Qiujuan Wang
The European Commission’s Farm to Fork Strategy aims for at least 25% of the EU’s agricultural land to be under organic farming by 2030. Yet organic pig and poultry production remains limited in Finland. One major reason is feed: in Finland, as in many other EU countries, livestock production still depends heavily on imported protein feeds such as soy. At the same time, Finland has one important local resource in abundance: grass.
Grass–clover mixtures are especially valuable in organic systems because clover, as a forage legume, is capable of biological nitrogen fixation and helps reduce the need for external nitrogen fertilisers. This makes grass-clover not only a common crop, but also a sustainable one.
This raises an important question: could grass be processed into a protein-rich feed ingredient for organic pigs and poultry, rather than being considered only as feed for ruminants and horses?
My thesis explored exactly that idea. The product studied was grass protein paste, produced through a green biorefinery process. In simple terms, green biorefining means separating fresh or ensiled plant material into different useful fractions so that nutrients can be recovered more efficiently and used for several purposes.
To investigate this, organic grass-clover biomass was mechanically separated into a solid fraction and a liquid fraction. The liquid fraction was further processed to produce grass protein paste. Some samples were left to ferment naturally, some were treated with different additives. The aim was not only to determine whether the paste contained enough protein and amino acids to be nutritionally meaningful, but also to understand how different processing methods affected its quality.
Results
The results were promising, although not without limitations. The grass-clover biomass contained a moderate but nutritionally relevant amount of crude protein, and the protein paste derived from it showed potential as a supplementary protein source for pigs and poultry. Its crude protein concentration 300g/kg dry matter was clearly higher than that of common cereals such as barley and was close to the level of faba bean. In other words, this was not merely a by-product of grass processing, but a material with real feeding value.
The amino acid profile, however, was less satisfactory. Amino acids are particularly important in pig and poultry nutrition because these animals require not just protein, but protein of suitable quality. Lysine is usually the first limiting amino acid in pigs, while in poultry methionine is often the first limiting amino acid, with methionine and cysteine together forming the limiting sulfur amino acids. Compared with traditional protein feeds, the amino acid composition of the grass protein paste was relatively weak.
Even so, the study highlights a broader opportunity within green biorefinery systems. Mechanical fractionation did not concentrate all nutrients into a single product. Instead, nutrients were distributed between the solid and liquid fractions, creating the possibility of developing several useful co-products from the same biomass. The liquid fraction by-product, for example, showed clear differences in fermentation quality depending on treatment, and was evaluated in another study as a supplement in crimped grain preservation. This fits well with the principles of circular agriculture, where one crop can produce several useful outputs.
So what is the overall message?
Grass-clover protein paste has genuine potential as a locally produced, sustainable supplementary protein source for organic pigs and poultry. It is unlikely to replace soybean meal completely, but it could help reduce dependence on imported protein, strengthen regional feed systems, and support a more resilient form of organic livestock production. For Finland, where grass already shapes much of the agricultural landscape, this research points to an encouraging possibility: the future of organic animal feeding may depend less on importing protein from abroad and more on unlocking the value of crops that are already growing at home.
This thesis is deliverable of “Novel feeds for organic pigs and poultry -NovOrgFeeds” a joint project of Natural Resources Centre of Finland and Helsinki University, funded by FORI. Read more about the project.
Photos: pigs by Marjo Hokka and clover by Sari Iivonen