Integrating duckweed into circular dairy farming
In 2016, Ecoferm, a dairy farm in Uddel, Netherlands, conducted a pioneering study on integrating duckweed into its farming operations. The research aimed to explore duckweed's potential to recycle nutrients from farm wastewater and use it as an alternative protein source in animal feed. The project examined both the environmental and economic benefits of cultivating duckweed on-site.
Description of the nutrient recycling
Scheme of the ecoferm stable where urine and the liquid fraction of digestate is used as a fertilizer to grow duckweed on the roof of the stable. Heat and CO2 produced by the cows is used by the duckweed that is eventually fed to the cows.
Scheme is copied from the ecoferm report
Key findings
- Light exposure was the most limiting factor, causing duckweed production to plateau at 11 tons DM/ha/yr. If the light transmittance of the roof were increased by 90%, production is estimated to reach 25 tons DM/ha/year. If light exposure were further supplemented with artificial light (LED), duckweed production could potentially increase to 50 tons DM/ha/year, if other growth factors are optimal.
- It is important to avoid stagnant areas in pond design, as duckweed easily accumulates in the corners, complicating harvesting and the choice of harvesting time.
- The financial benefit of using duckweed in the feed diet was relatively limited, but still meaningful. The nutritional value of duckweed for livestock needs to be improved (high OEB content, DVE comparable to grass but low compared to soy, and the dry matter content is very low when fed fresh). Currently, incorporating duckweed mainly replaces silage grass in the diet, but this could change if the price of soy increases.
- There is still great potential for duckweed, especially if cultivation costs decrease and technology for harvesting and preparing the nutrient medium improves.
Pictures
