A Question of Boundaries

One of the recurring questions in EROI analysis is where the boundaries should be drawn. How wide do you make the boundaries when calculating energy inputs? Do you include the roads wihch are needed to transport solar panels, for example? Should you include first world salaries of solar panel installers?

The new net energy metric I introduced in the prior article, and the ensuing discussion, can inform where the boundaries should be drawn.. When calculating a rate of exponential growth, the boundaries for net energy analysis should include the minimum energy investment to replicate an energy gathering device. Let me provide some examples.

In our scheme outlined in the prior article, energy investments would not include the entire transportation infrastructure or first world standards of living, which would happen after the exponential growth had already occurred. Energy investments would include, however, the energy investment needed to refine oil, in addition to its extraction, because refined oil products (such as diesel) are required to power the machinery to drill new oil wells.

As another example, refinery losses for oil production would count as an ongoing investment, because the refining doesn’t all need to occur at once before any oil from a well is produced. In this case, it makes no difference if the energy comes from the oil itself, or from some external source, since the effect is the same mathematically in either case. However, self-consumption of coal for underground coal gasification (for example) should simply be ignored and not countaed as an investment at all, since it never needed to be extracted in the first place, so it has no effect on replication time.

As another exmaple, the roads needed for installing solar panels would count as an energy investment, but any other transportation infrastructure would count as a return. The rest of the transportation network is not necessary for replication and could come after the exponential growth has occurred.

In this manner, the disagreements over boundaries could be narrowed considerably.

Of course, these above remarks hold only when calculating a replication time and its effect on economic growth. Another use of net energy metrics is to calculate CO2 emissions. In which case, the boundaries should be drawn differently. When calculating CO2 emissions, self-consumption of cola for underground coal gasification should be counted. Also, first-world transportation (car transportation, for example) to a solar power site should be counted. It depends upon the use to which the metric is being put.

Net energy metrics are only useful as part of a broader calculation, and the broader calculation informs where the boundaries should be drawn.