IMO, it kind of depend on your ventilation system as to whether it'd be worth your time and effort.
If you're recycling your air, or drawing in very little fresh air, then definately give it a try.
In my case, I'm pulling in so much fresh air - it should be totally exchanging the air about 3 time per minute. I don't think that a DIY CO2 gen would be able to keep up. A tank might be able to, but again, with that much air turnover - there should already be an excess of natural CO2 in the fresh air.