Thinking Clearly About Energy

If our society is to make good choices in this era of profound energy transition, we will need to think a lot more clearly and carefully about energy than we have in the past.  Appropriate metrics are needed to gauge our progress toward energy security—broadly defined.  The “energy return on investment” (EROI) metric has significant value, but it alone is not enough.   We also need to consider differences in energy quality, which EROI does not address.  Furthermore, we must absolutely insist that these metrics be used to make comparisons between reasonable fuel alternatives on a consistent basis, with consistent system boundaries.  This is seldom done. 
I propose several metrics and then apply them to the controversial case of biofuels, liquid fuels derived from plant material. Starting with EROI for biofuels, I consider two additional metrics.  First, national energy security is probably best measured as the ratio of liquid fuel produced per unit of liquid fuel input required to generate that unit of liquid fuel output.  For national energy security, we should also consider critical materials required to pursue different energy alternatives, for example, the availability of lithium for electric vehicles.  Second, climate security is probably best addressed as the total life cycle greenhouse gas emissions (GHG) per unit of fuel.  Compared to petroleum fuels, some biofuels perform very well in these comparisons, while others do not.
Once again, careful comparisons between realistic alternatives on a consistent basis, with consistent system boundaries are absolutely necessary if we are to make good choices. Far too much energy analysis starts with the answer and then constructs the analysis to arrive at the desired answer.