DC's water treatment plant does this. Solid waste goes into a biodigester which produces methane which is used to create electricity to help run the plant. Th

DC's water treatment plant does this. Solid waste goes into a biodigester which produces methane which is used to create electricity to help run the plant. The other product is "biosolids" which are rated safe for use on food crops. https://www.dcwater.com/biosolids https://www.dcwater.com/biosolids This wouldn't be nearly enough though. The amount of human waste is, however, dwarfed by animal waste.