Uncovering the Fate of Critical Metals: Tracking Dissipative Losses along the Product Life Cycle

An increasing number of elements from the periodic table are being used in a growing number of products, enabling new material and product functionalities. Materials of high importance and high supply risks are usually referred to as critical materials. Many materials that are often considered critical are used in ways leading to their dissipative loss along the product life cycle. So far, the issue of material dissipation has been dealt with mainly on a rather aggregated level. Detailed knowledge on the occurrence and amount of dissipative losses in the life cycle of specific products is only scarcely available. Addressing this, a substance flow analysis of different critical metals along the life cycle of selected products is presented in this article. With regard to products used in Germany, the flows of indium and gallium used in copper‐indium‐gallium‐selenide (CIGS) photovoltaic cells, germanium used in polymerization catalysts, and yttrium used in thermal barrier coatings (TBCs) have been analyzed. The results comprise detailed knowledge about the life cycle stages in which dissipative losses occur and about the receiving media. In all case studies, a complete or almost complete dissipative loss can be observed, mainly to landfills and other material flows. In all case studies, material production can be identified as hotspots for dissipative losses. In two case studies fabrication and manufacturing (F&M for CIGS and TBCs) and in one case study end of life (polymerization catalysts) can be identified as further hotspots for dissipative losses. In addition, actions for reducing dissipation along the life cycle are discussed, targeting aspects such as the recovery of critical metals as by‐products, efficiency in F&M processes, and lack of recycling processes. Lack of economic incentives to apply more‐efficient technologies and processes already available is a key aspect in this regard.     

Global Life Cycle Paper Flows,Recycling Metrics,and Material Efficiency

Despite major improvements in recycling over the last decades, the pulp and paper sector is a significant contributor to global greenhouse gas emissions and other environmental pressures. Further reduction of virgin material requirements and environmental impacts requires a detailed understanding of the global material flows in paper production and consumption. This study constructs a Sankey diagram of global material flows in the paper life cycle, from primary inputs to end‐of‐life waste treatment, based on a review of publicly available data. It then analyzes potential improvements in material flows and discusses recycling and material efficiency metrics. The article argues that the use of the collection rate as a recycling metric does not directly stimulate avoidance of virgin inputs and associated impacts. An alternative metric compares paper for recycling (recovered paper) with total fibrous inputs and indicates that the current rate is at just over half of the technical potential. Material efficiency metrics are found to be more useful if they relate to the reuse potential of wastes. The material balance developed in this research provides a solid basis for further study of global sustainable production and consumption of paper. The conclusions on recycling and efficiency should be considered for improving environmental assessment and stimulating a shift toward resource efficiency and the circular economy.     

Revisiting the Role of Conductivity and Polarity of Host Materials for Long‐Life Lithium–Sulfur Battery

Despite their high theoretical energy density and low cost, lithium–sulfur batteries (LSBs) suffer from poor cycle life and low energy efficiency owing to the polysulfides shuttle and the electronic insulating nature of sulfur. Conductivity and polarity are two critical parameters for the search of optimal sulfur host materials. However, their role in immobilizing polysulfides and enhancing redox kinetics for long‐life LSBs are not fully understood. This work has conducted an evaluation on the role of polarity over conductivity by using a polar but nonconductive platelet ordered mesoporous silica (pOMS) and its replica platelet ordered mesoporous carbon (pOMC), which is conductive but nonpolar. It is found that the polar pOMS/S cathode with a sulfur mass fraction of 80 wt% demonstrates outstanding long‐term cycle stability for 2000 cycles even at a high current density of 2C. Furthermore, the pOMS/S cathode with a high sulfur loading of 6.5 mg cm^?2 illustrates high areal and volumetric capacities with high capacity retention. Complementary physical and electrochemical probes clearly show that surface polarity and structure are more dominant factors for sulfur utilization efficiency and long‐life, while the conductivity can be compensated by the conductive agent involved as a required electrode material during electrode preparation. The present findings shed new light on the design principles of sulfur hosts towards long‐life and highly efficient LSBs.     

A Methodical Approach for Systematic Life Cycle Assessment of Wood‐Based Furniture

Existing life cycle assessment (LCA) studies for furniture focus on single pieces of furniture and use a bottom‐up approach based on their bill of materials (BOM) to build up the data inventories. This approach does not ensure completeness regarding material and energy fluxes and representativeness regarding the product portfolio. Integrating material and energy fluxes collected at company level into product LCA (top‐down approach) over‐rides this drawback. This article presents a method for systematic LCA of industrially produced furniture that merges the top‐down approach and bottom‐up approach. The developed method assigns data collected at the company level to the different products while, at the same time, considering that wood‐based furniture is a complex product. Hence, several classifications to reduce the complexity to a manageable level have been developed. Simultaneously, a systematic calculation routine was established. The practical implementation of the developed method for systematic LCA is carried out in a case study within the German furniture industry. The system boundary was set in accord with the EN 15804 specification cradle‐to‐gate‐with‐options. The analysis therefore includes the manufacturing phase supplemented by an end‐of‐life scenario. The case study shows that the manufacturing of semifinished products (especially wood‐based panels and metal components) as well as the electric energy demand in furniture manufacturing account for a notable share of the environmental impacts. A sensitivity analysis indicates that up to roughly 10% of the greenhouse gas emissions are not recorded when conducting an LCA based on a BOM instead of applying the developed approach.     

Economy‐wide Material Flow Indicators on a Sectoral Level and Strategies for Decreasing Material Inputs of Sectors

The article presents a method for the calculation of selected economy‐wide material flow indicators (namely, direct material input [DMI] and raw material input [RMI]) for economic sectors. Whereas sectoral DMI was calculated using direct data from statistics, we applied a concept of total flows and a hybrid input‐output life cycle assessment method to calculate sectoral RMI. We calculated the indicators for the Czech Republic for 2000–2011. We argue that DMI of economic sectors can be used for policies aiming at decreasing the direct input of extracted raw materials, and imported raw materials and products, whereas sectoral RMI can be better used for justifying support for or weakening the role of individual sectors within the economy. High‐input material flows are associated in the Czech Republic with the extractive industries (agriculture and forestry, the mining of fossil fuels [FFs], other types of mining, and quarrying), with several manufacturing industries (manufacturing of beverages, basic metals, motor vehicles or electricity, and gas and steam supply) and with construction. Viable options for reducing inputs of agricultural biomass include changes in people's diet toward a lower amount of animal‐based food and a decrease in the wasting of food. For FFs, one should think of changing the structure of total primary energy supply toward cleaner gaseous and renewable energy sources, innovations in transportation systems, and improvements in overall energy efficiency. For metal ores, viable options include technological changes leading to smaller and lighter products, as well as consistent recycling and use of secondary metals.     

Combining Material Flow Analysis,Life Cycle Assessment,and Multiattribute Utility Theory

Three assessment methods, material flow analysis (MFA), life cycle analysis (LCA), and multiattribute utility theory (MAUT) are systematically combined for supporting the choice of best end‐of‐life scenarios for polyethylene terephthalate (PET) waste in a municipality of a developing country. MFA analyzes the material and energy balance of a firm, a region, or a nation, identifying the most relevant processes; LCA evaluates multiple environmental impacts of a product or a service from cradle to grave; and MAUT allows for inclusion of other aspects along with the ecological ones in the assessment. We first systematically coupled MFA and LCA by defining “the service offered by the total PET used during one year in the region” as the functional unit. Inventory and impacts were calculated by multiplying MFA flows with LCA impacts per kilogram. We used MAUT to include social and economic aspects in the assessment. To integrate the subjective point of view of stakeholders in the MAUT, we normalized the environmental, social, and economic variables with respect to the magnitude of overall impacts or benefits in the country. The results show large benefits for recycling scenarios from all points of view and also provide information about waste treatment optimization. The combination of the three assessment methods offers a powerful integrative assessment of impacts and benefits. Further research should focus on data collection methods to easily determine relevant material flows. LCA impact factors specific to Colombia should be developed, as well as more reliable social indicators.     

Consumption‐based Material Flow Accounting

In 2007, imports accounted for approximately 34% of the material input (domestic extraction and imports) into the Austrian economy and almost 60% of the GDP stemmed from exports. Upstream material inputs into the production of traded goods, however, are not yet included in the standard framework of material flow accounting (MFA). We have reviewed different approaches accounting for these upstream material inputs, or raw material equivalents (RME), positioning them in a wider debate about consumption‐based perspectives in environmental accounting. For the period 1995–2007, we calculated annual RME of Austria's trade and consumption applying a hybrid approach. For exports and competitive imports, we used an environmentally extended input‐output model of the Austrian economy, based on annual supply and use tables and MFA data. For noncompetitive imports, coefficients for upstream material inputs were extracted from life cycle inventories. The RME of Austria's imports and exports were approximately three times larger than the trade flows themselves. In 2007, Austria's raw material consumption was 30 million tonnes or 15% higher than its domestic material consumption. We discuss the material composition of these flows and their temporal dynamics. Our results demonstrate the need for a consumption‐based perspective in MFA to provide robust indicators for dematerialization and resource efficiency analysis of open economies.     

Model for the Part Manufacturing and Vehicle Assembly Component of the Vehicle Life Cycle Inventory

A model is presented for calculating the environmental burdens of the part manufacturing and vehicle assembly (VMA) stage of the vehicle life cycle. The model is based on a process‐level approach, accounting for all significant materials by their transformation processes (aluminum castings, polyethylene blow molding; etc.) and plant operation activities (painting; heating, ventilation, and air conditioning [HVAC], etc.) germane to VMA. Using quantitative results for these material/transformation process pairings, a percent‐by‐weight material/transformation distribution (MTD) function was developed that permits the model to be applied to a range of vehicles, both conventional and advanced (e.g., hybrid electric, light weight, aluminum intensive). Upon consolidation of all inputs, the model reduces to two terms: one proportional to vehicle mass and a plant overhead per vehicle term. When the model is applied to a materially well‐characterized conventional vehicle, reliable estimates of cumulative energy consumption (34 gigajoules/vehicle) and carbon dioxide (CO₂) emissions (2 tonnes/vehicle) with coefficients of variation are computed for the VMA life cycle stage. Due to the more comprehensive coverage of manufacturing operations, our energy estimates are on the higher end of previously published values. Nonetheless, they are still somewhat underestimated due to a lack of data on overhead operations in part manufacturing facilities and transportation of parts and materials between suppliers and vehicle manufacturing operations. For advanced vehicles, the material/transformation process distribution developed above needs some adjusting for different materials and components. Overall, energy use and CO₂ emissions from the VMA stage are about 3.5% to 4.5% of total life cycle values for vehicles.     

A Stochastic Approach to Model Dynamic Systems in Life Cycle Assessment

This article presents a framework to evaluate emerging systems in life cycle assessment (LCA). Current LCA methods are effective for established systems; however, lack of data often inhibits robust analysis of future products or processes that may benefit the most from life cycle information. In many cases the life cycle inventory (LCI) of a system can change depending on its development pathway. Modeling emerging systems allows insights into probable trends and a greater understanding of the effect of future scenarios on LCA results. The proposed framework uses Bayesian probabilities to model technology adoption. The method presents a unique approach to modeling system evolution and can be used independently or within the context of an agent‐based model (ABM). LCA can be made more robust and dynamic by using this framework to couple scenario modeling with life cycle data, analyzing the effect of decision‐making patterns over time. Potential uses include examining the changing urban metabolism of growing cities, understanding the development of renewable energy technologies, identifying transformations in material flows over space and time, and forecasting industrial networks for developing products. A switchgrass‐to‐energy case demonstrates the approach.     

Tracking Construction Material over Space and Time: Prospective and Geo‐referenced Modeling of Building Stocks and Construction Material Flows

Construction material plays an increasingly important role in the environmental impacts of buildings. In order to investigate impacts of materials on a building level, we present a bottom‐up building stock model that uses three‐dimensional and geo‐referenced building data to determine volumetric information of material stocks in Swiss residential buildings. We used a probabilistic modeling approach to calculate future material flows for the individual buildings. We investigated six scenarios with different assumptions concerning per‐capita floor area, building stock turnover, and construction material. The Swiss building stock will undergo important structural changes by 2035. While this will lead to a reduced number in new constructions, material flows will increase. Total material inflow decreases by almost half while outflows double. In 2055, the total amount of material in‐ and outflows are almost equal, which represents an important opportunity to close construction material cycles. Total environmental impacts due to production and disposal of construction material remain relatively stable over time. The cumulated impact is slightly reduced for the wood‐based scenario. The scenario with more insulation material leads to slightly higher material‐related emissions. An increase in per‐capita floor area or material turnover will lead to a considerable increase in impacts. The new modeling approach overcomes the limitations of previous bottom‐up building models and allows for investigating building material flows and stocks in space and time. This supports the development of tailored strategies to reduce the material footprint and environmental impacts of buildings and settlements.     

Urban development and sustainability challenges chronicled by a century of construction material flows and stocks in Tiexi,China

Construction materials are considerable forces of global environmental impacts, but their dynamics vis‐à‐vis urban development are poorly documented, in part because their long lifespans require elusive and sometimes nonexistent decade‐long high‐resolution data. This study analyzes the construction material flow and stock trends that shaped and were shaped by the development, decline, and renewal of the Tiexi district of Shenyang, a microcosm of China's urban transformations since the early 20th century. Chronicling building‐by‐building the material flows and stock accumulations involved in the buildup of this area, we shed light on the physical resource context of its socioeconomic history. We find that 42 million tonnes of construction materials were needed to develop the Tiexi district from 1910 to 2018, and 18 million tonnes of material outflows were generated by end‐of‐life building demolition. However, over 55% of inflows and 93% of outflows occurred since 2002 during a complete redevelopment of the district. Only small portions of end‐of‐life materials could have been reused or recycled because of temporal and typological mismatches of supply and demand and technical limitations. Our analysis reveals a dramatic decrease in median building lifetimes to as low as 6 years in the early 21st century. These findings contribute to the discussion of long‐term environmental efficiency and sustainability of societal development through construction and reflect on the challenges of urban renewal processes not only in China but also in other developing and developed countries that lost (or may lose) their traditional economic base and restructure their urban forms. This article met the requirements for a Silver/Silver JIE data openness badge described at http://jie.click/badges .     

Assessing Socioeconomic Metabolism Through Hybrid Life Cycle Assessment

This article applies a combined input−output and life cycle inventory (LCI) method to the calculation of emissions and material requirements of the Czech economy in 2003. The main focus is on materials and emissions embodied in the international trade of the Czech Republic. Emissions and material extraction avoided due to imports are calculated according to an input−output approach that assumes the same production technology for imports as for domestic production. Because not all products are provided by the domestic economy, the LCI data are incorporated into the monetary input−output model.
The results show that incorporating the LCI data into an input−output model is reasonable. The emissions embodied in the international trade of the Czech Republic are comparable to the domestic emissions. We compare the economy-wide material flow indicators, such as direct material input, domestic material consumption, and physical trade balance, to their raw material equivalents. The results of our calculation show that the Czech Republic exerts environmental pressure on the environment in other countries through international trade.
We argue that raw material equivalents should be used to express the flows across national boundaries. Furthermore, we recommend a raw material consumption indicator for international comparisons.     

Integrated Life Cycle Assessment and Life Cycle Cost Model for Comparing Plug‐in versus Wireless Charging for an Electric Bus System

An integrated life cycle assessment and life cycle cost (LCC) model was developed to compare the life cycle performance of plug‐in charging versus wireless charging for an electric bus system. The model was based on a bus system simulation using existing transit bus routes in the Ann Arbor–Ypsilanti metro area in Michigan. The objective is to evaluate the LCCs for an all‐electric bus system utilizing either plug‐in or wireless charging and also compare these costs to both conventional pure diesel and hybrid bus systems. Despite a higher initial infrastructure investment for off‐board wireless chargers deployed across the service region, the wireless charging bus system has the lowest LCC of US$0.99 per bus‐kilometer among the four systems and has the potential to reduce use‐phase carbon emissions attributable to the lightweighting benefits of on‐board battery downsizing compared to plug‐in charging. Further uncertainty analysis and sensitivity analysis indicate that the unit price of battery pack and day or night electricity price are key parameters in differentiating the LCCs between plug‐in and wireless charging. Additionally, scenario analyses on battery recycling, carbon emission pricing, and discount rates were conducted to further analyze and compare their respective life cycle performance.     

Life Cycle Impacts and Benefits of Wood along the Value Chain: The Case of Switzerland

Sustainable use of wood may contribute to coping with energy and material resource challenges. The goal of this study is to increase knowledge of the environmental effects of wood use by analyzing the complete value chain of all wooden goods produced or consumed in Switzerland. We start from a material flow analysis of current wood use in Switzerland. Environmental impacts related to the material flows are evaluated using life cycle assessment–based environmental indicators. Regarding climate change, we find an overall average benefit of 0.5 tonnes carbon dioxide equivalent per cubic meter of wood used. High environmental benefits are often achieved when replacing conventional heat production and energy‐consuming materials in construction and furniture. The environmental performance of wood is, however, highly dependent on its use and environmental indicators. To exploit the mitigation potential of wood, we recommend to (1) apply its use where there are high substitution benefits like the replacement of fossil fuels for energy or energy‐intensive building materials, (2) take appropriate measures to minimize negative effects like particulate matter emissions, and (3) keep a systems perspective to weigh effects like substitution and cascading against each other in a comprehensive manner. The results can provide guidance for further in‐depth studies and prospective analyses of wood‐use scenarios.     

Emergy as a Life Cycle Impact Assessment Indicator

Founded in thermodynamics and systems ecology, emergy evaluation is a method to associate a product with its dependencies on all upstream environmental and resource flows using a common unit of energy. Emergy is thus proposed as an indicator of aggregate resource use for life cycle assessment (LCA). An LCA of gold mining, based on an original life cycle inventory of a large gold mine in Peru, is used to demonstrate how emergy can be incorporated as an impact indicator into a process‐based LCA model. The results demonstrate the usefulness of emergy in the LCA context. The adaptation of emergy evaluation, traditionally performed outside of the LCA framework, requires changes to the conventional accounting rules and the incorporation of uncertainty estimations of the emergy conversion factors, or unit emergy values. At the same time, traditional LCA boundaries are extended to incorporate the environmental processes that provide for raw resources, including ores. The total environmental contribution to the product, doré, is dominated by mining and metallurgical processes and not the geological processes forming the gold ore. The measure of environmental contribution to 1 gram (g) of doré is 6.8E + 12 solar‐equivalent Joules (sej) and can be considered accurate within a factor of 2. These results are useful in assessing a process in light of available resources, which is essential to measuring long‐term sustainability. Comparisons are made between emergy and other measures of resource use, and recommendations are made for future incorporation of emergy into LCA that will result in greater consistency with existing life cycle inventory (LCI) databases and other LCA indicators.     

Impact of Updated Material Production Data in the GREET Life Cycle Model

The Greenhouse gases, Regulated Emissions, and Energy use in Transportation (GREET) model developed by Argonne National Laboratory quantifies the life cycle energy consumption and air emissions resulting from the production and use of light‐duty vehicles in the United States. GREET is comprised of two components: GREET 1 represents the fuel cycle of various energy carriers, including automotive fuels, and GREET 2 represents the vehicle cycle, which accounts for the production of vehicles and their constituent materials. The GREET model was updated in 2012 and now includes higher‐resolution material processing and transformation data. This study evaluated how model updates influence material and vehicle life cycle results. First, new primary energy demand and greenhouse gas (GHG) emissions results from GREET 2 for steel, aluminum, and plastics resins are compared herein with those from the previous version of the model as well as industrial results. A part of the comparison is a discussion about causes of differences between results. Included in this discussion is an assessment of the impact of the new material production data on vehicle life cycle results for conventional internal combustion engine (ICE) vehicles by comparing the energy and GHG emission values in the updated and previous versions of GREET 2. Finally, results from a sensitivity analysis are presented for identifying life cycle parameters that most affect vehicle life cycle estimates.     

An Improved Li–SeS2 Battery with High Energy Density and Long Cycle Life

Selenium–sulfur solid solutions are a class of potential cathode materials for high energy batteries, since they have higher theoretical capacities than selenium and improved conductivity over sulfur. Here, a high‐performance cathode material by confining 70 wt% of SeS₂ in a highly ordered mesoporous carbon (CMK‐3) framework with a polydopamine (PDA) protection sheath for novel Li–Se/S batteries is reported. With a relatively high SeS₂ mass loading of 2.6–3 mg cm^?2, the CMK‐3/SeS₂@PDA cathode exhibits a high capacity of >1200 mA h g^?1 at 0.2 A g^?1, excellent C‐rate capability of 535 mA h g^?1 at 5 A g^?1, and prolonged life over 500 cycles. Benefitting from the unique advantages of SeS₂ and the rationally designed host framework, this new cathode material demonstrates a feasible strategy to overcome the bottlenecks of current Li–S systems for high energy density rechargeable batteries.     

Development of Dopant‐Free Organic Hole Transporting Materials for Perovskite Solar Cells

There has been considerable progress over the last decade in development of the perovskite solar cells (PSCs), with reported performances now surpassing 25.2% power conversion efficiency. Both long‐term stability and component costs of PSCs remain to be addressed by the research community, using hole transporting materials (HTMs) such as 2,2′,7,7′‐tetrakis(N,N′‐di‐pmethoxyphenylamino)‐9,9′‐spirbiuorene(Spiro‐OMeTAD) and poly[bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine] (PTAA). HTMs are essential for high‐performance PSC devices. Although effective, these materials require a relatively high degree of doping with additives to improve charge mobility and interlayer/substrate compatibility, introducing doping‐induced stability issues with these HTMs, and further, additional costs and experimental complexity associated with using these doped materials. This article reviews dopant‐free organic HTMs for PSCs, outlining reports of structures with promising properties toward achieving low‐cost, effective, and scalable materials for devices with long‐term stability. It summarizes recent literature reports on non‐doped, alternative, and more stable HTMs used in PSCs as essential components for high‐efficiency cells, categorizing HTMs as reported for different PSC architectures in addition to use of dopant‐free small molecular and polymeric HTMs. Finally, an outlook and critical assessment of dopant‐free organic HTMs toward commercial application and insight into the development of stable PSC devices is provided.     

Differential Influence of Life Cycle on Growth and Toxin Production of three Pseudo‐nitzschia Species (Bacillariophyceae)

We used a multistrain approach to study the intra‐ and interspecific variability of the growth rates of three Pseudo‐nitzschia species – P. australis, P. fraudulenta, and P. pungens – and of their domoic acid (DA) production. We carried out mating and batch experiments to investigate the respective effects of strain age and cell size, and thus the influence of their life cycle on the physiology of these species. The cell size – life cycle relationship was characteristic of each species. The influence of age and cell size on the intraspecific variability of growth rates suggests that these characteristics should be considered cautiously for the strains used in physiological studies on Pseudo‐nitzschia species. The results from all three species do not support the hypothesis of a decrease in DA production with time since isolation from natural populations. In P. australis, the cellular DA content was rather a function of cell size. More particularly, cells at the gametangia stage of their life cycle contained up to six times more DA than smaller or larger cells incapable of sexual reproduction. These findings reveal a link between P. australis life cycle and cell toxicity. This suggest that life cycle dynamics in Pseudo‐nitzschia natural populations may influence bloom toxicity.