The talk with present the key results of the IPCC Working Group III 5th assessment report. Concluding four years of intense scientific collaboration by hundreds of authors from around the world, the report responds to the request of the world's governments for a comprehensive, objective and policy neutral assessment of the current scientific knowledge on mitigating climate change. The report has been extensively reviewed by experts and governments to ensure quality and comprehensiveness.

Climate change 2014 - Mitigation of climate change

Purpose
Good background data are an important requirement in LCA. Practitioners generally make use of LCI databases for such data, and the ecoinvent database is the largest transparent unit-process LCI database worldwide. Since its first release in 2003, it has been continuously updated, and version 3 was published in 2013. The release of version 3 introduced several significant methodological and technological improvements, besides a large number of new and updated datasets. The aim was to expand the content of the database, set the foundation for a truly global database, support regionalized LCIA, offer multiple system models, allow for easier integration of data from different regions, and reduce maintenance efforts. This article describes the methodological developments.

The ecoinvent database version 3 (part I): overview and methodology

MoS2 is a promising and low-cost material for electrochemical hydrogen production due to its high activity and stability during the reaction. However, the efficiency of hydrogen production is limited by the amount of active sites, for example, edges, in MoS2. Here, we demonstrate that oxygen plasma exposure and hydrogen treatment on pristine monolayer MoS2 could introduce more active sites via the formation of defects within the monolayer, leading to a high density of exposed edges and a significant improvement of the hydrogen evolution activity. These as-fabricated defects are characterized at the scale from macroscopic continuum to discrete atoms. Our work represents a facile method to increase the hydrogen production in electrochemical reaction of MoS2 via defect engineering, and helps to understand the catalytic properties of MoS2.

Defects Engineered Monolayer MoS2 for Improved Hydrogen Evolution Reaction.

For over half a century, worldwide growth in affluence has continuously increased resource use and pollutant emissions far more rapidly than these have been reduced through better technology The affluent citizens of the world are responsible for most environmental impacts and are central to any future prospect of retreating to safer environmental conditions We summarise the evidence and present possible solution approaches Any transition towards sustainability can only be effective if far-reaching lifestyle changes complement technological advancements However, existing societies, economies and cultures incite consumption expansion and the structural imperative for growth in competitive market economies inhibits necessary societal change

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Scientists’ warning on affluence

Decarbonization of electricity generation can support climate-change mitigation and presents an opportunity to address pollution resulting from fossil-fuel combustion. Generally, renewable technologies require higher initial investments in infrastructure than fossil-based power systems. To assess the tradeoffs of increased up-front emissions and reduced operational emissions, we present, to our knowledge, the first global, integrated life-cycle assessment (LCA) of long-term, wide-scale implementation of electricity generation from renewable sources (i.e., photovoltaic and solar thermal, wind, and hydropower) and of carbon dioxide capture and storage for fossil power generation. We compare emissions causing particulate matter exposure, freshwater ecotoxicity, freshwater eutrophication, and climate change for the climate-change-mitigation (BLUE Map) and business-as-usual (Baseline) scenarios of the International Energy Agency up to 2050. We use a vintage stock model to conduct an LCA of newly installed capacity year-by-year for each region, thus accounting for changes in the energy mix used to manufacture future power plants. Under the Baseline scenario, emissions of air and water pollutants more than double whereas the low-carbon technologies introduced in the BLUE Map scenario allow a doubling of electricity supply while stabilizing or even reducing pollution. Material requirements per unit generation for low-carbon technologies can be higher than for conventional fossil generation: 11-40 times more copper for photovoltaic systems and 6-14 times more iron for wind power plants. However, only two years of current global copper and one year of iron production will suffice to build a low-carbon energy system capable of supplying the world's electricity needs in 2050.

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Integrated life-cycle assessment of electricity-supply scenarios confirms global environmental benefit of low-carbon technologies.

Many decisions are made during the life cycle of a product, e.g., whether to replace a product or to keep using it. To pinpoint the “greener” choice, the consequential environmental effects of each choice should be estimated. Hereto, only activities occurring after the decision should be considered and, thus, not necessarily the complete product life cycle. Decisions are taken at different levels in the economy, ranging from small scale (e.g., few individual purchases) to large scale (e.g., policies). In this article, we introduce a framework that mainly focuses on the small-scale decision of replacement of a product in usage, illustrated in case of a petrol versus an electric car. For a fixed time span of usage (functional unit), the product system composition varies based on the selected time of replacement. Many market mechanisms occur within the cause-effect chain, for which argued presumptions are necessary. For example, the purchase of the alternative product is reasoned to possibly induce an additional product supply. Moreover, if the product is not obsolete after initial usage, it is sold in the secondhand market and will thus displace the average market mix. The developed framework for this small-scale replacement decision is different from the alternative consequential approach of ecoinvent that covers a different decision, namely, a marginal increase in demand, e.g., of car usage, at market level. In our framework, a ratio for the amount of newly car produced per purchase is introduced. For the case study, the global warming potential over 100 years is estimated, this using general data from databases and time-varying market mix (in composition), car technology, and electricity mix. A set of equations is introduced that serves as a first simplified framework. Bearing in mind limitations, if the petrol car is disposed of as waste after initial usage whereas the electric car resold, it is estimated that a replacement of the petrol car by the electric car at any time lowers the impact on climate change. A better characterization of impact over time and market and agent-based modeling should be at the core of further efforts, especially when upscaling to large-scale decisions. Framework and insights are provided on the modeling of the environmental effects of a replacement decision. Finally, this article may serve as a stepping-stone towards an integrated consequential modeling of sustainability impact of product-related decisions, looking beyond a normative consideration of a fixed product life cycle.

When to replace a product to decrease environmental impact?—a consequential LCA framework and case study on car replacement

This paper proposes a new bi-objective optimization model, trading-off cost and environmental impacts, for sizing the key electrical and thermal devices in a zero energy building (ZEB), i.e., a building that roughly generates as much renewable energy as it consumes annually. A salient novel feature is the consideration of the environmental impacts, computed through a rigorous life cycle assessment approach, of buying electricity from the grid and manufacturing devices. Furthermore, an enhancement of the proposed model, as compared to the existing models, is to prioritize storing the ZEB excess of energy rather than selling it to the grid. The proposed solution approach of the initial mixed-integer nonlinear programming model relies on McCormick relaxation linearization to obtain a more tractable mixed-integer linear model. An augmented ϵ-constraint method is applied to solve the obtained bi-objective model. Finally, considering the building owners’ willingness-to-pay for environmental impacts, a decision-making criterion is proposed to select the optimal size of the devices among all non-dominated solutions of the Pareto front.

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A New Bi-Objective Approach for Optimal Sizing of Electrical and Thermal Devices in Zero Energy Buildings Considering Environmental Impacts

We appreciate the reply of Yang (2017a) to our letter (Gibon and Schaubroeck 2017). It became clear to us that Yang (2017b) does not mainly criticise the hybrid LCA method, but rather the misconception around the idea that hybrid LCA would lead for sure to higher accuracy if a more complete system boundary is obtained, as also well specified in another work of his (Yang et al. 2017). We agree that this is a misconception because of data and methodological restrictions. However, this does not mean that the method as such, from a conceptual point of view, should be solely criticised for general limitations in the linear framework and system boundaries in comparison to other linear LCA, what Yang (2017b) though appeared to do. This entails another discussion. Likewise, the discussion on rethinking system boundaries in his reply (Yang 2017a) seems to focus on the need (or intention) to have a flexible system boundary and a non-linear framework (which we frankly agree with), rather than on the hybrid LCA methodology itself, the original topic of discussion. The improvement in accuracy for hybrid LCA seems indeed not a guarantee and is of course, as already mentioned, dependent on data. Yang et al. (2017) in fact moreover point out that the degree of aggregation, a data issue, is of huge relevance for hybrid LCA accuracy. We in fact much more appreciate the latter publication because it addresses the specific issue at hand. The quality of an LCA study—in fact of any quantitative study—depends on both data and methodology. Furthermore, we also want to emphasise that in practice, the potential benefit of combining input–output-based and process-based life cycle inventories goes beyond a possible improvement in accuracy through expanding the system boundaries (Gibon and Schaubroeck 2017). For the sake of clarity, Table 1 lists some characteristics of both approaches that can be combined to provide an improved life cycle inventory. These other potential benefits are yet again not only methodology-dependent but also data-dependent. The (hybrid) LCA practitioner needs to find a combination that suits the goal of his study as best as possible, given practical limitations (e.g. available data). However, the practitioner should indeed not think that hybrid LCA is guaranteed better than any other type, as Yang et al. (2017) discuss and exemplify. The latter authors showcase that it is important to be sceptical towards hybrid LCA, e.g. consider the level of aggregation in IO tables, but judging, this is of course partially subjective as the accurate result is commonly unknown. One can in practice often only presume that a more complete system boundary leads to more accuracy, as is the case for other choices. The practitioner should though reason its choice for hybrid LCA, as should likewise be done for any (major) choice in LCA conductance. For example, Gibon et al. (2015) have applied hybrid LCA among else because they (1) presumed more accuracy through an expanded system boundary (to include business services via EXIOBASE) but also (2) to create a presumed better geospatially differentiated (using a multiregional but less detailed IO-database EXIOBASE) but also detailed (using the detailed but less spatially differentiated process-based ecoinvent 2.2 database) electricity production life cycle inventory. There are of course other more technical aspects and issues, which the practitioner Responsible editor: Mary Ann Curran

Outlining reasons to apply hybrid LCA—a reply to “rethinking system boundary in LCA” by Yi Yang (2017)

According to the Intergovernmental Panel on Climate Change (IPCC), in 2010 the transport sector was responsible for 23% of the total energy-related CO2 emissions (6.7 GtCO2) worldwide. Policy makers in Luxembourg are well-aware of the challenges and are setting ambitious objectives at country level for the mid and long term. However, a framework to assess environmental impacts from a life cycle perspective on the scale of transport policy scenarios, rather than individual vehicles, is lacking. We present a novel framework linking activity-based modeling with life cycle assessment (LCA) and a proof-of-concept case study for the French cross-border commuters working in Luxembourg. Our framework allows for the evaluation of specific policies formulated on the trip level as well as aggregated evaluation of environmental impacts from a life cycle perspective. The results of our proof-of-concept-based case study suggest that only a combination of: (1) policy measures improving the speed and coverage of the public transport system; (2) policy measures fostering electric mobility; and (3) external factors such as de-carbonizing the electricity mix will allow to counteract the expected increase in impacts due to the increase of mobility needs of the growing commuting population in the long term.

https://www.mdpi.com/2071-1050/11/15/4067/pdf

Thomas Gibon

Papers

When to replace a product to decrease environmental impact?—a consequential LCA framework and case study on car replacement

A New Bi-Objective Approach for Optimal Sizing of Electrical and Thermal Devices in Zero Energy Buildings Considering Environmental Impacts

Outlining reasons to apply hybrid LCA—a reply to “rethinking system boundary in LCA” by Yi Yang (2017)

Coupling Activity-Based Modeling and Life Cycle Assessment—A Proof-of-Concept Study on Cross-Border Commuting in Luxembourg

A Global Environmental Assessment of Electricity Generation Technologies with Low Greenhouse Gas Emissions