Consider the following materials: 1. Agricultural residues 2. Corn grain 3. Wastewater treatment sludge 4. Wood mill waste Which of the above can be used as feedstock for producing Sustainable Aviation Fuel?

Sustainable Aviation Fuel (SAF) is a biofuel used to power aircraft, produced from a wide variety of feedstocks. Agricultural residues such as straw and husks are converted via thermochemical or biochemical pathways to SAF. Corn grain (and other starch/sugar crops) is used through the alcohol-to-jet (ATJ) pathway and is an ASTM-approved feedstock. Wastewater treatment sludge contains organic matter and lipids that can be processed into SAF via hydrothermal liquefaction. Wood mill waste (lignocellulosic biomass) is also a recognized SAF feedstock via Fischer-Tropsch or gasification routes. Hence all four can serve as SAF feedstocks.