Unless you use a foot-pump to recharge the cylinders then you will use gas or oil to generate electricity to power the pump. Don't forget that compressing air takes power and looses some of it as heat.
Reading the article, I see that you get 'topped up' with compressed air at appropriate points for quite a cheap rate, I agree that it takes fuel to compress the air, but I can't see the supplier doing it at a loss. And whatever energy that supplier is using to run the compressor, surely it is using a lot less and, hence, producing less pollution!
The only way to reduce carbon emissions from cars is to ensure alternatives to petrol and diesel have less total emissions than the normal. For example, electric cars produce emissions at the power stations, as do hydrogen powered ones, and maybe compressed air too. Unless power stations capture the CO2 at source, you are just shifting the pollution to them. Carbon capture is absolutely vital. Ideally the captured CO2 would be "fed" to algae to produce fuel - a distant dream.