The gist as I see it quote: The rapid recovery of the D6/D4 price ratio back above 0.75 over the summer is not as easily explained. We believe the best explanation is that market participants initially believed that the EPA would keep renewable mandate volumes fixed in the final rules for 2014-2015 even if projections for gasoline and diesel use increased by the time the final rules are released (by the end of November 2015), but then expectations were altered as more evidence emerged that the EPA might target the fractional mandates in the initial proposal rather than fixed volume mandates (farmdoc daily, June 10, 2015). This altered expectation is most consistent with exhaustion dates for the EPA and Irwin and Good scenarios.
  Previously, at the consumption of gasoline (& diesel) declined the EPA allow Mandate volumes to slip to order to not exceed the 10% ethanol implicit in E10 (fixed volume mandate).  Now that the cost of crude is down and the demand for gasoline & diesel has apparently increase by 3% the EPA may go back to  fractional mandates in order to keep the percentage of finished gasoline at the 10% ethanol level.
  The fixed volume mandate meant that ethanol blending was capped at 13.25 billion gallons.  The fractional mandate means the ethanol blended might rise to 13.91 billion gallons or 660 million more gallons (near term) and to 15 billion (longer term)  This would require 235 million more bushels of corn this year & next (I think?)
   FarmDoc is using the price ratio of D4 & D6 rins to infer how likely the fuel blenders think this is a possibility.  Previously the ratio was 0.91 it dropped briefly to 0.45 (not likely) but now as risen above 0.75 (much more likely). 

  Jon's second paper is a Dept of Energy study concerning the problems & costs blenders encounter when they try to vary the percentages of ethanol in blends.  It turns out that it's not so easy to just cut back on the ethanol. 

  Jon, thanks for bringing these papers to our attention.  If I might offer a comment.  The market for corn is a lot more complicated than some lines on a futures price chart suggest.  Perhaps one of the reasons the price predictions implied by those lines fail so often is they don't account for such subtleties as above.