| dc.description.abstract | The aviation industry has embraced the production and use of renewable jet fuel (RJF) to bring down greenhouse gas (GHG) emissions associated with the aviation industry. Currently, four types of RJF are certified to be blended with conventional jet fuel for the use in aircrafts. These are: HEFA RJF from vegetable oils and used cooking oil, FT RJF from lignocellulosic biomass, DSHC RJF from sugars and ATJ RJF from butanol. Other conversion pathways are still in an experimental phase. These are HTL- and Pyrolysis- RJF from forest residue. Promising GHG performances are reported for all pathways, but a coherent comparison cannot be made.
Several challenges emerge regarding the comparison of GHG performance of RJF pathways. Globally accepted harmonized methods to assess biofuel GHG performance in a coherent way do not exist as different regional and national regulation standards such as the Renewable Energy Directive (RED) in the EU and the Renewable Fuel Standard (RFS) in the US impose different methods. The main difference between the methods imposed by the regulation standards is the treatment of co-products when processes have multiple outputs.
The aim of this study was to make a coherent comparison of GHG performance of RJF conversion pathways, different combinations of feedstock and conversion processes are assessed, including different co-product treatment methods and coherent data assumptions.
Results of the assessment showed that GHG performance of RJF conversion pathways depends on applied co-product methods, feedstocks, conversion pathways and hydrogen inputs. Depending on the co-product treatment method, the highest GHG performance was found for FT pathways, of which FT from forest residue has the highest performance with GHG emissions lower than 5 g CO2 /MJ RJF. The conversion pathways with the lowest GHG performance are found to be DSHC from sugarcane and ATJ from corn with GHG emissions larger than 50 g CO2 / MJ RJF depending on the combination of feedstocks and conversion processes. GHG performances of HEFA pathways differ between -39 - 54 g CO2 /MJ RJF, for ATJ pathways from sugar beet or sugar cane between 29 - 38 g CO2 /MJ RJF ,for HTL pathways between 17 – 21 g CO2 /MJ RJF and for Pyrolysis 23 – 63 g CO2 /MJ RJF.
The results of this study show that a clear ranking of conversion pathways can only be made for pathways that are based on coherent data inputs and the same co-product treatment method. | |
