Hybrid Life Cycle Assessment Model Research Articles

Evaluating Carbon Emissions during Slurry Shield Tunneling for Sustainable Management Utilizing a Hybrid Life-Cycle Assessment Approach

The construction sector is one of the principal contributors to carbon dioxide emissions (CDEs) and has a vital role to play in responding to the issue of long-term environmental sustainability. This research proposes a process-based hybrid life-cycle assessment (LCA) method depending on a process-based LCA and an input–output LCA. The process-based hybrid LCA model provides a supplementary method to quickly estimate carbon emissions that are not considered in the system boundary due to the limitation of inventory data. The proposed hybrid method was applied to a carbon emissions assessment in a slurry shield tunnel. The results suggest that 93.88% of emissions are from materials. Of the materials contribution, 55.9% comes from steel and 34.55% arises from concrete. It has also been found that emissions during the tunneling stage are negatively correlated with the efficiency of tunnel construction. Recommendations for carbon emissions reductions in tunnel construction are provided for promoting sustainable transportation and management.

Half of the greenhouse gas emissions from China’s food system occur during food production

Food systems are responsible for a third of global anthropogenic greenhouse gas emissions and there has been an increasing research focus on food-system greenhouse gases. However, limited attention has been paid to emissions from the regional trade network associated with food systems. Here we developed a multi-regional input-output-based hybrid life cycle assessment model and traced China’s food-system greenhouse gas emissions from farm to fork. China’s food system emitted 2.4 (95%; confidence interval range: 1.6–3.2) gigatons CO2-equivalent in 2019, and half were emitted at the production stage. There were substantial differences in the emission structure and sources among the provinces. Further analysis indicated that the differences among provinces were caused by the separation of food production and consumption. People living in wealthier coastal and central regions consumed food from western and northeastern regions. Therefore, the government should consider interregional synergies when developing strategies to reduce food-system greenhouse gas emissions.

A Novel Hybrid Life Cycle Assessment Approach to Air Emissions and Human Health Impacts of Liquefied Natural Gas Supply Chain

Global interest in LNG products and supply chains is growing, and demand continues to rise. As a clean energy source, LNG can nevertheless emit air pollutants, albeit at a lower level than transitional energy sources. An LNG plant capable of producing up to 126 MMTA was successfully developed and simulated in this study. A hybrid life cycle assessment model was developed to examine the social and human health impacts of the LNG supply chain’s environmental air emission formation. The Multiregional Input–Output (MRIO) database, the Aspen HYSYS model, and the LNG Maritime Transportation Emission Quantification Tool are the key sources of information for this extensive novel study. We began our research by grouping environmental emissions sources according to the participation of each stage in the supply chain. The MDEA Sweetening plant, LNG loading (export terminal), and LNG transportation stages were discovered to have the maximum air emissions. The midpoint air emissions data estimated each stage’s CO2-eq, NOx-eq, and PM2.5-eq emissions per unit LNG generated. According to the midpoint analysis results, the LNG loading terminal has the most considerable normalized CO2-eq and NOx-eq emission contribution across all LNG supply chain stages. Furthermore, the most incredible intensity value for normalized PM2.5-eq was recorded in the SRU and TGTU units. Following the midpoint results, the social human health impact findings were calculated using ReCiPe 2016 characterization factors to quantify the daily loss of life associated with the LNG process chain. SRU and TGTU units have the most significant social human health impact, followed by LNG loading (export terminal) with about 7409.0 and 1203.9 (DALY/million Ton LNG produced annually), respectively. Natural gas extraction and NGL recovery and fractionation units are the lowest for social human health consequences.

Hybrid life cycle assessment of potato pulp valorisation in biocomposite production

Biocomposites with by-products of agro-industrial feedstock are raising industrial interest. Potato pulp, as residue of the starch industry, can be valorised in polylactide (PLA) or polyhydroxyalkanoates (PHA) systems to replace the biomass feedstock for biocomposite production. In this study, biocomposites with up to 20% by weight of potato pulp were successfully produced on industrial scale and proposed for application in pots and rigid packaging. In order to evaluate and optimize the sustainability of biocomposite supply chain, a hybrid life cycle assessment model was developed to evaluate the economic, social and environmental impacts of potato pulp valorisation in the biocomposite supply chains. The results suggested potato pulp valorisation can bring positive social-economic impacts with adverse environmental effect to both PLA and PHA biocomposite supply chains. Improving the thermal energy used in drying potato pulp has potential to achieve positive performance in GHG reduction, especially for PLA based biocomposite supply chain. Given potato pulp valorisation has other benefits, such as reduce agricultural waste and improve biodegradability. Valorising potato pulp in PLA based biocomposite supply chain can potentially facilitate the transition to a sustainable bioeconomy. It deserves further research and support from financial and political aspects.

Understanding the resource-use and environmental impacts of bioethanol production in China based on a MRIO-based hybrid LCA model

To understand the resource and environmental costs of bioethanol production, this study estimates the water and farmland use and CO2 emissions in China due to first- and second-generation bioethanol production technologies using a multi-regional input-output-based hybrid life cycle assessment model. Sensitivity analysis and structural path analysis are combined to investigate the key pathways for bioethanol production impact mitigation. Results show that the first-generation technology has higher resource-use and environmental impacts compared to the second-generation technology. The gasoline-to-bioethanol transition enables CO2 emission reductions, but at the cost of increased water and farmland use. Key impact mitigation pathways are then investigated for the first four production layers (PL0→3) in bioethanol industries because these layers contribute to a significant environmental footprint. For PL0, water-saving technologies must be developed to reduce direct water use in first-generation bioethanol production. For PL1, the primary production material suppliers of the bioethanol industry, such as biomass feedstock, food and tobacco, and water supply industries were ascertained with high potential for impact mitigation. For PL2→3, key pathways are investigated by combining their sensitivity and impact values. The results highlight the significance and necessity of cross-sectoral collaboration for resource and environmental impact reduction.

The social, economic, and environmental implications of biomass ethanol production in China: A multi-regional input-output-based hybrid LCA model

As an alternative to conventional liquid fuels, bioethanol holds the promise of transitioning to a clean and low-carbon energy future. China’s bioethanol industry is at its nascent stage. In this study, we developed a hybrid life cycle assessment model that integrates the multi-regional input-output (MRIO) approach and specific production data to evaluate the social, economic, and environmental (i.e. the triple-bottom-line, TBL) impacts of the bioethanol sector in China’s economic systems. The MRIO model was constructed using the 2012 MRIO table, and the data for the typical technologies of bioethanol production were leveraged. To be specific, we evaluated employment creation, economic stimulus, and energy use of bioethanol production in 28 scenarios in Henan province. The results show that compared to petroleum refining, bioethanol production is more effective for economic stimulus and energy saving, but less effective at job creation. The impact of bioethanol production varies by technologies. For every 1 million yuan of bioethanol production in China’ economic system, first-generation technology offers a projected 1.92 million yuan in economic growth and job creation of 2.06 full-time equivalent, while the second-generation technology offers a lower energy consumption (1.19 TJ). In most scenarios, the upstream sectors account for more than half of the TBL impacts of biofuel production. This study helps to quantify the TBL impacts associated with the gasoline-to-bioethanol transition in China, envisions the green opportunities for impact mitigation, and sheds light on the potential direction for robust planning and policy making to advance the bioethanol industry’s development.

Hybrid life cycle assessment of agro-industrial wastewater valorisation

Wastewater from food processing facilities can have high nutrient valorisation potential. Valorising sugar-rich agro-industrial wastewater may have significant impacts on sustainability of wastewater treatment plant (WWTP). The objective of this study is to evaluate the environmental, economic and social impacts of a novel wastewater valorisation technology. This technology is designed to produce single cell protein (SCP) from wastewater of a fruit juice processing facility. To evaluate the comprehensive sustainability impacts on WWTP and overall background economy, a hybrid life cycle assessment model was developed by combining the multi-regional input-output database (Exiobase) with process-based life cycle inventories of conventional and AgroCycle WWTP. The results indicated the upstream impacts of wastewater could have significant influence on sustainability of WWTP with nutrient valorisation. Therefore the ‘zero burden assumption’ should not be adopted for upstream wastewater. For the sustainability performance, valorising nutrients from WWTP with AgroCycle technology can improve the environmental performance of WWTP. However, the positive social-economic impacts were directly associated with WWTP system, not the whole background economy. The production of SCP could reduce the Gross Value Added (GVA) and employment in the ‘oil seeds sector’. In order to improve the social-economic impacts and promote a circular bioeconomy model in the fruit juice sector, further development is required to improve valorisation productivity and create a better value chain for valorised products.

The socio-economic impacts of introducing circular economy into Mediterranean rice production

Abstract: A novel bio-fertilizer technology that utilizing paddy rice residues (bran and husk) through composting was assessed in the context of life cycle assessment application to circular bio-economy. The bio-fertilizer can recycle the nutrients in residues to replace synthetic fertilizer within the rice production system. To evaluate the feasibility and potential benefits of this circular rice production system, a hybrid life cycle assessment model was developed to estimate social-economic impact. The model combined the multi-regional input-output database (Exiobase), with engineering process data of conventional and circular rice production systems from the Agrocycle project. The gross value added and employment in each system were compared at functional unit and sectoral level. The results indicated the efficiency of fertilizer application has a significant effect on social-economic impacts. The circular system has the potential to increase the gross value added and employment in conventional rice production, but the circular rice system could not improve both economic and social impacts at the same time. The results indicated the circular system did not necessarily achieve more positive social-economic impacts than the convention linear system. Considering the circularity and efficient use of resources, the bio-fertilizer technology should not be dismissed. To derive better social-economic performance from the circular rice supply chain, further developments are required, such as technology development to reduce unit production cost and infrastructure development to support bio-fertilizer production.

A waste generation input output analysis: The case of Spain

In December 2015 the European Commission adopted the Circular Economy Package that includes legislative proposals on waste as well as long-term targets to reduce landfilling and increase recycling and reuse. A detailed and comprehensive accounting of waste arisings forms the quantitative basis for designing adequate policy instruments for a Circular Economy. The aim of this paper is to estimate total waste generation throughout the supply chain in Spain by applying an input-output based hybrid Life Cycle Assessment model. Both the waste generated by direct suppliers and indirect suppliers (that is, suppliers to suppliers) are estimated. The results show that there is high concentrations in total waste generation both in terms of sectors and waste types so the government should concentrate its waste prevention strategy on those sectors and types of waste that have a higher impact on total waste generation.

Total environmental impacts of biofuels from corn stover using a hybrid life cycle assessment model combining process life cycle assessment and economic input-output life cycle assessment.

Studies on the environmental analysis of biofuels by fast pyrolysis and hydroprocessing (BFPH) have so far focused only on the environmental impacts from direct emissions and have included few indirect emissions. The influence of ignoring some indirect emissions on the environmental performance of BFPH has not been well investigated and hence is not really understood. In addition, in order to avoid shifting environmental problems from one medium to another, a comprehensive assessment of environmental impacts caused by the processes must quantify the environmental emissions to all media (air, water, and land) in relation to each life cycle stage. A well-to-wheels assessment of the total environmental impacts resulting from direct emissions and indirect emissions of a BFPH system with corn stover is conducted using a hybrid life cycle assessment (LCA) model combining the economic input-output LCA and the process LCA. The Tool for the Reduction and Assessment of Chemical and other environmental Impacts (TRACI) has been used to estimate the environmental impacts in terms of acidification, eutrophication, global climate change, ozone depletion, human health criteria, photochemical smog formation, ecotoxicity, human health cancer, and human health noncancer caused by 1 MJ biofuel production. Taking account of all the indirect greenhouse gas (GHG) emissions, the net GHG emissions (81.8 g CO2 eq/MJ) of the biofuels are still less than those of petroleum-based fuels (94 g CO2 eq/MJ). Maize production and pyrolysis and hydroprocessing make major contributions to all impact categories except the human health criteria. All impact categories resulting from indirect emissions except eutrophication and smog air make more than 24% contribution to the total environmental impacts. Therefore, the indirect emissions are important and cannot be ignored. Sensitivity analysis has shown that corn stover yield and bio-oil yield affect the total environmental impacts of the biofuels more significantly than the biomass transportation distance and biofuel transportation distance. Integr Environ Assess Manag 2018;14:139-149. © 2017 SETAC.

Life Cycle Assessment and Optimization-Based Decision Analysis of Construction Waste Recycling for a LEED-Certified University Building

The current waste management literature lacks a comprehensive LCA of the recycling of construction materials that considers both process and supply chain-related impacts as a whole. Furthermore, an optimization-based decision support framework has not been also addressed in any work, which provides a quantifiable understanding about the potential savings and implications associated with recycling of construction materials from a life cycle perspective. The aim of this research is to present a multi-criteria optimization model, which is developed to propose economically-sound and environmentally-benign construction waste management strategies for a LEED-certified university building. First, an economic input-output-based hybrid life cycle assessment model is built to quantify the total environmental impacts of various waste management options: recycling, conventional landfilling and incineration. After quantifying the net environmental pressures associated with these waste treatment alternatives, a compromise programming model is utilized to determine the optimal recycling strategy considering environmental and economic impacts, simultaneously. The analysis results show that recycling of ferrous and non-ferrous metals significantly contributed to reductions in the total carbon footprint of waste management. On the other hand, recycling of asphalt and concrete increased the overall carbon footprint due to high fuel consumption and emissions during the crushing process. Based on the multi-criteria optimization results, 100% recycling of ferrous and non-ferrous metals, cardboard, plastic and glass is suggested to maximize the environmental and economic savings, simultaneously. We believe that the results of this research will facilitate better decision making in treating construction and debris waste for LEED-certified green buildings by combining the results of environmental LCA with multi-objective optimization modeling.

Quantification of building embodied energy in China using an input–output-based hybrid LCA model

In China, a substantial amount of building embodied energy has been consumed as a result of rapid urbanization and the corresponding enormous construction workload. However, it is difficult for conventional life cycle assessment (LCA) models to completely and precisely quantify the embodied energy of a building. To solve this problem, this study develops an input–output (I–O)-based hybrid LCA model. In the model, sensitivity analysis is used to identify the key linkages between sectors that significantly affect the building embodied energy; subsequently, the significant energy paths are extracted. In addition, more reliable process analysis data are used as a substitute for partial energy path data. Using China's 2010 I–O table and process analysis data of primary construction materials, the building embodied energy in China in 2010 was quantified to be 1.3528×109t of coal equivalent using the developed I–O hybrid LCA model. Based on the identification of the most intensive energy flows, various measures are proposed to limit the building embodied energy in China. A comparison of the results from different LCA models indicates that the I–O hybrid LCA not only ensures a complete assessment boundary but also improves the reliability of the results by substituting the energy path data with more precise physical process analysis data.

A Methodology for Integrated, Multiregional Life Cycle Assessment Scenarios under Large-Scale Technological Change.

Climate change mitigation demands large-scale technological change on a global level and, if successfully implemented, will significantly affect how products and services are produced and consumed. In order to anticipate the life cycle environmental impacts of products under climate mitigation scenarios, we present the modeling framework of an integrated hybrid life cycle assessment model covering nine world regions. Life cycle assessment databases and multiregional input-output tables are adapted using forecasted changes in technology and resources up to 2050 under a 2°C scenario. We call the result of this modeling "technology hybridized environmental-economic model with integrated scenarios" (THEMIS). As a case study, we apply THEMIS in an integrated environmental assessment of concentrating solar power. Life-cycle greenhouse gas emissions for this plant range from 33 to 95 g CO2 eq./kWh across different world regions in 2010, falling to 30-87 g CO2 eq./kWh in 2050. Using regional life cycle data yields insightful results. More generally, these results also highlight the need for systematic life cycle frameworks that capture the actual consequences and feedback effects of large-scale policies in the long term.

Hybrid LCA model for assessing the embodied environmental impacts of buildings in South Korea

The assessment of the embodied environmental impacts of buildings can help decision-makers plan environment-friendly buildings and reduce environmental impacts. For a more comprehensive assessment of the embodied environmental impacts of buildings, a hybrid life cycle assessment model was developed in this study. The developed model can assess the embodied environmental impacts (global warming, ozone layer depletion, acidification, eutrophication, photochemical ozone creation, abiotic depletion, and human toxicity) generated directly and indirectly in the material manufacturing, transportation, and construction phases. To demonstrate the application and validity of the developed model, the environmental impacts of an elementary school building were assessed using the developed model and compared with the results of a previous model used in a case study. The embodied environmental impacts from the previous model were lower than those from the developed model by 4.6–25.2%. Particularly, human toxicity potential (13kg C6H6 eq.) calculated by the previous model was much lower (1965kg C6H6 eq.) than what was calculated by the developed model. The results indicated that the developed model can quantify the embodied environmental impacts of buildings more comprehensively, and can be used by decision-makers as a tool for selecting environment-friendly buildings.

Integrating triple bottom line input–output analysis into life cycle sustainability assessment framework: the case for US buildings

With the increasing concerns related to integration of social and economic dimensions of the sustainability into life cycle assessment (LCA), traditional LCA approach has been transformed into a new concept, which is called as life cycle sustainability assessment (LCSA). This study aims to contribute the existing LCSA framework by integrating several social and economic indicators to demonstrate the usefulness of input–output modeling on quantifying sustainability impacts. Additionally, inclusion of all indirect supply chain-related impacts provides an economy-wide analysis and a macro-level LCSA. Current research also aims to identify and outline economic, social, and environmental impacts, termed as triple bottom line (TBL), of the US residential and commercial buildings encompassing building construction, operation, and disposal phases. To achieve this goal, TBL economic input–output based hybrid LCA model is utilized for assessing building sustainability of the US residential and commercial buildings. Residential buildings include single and multi-family structures, while medical buildings, hospitals, special care buildings, office buildings, including financial buildings, multi-merchandise shopping, beverage and food establishments, warehouses, and other commercial structures are classified as commercial buildings according to the US Department of Commerce. In this analysis, 16 macro-level sustainability assessment indicators were chosen and divided into three main categories, namely environmental, social, and economic indicators. Analysis results revealed that construction phase, electricity use, and commuting played a crucial role in much of the sustainability impact categories. The electricity use was the most dominant component of the environmental impacts with more than 50 % of greenhouse gas emissions and energy consumption through all life cycle stages of the US buildings. In addition, construction phase has the largest share in income category with 60 % of the total income generated through residential building’s life cycle. Residential buildings have higher shares in all of the sustainability impact categories due to their relatively higher economic activity and different supply chain characteristics. This paper is an important attempt toward integrating the TBL perspective into LCSA framework. Policymakers can benefit from such approach and quantify macro-level environmental, economic, and social impacts of their policy implications simultaneously. Another important outcome of this study is that focusing only environmental impacts may misguide decision-makers and compromise social and economic benefits while trying to reduce environmental impacts. Hence, instead of focusing on environmental impacts only, this study filled the gap about analyzing sustainability impacts of buildings from a holistic perspective.

Role of Urban Planning in Encouraging More Sustainable Lifestyles

Where urban planning is used to promote environmental sustainability, it has traditionally focused on reducing emissions from housing and traffic. However, cities are increasingly being recognized as consumption centers of the global economy, as the origin of demand, and as the point of termination for complex economic supply chains. Based on results produced by a hybrid life-cycle assessment model, which attributed the end-to-end emissions of supply chains to end users, consumption that is not related to housing or ground transportation was found to account for 30% of regional greenhouse gas emissions on average. In highly urbanized areas, the figure was even higher, at 45%. Furthermore, a literature review indicated that most environmental assessment tools for local city-level and subcity-level urban planning are neither able to identify the environmental impacts of personal consumption nor the relationships between urban structures and personal consumption. Thus, this study concludes that there is an apparent gap between the needs and the means of the regional environmental management of urban areas.

Life-Cycle Assessment of Concrete Dam Construction: Comparison of Environmental Impact of Rock-Filled and Conventional Concrete

AbstractMassive concrete dam projects will be constructed in the next 10 years to respond to the increasing demand for clean energy and water resources in developing countries. Because of their ample use of cement, these projects have a significant environmental impact, including the production of carbon dioxide (CO2) emissions. Rock-filled concrete (RFC) is an innovative dam construction method that promises better environmental performance than conventional concrete (CC) in the material production stage by saving a large amount of cement. However, the environmental loads throughout the entire life cycle of a dam must be quantified. Thus, this paper aims to evaluate the environmental loads in the lifetime of a dam and reveal the environmental impact of RFC relative to CC over the entire life cycle of a concrete dam. Through reviewing the limitations of the existing life-cycle assessment (LCA) models, a hybrid LCA model is applied to achieve this goal. The results from a case study of a concrete dam proje...

A hybrid life cycle assessment of water treatment chemicals: an Australian experience

Purpose Life cycle assessment (LCA) of chemicals is usually developed using a process-based approach. In this paper, we develop a tiered hybrid LCA of water treatment chemicals combining the specificity of process data with the holistic nature of input–output analysis (IOA). We compare these results with process and input–output models for the most commonly used chemicals in the Australian water industry to identify the direct and indirect environmental impacts associated with the manufacturing of these materials. Methods We have improved a previous Australian hybrid LCA model by updating the environmental indicators and expanding the number of included industry sectors of the economy. We also present an alternative way to estimate the expenditure vectors to the service sectors of the economy when financial data are not available. Process-based, input– output and hybrid results were calculated for caustic soda, sodium hypochlorite, ferric chloride, aluminium sulphate, fluorosilicic acid, calcium oxide and chlorine gas. The functional unit is the same for each chemical: the production of 1 tonne in the year 2008. Results and discussion We have provided results for seven impact categories: global warming potential; primary energy; water use; marine, freshwater and terrestrial ecotoxicity potentials and human toxicity potential. Results are compared with previous IOA and hybrid studies. A sensitivity analysis of the results to assumed wholesale prices is included. We also present insights regarding how hybrid modelling helps to overcome the limitations of using IOor process-based modelling individually. Conclusions and recommendations The advantages of using hybrid modelling have been demonstrated for water treatment chemicals by expanding the boundaries of process-based modelling and also by reducing the sensitivity of IOA to fluctuations in prices of raw materials used for the production of these industrial commodities. The development of robust hybrid life cycle inventory databases is paramount if hybrid modelling is to become a standard practice in attributional LCA.

Comparative sustainability assessment of warm-mix asphalts: A thermodynamic based hybrid life cycle analysis

Warm-mix asphalt (WMA) has received considerable attention in the past few years as a potential solution for the reduction of energy consumption and emissions during production and construction of asphalt mixtures. However, many concerns and questions are still unanswered regarding its environmental benefits. Although several studies have been conducted to quantify the atmospheric emissions of WMA pavements, the direct and indirect role of ecological resource consumption was generally excluded in these studies. In this study, a thermodynamic based hybrid life cycle assessment model was developed to evaluate the environmental impacts of different types of WMA pavements and compare it to that of a conventional hot mix asphalt (HMA) one. The impacts on the ecosystem were calculated in terms of cumulative mass, energy, industrial exergy, and ecological exergy. Monte Carlo simulation was also conducted to analyze the variability of critical input parameters. The results of this study showed that although the mixing phase is important, it should not be the only phase to evaluate the decreased amount of atmospheric emissions of WMA pavements.

Ecologically based hybrid life cycle analysis of continuously reinforced concrete and hot-mix asphalt pavements

An ecologically-based hybrid life cycle assessment model is used to evaluate the resource consumption and atmospheric emissions of continuously reinforced concrete and a hot-mix asphalt pavements. The cumulative mass and ecological resource consumption values are lower for continuously reinforced concrete, but the median values of cumulative energy and industrial energy consumption were lower for hot-mix asphalt. In addition, the use of reclaimed asphalt pavement results in a higher sensitivity for the ecological resource consumption of hot-mix asphalt compared to that of fly ash when use on the natural capital utilization of continuously reinforced concrete pavement. The cumulative and industrial exergy consumption values are significantly reduced with increases in reclaimed asphalt pavement and fly ash, and the use of low fuel transportation modes.