Yes but consider that the amount of CO2 produced by the machines...

Yes but consider that the amount of CO2 produced by the machines manufacturing and upkeep should be well below its usage. Dr. Karl stated that the manufacture of enough machines to counter the entire global CO2 production per year is roughly equivalent to the manufacturing of cars every year. This means that if we switched from manufacturing cars to these machines, in one year we would have enough to counter the CO2 emissions of the entire world. A small increase in emissions for a large and continuous decrease is a pretty easy choice, unfortunately decreasing emissions is the only use these machines have, and that is not very profitable.