Resource limits are invisible, so most people don’t realize that we could possibility be approaching them. In fact, my analysis indicates resource limits are really financial limits, and in fact, we seem to be approaching those limits right now.
Many analysts discussing resource limits are talking about a very different concern than I am talking about. Many from the “peak oil” community say that what we should worry about is a decline in world oil supply. In my view, the danger is quite different: The real danger is financial collapse, coming much earlier than a decline in oil supply. This collapse is related to high oil price, and also to higher costs for other resources as we approach limits (for example, desalination of water where water supply is a problem, and higher natural gas prices in much of the world).
The financial collapse is related to Energy Return on Energy Invested (EROEI) that is already too low. I don’t see any particular EROEI target as being a threshold–the calculations for individual energy sources are not on a system-wide basis, so are not always helpful. The issue is not precisely low EROEI. Instead, the issue is the loss of cheap fossil fuel energy to subsidize the rest of society.
If an energy source, such as oil back when the cost was $20 or $30 barrel, can produce a large amount of energy in the form it is needed with low inputs, it is likely to be a very profitable endeavor. Governments can tax it heavily (with severance taxes, royalties, rental for drilling rights, and other fees that are not necessarily called taxes). In many oil exporting countries, these oil-based revenues provide a large share of government revenues. The availability of cheap energy also allows inexpensive roads, bridges, pipelines, and schools to be built.
As we move to energy that requires more expensive inputs for extraction (such as the current $90+ barrel oil), these benefits are lost. The cost of roads, bridges, and pipelines escalates. It is this loss of a subsidy from cheap fossil fuels that is significant part of what moves us toward financial collapse.
Renewable energy generally does not solve this problem. In fact, it can exacerbate the problem, because the cost of its inputs tend to be high and very “front-ended,” leading to a need for subsidies. What is really needed is a way to replace lost tax revenue, and a way to bring down the high cost of new bridges and roads–that is a way to get back to the cost structure we had when oil (and other fossil fuels) could be extracted cheaply.