English: A schematic of a composting toilet with urine diversion and dehydration (UDD). It is best to use two urine collection bins, instead of one as shown in the image, so that the sludge can periodically be emptied in an agricultural plot, similar to the compost. The urine collection bin is to be made of glass or of a transparent plastic material to allow solar heating. In some areas, it may be useful to add a black wooden board behind the urine collection bin. Just as with regular composting toilets, sawdust needs to be added in the appropriate C/N (carbon-nitrogen) ratio to the faeces to obtain compost. The sawdust is usually introduced via the defecation hole.