EROEI stands for Energy Returned On Energy Invested, a concept used as an indicator of Net Energy (gain or loss) when calculating efficiency -- whether of a simple tool or a complex system.
As a commonly cited example in agriculture, it has been calculated that a modern farmer in Iowa uses ten units of energy for each unit he obtains in the form of the corn he grows. Regarding efficiency, he is put to shame by the peasant in Mexico who still practices the traditional agriculture and receives seven units of energy (also in corn) for each unit he expends by powering his hoe by hand!
How humanity will use the dwindling natural resources and what attitude it adopts to energy use in general is one of the pivotal issues of our times. To those readers who would like more information on the subject, I highly recommend reading -- a 70 page document written by Richard Heinberg, one of the internationally respected analysts on the subject of peak oil and resulting repercussions. (available in print format as #4 in a series of reports titled False Solutions, or downloadable for free at ) Richard examines the realistic (as opposed to the promotion-oriented) potential of all the various alternatives to our society's unabashed addiction, namely oil.In any case, there is a wide-ranging consensus among the authors who do not represents some corporate or political interests that during one version or another of the transition into the post-oil era, some relatively comfortable level of green philosophy will NOT suffice to keep our present infrastructure afloat. Instead, the need for upgrading even the respected old conservation ethic is likely in store. The term many of them have lately been using is CONTRACTION, with some adding the prefix severe...
Whether we will take two years or twenty to accomplish anything of lasting substance remains to be seen, but vascular plants will need to be cut just the same. I am certain that sometimes soon into that period the mainstream will come to fully embrace the fact that -- if the EROEI of the various options is considered -- there simply is no other more efficient way to cut forage than with the scythe.
Communicating that fact beforehand is an important role of those to whom, in this paper (and elsewhere) I've referred to as "the scythe activists". If they don't, the scythe blades of the future may well have considerably lower EROEI value, if they are readily available at all...