As global food demand grows, competition for natural resources and the need for climate-smart agricultural systems present major challenges. Grass is an important resource not only as feed and food, but also for its environmental benefits, including carbon sequestration and biodiversity support. Traditionally, grass has been used to feed ruminants, but intensive use can lead to increased enteric methane production. Moreover, with livestock numbers in the EU expected to decline due to improved productivity and societal pressures, large areas of grassland could become underutilized. Green biorefineries offer a promising alternative by converting grass into products like human food, feed, biogas, paper, and other value-added materials. However, challenges remain, such as ensuring year-round availability of grass as feedstock for green biorefineries and preserving the quality of derived products.
The thesis had three main aims. The first aim was to investigate whether supplementing high forage diets with lipid-rich concentrates containing rapeseed cake and oats could lower the elevated enteric methane production in dairy cows without affecting feed intake or milk yield. The second aim was to examine how different preservation methods, such as ensiling, freezing-and-thawing and drying-and-rehydrating, and the use of formic acid-based additive influence the yield and composition of liquid extracts from grass. The third aim was to assess how the type of grass (first or second cut timothy), its condition (fresh or ensiled), and additives (lactic acid bacteria inoculant or formic acid) affect the efficiency and quality of biorefinery outputs.
Key findings indicated that lipid supplementation through natural feed ingredients effectively reduced methane emissions in cows fed high-forage diets without compromising feed intake or the production efficiency of energy-corrected milk. All preservation methods examined improved liquid yield and composition compared to fresh grass, with ensiling showing the highest yield. The results also showed that the choice of raw material and additives significantly affected the biorefinery output. Using formic acid as an additive reduced protein solubility, while lactic acid bacteria inoculant increased protein concentration in the liquid.
The insights from this thesis offer practical guidance for dairy farmers, industrial stakeholders and policymakers. By adopting practical changes in feeding practices, the climatic impact of grass-based dairy production could be reduced, and grass production can be enhanced to support carbon sequestration and lower greenhouse gas emissions associated with concentrate feed production. Additionally, green biorefineries present new economic potential for farmers and innovation opportunities for industries by transforming grass into valuable products.
MSc Nisola Ayanfe will defend her doctoral dissertation entitled "Optimizing grass utilization: Sustainable approaches for enhanced dairy production and green biorefinery performance" in the Faculty of Agriculture and Forestry, University of Helsinki, on 5 September 2025 at 13:00. The public examination will take place at the following address: Metsätieteiden talo, Raisio-sali (ls B2), Latokartanonkaari 7. Professor Jon Moorby, Aberystwyth University, will serve as the opponent, and Professor Aila Vanhatalo as the custos. The defence can be followed remotely using the following link: https://video.helsinki.fi/unitube/live-stream.html?room=l12.
The dissertation is available in electronic form in Helda.
Contact: Nisola Ayanfe nisola.ayanfe@luke.fi