Life-Cycle Assessment of Sustainable Aviation Fuel Derived from Paper Sludge
Kai Lan, David Cruz, Jinyue Li, Amma Asantewaa Agyei Boakye, Hyeonji Park, Phoenix Tiller, Ashutosh Mittal, David K. Johnson, Sunkyu Park, Yuan Yao
Abstract
Converting waste paper sludge to sustainable aviation fuel (SAF) offers a circular economy strategy to decarbonize the aviation sector. This study develops a life-cycle assessment (LCA) for converting high-ash paper sludge to SAF in the U.S. using a catalytic sugar upgrading system that consists of ash removal, enzymatic hydrolysis, dehydration, aldol condensation, and hydroprocessing. The LCA is coupled with a process simulation for an industrial-scale biorefinery based on experimental data. We quantified the carbon intensity as 35.7–41.8 gCO 2 eq MJ –1 SAF (−636 to −584 gCO 2 eq per dry kg paper sludge) with acetone as a solvent, renewable fuel, and biobased chemicals; this is further reduced to 5.1–11.1 gCO 2 eq MJ –1 (−925 to −873 gCO 2 eq per dry kg paper sludge) if ash is recycled and used for substituting cement. Converting 1 dry kg paper sludge to SAF with acetone, renewable fuel, and biobased chemicals (−925 to −584 gCO 2 eq) is more climate beneficial than landfilling without landfill gas recovery (791 gCO 2 eq) and with landfill gas recovery (−294 gCO 2 eq). More than 330 million gallons of SAF can be produced annually (>4 million dry t paper sludge/year in the U.S.), resulting in a reduction of 2–7 million tCO 2 eq.