Stupid ideas. Carbon dioxide and Nitrous Oxides are valuable commodities, if you recognize and use them as such. Pumping them underground is a stupid waste.
Algae based biodiesel can be downright simple, and with the addition of CO2 and NOx gases, the algae grows much, much faster. Some types of algae are 50% vegetable oil by weight.
Squeeze out the oil, mix it with ethanol and lye, as a catalyst, then filter it, add 1% petroleum diesel as a preservative, and bingo you have biodiesel. The leftover algae makes good animal fodder.
You can use gray (non-potable) waste water, even before the first drop of biodiesel is produced it is profitable, because it is expensive as hell to dispose of CO2 and NOx otherwise. There are a vast number of diesel engines on the road right now, from motorcycles to cars and trucks to trains, and even ships. Minor modification and they work fine with it.
South of the Mason-Dixon, continual production is probably good for 10 months out of the year.
Add it all up: waste disposal, minimal infrastructure, small resource demand, existing engines and diesel pumps, and it probably even beats gasoline as being efficient.
I think most of us would rather live next to an oil well than the algae pond that will produce anything close to the equivalent. YMMV...