The 20% rollover cap under RFS2 is the same as the rollover cap under the RFS1 program. However, the rollover cap only places a limit on previous year RINs that were NOT used for compliance in 2008 or 2009 ("excess" RINs). Any 2008 or 2009 RINs that were used to comply with the 2009 total renewable fuel standard are not subject to the 20% rollover cap, as they are subtracted off of the biomass-based diesel RVO prior to the determination of the number of RINs an obligated party needs for compliance.
See 80.1427(a)(7)(i). After accounting for any 2008 or 2009 RINs that were used to comply with the 2009 total renewable fuel standard, as well as any 2008 or 2009 excess RINs that are applied to the 2010 biomass-based diesel standard under the rollover cap, the obligated party must meet the remaining portion of its 2010 RVO for biomass-based diesel with 2010 RINs (unless it carries a deficit into 2011). This remaining portion may not be equal to 80% of the 2010 biomass-based diesel RVO since the 20% rollover cap only applies to excess 2008 and 2009 RINs, not 2008 and 2009 RINs used for compliance in 2009.