The RFS2 has resulted in aggregate GHG emissions reductions from the use of biofuels, which exceed the original projections from the final Rule for the first 13 years of its implementation. The RFS2 has resulted in significant GHG reductions, with cumulative CO2 savings of 980 million metric tonnes over the period of implementation to date. The GHG reductions are due to the greater than expected savings from ethanol and other biofuels. These emissions savings occur even though cellulosic biofuels have not met the RFS2 production targets. In addition, EPA underestimated the petroleum baseline in the Rule. Studies by Life Cycle Associates and the Carnegie Institute have shown that the GHG emissions from U.S. petroleum are higher than the EPA calculated in 2005 (Boland, 2014; Gordon, 2012, 2015). This study calculates the annual U.S. petroleum GHG intensity based on the changing trends in feedstock availability over time and determines the GHG savings calculated from the aggregate mix of renewable fuels. The GHG intensity for each category of ethanol plant and biodiesel feedstock is estimated for the resource mix over the past 13 years and combined to determine an aggregate estimate. Figure 1 shows the total emissions reductions from the RFS2 compared with the GHG reductions projected from the rule.
The RFS2 has resulted in GHG emissions reductions, which exceed the original projections from the 2010 final Rule. The increased GHG reductions are due to the following:
1. Corn ethanol has adopted technology improvements, which results in greater than the 20% reduction in GHG emissions originally required under the RFS.
2. Petroleum GHG emissions are higher than the baseline projected by EPA.
3. The mix of other renewable fuels has also contributed to additional GHG reductions even though cellulosic ethanol targets in the original rule have not been met.
Biofuels have achieved and exceeded the GHG reductions estimated by EPA. The reductions are greater than the categories within the RFS2 because technology improvements have resulted in reductions in energy use and the RFS categories characterize typical renewable fuels. These categories were not intended to represent the weighted GHG reductions of all fuels produced under the rule.