A primary objective of the federal Renewable Fuel Standard (RFS), when it was expanded back in 2007, was to stimulate by 2022 the production of at least 16 billion gallons/year of gasoline and diesel made from cellulosic biomass in conversion plants resembling small refineries. After getting lots of headlines in the early days of renewable fuels, that vision faded into the background and attention shifted to the use of ethanol in gasoline and the production of diesel from soybean oil, but cellulosic biofuels — non-food crops and waste biomass like animal manure, corn cobs, corn stalks, straw and wood chips — are back in the spotlight thanks to a regulatory quirk. In today’s RBN blog, the first in a series, we review the unusual history of the D3 Renewable Identification Number (RIN), the subsidy designed to stimulate cellulosic biofuel production, and the recent impact on heavy-duty trucking.