Feed-Lots

The BTWM system can do more than clean the waste generated by feed-lots and other intensive livestock operations. The duckweed can be processed and used to provide a high protein feed supplement.

Cattle feed-lots are a prime example. These typically produce large quantities of semi-liquid manure, which can pollute underground water sources or local rivers. The BTWM system can clean this waste to EPA standards, and turn it into cattle feed. Experience in the United States have shown that the amount of duckweed grown on ponds fertilised with feedlot manure can meet 10% or more of the protein requirements for the cattle numbers supported in the feedlot.

Duckweed raised on piggery effluent or waste from intensive chicken farms can also be processed and used to supplement soybean meal as a protein source, permitting significant savings in feed costs.

Duckweed as Feed

Duckweed harvested from wastewater ponds can be used as an inexpensive, high-protein feed supplement, providing owners of the BTWM installations with an optional revenue source.

By FAO standards, the protein in duckweed is of very high quality for feeding to animals. Duckweed is one of the richest sources of protein in the plant kingdom. At 30-40%, the protein content of duckweed is equal to that of dried soybean meal. Chickens, ducks, sheep, pigs, cattle and rabbits: all thrive on duckweed.

Moreover, duckweed is far more productive than other feedcrops on a per hectare basis. In terms of protein yields per hectare, duckweed is at least 10 times more productive than soya beans.

Studies carried out by University of New England (Armidale, NSW) and the Department of Primary Industry (DPI) Queensland have shown that duckweed has enormous potential as a vitamin-rich feed supplement.

Duckweed has particular value as a poultry-feed. The plant contains high concentrations of calcium equal to 10-25 g/kg dry matter, ideal for stimulating healthy egg production. In addition, harvested duckweed has large amounts of xanthophylls and carotene, which impart a rich yellow/orange colour to egg yolks.

Duckweed in Aquaculture

As wild fish stocks dwindle, fish-farming has grown. However, conventional aquaculture has a downside: it can actually increase the pressure on marine ecosystems. The reason is that to make 1 kg of fish-meal, it takes 4.5 kg of wild fish. Fish-farming using pond-grown duckweed offers an alternative.

Duckweed provides a complete nutritional package for a range of commercial fish species. It can also be used to as supplement to other feeds. Fish breeds which thrive on duckweed include many commercial varieties of carp, catfish and tilapia. Fish-farmers in many parts of Asia, including Vietnam, India, Bangladesh and China, have used Lemnaceae in commercial aquaculture for many decades.

Duckweed with its high levels of carotene has also been used as a feed for crayfish and fresh water prawns, although this practice is in its infancy.