It seems logical that shifting over time to aviation fuel with a lower carbon footprint would represent the most practical way for the global airline industry to reduce its greenhouse gas (GHG) emissions. But for that shift to happen, there needs to be an economic rationale for producing sustainable aviation fuel and, despite a seemingly generous production credit for SAF in the Inflation Reduction Act (IRA), that rationale is a least a little shaky when compared to renewable diesel (RD) credits available today. In today’s RBN blog, we conclude our two-part series on SAF with an examination of RD and SAF economics (which are remarkably similar), the degree to which existing SAF incentives may fall short of RD, and what it all means for SAF producers and production.
As we said in Part 1, jet fuel is the planet’s third-most consumed transportation fuel (after diesel and gasoline), and its considerable volume (7 MMb/d) is a meaningful target for carbon emissions reduction. Many airlines have set targets of “net-zero-by-2050” — which may be hard to fathom given the nature of an industry reliant on transportation fuels. If they are to have any degree of success in approaching their goals, lowering Scope 2 emissions through the increased use of SAF will be critical, particularly given the recent skepticism being heaped on the airlines’ other decarbonization strategy — carbon offsets.
Like RD, SAF is the chemical twin of its petroleum-based alternative and therefore can serve as a “drop-in” replacement for it. We also explained the processes most often used to produce RD — and from it, SAF. The most mature technology for producing RD from plant oils or other recycled fats uses hydrogen to remove oxygen (primarily hydrodeoxygenation, or HDO) to produce hydroprocessed esters and fatty acids (HEFA). This same HEFA process can be used to produce SAF (which contains the same molecules as petroleum-sourced jet fuel) by adding a hydrocracking processing step. SAF molecules are shorter chains of hydrocarbons; therefore, the diesel-sized molecules in RD must be broken (or “cracked”).
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