Conventional Life Cycle Assessment Research Articles

Modelling environmental life cycle performance of alternative marine power configurations with an integrated experimental assessment approach: A case study of an inland passenger barge

There is pressure on the global shipping industry to move towards greener propulsion and fuel technologies to reduce greenhouse gas emissions. Hydrogen and electricity are both recognised as pathways to achieve a net-zero. However, in the evaluation of the environmental performance of these alternative marine power configurations, conventional life cycle assessment (LCA) methods have limitations reflecting the varied nature of ship design and operational modes. The integration of LCA with experimental assessment could remedy the shortcoming of conventional approaches to data generation. The system energy demand data in this study was generated based on specific ship design and directly fed into life cycle assessment. To demonstrate the effectiveness and potential the approach was applied to a case study of inland waterway vessel. Suitable hybrid PV/electricity/diesel and hydrogen powered fuel cell systems for the case vessel were modelled; and hydrodynamic testing and dynamic system simulation was undertaken to provide ship performance data under various operational/environmental profiles. Lifecycle assessment (LCA) indicated hydrogen and electrical propulsion technologies have the potential for 85.7 % and 56.2 % emissions reduction against an MGO base case, respectively. The results highlight that implementation of both technologies is highly dependent on energy production pathways. Hydrogen systems reliant on fossil feedstocks risk an increase in emissions of up to 6.3 % against the MGO base case. Sensitivity analysis indicated an electrical system with electricity production from 79.5 % renewables could achieve savings of 82.2 % in GHG emissions compared to the MGO base case. Crucially, the results demonstrate a further development of the LCA approach which can enable a more accurate environmental performance evaluation of alternative marine power configurations considering specific ship design and operational characteristics. Ultimately this addition makes the results more meaningful for commercial operations and decision making in the selection of alternative marine power systems to support the transition to net-zero.

“If less is more, how you keeping score?” Outlines of a life cycle assessment method to assess sufficiency

It is increasingly clear that reaching environmental sustainability requires not only efficiency (reduced environmental impact per functionality) but also sufficiency measures (reduced environmental impact through reduced or changed functionality). Life cycle assessment (LCA) is a widely used tool to study environmental impacts related to consumption. However, because of the LCA convention of only comparing alternative products with equal functionality, it is currently inept as a method for assessing the environmental impacts of sufficiency measures. Against this background, this short paper aims to stimulate a discussion on how sufficiency measures can be assessed with LCA methodology. By analyzing the very few LCAs of explicit sufficiency measures in terms of the components of a functional unit (what function is provided, how much, for how long, and how well) features of a potential new branch of LCA methodology are outlined, called Sufficiency LCA. In Sufficiency LCA, product alternatives need to be similar enough so that the what component of the functional unit can be equal, while the other components, how much, how long, and how well, are allowed to be non-equal. Thus, a key feature of Sufficiency LCA concerns functional non-equivalence of compared product alternatives, which is not allowed or neglected in conventional LCA, but which could be allowed, acknowledged and quantified in Sufficiency LCA. Developing Sufficiency LCA could be critical considering that sufficiency measures are expected to be required, and that LCA is expected to be serviceable as decision-making support, in the transition toward environmental sustainability.

Evaluating source separation wastewater systems using traditional life cycle assessment and the planetary boundaries approach

Life cycle assessment (LCA) is a commonly used method for assessing environmental impacts of systems, but cannot produce absolute values, i.e. a comparison with existing calculated values, which represents limits of what can be emitted into the environment. Therefore, absolute environmental sustainability assessments have been developed to assess impacts against the planetary boundaries (PBs) of the safe operating space for humanity. Since PB-LCAs are novel, it is useful to analyze both results from this method and conventional LCAs, something which has not been done before. This study applied both methods to two full-scale sanitation systems in the city of Helsingborg, Sweden. The current conventional system for handling wastewater with active sludge and food waste to biogas production was compared with the novel project H+ source separation system with three pipes (food waste, grey and black water) with increased resource recovery through anaerobic digestion, ammonia stripping, struvite precipitation and pelletization. The Planetary Boundaries LCA (PB-LCA) results showed that both systems exceeded eight of the assigned shares of PBs, including climate change and biogeochemical flows of nutrients. Traditional LCA (ReCiPe impact assessment) showed net savings for the H+ system in a few categories and considerable reductions in several impacts, e.g., global warming potential (GWP), stratospheric ozone depletion, terrestrial acidification, and water consumption. In PB-LCA the H+ system gave additional impacts in both assessments for a few categories, mostly due to high consumption of chemicals in the ammonium stripping process used for nutrient recovery. In conclusion, the combined assessments highlight hot-spots for process optimization in the H+ system. From a methodological standpoint, PB-LCA still needs improvements to better reflect avoided burdens and results from traditional LCA should be fully transparent and analyzed carefully. The assessment methods complement each other and can be combined to better represent environmental performances of systems.

Ten questions concerning prospective LCA for decision support for the built environment

It is essential to provide quantitative decision support when pursuing environmental impact mitigation efforts, particularly when considering resource and energy-demanding sectors such as the built environment. Life cycle assessment (LCA) provides widely recognized quantitative decision support regarding environmental performance. However, for long-lived products such as buildings, the usefulness of conventional LCA is limited as it relies on databases that only give a current or past representation of industrial processes. The emerging field of prospective LCA (pLCA) allows us to evaluate the results at a future point in time based on technological and socio-economic projections. This article builds on a systematic literature screening, ongoing discussions in the pLCA academic community, and hands-on experimentation with available software. The goal of the study is to 1) understand implications of how pLCA is conducted, and how it relates to the built environment; 2) Improve the documentation and credibility of pLCA and applied scenarios; And 3) identify practical tools and workflows that can make pLCA more accessible to practitioners. The study raises ten relevant questions when considering how to use pLCA for decision support in the built environment. This list of questions is not exhaustive nor definite, and recommendations are possible answers suggested by the authors. Using scenario narratives from energy and Integrated Assessment Models allows for systematic and consistent transformation of LCA databases to represent possible futures. However, there is a need for pLCA practitioners to improve documentation to ensure that the goal and scope of the LCA are compatible with the chosen future scenario. In the case of built environment, it is relevant to consider different projection years when modeling construction, operation, renovation, and demolition phases, respectively, as they span several decades. Not doing so can misestimate the effects changing socio-economic and technological contexts have on the life-cycle impact of buildings.

Research on Carbon Emission of Solar Grade Polysilicon Produced by Metallurgical Route Using Digital Simulation Technology

Under the enormous pressure of carbon reduction, we need to have a clear understanding of the environmental impact of the energy-intensive and high-emission polysilicon industry. With the rapid development of technology, we now have the ability to monitor the inflow and outflow of materials in enterprises, so as to obtain the life cycle inventory required for environmental impact assessment. And solve the problems of large data collection workload and long working cycle encountered in conventional life cycle assessment. By combining digital simulation technology and life cycle assessment, we analyze carbon dioxide (CO2) emission in each production process of 1 kg solar grade polysilicon (SoG-Si) by metallurgical route (MR) in detail. We not only analyze four typical production processes of MR, namely slag refining, hydrometallurgy, directional solidification and electron beam refining. The production process of metallurgical grade silicon is also analyzed. It is obtained that the production of 1 kg SoG-Si by MR will produce 69.77 kg CO2. The contribution analysis shows that the CO2 produced by electron beam refining, metallurgical silicon smelting, secondary directional solidification and primary directional solidification is more significant, reaching 38.47%, 20.88%, 15.84% and 14.50%, respectively. The sensitivity analysis shows that the sensitivity of electric power in the process of electron beam refining, secondary directional solidification, primary directional solidification and metallurgical silicon smelting is significant, reaching 38.47%, 15.77%, 14.45% and 13.81%, respectively. In addition, according to the analysis results, the improvement suggestions to reduce CO2 emission are given.

Scheme for generating upscaling scenarios of emerging functional materials based energy technologies in prospective LCA (UpFunMatLCA)

AbstractUpscaling scenarios are indispensable elements of prospective life cycle assessment (LCA). However, current studies reveal confusing terminology and a wide range of approaches in this area. Therefore, we first defined the term upscaling scenario as the description of a possible future target stage of emerging technology, including the development pathway from a current stage within the course of research and development to this future stage. Second, we developed the novel systematic scheme UpFunMatLCA for generating explorative scenarios based on possible development pathways of the specific group of emerging functional material (FunMat)‐based energy technologies, including status quo developments. UpFunMatLCA represents a three‐step extension of conventional LCAs to upscale the life cycle inventory of emerging FunMats. UpFunMatLCA is based on a clear definition of a current status quo (conceptual, lab, or pilot stage) and a target matured (fab) development stage. A core part of UpFunMatLCA is the so‐called upscaling module, providing specific modeling methods and data for the upscaling of FunMats. Using perovskite solar cells, photovoltaic devices based on several FunMats and attached with great expectations regarding the future efficient provision of solar energy, we demonstrate the application of UpFunMatLCA, focusing on the upstream greenhouse gas (GHG) emissions of the prospective manufacturing. In the discussion, we point out the application area of UpFunMatLCA and the possible extension to depict further environmental impacts beyond GHG to contribute to the sustainability assessment of emerging technologies in the early stages of development.

Occupant's health and energy use in an office building: A sensor-enabled life cycle assessment

Indoor air quality (IAQ) has an important impact on human health and productivity. For this reason, its integration into the life cycle assessment (LCA) framework contributes to sustainably manage the operation of a building and improve the living and working conditions in homes and offices. In this study, the damages on human health caused by IAQ are quantified starting from the air pollutants’ concentrations recorded by dedicated sensors placed in an office building located in Luxembourg. Data on concentrations of total volatile organic compounds, particulate matter and radon are combined with estimated occupancy and intake fractions to calculate the total human health impact expressed in Disability Adjusted Life Years (DALYs). The impacts of indoor air quality on human health prove to be relevant, representing one tenth of the score obtained in a conventional LCA on the operational phase of the building. It can be highlighted that radon, a substance usually overlooked in IAQ studies, had the highest impact, contributing to 46% of the impact caused by exposure to indoor pollutants. The heating loads and the influence of different air exchange rates are analyzed starting from a simplified energy model of the building fed with real energy use data. LCA has proven a useful tool to analyze this trade-off in the operation of the building, where it is found that doubling the ventilation rate would reduce the impact of indoor pollutants on human health by 34% while resulting in less than 1% increase in the total energy demand over the studied period.

Machine learning to forecast electricity hourly LCA impacts due to a dynamic electricity technology mix

Conventional Life Cycle Assessment (LCA) that relies on static coefficients is usually based on yearly averages. However, the impacts of electricity supply vary remarkably on an hourly basis. Thus, a company production plan is reassessed to reduce selected LCA impacts due to electricity consumption. To achieve this, the company will need a forecast of hourly LCA impacts due to electricity consumption, which can be directly forecast with the Direct Forecasting (DF) approach. Alternatively, the Electricity Technological Mix Forecasting (ETMF) forecasts the electricity production of the technologies in the mix and subsequently linearly combines it with unitary LCA impact indicators. Here, we assessed different machine learning models to forecast two LCA impact indicators for the consumption of electricity in the Italy-North control zone. The feed-forward neural network (NN) with the ETMF approach was the best perfomer among the assessed forecasting models. In our dataset, recurrent neural networks (RNNs) performed worse than feed-forward neural networks. Due to its better forecasting performance, the ETMF approach was preferred over the DF approach. This was due to its flexibility and scalability with easy updates or expansion of the selected forecast indicators, and due to its ability to assess technology-specific errors in the forecasting. Finally, we propose to adopt the correlation of LCA impact indicators within the dataset to select indicators while avoiding unconscious burden-shifting.

Modified life cycle assessment for Low-Noise urban roads including acoustics and monetarization

The evaluation of environmental impacts for low-noise roads is a challenging topic in life cycle assessment (LCA) due to noise reduction considerations. This paper presents hybrid modifications of conventional LCA, using acoustical pavement characterization data from the close proximity (CPX) test, and models of noise emission, propagation and exposure to incorporate the inventories and impacts of road traffic noise. Furthermore, based on the system and indicators considered in LCA, the monetarization of direct and external costs of low-noise roads was included, in order to extend environmental interpretation to a monetary perspective. The modified LCA was applied in a realistic road test section, comparing (1) traditional stone mastic asphalt (SMA) with low-noise semi-dense asphalt (SDA) surfaces, and (2) different strategies for using SDA. The results of the test section indicated the significant role of road traffic noise in human health impacts, that translate to economic benefits for using low-noise pavements.

A Comprehensive Dynamic Life Cycle Assessment Model: Considering Temporally and Spatially Dependent Variations.

Life cycle assessment (LCA) is a widely-used international environmental evaluation and management method. However, the conventional LCA is in a static context without temporal and spatial variations considered, which fails to bring accurate evaluation values and hinders practical applications. Dynamic LCA research has developed vigorously in the past decade and become a hot topic. However, systematical analysis of spatiotemporal dynamic variations and comprehensive operable dynamic models are still lacking. This study follows LCA paradigm and incorporates time- and space-dependent variations to establish a spatiotemporal dynamic LCA model. The dynamic changes are classified into four types: dynamic foreground elementary flows, dynamic background system, dynamic characterization factors, and dynamic weighting factors. Their potential dynamics and possible quantification methods are analyzed. The dynamic LCA model is applied to a residential building, and significant differences can be observed between dynamic and static assessment results from both temporal and spatial perspectives. This study makes a theoretical contribution by establishing a comprehensive dynamic model with both temporal and spatial variations involved. It is expected to provide practical values for LCA practitioners and help with decision-making and environmental management.

Dynamic LCA of the increased use of wood in buildings and its consequences: Integration of CO2 sequestration and material substitutions

Wood products can have a lower impact on climate change (CC) than other building materials, and their carbon content can transform buildings into temporary carbon sinks. However, the large-scale use of wood products in buildings requires a better understanding of their consequences to support CC policies. The consequential life cycle inventory of such products contains elementary flows with values sometimes greater sometimes less than zero. Therefore, their static assessment did not show the influence of carbon uptake and release, either during or after the temporal boundary of the system. The originality lies in the combination of the dynamic modeling of tree harvesting and growth, temporary carbon storage, end-of-life (EOL) strategies, material substitution, and characterization factors in a consequential life cycle assessment (LCA). This combination highlights the extent to which material substitution, EOL strategies, and carbon sequestration can be decisive. In addition, it addresses the static and dynamic measurements of radiative forcing (W.m−2) and the carbon dioxide (CO2) equivalent (CO2eq.). In this case study, material substitution contributed the most to result, followed by post-harvest CO2 sequestration. In terms of metrics, the conventional static LCA overestimates the long-term cumulative impact on CC (tonne CO2eq.) without providing information on the short-term impact of the case study. In addition, the assessment of such a dynamic consequential life cycle inventory (LCI) with a dynamic metric provides more specific information, regardless of the temporal boundary. However, the absolute dynamic metrics (W.m−2) should support the relative dynamic metric (tonne CO2eq.1st year) to avoid misleading conclusions.

Paving the way towards circularity in the building sector. Empa’s Sprint Unit as a beacon of swift and circular construction

In order to achieve the CO2 targets stipulated within the Paris Agreement, future buildings must be constructed in such a way, that their emission profile will be close to zero. In order to achieve this, a radical shift towards a circular construction manner which encompasses topics like material reuse (i.e. design for multiple lifecycles), design-for-disassembly (allowing for maximum recovery of materials and minimization of construction waste) must be promoted against todays, conventional construction practices. Furthermore, the current Covid-19 pandemic has shown that buildings must be constructed in a more flexible manner, in order to be adaptable to changing needs as quickly as possible – including new types of needs. A transition to such a circular construction practice requires also new approaches for Life Cycle Assessment (LCA), taking into account issues such as the circularity or multiple life cycle of materials. Conventional LCA methods fail to deliver trustworthy results as they are designed to assess products and buildings that have only a single life cycle. In this context, a newly constructed unit, set to be the embodiment of the circular construction principle that incorporates all the above-mentioned concepts in the form of a cluster of flexible office spaces, has been integrated into the research building NEST (Next Evolution in Sustainable Building Technologies) – a platform located at the Empa campus in Dübendorf (Switzerland), where novel building technologies can be tested and validated under realistic conditions. Its name: Sprint. In this paper, the environmental performance of Sprint is assessed through LCA, using three different approaches – the EN15804 method, the Product Environmental Footprint method and the Linear Degressive approach – with the latter two approaches considering the circularity of materials, while each one having an own, distinctive allocation rule for the split of the impacts between the current, the previous and the subsequent lifecycles.

Business model life cycle assessment: A method for analysing the environmental performance of business

This paper introduces business model life cycle assessment (BM-LCA), a new method for quantifying the environmental impacts of business models. Such a method is needed to guide business decisions towards decoupling economic activity from environmental impact. BM-LCA takes the business model itself as the unit of analysis and its economic performance as the basis of comparison. It can be applied to any type of business model involving material or resource use. In BM-LCA, monetary flows are coupled to material and energy flows. The methodology expands on conventional life cycle assessment (LCA) by elaborating the goal and scope definition and dividing it into two phases. The first descriptive phase details the business models to be compared. It includes a mapping of product chain actors and identifying business operations and transactions related to the product. The second coupling phase defines a profit-based functional unit and sets up the coupling equations expressing the economic relations to the product. Thereafter, conventional LCA procedures are followed to assess environmental impacts. The key innovation on LCA methodology is the development of a functional unit that captures the economic performance of a business model and links it to a product system. BM-LCA provides thus an important link between LCA and business competitive advantage.

Life-Cycle and Techno-Economic Assessment of Early-Stage Carbon Capture and Utilization Technologies—A Discussion of Current Challenges and Best Practices

The mitigation of climate change requires research, development, and deployment of new technologies that are not only economically viable but also environmentally benign. Systematic and continuous technology assessment from early technology maturity onwards allows assessment practitioners to identify economic and environmental characteristics. With this information, decision-makers can focus time and resources on the most promising technologies. A broad toolset for technology assessment exists—stretching from the well-established life cycle assessment (LCA) methodology to more loosely defined techno-economic analysis (TEA) methods and the increasingly popular principles of technology maturity assessment such as the concept of technology readiness levels (TRL). However, current technology assessment practice faces various challenges at early stages, resulting in a potential mismatch of study results and stakeholders' needs and an escalation of assessment effort. In this practice review, we outline current challenges in the interplay of LCA, TEA, and TRL and present best practices for assessing early-stage climate change mitigation technologies in the field of carbon capture and utilization (CCU). The findings help practitioners systematically identify the TRL of a technology and adapt technology assessment methodologies accordingly. We highlight the methodological challenges for practitioners when adapting the goal and scope, identifying benchmark technologies, creating a comprehensive inventory, comparing early stage to commercial stage, ensuring clarity of recommendations for decision-making under high uncertainty, and streamlining conventional LCA and TEA assessment approaches and provide actionable recommendations. Overall, this work contributes to identifying promising technologies faster and more systematically, accelerating the development of new technologies for climate change mitigation and beyond.

Towards sustainable business models with a novel life cycle assessment method

AbstractBusiness model (BM) innovation for sustainability is hampered by a lack of tools for environmental assessment and guidance at the BM level. Conventional life cycle assessment (LCA) neglects the economic and socio‐technical mechanisms within a BM, and tools based on the BM canvas (BMC) cannot provide recommendations substantiated by environmental data. Here, a new method, BM‐LCA, is applied to a case comparing the selling and renting of jackets, using profit as basis of comparison. Results identify how business parameters influence environmental performance, permitting analysis for decoupling within a business practice. This is made possible by the unique way the method links physical life cycle and the monetary flows of a BM. Usefulness of BM‐LCA is discussed relative to BM innovation, business strategy and similar tools. BM‐LCA provides insights into a broad range of BM elements and emerges as useful for business strategy. By measuring BM environmental performance, it helps determine what BM to compete with and support critical analysis of business against greenwashing. BM‐LCA also enables identification of BM elements in greatest need of environmental innovation. BM‐LCA appears as a promising tool for guiding business companies towards sustainability, filling a space between LCA and BMC. The method offers a practical way for business and LCA experts to merge their respective knowledge.

Life Cycle Assessment for Adaptive Remanufacturing: incorporating ecological considerations into the planning of maintenance activities – a case study in the German heavy machinery industry

Driven by the awareness of the global depletion of irrecoverable materials, cradle-to-cradle approaches like remanufacturing are enablers for increasing sustainability and resource efficiency in the manufacturing sector. In this context, the research project Adaptive Remanufacturing for Life Cycle Optimization of Capital Goods (ReLIFE) offers a holistic approach for a proactive, intelligent maintenance strategy with a focus on the life cycle extension of capital goods. As quantitative input to a decision-making model, Life Cycle Assessment (LCA) has been used to present comparative results between a traditional maintenance strategy and an Adaptive Remanufacturing (AdR) strategy. In contrast to conventional LCA, the contribution of this paper is on the impacts incurred by specific maintenance measures. Therefore, the scope of assessment encompasses a life cycle on measure level to model and assess long-term ecological effects. For a decision-making model created in the project, the LCA results enable plant operators to select maintenance strategies that factor in long-term ecological implications.

Exergy-Based Life Cycle Assessment of Buildings: Case Studies

The relevance of exergy to the life cycle assessment (LCA) of buildings has been studied regarding its potential to solve certain challenges in LCA, such as the characterization and valuation, accuracy of resource use, and interpretation and comparison of results. However, this potential has not been properly investigated using case studies. This study develops an exergy-based LCA method and applies it to three case-study buildings to explore its benefits. The results provide evidence that the theoretical benefits of exergy-based LCA as against a conventional LCA can be achieved. These include characterization and valuation benefits, accuracy, and enabling the comparison of environmental impacts. With the results of the exergy-based LCA method in standard metrics, there is now a mechanism for the competitive benchmarking of building sustainability assessments. It is concluded that the exergy-based life cycle assessment method has the potential to solve the characterization and valuation problems in the conventional life-cycle assessment of buildings, with local and global significance.

A climate goal–based, multicriteria method for system evaluation in life cycle assessment

Our ability to restrict global warming to the established objectives in the Paris Agreement depends on the metrics used to evaluate the climate change impact. Stemmed on the criticism of the current GWP metrics used with life cycle assessment (LCA), this study proposes new indicators and an interpretation grid for climate change impact in LCA, which are adaptive to present, short-term, and long-term climate goals. The global mean temperature change (GMTC) is used in the indicators’ definition and time parameters are introduced for a multicriteria evaluation of climate change impact. We adopt calendar-related time targets instead of a fixed time horizon. The systems are analyzed on a real-time scale and with respect to a climate-target point in time (for example, 2050 as objective for climate neutrality), in contrast with conventional LCA. The objective is to provide flexibility in system evaluation, adaptable to current and future targets. Four indicators are introduced: (1) the amplitude of the temperature change (GMTCmax), representative for climate extreme events; (2) the time at which GMTC starts to definitely decrease and its distance with respect to the goal (tlast_peak); (3) the time climate neutrality is reached and its distance with respect to the goal (tneutral); and (4) the accumulated warming until a targeted time, representative for sea-level rise and ice melting (integrated GMTC at a given time target, for example at the end of century iGMTC2100). An analysis grid is proposed based on these indicators and illustrated on 26 emission profiles involving long- and short-lived greenhouse gases with various temporalities, as well as on two dynamic LCA case studies. In the group of neutral systems, temporality is responsible for variations in GMTCmax and iGMTC2100. Increasing the frequency of emission/capture events flattens both indicators and provides the best performance. Equal CO2 emission systems are discriminated primarily by tlast_peak, while in the case of methane, more relief is observed for all indicators. The method allows for the design of tailored mitigation solutions in LCA application examples. The indicators are able to discriminate and rank systems that are considered to be non-impacting, equivalently impacting, or neutral in LCA-GWP metrics. Such metrics is necessary to correctly (avoid strong simplifications) and unambiguously (with unaltered physical parameters, closer to climate physics) evaluate the effect on climate, mitigation solutions, neutrality, and support decision-making.

Application of the absolute environmental sustainability assessment framework to multifunctional systems – The case of municipal solid waste management

The Absolute Environmental Sustainability Assessment (AESA) framework is an emerging field in environmental research that aims at comparing the estimated environmental burden generated by a system on its life cycle to the carrying capacity that can be assigned to this system, i.e. the amount of impacts that it can cause without causing unacceptable impairment of ecosystem functional integrity. This paper aims to expand the AESA framework to multifunctional systems. We applied it to a simplified case study based on municipal solid waste (MSW) management, since such a system provides several functions such as reduction of the quantity and toxicity of waste, production of heat, electricity or secondary materials. Thus, we could identify the specific questions that arise from this multifunctionality in the context of AESA.Based on the theory of AESA, we developed a four-steps methodology to identify the most significant impacts at both system and global scales. That methodology consisted of (step 1) quantifying the impacts of the studied system with conventional Life Cycle Assessment (LCA) followed by a normalisation step; (step 2) quantifying the number of beneficiaries from this system; (step 3) identifying impact categories for which the studied system causes significant impacts and global carrying capacities are exceeded; and (step 4) quantifying the Assigned Carrying Capacity (ACC) of the system, based on a utilitarian perspective and its contribution to the satisfaction of human needs.We then applied this methodology to a simplified model of the MSW management implemented in the Lyon Metropolitan Area (France), as a proof of concept. Steps 1 to 3 helped elaborate a hierarchy of impact categories, highlighting which ones should be reduced in priority. Step 4 required significant knowledge about how the functions of the studied system were used, both directly and indirectly, to satisfy human needs. We used national Supply and Use Tables and several simplifying hypotheses to that end. We also tested different sharing principles based on macroeconomic indicators. This variety of sharing principles helped refine the hierarchy developed in Step 3 by identifying which carrying capacities were most certainly exceeded by the studied system.

Environmental impacts of aquifer thermal energy storage (ATES)

Aquifer Thermal Energy Storage (ATES) is an open-loop geothermal system allowing long-term storage of thermal energy in groundwater. It is a promising technology for environmentally friendly energy generation that can reduce greenhouse gas (GHG) emissions. In the literature, there are few studies on the greenhouse gas emissions caused by ATES systems over their entire life cycle. Thus, this study presents a novel life cycle assessment (LCA) regression model that can be used for a wide range of ATES configurations due to its parametric structure. This model is a fast alternative to conventional time-consuming LCAs. Combined with a Monte Carlo simulation, it enables the analysis of the environmental impacts of a large variety of hypothetical ATES systems and therefore the evaluation of the technology as a whole. Compared to conventional heating systems based on heating oil and natural gas, the median value of the Monte Carlo simulation results in GHG savings of up to 74%. In comparison to cooling techniques using today's electricity mix, ATES can save up to about 59% of GHG emissions, while also being economically competitive. When considering a projected electricity mix for the year 2050, the GHG emission savings resulting from a second LCA regression model are as high as 97%. The findings of our sensitivity analysis show which ATES design parameters should be optimized when planning new systems. In particular, the most important design parameters operating time cooling and coefficient of performance (COP) of the heat pump should be carefully considered.