Diluent Emissions

[SHayton-ERCE]

The calculation of emissions associated with the use of diluent appears to originate from the following equation:

diluent_bbl_per_day * LHV_diluent_mmbtu_per_bbl [MMbtu/d]; Energy Summary Cell F88

• NG GHG density [gCO2e/MMBtu]; Fuel Cycle Cell D72
  / output denominator [MJ/d]; Energy Summary Cell F128

This would assume that all of the diluent is combusted, and calculates the emissions of the same, resulting in quite a significant over-estimate. In practice, the emissions are more likely to be associated with (1) the heat required to separate diluent (e.g. by vaporisation in a separator/column) and (2) transport it back and forth.

The calculation for (1) is as follows, and should replace the terms (above) contained within the formula in Energy Summary Cell F88:
diluent_bbl_per_day * (diluent_sensible_heat_mmbtu/bbl + diluent_heat_of_vaporisation_mmbtu/bbl)
For a diluent which is 55 °API, the sensible heat is 61155 btu/bbl, and latent heat is 29326 btu/bbl

The calculation for (2) is already performed on sheet 'Diluent Transport' and included within the "Crude transport & storage" category. This appears to be correct as it includes back-haul from destination to origin.