Graphene and its derivatives are heralded as “miracle” materials with manifold applications in different sectors of society from electronics to energy storage to medicine. The increasing exploitation of graphene-based materials (GBMs) necessitates a comprehensive evaluation of the potential impact of these materials on human health and the environment. Here, we discuss synthesis and characterization of GBMs as well as human and environmental hazard assessment of GBMs using in vitro and in vivo model systems with the aim to understand the properties that underlie the biological effects of these materials; not all GBMs are alike, and it is essential that we disentangle the structure–activity relationships for this class of materials.

No abstract

This study proposes a method to estimate the appropriability of renewable energy resources at the global scale, when Earth system boundaries/needs and the human demand for chemical energy are respected. The method is based on an engineering approach, i.e., uncertainties of parameters and models are considered and potentials calculated with 99% confidence. We used literature data to test our method and provide initial results for global appropriable technical potentials (ATP) that sum up to 71 TW, which is significantly larger than the current global energy demand. Consequently, there is sufficient renewable energy potentially available to increase energy access for a growing world population as well as for a development towards increasingly closed material cycles within the technosphere. Solar energy collected on the built environment (29%) and in desert areas (69%) represent the dominant part of this potential, followed in great distance by hydro (0.6%), terrestrial heat (0.4%), wind (0.35%), and biomass (0.2%). Furthermore, we propose indicators to evaluate an energy mix on different levels, from an energy mix in single products to the mix used by the global economy, against the estimated RE potentials, which allow an evaluation and consideration in the design of sustainable-circular products and systems.Energies 2019, 12, 4723 2 of 18 drivers for global environmental disruption [7], for example triggering a climate crisis [8][9][10][11]. Nuclear energy harvested in today's fission reactor fleet, though contributing little to the climate crisis, rapidly depletes the uranium stock, poses catastrophic risks for human and ecosystem health in case of accidents, increases the possibility for development and proliferation of nuclear weapons, and leaves radioactive waste to be managed for millennia by future generations [12]. Both fossil and nuclear energy resources are therefore incompatible with the notion of sustainable development, since it is defined as a "development that meets the needs of the present without compromising the ability of future generations to meet their own needs" [13]. Consequently, a sustainable CE can only be powered by RE fluxes in the future.The Earth system is powered by three incoming RE fluxes: solar irradiance, terrestrial heat, and tides. The latter two contribute very little to the Earth's energy budget, i.e., 0.03% and 0.002%, respectively [14][15][16][17]. Solar irradiance is therefore the pivotal power source for the circulation of natural and anthropogenic materials in an otherwise closed Earth system. The Earth system balances these energy inflows mainly with infrared emittance, which is adjusted by the Earth's surface temperature [18]. All material cycles within the Earth system, be they natural or anthropogenic, are enabled by these energy fluxes, which are approximately five orders of magnitude larger than the current human demand for technical energy (i.e., energy used to power technical processes, such as electric energy) [6]. Throughout the Earth's history, these energy flu...

This study characterizes the environmental performances of large-scale ground-mounted PV installations by considering a life-cycle approach. The methodology is based on the application of the existing international standards of Life Cycle Assessment (LCA). Four scenarios are compared, considering fixed-mounting structures with (1) primary aluminum supports or (2) wood supports, and mobile structures with (3) single-axis trackers or (4) dual-axis trackers. Life cycle inventories are based on manufacturers' data combined with additional calculations and assumptions. Fixed-mounting installations with primary aluminum supports show the largest environmental impact potential with respect to human health, climate change and energy consumption. The climate change impact potential ranges between 37.5 and 53.5 gCO 2 eq/kWh depending on the scenario, assuming 1700 kWh/m².yr of irradiation on an inclined plane (30°), and multi-crystalline silicon modules with 14% of energy production performance. Mobile PV installations with dual-axis trackers show the largest impact potential on ecosystem quality, with more than a factor 2 of difference with other considered installations. Supports mass and composition, power density (in MWp/acre of land) and energy production performances appear as key design parameters with respect to large-scale ground mounted PV installations environmental performances, in addition to modules manufacturing process energy inputs.

No abstract

Purpose By analyzing the latest developments in the dynamic life cycle assessment (DLCA) methodology, we identify an implementation challenge with the management of new temporal information to describe each system we might want to model. To address this problem, we propose a new method to differentiate elementary and process flows on a temporal level, and explain how it can generate temporally differentiated life cycle inventories (LCI), which are necessary inputs for dynamic impact assessment methods. Methods First, an analysis of recent DLCA studies is used to identify the relevant temporal characteristics for an LCI. Then, we explain the implementation challenge of handling additional temporal information to describe processes in life cycle assessment (LCA) databases. Finally, a new format of temporal description is proposed to minimize the current implementation problem for DLCA studies. Results and discussion A new format of process-relative temporal distributions is proposed to obtain a temporal differentiation of LCA database information (elementary flows and product flows). A new LCI calculation method is also proposed since the new format for temporal description is not compatible with the traditional LCI calculation method. Description of the requirements and limits for this new method, named enhanced structural path analysis (ESPA), is also presented. To conclude the description of the ESPA method, we illustrate its use in a strategically chosen scenario. The use of the proposed ESPA method for this scenario reveals the need for the LCA community to reach an agreement on common temporal differentiation strategies for future DLCA studies. Conclusions We propose the ESPA method to obtain temporally differentiated LCIs, which should then require less implementation effort for the system-modeling step (LCA database definition), even if such concepts cannot be applied to every process.

Purpose This study compares prior life cycle assessment (LCA) studies on graphene-based materials (GBMs) with new results from original data on ball milling of few-layer graphene. The analysis thus offers an overview of the current state of knowledge on the environmental sustainability of GBM production. Possible future development pathways and knowledge gaps are identified and explained to provide guidance for the future development of GBMs. Methods Comparable scopes, aggregation levels, and impact assessment methods are used to analyse diverse GBMs with three different functional units for graphene oxide, pristine graphene, and other GBMs with different carbon/oxygen ratios or thickness. The ecoinvent v3.4 cut-off database is used for background data in all models to provide a common basis of comparison. Furthermore, uncertainty calculations are carried out to give insights on the current level of knowledge and to check if GBM production methods can be differentiated. Finally, a sensitivity analysis is performed on the energy inputs with a detailed description of three future scenarios for the European electricity mix. Results and discussion The general analysis of all results highlights three key strategies to improve the environmental sustainability of GBM production. (1) The use of decarbonised energy sources reduces substantially the impacts of GBMs. This benefit is decreased, however, when conservative forecasts of the future European electricity mix are considered. (2) Increased energy efficiency of production is useful mainly for the processes of electrochemical exfoliation and chemical vapour deposition. (3) The principles of green chemistry provide relevant ideas to reduce the impacts of GBMs mainly for the processes of chemical and thermal reduction and for the production of graphene oxide. Furthermore, the analysis of new data on ball milling production reveals that transforming GBM solutions into dry-mass can substantially increase the environmental impacts because of the energy-intensive nature of this conversion. The uncertainty analysis then shows that it is still difficult to differentiate all production methods with the current knowledge on this emerging technology. Conclusions With our current level of knowledge on GBMs, it is clear that more accurate data is needed on different production methods to identify frontrunners. Nevertheless, it seems that unknowns, like the state of future electricity mixes, might not often hinder such comparisons because conservative forecasts bring similar changes on many production options. Additionally, functional properties and toxicity for GBMs will require further attention to improve our confidence in the comparison of production methods in the future.

International audienceThis work contributes to the development of a dynamic life cycle assessment (DLCA) methodology by providing a methodological framework to link a dynamic system modeling method with a time-dependent impact assessment method. This three-step methodology starts by modeling systems where flows are described by temporal distributions. Then, a temporally differentiated life cycle inventory (TDLCI) is calculated to present the environmental exchanges through time. Finally, time-dependent characterization factors are applied to the TDLCI to evaluate climate-change impacts through time. The implementation of this new framework is illustrated by comparing systems producing domestic hot water (DHW) over an 80-year period. Electricity is used to heat water in the first system, whereas the second system uses a combination of solar energy and gas to heat an equivalent amount of DHW at the same temperature. This comparison shows that using a different temporal precision (i.e., monthly vs. annual) to describe process flows can reverse conclusions regarding which case has the best environmental performance. Results also show that considering the timing of greenhouse gas (GHG) emissions reduces the absolute values of carbon footprint in the short-term when compared with results from the static life cycle assessment. This pragmatic framework for the implementation of time in DLCA studies is proposed to help in the development of the methodology. It is not yet a fully operational scheme, and efforts are still required before DLCA can become state of practice