The diesel particulate filter (DPF) forces the engine to burn more fuel periodically in order to burn off the particles in the filter. The net result is more CO2 than would be produced ordinarily.
I watched some farming videos, and the farmers calculate the hourly cost of their combine, it's in the 100's of dollars per hour. They hate it when the engine goes into the regen cycle, and they are forced to let the engine run.