Co2 on a budget

I am looking for a cost effective way to supply my grow area with proper Co2 levels. My grow area is 8' tall x 4' wide x 2' deep. I have read "How much co2 should I add?" in the FAQ and have calculated that i need to add about .075 cubic feet of Co2 to my area to raise the levels to 1500 ppm. If i use a method like ( "Stickydank's basic CO2 method" Text ) how would i maintain the propler lever with an exaust fan and intake ports working 12 hours a day??

That's a decent method if you can then distill the alcohol into something drinkable. However, if you have intake and exhaust fans working 12 hours a day, your plants will be supplied with plenty of CO2, and supplementing it will not have much of an effect.

I bought a tank and regulator and it was a huge waste of money I don't even use it anymore.