To reduce CO2 emissions, all animal life, including humans, must be wiped from the Earth ... to save it ... or plant more trees.
In the 1970s/1980s, they were worried about acid rain, aerosols, smog ozone ... but not volcanic ash from Mt St Helens ... so we switched to unleaded gas ... why did they put lead in gasoline to begin with, who knows? It was the olden days.
We can also perpetuate cyanobacteria in bodies of water to increase oxygen production. Just don't drink or swim in that water.