Duckweed has been proven to be an important "missing link" in the connection of terrestrial and aquatic production of food, feed, fuel, and fertilizer. Farmers are discovering how leaching nutrients from fields can be recaptured in run-off ponds and be returned to fields as soil-building, high nitrogen organic biomass. In developing countries, many small farmers practice semi-closed loop production of such cycles as ducks, fish, food plants, and duckweed. A typical cycle might consist of the following:

The irrigation in this instance goes to food plants. Residual plants get chopped and go back into the biogas digestor.
Note: Diagram credits to R.A. Lang/www.UTAFoundation.org