Assessment of Environmental Impacts Related to Shale Gas Extraction in the Polish Contex

In the last decade, the exponential development of shale gas activities in United States resulted in a real revolution both in terms of gas prices and energy security. However, next to these positive effects, many risks and impacts for the environment and for human health related to shale gas activities have been identified. Risks of water and soil contamination or air pollution issues related to shale gas activities have been revealed in different recent scientific studies. During the last years, and because of the growing concern of local populations, shale gas became very debated in the media. In the scientific community as well, shale gas is a debated issue but in terms of greenhouse gases (GHG) emissions. This study is a scientific assessment of the environmental impacts related to shale gas extraction trying to synthesize information available from different scientific studies and providing potential mitigation measures. As Poland currently plays the most active role in European shale gas exploration, it has been chosen has the reference location in order to evaluate the different impacts. The results are that potential impacts on both human health and the environment can potentially be important but that an important lack of reliable information exists in order to fully assess most of the potential risks related to shale gas activities. Due to the high sensitivity of this issue among scientists, shale gas GHG emissions have been calculated in this study using a Monte Carlo simulation in order to define potential results based on variable parameters instead of using fixed values. The results show that shale gas GHG emissions could be 28% larger than coal over a 20 year timeframe and identical to coal over a 100 year timeframe. Mitigation measures can however reduce shale gas emission and most of the other impacts. The largest problem in order to currently asses and adequately reduce the risks related to shale gas activities is the current paucity of reliable information. An important uncertainty indeed exists in the evaluation of most of the risks. Many more scientific studies are therefore urgently needed in order to fully assess the potential impacts of shale gas activities and in order to ensure that the development of such activities will be done in Poland in the best possible conditions. In the meantime, the biggest risk would be to not accept our current ignorance and a precautionary approach should therefore be adopted.

Approche mathématique de l'impact des sites contaminés sur les eaux souterraines dans un contexte d'analyse de risque

Dominique Guyonnet

The primary objectives of this thesis are, firstly, to develop analytical solutions for estimating the impact of contaminated sites (in particular landfills, and to a lesser extent accidentally contaminated soils) on groundwater, and secondly to evaluate methods for taking into account the uncertainty relative to the different relevant parameters. These developments are performed with particular reference to a risk analysis framework. One of the distinctive features of such a framework is the incomplete and uncertain nature of the information that is generally available in practice. This has a direct influence on the choice of tools and approaches. It is proposed, in the introductory chapter, to define risk as the likelihood that a damage may occur, thus avoiding the more frequently used term probability. The latter refers to a strictly statistical description of the uncertainty, and assumes a degree of knowledge with respect to the various relevant parameters that is not necessarily available in practice. A presentation of several risk analysis models underlines their respective areas of application. Chapter 2 presents analytical solutions for estimating the impact of contaminated sites on groundwater, several of which are original. The mathematical development of the original solutions is presented in detail in the appendix. The succession of proposed solutions goes from the simpler to the more complex, starting with solutions for a one-layer domain and one-, two- and three-dimensional contaminant migration, and then passing to solutions for a multi-layer domain. These solutions are presented in terms of dimensionless variables that allow the equations to be written in a compact fashion, and independently of any system of units. The dimensionless variables serve to construct type curves that provide a visual analysis of solution behaviour with respect to variations of input parameter values. The proposed original solutions are of particular interest for estimating the potential impact of waste disposal sites, as they take into account the effect of the diffusive-dispersive flux on the impact on groundwater. This component of the mass flux is generally either omitted by existing risk analysis tools, or else it is not truly coupled with the mass balance in the groundwater (via the boundary conditions). The proposed solutions are applied to several practical examples. The example involving the original solution developed for estimating the impact of a stabilized waste-disposal site, illustrates the solution's usefulness as an aid for site conception and design. The example also shows how, by providing a picture of the site's global performance with respect to its potential impact, the model can bring the designer to question some of his choices. Another example helps to clarify the concept of "equivalence" between different barrier systems. An original solution is also proposed for the problem of early contaminant detection using inorganic trace elements. A comparison with another approach proposed in the literature illustrates the limits of the latter. Chapter 3 addresses the question of how to take imperfection of knowledge into account in the calculations. Two methods for accounting for uncertainty with respect to input parameter values are described and compared. The first method is the Monte Carlo method, which relates to a statistical and probabilistic framework. The second method is based on the theory of possibilities and on so-called fuzzy calculus. The representation of the main model parameters (hydraulic conductivity, porosity, etc.) using fuzzy numbers rather than probability distributions, is often more consistent with the basic nature of the information that is available in practice. The comparison between the two methods, underlines the conservative character of the fuzzy approach. This is related to the fact that the calculation based on fuzzy numbers considers all possible combinations of fuzzy input parameter values, but does not transmit (through multiplication) the degrees of unlikelihood of the different values. In the Monte Carlo calculation, on the other hand, a scenario that combines low-probability values of the input parameters, has all the less chance of being randomly selected. Nevertheless, when the mere possibility that an unfavourable scenario may occur becomes an element of decision, the fuzzy approach may seem preferable. This situation can appear in an environmental context, where human health is often at stake. The examples presented herein contribute to introducing an "impact framework" to the management of contaminated sites. Such a framework tends to define the acceptability of choices with respect to the management of these sites, on the basis of a comparison between emitted pollutant fluxes and fluxes considered acceptable for the local environment. They also underline the usefulness of having a certain degree of freedom with respect to the choice of the conceptual model underlying the mathematical model, in order to provide reasonable appropriateness between the calculation tool and the various situations that might appear in practice. Existing risk analysis models are often difficult to apply to specific sites, due to the rigidity of their conceptual models. In some cases, these models are better described as tools for ranking chemical substances as a function of their contamination potential. Some of the original analytical solutions proposed herein can be readily incorporated into the "vector" module of a risk analysis tool.

EPFL1998

La négociation des risques technologiques

Marc Audétat

This thesis considers technological risks and their constitution as public problems. It supports that the main difference among risks is not to see between proved risks and uncertain risks, on the basis of the objective knowledge, but rather separates risks which have already reached compromises at both levels of evaluation and responsibility and those which are still controversial. The starting observation is that social acceptability of risk is out of the scope of the objective approach. Actors use categories of "objective risk" and "perception of risk" within struggles to define what is at stake. It shows how risks, as soon as their evaluation starts, are negotiated within controversies, mobilizing experts, stakeholders, and actors of society. With many environmental risk, and with the globalization of hazards such as climate change, the preventive paradigm is overflowed; and with the emergence of new uncertainties, such as the introduction of genetically modified organisms in agriculture and food, expertise as the only method to deal with risk is contested in society. The precautionary approach, which asks to act against uncertainty before the completion of scientific evidence of risk is declining in the United-States while its integration is increasing in public policy in Europe. Have we entered the risk society? Or, is the society of the developed countries safer than it has ever been? Are risk increasing or decreasing? These apparent paradoxes shows there is different social theories of risk with different possible balance between objective and social factors to explain them. The role of technology is ambivalent, generating new risk and in the same time privileged as a solution to uncertainty. The thesis puts forward "science, technology and society" approach in risk studies, and it aims at a sociology where experts are not considered neutral actors. In this perspective, robustness of expertise does not rely directly on objective knowledge, but on the relation of this knowledge with its context of application. After studying the role of risk in modernization and rationalization processes, the thesis focuses the mobilization of actors in risk controversies and the role of some new institutions in the public sphere such as the ethical committees and the technology assessment agencies. Two case studies are investigated which take place in Switzerland end of the 1990s. The first relates to the introduction of genetically modified organisms in agriculture and environment. A controversy occurred about field test, i.e. scientific experiments refused by the authorities in 1999 and 2001. The role of research in biotechnology is considered as well as the different role of expertise in the public sphere. Expertise in biosafety and social acceptability of biotechnology are negotiated simultaneously. The second case study is the climate change issue and the negotiation of measures to control greenhouse gas. The role of research policy in the governance of climate risk is studied. Both case studies are interested with the role of experts in the public sphere, with the coordination of expertise and decision making, and with the degree of democracy achieved in sociotechnical controversies. The main result of this study is that a linear model of risk dominates approaches and constitutes an obstacle to the democratization of technological change. Instead, the thesis proposes a model where rationality is not defined beforehand, but appears as the proper result of controversies. In this view, risks are socially negotiated, already during the production of expertise, and all along the decision making and the implementation processes.

EPFL2004

Design approach for the improvement of the economic and environmental performances of potable water supply

François Vince

Triggered by the Kyoto Protocol and by the aggravation of freshwater scarcity, environmental impacts should soon become key decision criteria for the planning of potable water supply projects, especially when advanced systems such as seawater desalination are at stake. In order to foster the transition of the water industry towards sustainable practices, the present work proposes an integrated design approach dedicated to potable water supply that targets both economic and environmental objectives. At first, the current industrial practices (Chapter I) and the technical characteristics of potable water supply systems (Chapter II) are analyzed via the modeling of the process units used for potable water supply: pumping systems, conventional water treatment processes (e.g. clarification, filtration, disinfection) and advanced water treatment processes (e.g. membrane processes, thermal processes). Using the ISO 14040 standardized Life Cycle Assessment (LCA) method, Chapter III presents the development of a performance indicator that assesses the environmental impacts generated through all stages of the life cycle of potable water supply (i.e. from "cradle to grave"): from the construction of the potable water treatment plant, to its operation and decommissioning. This LCA-based indicator provides a holistic overview of all potential environmental impacts (e.g. green house gases (GHG) emissions, impacts on ecosystems and on human health). It allows to stress out the impact sources and the penalizing steps within potable water supply (Chapter IV): The production of electricity and chemicals required by the potable water treatment plant is highlighted to generate respectively 75% and 15% of the total impacts generated during the life cycle of potable water supply. Different potable water supply scenarios (e.g. potable water supply from ground water, from surface water, seawater desalination, water import from distant water resources) are benchmarked, in order to identify the best solutions as a function of the local context (e.g. type of electricity supply, topographic conditions, feed water quality). Based on the results of the environmental assessment, Chapter V proposes measures for the improvement of the industrial practices of the water sector, targeting energy and chemicals management, electricity sourcing and effluent disposal. Within the same perspective, Chapter VI details an optimization method for the design of the reverse osmosis (RO) membrane process, i.e. the key treatment process for desalination and wastewater reclamation. This method systematically synthesizes RO process configurations and evaluates their performances on economical (total annualized costs), technical (energy requirement, water conversion rate) and environmental criteria (GHG emissions). Evolutionary algorithms are then used to optimize the design of these configurations (process layout and operating conditions) and to identify those featuring the best trade-offs between economical costs and environmental impacts. As case study, the optimization method is applied on a brackish water reverse osmosis (BWRO) desalination project. The characteristics of the optimal BWRO process configurations are calculated as a function of the project constraints (e.g. economical and technical settings, minimum potable water quality), in order to illustrate how this method may support process engineers for the design of desalination plants.

EPFL2008