Humanure Composting and Carbon sequestration

Had a difficult conversation with ChatGPT today running some numbers, since this kind of math is difficult for me. Obviously, there are some missing factors here demanding a more robust audit. For example, this assumes we are not already composting any percentage of global human feces, which must be factored in. However, it's a starting point for further research. Annual composting of human wastes can offset anthropogenic CO2 loads in the atmosphere, at an annual rate of 4.6%, in only 64 years.

I'd be curious if anyone could run the numbers better.

Hi Jesse,
While I am all for the increase in composting, I think some of these numbers give a false sense of the problem. My friend google says that (in the US at least) 1 in 4 homes uses a septic system. Most septic systems break down feces and are eventually drained out in a leach field of some kind. Many city septic systems do actually have a kind of composting that they do with the solids. It may not end up as "compost", but it turns back into soil even if its dumped in a landfill. I think the actual amount of human feces that get "composted" (and I'm using that loosely to mean turning back into humus or soil), is actually quite high. It may not be done on site, and it may not be done in a way that keeps stuff out of the rivers, and it may not be done in a way that completely gets rid of all bad bacteria, but they are processing it. Sometimes people go to an extreme and seem to think that anything that is not composted yourself in the back yard, is just being piled up somewhere spreading diseases constantly forever. I think they could do better, but if they were not composting the solids somewhat, then we would have a lot more people getting sick from it.  

ChatGPT got its numbers wrong (again). Our CO2 excess since 1750 is 850 gigatons and climbing. But the main thing to consider in humanure systems is that the more aerobic they are, the less methane comes out of the process. If you accept that a certain amount of carbon is going back to the atmosphere regardless of what you do, it's far better to make that CO2 and get all the nutrient benefits for your soil (which could very well offset some if not all of the emissions by enhancing microbial life and humus formation), rather than a septic or municipal sewer system that digests anaerobically and puts out methane.

There's a "middle way" possibility and that's to use AD to produce biogas, but it's fiddly and most households don't produce enough to really keep one going.