarios investigated. Additionally, incorporating biochar and adopting cascading methods contribute to lower emissions. Notably, biochar has the most significant impact, as its amount correlates with higher emission reductions. Additionally, costs for cascading miscanthus-based substrates are lower compared to conventional substrates. Overall, there is only a slight variance in costs between conventional and miscanthus-based substrates. However, with the introduction of carbon emission pricing and carbon removal certificates, miscanthus-based and biochar-containing substrates may emerge as more cost-efficient alternatives. Thus, by advancing financial instruments on carbon emissions and removal, introducing cascade use within and beyond the horticulture sector, and supporting cultivation of sustainable biomasses, miscanthus and biochar can effectively contribute to the development of a sustainable bioeconomy.

Tecno-econo-enviro-social assessment of clean electrification for a marine equipment manufacturing plant in Türkiye through hybrid renewable energy system with demand response

Marine equipment manufacturing plants (MEMPs) are the backbone of the shipbuilding industry, producing equipment and machinery for the functioning of ships and marine transportation. This is achieved at the expense of substantial energy consumption, resulting in financial and environmental consequences that MEMPs are compelled to deal with. Hybrid renewable energy systems (HRESs) can assist MEMPs in reducing their energy costs and emissions through increased use of renewable energy and demand response with intelligent use of energy. This study develops and implements a comprehensive HRES design framework for an energy-intensive MEMP in Türkiye. The framework considers techno-economic, enviro-social assessments, and demand response participation. The environmental assessment was performed to minimise the life-cycle carbon footprint. Social benefits were evaluated based on job creation and external health cost reduction. The best HRES design was identified as a grid-connected system comprising a 329-kWp PV system and a 1.8-MW wind turbine. It offered a NPV of €294.236 and a cost-of-energy of −0.002 €/kWh, along with an initial investment of €2.095.846. The proposed demand response strategies of peak shaving and grid arbitrage were found to increase economic viability. Significant improvements in energy self-sufficiency, cost savings, carbon footprint reductions, and social benefits through HRES application were demonstrated.

Characteristics and life cycle carbon emission reduction potential of waste recycling after implementing new waste classification policy in China: From case study to national perspective

Under the background of resource shortage and global warming, it is of great significance to explore the status, influencing factors and carbon emission reduction effect of waste recycling in China after the implementation of new waste classification policy for guiding waste classification and carbon emission accounting. In this research, the temporal and spatial changes and influencing factors of waste recycling were studied from subdistrict level, life-cycle carbon emission reduction was predicted and policy suggestions for waste recycling were proposed. The results showed that after the implementation of new waste classification policy, the amount of recycled waste and the proportion of low-value recycled waste increased by 420.93 t and 2.29 % per month on average, respectively. The district center has the largest amount of recycled waste. Income was the main factors affecting waste recycling, and online shopping and takeout could become important sources of recyclable waste. Accounting cradle-to-grave life cycle carbon footprint, waste plastics takes up the most contribution, accounting for 39.11 %, and nearly 391.68 Mt CO2eq would be reduced by waste recycling in China by 2030. Therefore, in the process of waste classification, refining waste classification to increase the amount of low-value recyclables, and rationally deploying collection and transportation vehicles to ensure efficient waste recycling are of great significance to achieve the goal of “carbon peaking and carbon neutrality”.

Development and assessment of an integrated wind energy system for green steelmaking based on electric arc furnace route

Optimizing energy structure is important for coping with the increasing environmental problems in iron and steel industry. Wind energy is one of typical zero-carbon, inexhaustible, and accessible energy source for alleviating energy dilemma. In this paper, the electric arc furnace steelmaking processes integrated with wind energy system (EAF-WES) is developed. The input-output data of 1214 and 1536 heats with 30 % and 50 % hot metal ratio are traced and collected. Life cycle assessment and techno-economic analysis of EAF route integrated with traditional energy system (EAF-TES) and EAF-WES are further researched and compared from perspectives of life cycle carbon footprint (LCCF), production cost, wind energy price (WEP), carbon efficiency, carbon reduction benefit (CRB), and carbon tax. The results indicate that EAF-WES enjoys lower LCCF but higher production cost and carbon efficiency than EAF-TES. Considering the price fluctuations, the optimal EAF steelmaking pattern with lowest production cost under different extent of WEP and carbon tax is suggested. When the electricity price is 0.043 and 0.046 $/kWh, the CRB is balanced. It is concluded that EAF-WES is a low-carbon, high-productive, environmentally friendly, and economical route. This research is expected to supply a technical idea for energy conservation and emission reduction in future steel production.

Carbon footprint accounting of prefabricated buildings: A circular economy perspective

Prefabricated buildings have gained significant attention as a solution for reducing carbon footprint in the construction industry. However, there is a lack of a comprehensive accounting approach tailored to the construction features of prefabricated buildings. To address this issue, this study develops a framework to account the life-cycle carbon footprint of prefabricated buildings within the circular economy principles. The developed framework is applied to a prefabricated building in Chengdu, China, revealing that a significant carbon footprint is attributed to the material production and transportation stages. Moreover, an uncertainty analysis is conducted based on Data Quality Indicator evaluation method and Monte Carlo Simulation to validate the accounting framework, and a minor deviation of 0.085 % between the uncertain and calculated values validates the proposed accounting framework. Furthermore, key processes to mitigate the carbon footprint are identified. The results show that cast-in-place concrete is a key process at the construction materials level. Building upon these findings, this study offers recommendations on accurately and efficiently accounting the carbon footprint of prefabricated buildings. The research findings contribute to fostering the accounting of the life-cycle carbon footprint for prefabricated buildings, establishing a theoretical and empirical basis for circular economy implementation in prefabricated buildings, and offering insights for making informed carbon emission reduction decisions in prefabricated buildings.

Lifecycle carbon footprints of buildings and sustainability pathways in China

The Paris Agreement, with a 2 °C temperature increase baseline and a 1.5 °C target temperature increase, imposes challenges to the sustainability of buildings. However, as an end-user or end-of-the-art, the building sector overlaps with other sectors, such as industry and transportation in building materials manufacturing (such as steel, concrete, cement, etc. ) and electricity use (such as building-to-vehicle charging), imposing difficulties in lifecycle carbon footprint quantification in buildings. In this study, the lifecycle carbon footprint of buildings and sustainability pathways in China are provided. Tools and platforms for lifecycle carbon footprint quantification in buildings are reviewed. A global database for lifecycle carbon footprint quantification in buildings is reviewed and compared, together with an analysis of the advantages and disadvantages. Furthermore, decarbonization technologies in the building operation stage are comprehensively reviewed, including the decarbonization potential, technology readiness level (TRL), techno-economic performance, and current technical status. Pathways on carbon neutrality in building sectors in China are provided. The results indicate that inconsistencies in global databases, unclear definitions of lifecycle carbon emissions, and inaccurate models of building energy consumption are the main challenges for accurate lifecycle carbon analysis in buildings. Various carbon neutrality transformation technologies can be classified into ultralow energy building and near zero-energy building technologies and into efficient heat pump and smart metering technologies. Pathways for low-carbon transition in building sectors include building energy saving (330 million tCO2 with 22%), renewable energy supply (299 million tCO2 with 20%), building electrification and power sector decarbonization (450 million tCO2 with 30%), and carbon capture, utilization and storage (CCUS) technology (420 million tCO2 with 28%). These research results can pave the way for upcoming studies on the lifecycle carbon footprint in buildings and sustainability pathways in China.

The influence of disclosing product lifecycle carbon footprint information on consumer purchase intentions based on the APE model perspective: An ERP and questionnaire study

BackgroundCarbon emissions are increasingly becoming the primary cause of climate change, and carbon information disclosure can affect consumer purchase intentions. However, existing studies only focus on the disclosure of carbon information for a single lifecycle stage, gnoring consumers' overall perception process. MethodsThis study uses scenario experiments and event-related potential experiments in combination, based on the associative-propositional evaluation (APE) model, to explore the differences in the impact of disclosing product information with high carbon emissions in different lifecycle stages (production stage, use stage, recycling stage) on consumers' purchase intentions. ResultsThe questionnaire results found that consumers' willingness to purchase products with high carbon emissions in the use stage was the lowest; The behavioral results found that the purchase rate of products with high carbon emissions in the recycling stage was the lowest; The brain electricity results found that products with high carbon emissions in the use stage induced the largest P2 component; Products with high carbon emissions in the recycling stage induced the largest N2 component. ConclusionThe attitudes of evaluation with proposition dominance among consumers tend to attribute carbon emissions in the use stage to their own behavioral choices. The attitudes of evaluation with association dominance among consumers reflect the cognitive conflicts existing in consumers' understanding of carbon emission information during recycling. This study expands the perspective of researching the disclosure effects of product carbon footprints and provides references for corporate marketing strategies and policy formulation.

Potential solution to the sustainable ethanol production from industrial tail gas: An integrated life cycle and techno-economic analysis

Utilising industrial tail gas for ethanol production is a viable pathway to significantly mitigate CO2 emissions whilst simultaneously producing value-added fuels and chemicals, which has received great attention in recent years. While some technologies have been commercial deployed, new technological concepts continue to emerge in order to improve the life cycle and techno-economic performance. In this investigation, a novel ethanol production technology integrating tail gas-based ethanol (TG-ethanol) with electro-catalytic CO2 reduction (ECR), called TGEE technology, was first proposed to address the energy and carbon efficiency issues associated with the state-of-the-art TG-ethanol technologies. The process was modularly modelled for to accommodate different ECR integration scenarios for three typical industrial tail gas streams (steel, iron alloy and calcium carbide). In addition, life cycle & techno-economic analysis based on Monte Carlo simulation were employed to evaluate the environmental and economic performance of the TGEE process. Results show that ethanol capacity can be increased by 1.3–2.9 times with carbon efficiency up to 36–82%. Life cycle carbon footprints of TGEE-ethanol were estimated to be 1.77–3.93 t CO2eq/t ethanol, with a carbon reduction potential of 32–63% higher than the TG-ethanol. Minimum ethanol selling price is estimated to be 428–962 $/t ethanol, which is lower than the current ethanol market price (900–1080 $/t). Overall, the comprehensive analysis suggests that the TGEE process emerges as a more economically and environmentally benign next-generation technology for ethanol production from industrial tail gas.

Characterization of the life cycle carbon footprint of the automobile industry in the Republic of Korea by environmentally extended input-output model

The automobile industry is a major economic driver in Republic of Korea (Korea). However, little is known about its climate change contribution. This study estimates the direct and indirect greenhouse gases (GHG) emissions of the Korean automobile industry for the first time, by using a 2017 environmentally extended input-output (EEIO) model integrated by energy balance, GHG inventory and input-output table of 2017. The results show that the final demand of Korean automobile industry led to 8.4% of national GHG emissions in 2017, mostly because of indirect emissions embodied in the supply chain. The study also found that the Scope 1, Scope 2 and Scope 3 emissions on average accounted for 3.0%, 2.9%, and 94.7%, respectively. This highlights the contribution of the upstream supply chain such as primary metals (40.9%) and electricity (32.5%) when assessing the GHG emissions. Finally, the study underscores that carbon taxes could have a significant impact on the competitiveness of automobile export. Overall, this study provides valuable insights on countermeasures by identifying the GHG emissions characteristics of the automobile industry. The results of the study could be used to develop policies and strategies to reduce the GHG emissions and promote sustainable practices in the Korean automobile industry.

The material selection method for functional packaging of electromechanical products based on low carbon and cost constraint

Abstract Packaging is an important but easily overlooked part of the study of low-carbon lifecycle of electromechanical products, but with the significant growth of the express delivery business, the carbon emissions caused by packaging are increasingly noteworthy. In order to explore the carbon emissions of packaging lifecycle, the electromechanical products are used as the packaging object to discuss the connotation of functional packaging, low-carbon design boundary and research methods of packaging lifecycle and establish the calculation models of carbon footprint and cost of packaging lifecycle and the evaluation method of material selection. The case study of gasoline engines shows that material selection plays a decisive role in the packaging of electromechanical products based on low carbon and cost constraints.

Impact of additional carbon storage of natural plant fiber on product carbon footprint: A case study of cotton/kapok blended T-shirt VS pure cotton T-shirt

Researchers have drawn their attention to natural plant fibers in recent years owing to the significant energy consumption and detrimental environmental impact of textile and apparel industry and the imperative of environmental protection. While the potential for mitigating carbon emissions of apparel products deriving from woody versus herbaceous fiber crops remains unclear. Moreover, extant studies only take limited processes as a case demonstration, rather than exploring the impact of additional carbon storage throughout the whole life cycle. Therefore, this study extended the system boundary to the whole life cycle of products from the raw material extraction to the end-of-life disposal stage, conducted a whole life cycle carbon footprint (CF) analysis of cotton/kapok blended T-shirts and pure cotton T-shirts at each stage of their life cycle based on carbon storage accounting method. The results revealed that the CF of 1 kg pure cotton T-shirt is 9.469 kg CO2eq, while for 1 kg cotton/kapok blended T-shirt, it's −24.249 kg CO2eq. Correspondingly, the carbon storages of these T-shirts are −15.653 kg CO2eq and −43.442 kg CO2eq, respectively. This proved that long-term additional carbon storage may possess relatively higher carbon storage due to woody crops' multi-annuality compared with herbaceous crops. When considering carbon emissions during industrial manufacturing and consumer use stages, it's recommended to opt for heavier T-shirts when fabric thickness between pure cotton and cotton/kapok blended T-shirts are comparable, as this choice may align better with environmental considerations, and adopting appropriate washing and caring practices such as choosing lighter-weight garments, utilizing appropriate washing program and detergent dose, opting for air-drying and avoiding ironing when caring for clothing are also advised. The study results affirmed the feasibility of achieving carbon neutrality in apparel products and could provide methodological guidance for future assessment for future research.

A novel lightweight CF decision-making approach for highway reconstruction and operation

Road infrastructure is a major emitter of greenhouse gases (GHGs), contributing significantly to the overall carbon emissions of many countries. Due to their importance in the life-cycle carbon footprint (CF) assessment of highway projects, highway reconstruction, rehabilitation, and operation have garnered increased attention. Existing highway CF studies have relied heavily on on-site data. They were often limited by a handful of operation or reconstruction scenarios. Most existing highway CF studies focused solely on mitigating the infrastructure CF and ignored the potential savings of highway traffic CF resulting from different traffic behaviour and technology options. A comprehensive CF saving potential comparison between the highway infrastructure and traffic for the city- or nation-wide policy decision-making is needed. Moreover, the loss of design and operation information for many existing highway projects with long operational periods necessitates a new approach to assess and manage the CF of highway reconstruction, rehabilitation, and operation. As a result, this study has proposed a new lightweight CF decision-making approach to help highway reconstruction, rehabilitation, and traffic operation management with informative stage-based highway decision-making supporting framework and digital platform that enable the comparison between highway infrastructure and traffic CF's potential savings. With the help of the developed framework and platform, the project decision-maker and government policymaker can leverage better information support and dynamically compare CF decision-making scenarios regarding different highway infrastructure and traffic options. This study contributes to knowledge in three ways: (1) evaluating and validating an informative highway CF decision-making framework for highway infrastructure and traffic assessment and management, (2) proving the applicability of using a lightweight data collection and model building method for highway infrastructure CF assessment and management practice, and (3) providing an applicable way of building a highway CF digital twins (DT) platform for visualisation, decision-making, and management of the highway infrastructure and traffic.

Carbon reduction potential of a rain garden: A cradle-to-grave life cycle carbon footprint assessment

With emphasis on constructing low-carbon cities, the renovation of old communities highlights the importance of renewing rainwater management facilities. Rain garden is an exceptional Nature-based Solution for rainwater management. When applying them to renovate old communities, the carbon footprint should be considered. This study focused on renovating facilities in the Greater Bay Area and utilized the Energy Expert platform to calculate rain garden carbon footprint with the Life Cycle Assessment. The carbon reduction benefits during the operation were estimated. This study accounting the life cycle carbon footprint of the 5455 m2 rain garden was 1117.42 tCO2e. The carbon footprint contribution, from highest to lowest was the end-of-life phase, materials production phase, construction phase, use and maintenance phase. Regarding carbon emission inventory, waste soil landfill, fertilizer acquisition, and waste soil recycling ranked high. Transportation also accounted for a remarkable carbon emission. The rain garden showed great potential for climate change mitigation, with a total and net carbon reduction of 1927.41 and 809.99 tCO2e, respectively. To reduce the carbon footprint of the rain garden, we should focus on waste soil treatment and transportation. Recommendations included increasing waste soil recycling, in situ recycling and green transportation.