What about circulatory systems?
By eating animals for example, bones and other material remain, which could be burned to ashes and used as a supplement for a compost heap, which is used to keep the soils fertile. Also faeces could go that way.
Residue of old homes could be used as biomass -> compost, or burned as firewood -> ashes to the compost -> field
Fertility of the topsoil should increase and so should the harvest.
Durability of old harvest should expire after some time, then -> compost -> field
Increase of durability of the harvest -> conserves, smoked and air dried beef and sausages, drying, canning, fermenting,...