Not quite, it depend where the carbon forming the CO2 comes from. Carbon extracted from sewage is already in the carbon cycle giving a net 0 carbon when burned. Extracting and burning fossile carbon ADDS carbon to the cycle, hence the problem
Or we could extract it and not burn it, making it "carbon negative".
Though your comment has a problem. It isn't carbon that is the problem, it is carbon in the air. If we did 100% CO2 extraction from coal fire plants they wouldn't be a real climate issue (overly simplified). Similarly we can't consider sewage as a carbon 0 cycle because eating turns a solid carbon source (food) into a gas. Carbon is fine, carbon in the air is not fine. Sewage is only neutral in the respect that we've already converted it to a gas (unless we accelerate this process, which is typically done) but doesn't account for the conversion process that happens.
Yes, thank for this! Not burning are net 0 biofuels is equivalently the cheapest carbon capture we can do.
It's very good to analyze specific flows, but at the end of day, greenhouse gases (appropriately weighted) in the air are a fungible liability, and taking some specific process and sanctifying it's net greenhouse gas emissions in isolation is silly.
