Life Cycle Assessment of Petroleum Coke Gasification to Fischer-Tropsch Diesel

This work presents a novel study on the life cycle assessment of Fischer-Tropsch diesel (FTD) production via petroleum coke (petcoke) gasification with and without carbon capture and sequestration (CCS). A detailed analysis which focuses on evaluating and quantifying the well-to-wheel (WTW) environmental impacts of converting petcoke to FTD and its subsequent combustion is discussed. The overall process inventory includes mass and energy balances data from our Aspen Plus model, the US Life Cycle Inventory Database, and the GREET model. Life cycle impact assessment (LCIA) categories of the petcoke-derived diesel (PDD) were calculated using TRACI 2.1 v1.04 in SimaPro 8.5.0.0 which is compared against both conventional petroleum and oil-sands derived diesel. In addition, two different plant locations in Canada (Alberta and Ontario) which respectively have very high and low electricity grid emissions were considered as they are representative of grid emissions across the world. Results of the analysis showed an overall reduction in fossil fuel depletion of up to 80% and 83% for Alberta and Ontario respectively when compared to the fossil derived diesel. When operated with CCS, the WTW GHG emissions were 7% lower than conventional petroleum diesel and 18% lower than oil-sands diesel for the plant located in Ontario. However, when located in Alberta, the WTW GHG emissions were 49% higher than conventional petroleum diesel and 30% higher than oil-sands diesel. This is due to the significant electricity requirement for the PDD process and the vast differences in carbon intensities of the Ontario and Alberta grids. Overall, the other impact categories for the PDD process showed to be significantly lower than the petroleum and oil-sand derived diesel.