Factors driving refinery CO2 intensity, with allocation into products

Background and scope Attempts to develop adequate allocation methods for CO 2 emissions from petroleum products have been reported in the literature. The common features in those studies are the use of energy, mass, and/or market prices as parameters to allocate the emissions to individual products. The crude barrel is changing, as are refinery complexities and the severity of conversion to gasoline or diesel leading to changes in the emissions intensity of refining. This paper estimates the consequences for CO 2 emissions at refineries of allowing these parameters to vary. Materials and methods A detailed model of a typical refinery was used to determine CO 2 emissions as a function of key operational parameters. Once that functionality was determined, an allocation scheme was developed which calculated CO 2 intensity of the various products consistent with the actual refinery CO 2 functionality. Results The results reveal that the most important factor driving the refinery energy requirement is the H 2 content of the products in relation to the H 2 content of the crude. Refinery energy use is increased either by heavier crude or by increasing the conversion of residual products into transportation fuels. It was observed that the total refinery emissions did not change as refinery shifted from gasoline to diesel production. Discussion The energy allocation method fails to properly allocate the refinery emissions associated with H 2 production. It can be concluded that the reformer from a refinery energy and CO 2 emissions standpoint is an energy/CO 2 -equalizing device, shifting energy/CO 2 from gasoline into distillates. A modified allocation method is proposed, including a hydrogen transfer term, which would give results consistent with the refinery behavior. Conclusions The results indicate that the refinery CO 2 emissions are not affected by the ratio of gasoline to distillate production. The most important factors driving the CO 2 emissions are the refinery configuration (crude heaviness and residual upgrading) which link to the refinery H 2 requirement. Using the H 2 -energy equivalent allocation proposed in this study provides a more reliable method to correctly allocate CO 2 emissions to products in a refinery in a transparent way, which follows the ISO recommendations of cause-effect and physical relationship between emissions and products. Recommendations and perspectives Regulatory activity should recognize that there is no functional relations