Why does the FAA not support UL102 (formerly 100SF) unleaded av-gas as an alternative to 100LL fuel? The specifications for UL 102 are described in this Wikipedia article.  The fuel appears to exceed the specifications of 100LL in octane number and energy per unit volume although the fuel weighs 7 pounds per gallon instead of the 6 pounds per gallon for 100LL.  Is the additional weight the reason the FAA rejected this fuel as an 100LL alternative?
The problem is basically bureaucratic delays, helped along by easing of EPA timetables on the banning of leaded fuel, taking some of the pressure off, which has caused the developer of UL102, Swift Fuels, to suspend its 2nd Phase testing until the machine gets moving.