The Circular Economy (CE) concept is receiving increasing global attention and has captivated many disciplines, from sustainability through to business and economics. There is currently a strong ...drive by companies, academics and governments alike to implement the CE. Numerous “circularity indicators” have emerged that measure material flow or recirculated value of a system (e.g. product or nation). However, if its implementation is to improve environmental performance of society, the action must be based on scientific evidence and quantification or it may risk driving “circularity for circularity's sake”. This paper, therefore, aims to review the recent circular economy literature that focuses on assessing the environmental implications of circularity of products and services. To do this we divide the system levels into micro (product level), meso (industrial estate/symbiosis) and macro (national or city level). A scoping literature review explores the assessment methods and indicators at each level.
The results suggest that few studies compare circularity indicators with environmental performance or link the circularity indicators between society levels (e.g. the micro and macro-levels). However, adequate tools exist at each level (e.g. life cycle assessment (LCA) at the micro-level and multi-regional input-output (MRIO) analysis at the macro-level) to provide the ability to adequately assess and track the CE performance if placed within a suitable framework. The challenge to connect the micro and macro-levels remains. This would help understand the link between changes at the micro-level at the macro-level, and the environmental consequences. At the meso-level, industrial symbiosis continues to grow in potential, but there is a need for further research on the assessment of its contribution to environmental improvement. In addition, there is limited understanding of the use phase. For example, national monitoring programmes do not have indicators on stocks of materials or the extent of the circular economy processes (such as the reuse economy, maintenance and spare parts) which already contribute to the CE. The societal needs/functions framework offers a promising meso-level link to bridge the micro and macro-levels for assessment, monitoring and setting thresholds.
Direct air carbon capture and storage (DACCS) is an emerging carbon dioxide removal technology, which has the potential to remove large amounts of CO2 from the atmosphere. We present a comprehensive ...life cycle assessment of different DACCS systems with low-carbon electricity and heat sources required for the CO2 capture process, both stand-alone and grid-connected system configurations. The results demonstrate negative greenhouse gas (GHG) emissions for all eight selected locations and five system layouts, with the highest GHG removal potential in countries with low-carbon electricity supply and waste heat usage (up to 97%). Autonomous system layouts prove to be a promising alternative, with a GHG removal efficiency of 79–91%, at locations with high solar irradiation to avoid the consumption of fossil fuel-based grid electricity and heat. The analysis of environmental burdens other than GHG emissions shows some trade-offs associated with CO2 removal, especially land transformation for system layouts with photovoltaics (PV) electricity supply. The sensitivity analysis reveals the importance of selecting appropriate locations for grid-coupled system layouts since the deployment of DACCS at geographic locations with CO2-intensive grid electricity mixes leads to net GHG emissions instead of GHG removal today.
A large portion of plastic produced each year is used to make single-use packaging and other short-lived consumer products that are discarded quickly, creating significant amounts of waste. It is ...important that such waste be managed appropriately in line with circular-economy principles. One option for managing plastic waste is chemical recycling via pyrolysis, which can convert it back into chemical feedstock that can then be used to manufacture virgin-quality polymers. However, given that this is an emerging technology not yet used widely in practice, it is not clear if pyrolysis of waste plastics is sustainable on a life cycle basis and how it compares to other plastics waste management options as well as to the production of virgin plastics. Therefore, this study uses life cycle assessment (LCA) to compare the environmental impacts of chemical recycling of mixed plastic waste (MPW) via pyrolysis with the established waste management alternatives: mechanical recycling and energy recovery. Three LCA studies have been carried out under three perspectives: waste, product and a combination of the two. To ensure robust comparisons, the impacts have been estimated using two impact assessment methods: Environmental footprint and ReCiPe. The results suggest that chemical recycling via pyrolysis has a 50% lower climate change impact and life cycle energy use than the energy recovery option. The climate change impact and energy use of pyrolysis and mechanical recycling of MPW are similar if the quality of the recyclate is taken into account. Furthermore, MPW recycled by pyrolysis has a significantly lower climate change impact (−0.45 vs 1.89 t CO2 eq./t plastic) than the equivalent made from virgin fossil resources. However, pyrolysis has significantly higher other impacts than mechanical recycling, energy recovery and production of virgin plastics. Sensitivity analyses show that some assumptions have notable effects on the results, including the assumed geographical region and its energy mix, carbon conversion efficiency of pyrolysis and recyclate quality. These results will be of interest to the chemical, plastics and waste industries, as well as to policy makers.
Display omitted
•Pyrolysis of mixed plastic waste (MPW) emits 50% less CO2 eq. than energy recovery.•Chemically recycled plastic generates 2.3 t CO2 eq./t less than the virgin plastic.•The global warming potentials of pyrolysis and mechanical recycling are comparable.•Pyrolysis has significantly higher other impacts than the alternatives considered.•Results are sensitive to assumptions on location, energy mix and recyclate quality.
Food supply chains are increasingly associated with environmental and socio-economic impacts. An increasing global population, an evolution in consumers' needs, and changes in consumption models pose ...serious challenges to the overall sustainability of food production and consumption. Life cycle thinking (LCT) and assessment (LCA) are key elements in identifying more sustainable solutions for global food challenges. In defining solutions to major global challenges, it is fundamentally important to avoid burden shifting amongst supply chain stages and amongst typologies of impacts, and LCA should, therefore, be regarded as a reference method for the assessment of agri-food supply chains. Hence, this special volume has been prepared to present the role of life cycle thinking and life cycle assessment in: i) the identification of hotspots of impacts along food supply chains with a focus on major global challenges; ii) food supply chain optimisation (e.g. productivity increase, food loss reduction, etc.) that delivers sustainable solutions; and iii) assessment of future scenarios arising from both technological improvements and behavioural changes, and under different environmental conditions (e.g. climate change). This special volume consists of a collection of papers from a conference organized within the last Universal Exposition (EXPO2015) “LCA for Feeding the planet and energy for life” in Milan (Italy) in 2015 as well as other contributions that were submitted in the year after the conference that addressed the same key challenges presented at the conference. The papers in the special volume address some of the key challenges for optimizing food-related supply chains by using LCA as a reference method for environmental impact assessment. Beyond specific methodological improvements to better tailor LCA studies to food systems, there is a clear need for the LCA community to “think outside the box”, exploring complementarity with other methods and domains. The concepts and the case studies presented in this special volume demonstrate how cross-fertilization among difference science domains (such as environmental, technological, social and economic ones) may be key elements of a sustainable “today and tomorrow” for feeding the planet.
•Life cycle thinking represents a reference method for assessing agro-food supply chains.•LCA should be improved towards better assessing sustainability questions related to food systems.•This special volume illustrates challenges and pathways for improving food supply chains.•Food waste management, nutrient recovery, and resource efficiency are at the hearth of sustainability of food systems.•Complementing LCA with other methods and scientific domains is more and more needed.
PURPOSE: This paper uses a dynamic life cycle assessment (DLCA) approach and illustrates the potential importance of the method using a simplified case study of an institutional building. Previous ...life cycle assessment (LCA) studies have consistently found that energy consumption in the use phase of a building is dominant in most environmental impact categories. Due to the long life span of buildings and potential for changes in usage patterns over time, a shift toward DLCA has been suggested. METHODS: We define DLCA as an approach to LCA which explicitly incorporates dynamic process modeling in the context of temporal and spatial variations in the surrounding industrial and environmental systems. A simplified mathematical model is used to incorporate dynamic information from the case study building, temporally explicit sources of life cycle inventory data and temporally explicit life cycle impact assessment characterization factors, where available. The DLCA model was evaluated for the historical and projected future environmental impacts of an existing institutional building, with additional scenario development for sensitivity and uncertainty analysis of future impacts. RESULTS AND DISCUSSION: Results showed that overall life cycle impacts varied greatly in some categories when compared to static LCA results, generated from the temporal perspective of either the building's initial construction or its recent renovation. From the initial construction perspective, impacts in categories related to criteria air pollutants were reduced by more than 50 % when compared to a static LCA, even though nonrenewable energy use increased by 15 %. Pollution controls were a major reason for these reductions. In the future scenario analysis, the baseline DLCA scenario showed a decrease in all impact categories compared with the static LCA. The outer bounds of the sensitivity analysis varied from slightly higher to strongly lower than the static results, indicating the general robustness of the decline across the scenarios. CONCLUSIONS: These findings support the use of dynamic modeling in life cycle assessment to increase the relevance of results. In some cases, decision making related to building design and operations may be affected by considering the interaction of temporally explicit information in multiple steps of the LCA. The DLCA results suggest that in some cases, changes during a building's lifetime can influence the LCA results to a greater degree than the material and construction phases. Adapting LCA to a more dynamic approach may increase the usefulness of the method in assessing the performance of buildings and other complex systems in the built environment.
The developing agri-food sector significantly boosts food production and plays a crucial role in resolving the global food crisis. This development is valuable when accompanied by environmental ...sustainability. The indiscriminate use of fossil energy sources in these industries has raised serious environmental concerns in recent years. As a result, researchers have explored the substitution of renewable energies, particularly solar energy, as a means of resource conservation. However, concerns about the environmental effects of solar technology establishment have prompted investigations into their environmental footprints. Life cycle assessment (LCA) has emerged as a valuable tool for systematically evaluating the potential environmental impacts of solar energy. Furthermore, combining LCA with exergetic analysis as the main tool for assessing energy utilization can help identify the most sustainable scenarios. In this context, the present study provides a systematic and comprehensive review and critical discussion of the environmental LCA and exergetic analysis of applied solar technologies in the agri-food sector. The study first introduces all the utilized technologies in detail. It then discusses the principles, steps, and methods of LCA and exergetic analysis employed by researchers. Based on the analysis of 116 considered studies, it is concluded that photovoltaic (PV), photovoltaic/thermal (PV/T), and concentrated solar power systems (CSP) are the leading solar technologies in the agri-food sector. The study further concludes that PV systems are the most exergoenvironmentally friendly among all solar systems, while the CSP system exhibits favorable characteristics compared to PV/T, particularly from the perspective of LCA.
•Three hydrocarbon-based ethylene production routes’ performances were studied.•Foreground processes of three routes were modeled by integrating COSILSIM1D and Aspen Plus.•A framework integrating ...LCA, exergetic LCA, and life cycle costing was constructed.•Sensitivity analysis of mass ratios of feedstocks on different categories was carried out.
Currently and in the foreseeable future, steam cracking with sequential cryogenic separation, steam cracking with de-ethanization cryogenic separation (SC-DES), and steam cracking with de-propanization cryogenic separation are the primary ethylene production routes in China. In the era of carbon peaking and carbon neutrality, academia and industry focus on the high-quality development of manufacturing. In this study, a general framework integrating life cycle assessment (LCA), exergetic life cycle assessment (ELCA), and life cycle costing (LCC) was constructed to compare the comprehensive performance of three routes systematically. Furthermore, the model of the foreground process was developed by COILSIMID and Aspen Plus with two typical cracking feedstocks, naphtha and LPG. Based on these, eleven significant indicators from the LCA, ELCA, and LCC integrating framework were calculated to reflect the production performance from environmental, exergetic, and economic perspectives in three ethylene production routes. The results indicated that the overall categories of the SC-DES route are better than the other two routes, but a few indicators lack competitiveness. Since no route showed excellent performance in all indicators, it was not easy to declare that a certain path has the best sustainable performance. However, decision-makers can utilize the obtained results to make optimal decisions beneficial to industrial ethylene production.
On the basis of a review of existing life cycle assessment studies on lithium‐ion battery recycling, we parametrize process models of state‐of‐the‐art pyrometallurgical and hydrometallurgical ...recycling, enabling their application to different cell chemistries, including beyond‐lithium batteries such as sodium‐ion batteries. These processes are used as benchmark for evaluating an advanced hydrometallurgical recycling process, which is modeled on the basis of primary data obtained from a recycling company, quantifying the potential reduction of environmental impacts that can be achieved by the recycling of different cell chemistries. Depending on the cell chemistry, recycling can reduce significantly the potential environmental impacts of battery production. The highest benefit is obtained via advanced hydrometallurgical treatment for lithium nickel manganese cobalt oxide and lithium nickel cobalt aluminum oxide‐type batteries, mainly because of the recovery of cobalt and nickel. Especially under resource depletion aspects, recycling of these cells can reduce their impact to an extent that even leads to a lower “net impact” than that of cells made from majorly abundant and cheap materials like lithium iron phosphate, which shows a more favorable performance when recycling is disregarded. For these cells, recycling does not necessarily provide benefits but can rather cause additional environmental impacts. This indicates that maximum material recovery might not always be favorable under environmental aspects and that, especially for the final hydrometallurgical treatment, the process would need to be adapted to the specific cell chemistry, if one wants to obtain maximum environmental benefit.
In comparative life cycle assessment (LCA) studies of materials, there is a mismatch between the current practice and existing guidelines regarding functional unit definition. The purpose of this ...study is to develop a practice‐based framework for defining functional units in comparative LCAs of materials and provide guidance regarding in which situations different functional unit types are relevant. A literature review of comparative LCAs of materials identified three types of functional units: (i) the reference flow functional unit, (ii) the property functional unit, and (iii) the performance functional unit. These functional unit types, of which only the latter strictly complies with LCA guidelines, represent varying degrees of functional equivalence and technological maturity. The most relevant functional unit type depends on the goal of the study. We suggest that screening assessments of whether materials have comparable environmental impacts can apply reference flow functional units. Material comparisons for certain application areas with some important properties can apply property functional units. For comparisons of end products, performance functional units can be applied. However, even in such cases, complete functional equivalence can hardly be achieved due to more or less relevant product differences. The applicability of the framework is demonstrated for the case of comparing cemented carbide and polycrystalline diamond hard materials.
PDF
