A hydrocarbonaceous fuel additive, fuel composition, and method all lower both carbon particulate emissions and improve slag properties in combustion systems including, for instance, utility furnaces and boiler systems. For a problem with a single output, a backward algorithm or method is used that produces an optimal solution in linear time. The method comprises dispersing a precursor preparation into a spray of charged droplets through subjecting the liquid precursor preparation to electrostatic forces; directing the charged droplets to move toward the substrate; and allowing the charged droplets to generate a beam of gas-phase ions as the charged droplets move toward the substrate. A method of installation and removal of a print cartridge employs access along a primarily vertical path through an open top of the chute. The seat element is composed of a resilient upper body removably connected to a semirigid lower body.