> It's not safe to grow veggies and grains with human manures.
Not true. My wife does research on this and post-sewage treatment dried sludge actually has better values than some of the food the used as reference samples.
Have you explored humaneur production? It strikes me that properly composting the waste ought to be enough to destroy any problematic bacteria. Would love to know what you ran into that may have prevented doing that. Been thinking about incorporating regenerative systems to build a food forest and trying to figure out safely handling biowaste. Even goose poop is potentially toxic.
Yes you can properly compost human manure, to make it safe... But the process is more complicated and involves processes which cannot be skipped. I would rather do less work and be safer.
This means I simply don't use human manure on my agriculture crops, I use it in my forested areas.
That said, I do use urine in my grass/leaf compost, and recently I started charging biochar with human urine. Urine is much safer that feces.
It's just a superstition but I wouldn't eat veggies grown directly in human manure (although the guy has done and hasn't gotten the sponge-brain: https://humanurehandbook.com/ )
Being unfit for human consumption is actually a feature not a draw back. We need to trigger growth and get humans off the sand so that nature can do her thing.
I met someone once who after sinking tons of his own money into projects argued you need poop and some kind of toxins to keep people and their goats away for at least 30-50 years. His experience was that people destroying everything scales much faster than constructive effort. You turn your back and everything is gone.
Of course something is to be said for economically viable greening but if you just want to restore nature you should aim to do just that.
I don't have the numbers here but I found calculating how many large trees you need to sustain 1 human vs how much electrolysis it would take pretty mind boggling.