In older systems, wastewater is vented into space, and any solids are compressed and stored for removal upon landing. More modern systems expose solid waste to vacuum pressures to kill bacteria, which prevents odor problems and kills pathogens.
Older systems discharge wastewater into the atmosphere, compressing and storing any solids until landing. In contrast, more contemporary systems subject solid waste to vacuum pressure to destroy bacteria, thereby avoiding odors and eliminating pathogens.