I was just researching emergency turf protocols for use during a civil emergency (economic meltdown, earthquake, civil war, etc) and I realized that a family of 4 actually produce enough urea to fertilize an average sized lawn, assuming they had access to adequate dietary nitrogen (i.e. protein).
I haven't run the numbers on nitrogen percentages and PH levels but I think it would have to be collected in a tank and diluted to the correct % with rain water to avoid "nitrogen burn", then spread on the lawn every week or so. And because it would be supplied at a more steady rate instead of quick bursts, you should get less top growth and stronger roots compared to commercial synthetic fertilizer, requiring less watering and mowing which would save fuel for more useful things like running the generator.
I haven't run the numbers on nitrogen percentages and PH levels but I think it would have to be collected in a tank and diluted to the correct % with rain water to avoid "nitrogen burn", then spread on the lawn every week or so. And because it would be supplied at a more steady rate instead of quick bursts, you should get less top growth and stronger roots compared to commercial synthetic fertilizer, requiring less watering and mowing which would save fuel for more useful things like running the generator.