[AlexanderHowl]

It is still going to be ten times as expensive to mine the Earth for nitrogen than to just get it from Titan. Or you couod mine the atmosphere of Venus for nitrogen, which costs half as much to mine than the atmosphere of Earth (normal air mixtures are lifting gases in the atmosphere of Venus, so you can support floating harvesters that use fusion-powered railguns to accelerate canisters to Venutian escape velocity). Or you could mine ammonia ice from Triton, which still costs half as much as mining the Earth for nitrogen. The only reason to take nitrogen from the Earth is if you lack the technology to get it from anywhere else.