Summary
Epitaxial growth is a potential production process for the new material graphene, where it is grown on silicon carbide (SiC) wafers at high temperatures. We provide first estimates of the ...life cycle cumulative energy demand, climate change, terrestrial acidification, and eco‐toxicity of this production. For this purpose, we applied prospective life cycle assessment (LCA) for three production scenarios (lab, pilot, and an industrial scenario), which reflect different production scales and technological maturity. The functional unit was one square centimeter of graphene. Results show that the three scenarios have similar impacts, which goes against previous studies that have suggested a decrease with larger production scale and technological maturity. The reason for this result is the dominance of electricity use in the SiC wafer production for all impacts (>99% in the worst case, >76% in the best case). Only when assuming thinner SiC wafers in the industrial scenario is there a reduction in impacts by around a factor of 10. A surface‐area–based comparison to the life cycle energy use of graphene produced by chemical vapor deposition showed that epitaxial graphene was considerably more energy intensive—approximately a factor of 1,000. We recommend producers of epitaxial graphene to investigate the feasibility of thinner SiC wafers and use electricity based on wind, solar, or hydropower. The main methodological recommendation from the study is to achieve a temporal robustness of LCA studies of emerging technologies, which includes the consideration of different background systems and differences in production scale and technological maturity.
Summary
The challenge of assessing emerging technologies with life cycle assessment (LCA) has been increasingly discussed in the LCA field. In this article, we propose a definition of prospective ...LCA: An LCA is prospective when the (emerging) technology studied is in an early phase of development (e.g., small‐scale production), but the technology is modeled at a future, more‐developed phase (e.g., large‐scale production). Methodological choices in prospective LCA must be adapted to reflect this goal of assessing environmental impacts of emerging technologies, which deviates from the typical goals of conventional LCA studies. The aim of the article is to provide a number of recommendations for how to conduct such prospective assessments in a relevant manner. The recommendations are based on a detailed review of selected prospective LCA case studies, mainly from the areas of nanomaterials, biomaterials, and energy technologies. We find that it is important to include technology alternatives that are relevant for the future in prospective LCA studies. Predictive scenarios and scenario ranges are two general approaches to prospective inventory modeling of both foreground and background systems. Many different data sources are available for prospective modeling of the foreground system: scientific articles; patents; expert interviews; unpublished experimental data; and process modeling. However, we caution against temporal mismatches between foreground and background systems, and recommend that foreground and background system impacts be reported separately in order to increase the usefulness of the results in other prospective studies.
Purpose
How to assess impacts of mineral resources is much discussed in life cycle assessment (LCA). We see a need for, and a lack of, a mineral resource impact assessment method that captures the ...perspective of long-term global scarcity of elements.
Method
A midpoint-level mineral resource impact assessment method matching this perspective is proposed, called the crustal scarcity indicator (CSI), with characterization factors called crustal scarcity potentials (CSPs) measured as kg silicon equivalents per kg element. They are based on crustal concentrations, which have been suggested to correlate with several important resource metrics (reserves, reserve base, reserves plus cumulative production, and ore deposits), thereby constituting proxies for long-term global elemental scarcity.
Results and discussion
Ready-to-use CSPs are provided for 76 elements, through which the CSI can be calculated by multiplying with the respective masses of elements extracted from Earth’s crust for a certain product. As follows from their crustal concentrations, the three platinum-group metals iridium, osmium, and rhodium have the highest CSPs, whereas silicon, aluminum, and iron have the lowest CSPs.
Conclusion
An evaluation of the CSPs and the characterization factors of four other mineral resource impact assessment methods in LCA (the abiotic depletion, the surplus ore, the cumulative exergy demand, and the EPS methods) were conducted. It showed that the CSPs are temporally reliable, calculated in a consistent way, and have a high coverage of elements in comparison. Furthermore, a quantitative comparison with the characterization factors of the four other methods showed that the CSPs reflect long-term global elemental scarcity comparatively well while requiring a minimum of assumptions and input parameters.
Recommendations
We recommend using the CSI for assessments of long-term global elemental scarcity in LCA. Since the CSI is at the midpoint level, it can be complemented by other mineral resource impact assessment methods (both existing and to be developed) to provide a more comprehensive view of mineral resource impacts in an LCA.
Purpose
Life cycle assessments (LCAs) of textile products which do not include the use and emission of textile chemicals, such as dyes, softeners and water-repellent agents, will give ...non-comprehensive results for the toxicity impact potential. The purpose of this paper is twofold: (1) to provide a set of characterisation factors (CFs) for some of the most common textile chemicals and (2) to propose a data source selection strategy in order to increase transparency when calculating new CFs.
Methods
A set of 72 common textile-related substances was matched with the USEtox 2.01, USEtox 1.01 and the COSMEDE databases in order to investigate coverage and coherence. For the 25 chemicals that did not already have established CFs in any of these databases, new CFs were calculated. A data source selection strategy was developed and followed in order to ensure consistency and transparency, and USEtox 2.01 was used for calculations. The parameters that caused the most uncertainty were identified during the modelling and strategies for handling them were developed.
Results and discussion
Of the 72 textile-related substances, 48 already had calculated recommended or indicative CFs in existing databases, which showed good coherence. The main uncertainty identified during the calculation of 25 new CFs was the selection of input data regarding toxicity and degradation in water. However, for substances such as per- and polyfluoroalkyl substances (PFAS), the acid dissociation constant (pK
a
) and partitioning coefficients (
K
ow
and K
OC
) also require special considerations. Other input parameters had less than one order of magnitude impact on the CF result for essentially all substances.
Conclusions
The paper presents a strategy for how to provide a complete set of toxicity CFs for a given list of substances. In addition, such a set of CFs for common textile-related substances is presented. The data source selection strategy provides a structured and transparent way of calculating additional CFs for textile chemicals with USEtox. Consequently, this study can help future LCA studies to provide relevant guidance towards environmentally benign chemical management in the textile industry.
Rockström et al. (2009a, 2009b) have warned that humanity must reduce anthropogenic impacts defined by nine planetary boundaries if “unacceptable global change” is to be avoided. Chemical pollution ...was identified as one of those boundaries for which continued impacts could erode the resilience of ecosystems and humanity. The central concept of the planetary boundary (or boundaries) for chemical pollution (PBCP or PBCPs) is that the Earth has a finite assimilative capacity for chemical pollution, which includes persistent, as well as readily degradable chemicals released at local to regional scales, which in aggregate threaten ecosystem and human viability. The PBCP allows humanity to explicitly address the increasingly global aspects of chemical pollution throughout a chemical's life cycle and the need for a global response of internationally coordinated control measures. We submit that sufficient evidence shows stresses on ecosystem and human health at local to global scales, suggesting that conditions are transgressing the safe operating space delimited by a PBCP. As such, current local to global pollution control measures are insufficient. However, while the PBCP is an important conceptual step forward, at this point single or multiple PBCPs are challenging to operationalize due to the extremely large number of commercial chemicals or mixtures of chemicals that cause myriad adverse effects to innumerable species and ecosystems, and the complex linkages between emissions, environmental concentrations, exposures and adverse effects. As well, the normative nature of a PBCP presents challenges of negotiating pollution limits amongst societal groups with differing viewpoints. Thus, a combination of approaches is recommended as follows: develop indicators of chemical pollution, for both control and response variables, that will aid in quantifying a PBCP(s) and gauging progress towards reducing chemical pollution; develop new technologies and technical and social approaches to mitigate global chemical pollution that emphasize a preventative approach; coordinate pollution control and sustainability efforts; and facilitate implementation of multiple (and potentially decentralized) control efforts involving scientists, civil society, government, non-governmental organizations and international bodies.
•Planetary boundaries of Rockström et al. (2009) to avoid “unacceptable global change”•Boundary for chemical pollution (PBCP) reflects Earth's finite assimilative capacity.•While conceptually necessary, a PBCP is challenging to operationalize.•To meet the need of abating global pollution, four recommendations are presented.•Recommend devising new, preventative technologies and social approaches.
Purpose
Most approaches for energy use assessment in life cycle assessment do not consider the scarcity of energy resources. A few approaches consider the scarcity of fossil energy resources only. No ...approach considers the scarcity of both renewable and non-renewable energy resources. In this paper, considerations for including physical energy scarcity of both renewable and non-renewable energy resources in life cycle impact assessment (LCIA) are discussed.
Methods
We begin by discussing a number of considerations for LCIA methods for energy scarcity, such as which impacts of scarcity to consider, which energy resource types to include, which spatial resolutions to choose, and how to match with inventory data. We then suggest three LCIA methods for physical energy scarcity. As proof of concept, the use of the third LCIA method is demonstrated in a well-to-wheel assessment of eight vehicle propulsion fuels.
Results and discussion
We suggest that global potential physical scarcity can be operationalized using characterization factors based on the reciprocal physical availability for a set of nine commonly inventoried energy resource types. The three suggested LCIA methods for physical energy scarcity consider the following respective energy resource types: (i) only stock-type energy resources (natural gas, coal, crude oil and uranium), (ii) only flow-type energy resources (solar, wind, hydro, geothermal and the flow generated from biomass funds), and (iii) both stock- and flow-type resources by introducing a time horizon over which the stock-type resources are distributed. Characterization factors for these three methods are provided.
Conclusions
LCIA methods for physical energy scarcity that provide meaningful information and complement other methods are feasible and practically applicable. The characterization factors of the three suggested LCIA methods depend heavily on the aggregation level of energy resource types. Future studies may investigate how physical energy scarcity changes over time and geographical locations.
Concerns about environmental risks related to engineered nanomaterials (ENMs) have spurred research into these risks that has been ongoing since the early 2000s. There still remain a number of data ...gaps and challenges related to the production of ENMs, the release of ENMs from products, the measurement of ENMs in environmental media, the assessment of ENMs exposure to different organisms and the ecotoxicity testing of ENMs. However, an early indication might be obtained by considering the environmental risk assessments of ENMs conducted so far. In particular, a parameter called the risk characterization ratio (RCR, sometimes called risk quotient) might offer guidance.
This study presents a review of how the end-of-life (EOL) stage is modelled in life cycle assessment (LCA) studies of lithium-ion batteries (LIBs). Twenty-five peer-reviewed journal and conference ...papers that consider the whole LIB life cycle and describe their EOL modelling approach sufficiently were analyzed. The studies were categorized based on two archetypal EOL modelling approaches in LCA: The cutoff (no material recovery, possibly secondary material input) and EOL recycling (material recovery, only primary material input) approaches. It was found that 19 of the studies followed the EOL recycling approach and 6 the cutoff approach. In addition, almost a third of the studies deviated from the expected setup of the two methods by including both material recovery and secondary material input. Such hybrid approaches may lead to double counting of recycling benefits by both including secondary input (as in the cutoff approach) and substituting primary materials (as in the EOL recycling approach). If the archetypal EOL modelling approaches are not followed, it is imperative that the modelling choices are well-documented and motivated to avoid double counting that leads to over- or underestimations of the environmental impacts of LIBs. Also, 21 studies model hydrometallurgical treatment, and 17 completely omit waste collection.
A variety of hydrokinetic turbines are currently under development for power generation in rivers, tidal straits and ocean currents. Because some of these turbines are large, with rapidly moving ...rotor blades, the risk of collision with aquatic animals has been brought to attention. The behavior and fate of animals that approach such large hydrokinetic turbines have not yet been monitored at any detail. In this paper, we conduct a synthesis of the current knowledge and understanding of hydrokinetic turbine collision risks. The outcome is a generic fault tree based probabilistic model suitable for estimating population-level ecological risks. New video-based data on fish behavior in strong currents are provided and models describing fish avoidance behaviors are presented. The findings indicate low risk for small-sized fish. However, at large turbines (≥5 m), bigger fish seem to have high probability of collision, mostly because rotor detection and avoidance is difficult in low visibility. Risks can therefore be substantial for vulnerable populations of large-sized fish, which thrive in strong currents. The suggested collision risk model can be applied to different turbine designs and at a variety of locations as basis for case-specific risk assessments. The structure of the model facilitates successive model validation, refinement and application to other organism groups such as marine mammals.
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