Most simply an inground tube with no sun protection and effluent flow into collection pit.
PE (poly ethylne) tube digesters are applied in Bolivia (Peru, Ecuador, Colombia and Mexico). The tube PE film is about 300 microns thick. It is bended at the ends and has PVC drainage pipe. PE tubes are very cheap but quite fragile.
Sausages can be produced using EPDM (ethylene propylene diene monomer (M-class).