Duckweed is the common name given to the simplest and smallest flowering plant that grows ubiquitously on fresh or polluted water throughout the world. If water is not a limiting resource the most appropriate way of using the effluent from the biodigester is for the construction of duckweed ponds. FAO's publication "Productive use of livestock wastes", is a manual for the use of biodigester effluent and ponds for duckweed production. It describes how to produce duckweed in order to produce biodigester from livestock waste.