Grass refinery as a key to more sustainable dairy farming

Founded in 2014, Grassa processes grass into high-value products: protein-rich ingredients as a sustainable alternative to soy, a prebiotic sugar that can support gut health, and plant-based fertiliser. Grass protein contains seventeen per cent more essential amino acids than soy and can already be used to feed pigs, poultry, fish and pets. Approval for human consumption is currently under review by the European Food Safety Authority.

Grass refinery thus turns grass into a remarkably versatile crop. However, the journey from technological development to practical application is a long one. “Hard data on the impact of grass refinery on nutrient cycles and dairy farm economics was lacking. ‘Farmers need that insight before they decide to join,’ says Smook, Managing Director of Grassa.” 

Two years ago, Grassa moved from Venlo to Wageningen Campus, driven by the opportunities for collaboration and access to research. During a meeting with Gert van Duinkerken, Director of Wageningen Livestock Research, a research question emerged.

An earlier joint study at the Dairy Campus had shown that fifty per cent of the protein can be extracted from grass while the remaining fibres can still be fed to cows. When part of the regular feed is replaced by these grass fibres, cows continue to produce the same quantity and quality of milk, while emitting less Nitrogen and Phosphate via manure and urine. The logical follow-up question was: What does this mean concretely for the nutrient cycle and the economics of a dairy farm? Van Duinkerken proposed tackling this question together.

Smook was able to agree quickly thanks to a new SME fund launched as a pilot by TKI Agri&Food in collaboration with WUR. The fund enables exactly these types of practice-oriented research for small businesses. Questions like these are highly relevant, but as a small company, it’s not easy to secure funding to explore them. Without this pilot, we would not have been able to answer our question. Van Duinkerken adds: “The fact that Rieks and I spent time during the summer holidays writing a project proposal says it all. We are pleased with instruments like this that enable collaboration between industry and research.”

In the project, which ran from September 2025 to January 2026, Wageningen Livestock Research carried out model calculations for three types of dairy farms: an intensive farm on clay soil with both grass and maize in the crop plan; an extensive grass-based farm on peat soil; and an extensive farm on sandy soil, also combining grass and maize.

The calculations were carried out using the Dairy Farm Budgeting Program (DairyWise). The researchers mapped the effects of grass refining on Nitrogen and Phosphate flows and greenhouse gas emissions for different farm types, and also conducted an exploratory economic analysis. The calculations were calibrated against the KringloopWijzer and the farm-specific excretion (BEX) records. These tools were developed by WUR and are widely used by dairy farmers on a daily basis. “This means the outcomes of our research can be directly applied on the farm”, says Van Duinkerken.

A key question for Grassa was how much Nitrogen and Phosphate actually leave the farm through the refining process. “Our initial calculations turned out to be too optimistic,” says Smook. The validated model showed that slightly more Nitrogen remains in the manure than expected. “That’s disappointing, but I’m pleased that the methodology is now sound. A validated method is worth more to us than an overly optimistic calculation.”

At the same time, the model revealed unexpected opportunities: grass refinery can also reduce costs on the feed side, as the protein-reduced fibres make the feed ration more efficient. Expensive components in feed could potentially be replaced by self-produced, processed grass. Van Duinkerken explains: “The environmental and economic benefits of grass refining are somewhat smaller than Grassa had anticipated. However, our calculations do confirm that their line of thinking is correct. Grass refining benefits both the environment and farm economics, making it a viable solution in practice.”

For Grassa, collaboration with WUR is also strategically important. Smook says: “As a growing company, we rely heavily on investors and government support. These parties have confidence in our approach, partly because of the involvement of Wageningen University & Research. They know the quality of research here is high.”

The next step is turning the results into practical applications: Grassa will start collaborating with fifteen dairy farmers in Kootwijkerbroek to implement grass refining this spring. The real-time data generated will be compared with the model, gradually bringing Smook’s vision closer to reality. “Ultimately, I want to demonstrate that with forty per cent of Dutch grassland we can solve the manure surplus, and that the alternative to soy is already growing on Dutch grasslands, with the potential to replace the entire domestic demand for soy. These are the kinds of statements that matter to governments and investors.”

He encourages other SMEs to collaborate with knowledge institutions as equal partners rather than solely as clients. Although he remarks, in a light-hearted manner, that relocating to Wageningen Campus could be advantageous.