Optimal Nuclear Waste Burial Policy under Uncertainty

The aim of this paper is to study the optimal nuclear waste burial policy under an uncertainty : the possibility that an accident might occur in the future. The framework is an optimal growth model with pollution disutility. We show, under some conditions on the waste burial policy, that nuclear power may be a long-term solution for the world energy demand. Under uncertainty on the future safety of the buried waste, the social planner will decide to decrease the rate of waste burying, but the evolution of consumption and hence the evolution of the level of buried waste, are ambiguous. Depending on some simple conditions on the balanced growth rate of the economy and on the preference parameters of the households, the optimal amount of buried waste may increase, even if there is a risk of accident in the future.Nuclear waste; pollution; growth; uncertainty

La consommation de ressources environnementales en incertitude

Cet article présente un modèle dans lequel un individu représentatif consomme une unique ressource environnementale, que l'on suppose renouvelable. Nous supposons, par ailleurs, qu'il existe un ensemble de phénomènes naturels aléatoires susceptibles d'affecter le stock de ressource disponible pour la consommation. Nous analysons à l'aide de ce modèle les comportements de consommation face à une incertitude sur la disponibilité d'une ressource environnementale dans le futur. Notre objectif étant de dépasser les résultats, somme toute triviaux, qui font l'essentiel de la littérature sur la décision en incertitude, et qui consistent à remarquer qu'en présence d'incertitude, l'agent adopte généralement un comportement plus prudent quant à son usage de l'environnement que dans le cas où l'incertitude n'existerait pas. Nous montrons d'une part comment la prise en compte successive des contraintes physiques, de disponibilité de la ressource et de solvabilité (ou de survie), auxquelles font face les consommateurs, modifie fondamentalement leur comportement, relativement à l'hypothèse de cycle de vie. Et, d'autre part pourquoi leur omission, ce qui est généralement le cas dans la littérature, peut amener à des conclusions erronées.Choix intertemporels de consommation, Incertitude, Ressources renouvelables

Growth, Environment and Uncertain Future Preferences

The attitude of future generations towards environmental assets may well be different from ours, and it is necessary to take into account this possibility explicitly in the current debate about environmental policy. The question we are addressing here is: should uncertainty about future preferences lead to a more conservative attitude towards environment? Previous literature shows that it is the case when society expects that on average future preferences will be more in favor of environment than ours, but this result relies heavily on the assumption of a separability between consumption and environmental quality in the utility function. We show that things are less simple when preferences are non-separable: the attitude of the society now depends not only on the expectation of the change in preferences but also on the characteristics of the economy (impatience, intertemporal flexibility, natural capacities of regeneration of the environment, relative preference for the environment), on its history (initial level of the environmental quality) and on the date at which preferences are expected to change (near or far future).Growth ; Environment ; Preferences ; Uncertainty c ° 2002 Kluwer Academic Publishers. Printed in the Netherlands.

Optimal Emission Policy under the Risk of Irreversible Pollution

We consider an optimal consumption and pollution problem that has two important features. Environmental damages due to economic activities may be irreversible and the level at which the degradation becomes irreversible is unknown. Particular attention is paid to the situation where agents are relatively impatient and/or do not care a lot about the environment and/or Nature regenerates at low rate. We show that the optimal policy of the uncertain problem drives the economy in the long run toward a steady state while, when ignoring irreversibility, the economy follows a balanced growth path accompanied by a perpetual decrease in environmental quality and consumption, both asymptotically converging toward zero. Therefore, accounting for the risk of irreversibility induces more conservative decisions regarding consumption and polluting emissions. In general, however, we cannot rule out situations where the economy will optimally follow an irreversible path and consequently, will also be left, in the long run, with an irreversibly degraded environment.Optimal Control, Irreversibility Threshold, Uncertainty, Optimal Reversible, Irreversible Policy

A note on the consequences of an endogenous discounting depending on the environmental quality

International audienceOur intention is to study, in the framework of a very simple optimal growth model, the consequences on the optimal paths followed by consumption and the environmental quality of an endogenous discounting. Consumption directly comes from the use of environmental services and so is a direct cause of environmental degradation. The environment is valued both as a source of consumption and as an amenity. For a sustainability concern, we introduce an endogenous discount rate growing with the environmental quality, and compare the optimal growth paths with the ones obtained in the usual case of exogenous and constant discounting. We show that the convergence of the environmental quality towards a steady state occurs only for a very special configuration of the parameters in the exogenous discounting case, while it occurs generically in the endogenous discounting one. This happens for a utility discount rate becoming suficiently high when the environmental quality is high and suficiently low when the environmental quality is poor. In this case then, endogenous discounting with a positive marginal discount rate allows us to avoid the depletion of the environment

Optimal Nuclear Waste Burial Policy under Uncertainty

URL des Documents de travail : http://ces.univ-paris1.fr/cesdp/CESFramDP2008.htm Voir aussi l'article paru dans Optimal Control, Applications and Methods : http://hal.archives-ouvertes.fr/hal-00639501Documents de travail du Centre d'Economie de la Sorbonne 2008.92 - ISSN : 1955-611XThe aim of this paper is to study the optimal nuclear waste burial policy under an uncertainty : the possibility that an accident might occur in the future. The framework is an optimal growth model with pollution disutility. We show, under some conditions on the waste burial policy, that nuclear power may be a long-term solution for the world energy demand. Under uncertainty on the future safety of the buried waste, the social planner will decide to decrease the rate of waste burying, but the evolution of consumption and hence the evolution of the level of buried waste, are ambiguous. Depending on some simple conditions on the balanced growth rate of the economy and on the preference parameters of the households, the optimal amount of buried waste may increase, even if there is a risk of accident in the future.L'objectif de ce travail est l'étude de la politique optimale d'enfouissement des déchets nucléaires en présence d'un risque : les déchets enfouis peuvent réapparaître accidentellement dans le futur. Le cadre théorique est celui des modèles de croissance optimale avec désutilité de la pollution. Nous montrons que, sous certaines conditions portant sur la politique publique d'enfouissement des déchets, la production d'électricité nucléaire peut être une solution de long terme aux problèmes de fourniture d'énergie. En présence d'incertitude sur la sécurité des stocks de déchets enfouis, le planificateur social choisira un taux d'enfouissement des déchets plus faible que celui défini dans un monde certain. En revanche, en ce qui concerne l'évolution de la consommation optimale, ainsi que l'évolution des stocks de déchets enfouis, les choix du planificateur sont ambigus. Ainsi, selon la valeur de certains paramètres portant sur les préférences des ménages, la quantité de déchets enfouis peut augmenter, malgré le risque d'accident futur

Ressources renouvelables et incertitude sur lespréférences des générations futures

Rien ne nous permet d'être certains que les générations futures auront les mêmes préférences que nous concernant les biens environnementaux. En outre, même si nous sommes tentés, en raison de la dégradation de la qualité de l'environnement, de croire que leur sensibilité à l'environnement sera plus grande que la notre, rien ne nous permet de l'affirmer avec certitude. Cet article étudie alors, dans un cadre très simple, les conséquences en termes de trajectoires optimales de consommation d'une incertitude sur les préférences des générations futures en matière de consommation d'une ressource environnementale renouvelable. Une telle incertitude va-t-elle induire un comportement optimal plus "conservateur" vis-à-vis de la ressource ? Nous montrons que tel est le cas uniquement si nous anticipons aujourd'hui que les générations futures seront en moyenne plus sensibles que nous ne le sommes à la consommation permise par l'utilisation de la ressource environnementale. Nous montrons en outre que la prise en compte de cette incertitude conduit à une profonde modification de la trajectoire optimale de consommation, qui non seulement devient non-continue mais en outre peut devenir non-monotone.ressources renouvelables, croissance, préférences, incertitude

Optimal Carbon Capture and Storage Policies

Following the IPCC's report (2005), which recommended the development and the use of carbon capture and sequestration (CCS) technologies in order to achieve the environmental goals, defined by the Kyoto Protocol, the issue addressed in this paper concerns the optimal strategy regarding the long-term use of CCS technologies. The aim of this paper is to study the optimal carbon capture and sequestration policy. The CCS technologies has motivated a number of empirical studies, via complex integrated assessment models. This literature always considers that the existing technology allows sequestrating a fraction of the carbon emissions and concludes that the early introduction of sequestration can lead to a substantial decrease in the cost of environmental externality. But, the level of complexity of such operational models, aimed at defining some specific climate policies. We develop a very simple growth model so as to obtain analytical and tractable results and therefore exhibit the main driving forces that should determine the optimal CSS policy. We show within on the cost of extractions, CSS may be a long-term solution for the carbon emissions problem. Besides, it is also shown that the social planner will optimally choose to decrease the rate of capture and sequestration. Besides, we also introduce the decentralization of this simple economy, by considering the individual program of the fossil resource-holder and the one of the representative consumer. This helps us to compute analytically the optimal environmental policy, that is the also the optimal fossil fuel price profile