Annual protein yield and extractable protein potentials in three legumes and two grasses

Background: New protein sources with low environmental and climatic impact are needed. Perennial crops show advantages as compared to annual crops and the upcoming biorefinery technology can extract proteins from the perennial biomass for protein concentrate production. The search for best-suited biomass crops needs to include harvest during the full growing season to support economic viability of biorefinery plants. Here we examined two grasses under increasing N fertilizer regime (175, 350 and 525 kg N ha^-1 ) and three legumes, subject to a four-cut strategy. The well-defined Cornell Net Carbohydrate and Protein System (CNCPS) was used to estimate potential extractable protein. A key, previously presented in the literature, was applied in order to translate the CNCPS results into potential extracted protein concentrate.

Results: Crude protein (CP) yield per hectare was highest in red clover in 2015 (2907 kg CP ha^-1 ) and the fertilized (525 kg N ha^-1 ) tall fescue in 2016 (2435 kg CP ha^-1 ). When translating the numbers into potential extraction of protein concentrate, the red clover had the highest protein concentrate yield per hectare in 2015 (835 kg CP ha^-1 ) and lucerne in 2016 (803 kg CP ha^-1 ).

Conclusion: The results revealed that the entire season needs attention for optimization and not only the first cut, since both CP yields and quality peaks in different cuts across the five species and 2 years. Further knowledge of CP yield responses to field management and species mixtures are needed in order to advise farmers on the optimal crop for biorefining. © 2021 Society of Chemical Industry.