http://europe.theoildrum.com/node/5989
[quote]The question regarding the reasons for the “bell shaped” Hubbert Curve has been around for a long time. Is the curve something that is only associated with crude oil? Does it hold for all fossil fuels? Or is it characteristic of all non-renewable resources? With time, evidence has accumulated that the Hubbert Curve is a very general phenomenon that occurs for all cases where a resource is exploited in conditions of free or nearly free market. The curve is observed also for renewable resources, when the rate of production is much faster than the replacement rate. It is, however, a typical characteristic of non-renewable mineral resources.
In the case of energy resources, the Hubbert Curve is directly related to EROI or EROEI (energy return of energy invested). Declining values of the EREOI reduce the producers’ profit and, eventually, lead to a reduction in investments on exploration and development. In the more general case of mineral resources, the curve is still related to energy but, in this case, to the increasing need of energy for exploiting progressively lower grade ores. The case of gold is especially interesting since it deals with a resource whose extraction rate would be expected to be dominated by market prices rather than energy constraints. Indeed, the historical gold production curve is best interpreted in terms of multiple production cycles, each one following a Hubbert Curve. Nevertheless, it is still possible to interpret the curve in terms of an overall Hubbert behaviour which, therefore, appears to be a nearly universal phenomenon in resource exploitation.[/quote]
