That's a red herring. Most modern engines are designed to burn cleanly enough that their direct pollution won't overwhelm the atmosphere. When you burn fossil

That's a red herring. Most modern engines are designed to burn cleanly enough that their direct pollution won't overwhelm the atmosphere. When you burn fossil fuels, CO2 production is unavoidable, and reversing the process necessarily requires more energy than the fuel released. The atmosphere and fuels form a giant battery that takes millions of years to recharge, where the discharged state produces a hotter climate.