Green grass as a valuable resource

Gepubliceerd op
20 juni 2014

It’s a common misconception that grass can be used only to feed cows. Grass is an important source of protein – in fact, it contains so much protein that cows’ rations are often diluted with lower-protein products. At the same time, pig feed and chicken feed producers are experiencing a protein shortage. This is why the Frisian company Grassa! decided to examine, together with Wageningen UR, whether grass could be put to better use by means of refinery.

“Grass refinery is relatively simple,” Arie Klop, scientist at Wageningen UR Livestock Research, says. “The process consists of two steps: the grass is broken and then pressed. This allows the protein-rich grass juice to be separated from the fibre-rich press cake. It's a bit like what happens when you wring out grass with your hands. This releases juice as well.”

Pressed grass as cattle feed

Arie Klop has recently been conducting research into whether the press cake – i.e. grass fibre – can be used as cattle feed. And this has taken some time to arrange. “The grass fibres produced by the refining process have a very limited shelf life. In fact, they need to be fed to cows within a day.”

This is why the scientists decided to ensilage the grass fibres, as is also done with ordinary grass. “Once we did this, we came to the conclusion that refining causes the sugars from the grass to also end up in the grass juice, and that the cows therefore no longer wanted to eat the grass fibres. Fortunately, we were able to find a solution to this problem - adding molasses, a by-product of the sugar industry which is also used in compound feed, to the grass fibres. Now that the conservation is better, the cows find the feed more to their taste."

Twice as efficient

While Klop’s project focused on nutrition, this is by no means the only possible application for ‘cracked’ grass. “The fibres can also be used to make egg cartons, cardboard and even dashboards for cars,” Bram Koopmans of Grassa! says. “And the grass juice can also be used as a source for fine chemicals such as fructose and glucose, and fertilisers such as potassium and phosphate. Moreover, the proteins in the grass are handled in a much more efficient way during refining – twice as efficiently, in fact.”

The future of grass refinery

Both Arie Klop and Grassa! feel that there is plenty of reason to continue to work on the optimal utilisation of grass and other green leafy plants. “We are currently designing a system that can process around five tons of grass per hour, and which farmers will be able to rent,” Koopmans says. In addition, Grassa! is also looking to see if the same method could be used to refine other protein-rich crops such as the Ghanaian water hyacinth or the Colombian moringa.

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