interesting re carbon emissions by jets. years ago, most jets left a trail of black ( carbon ) smoke. but for a variety of ' non scientific ' reasons re carbon emissions, the carbon smoke disappeared. One reason was efficiency, one reason was military - smoke trail make a good pointer as to where you are. one reason was the ' appearance ' of evil carbon.
OK- but to eliminate the carbon smoke trail, absent some real expensive methods- and generally impractical for airplanes - the easiest way was relatively simple - raise the combustion temperature. ( simplified explanation ). OK but when you do that, you create more Nitrous oxide ( disassociation of the 72 percent N2 in the air ). Nitrous oxide and related combustion products mixed with moisture- becomes ..."acid " rain . And in the extreme ( industrial ) process, can be made into Nitric Acid.
carbon is essential for life, nitrous ..... is NOT