Biorefining of perennial grasses: Development of visible and near infrared tools for assessing fineness of extracted fibre

The biorefining of grass offers an opportunity to integrate primary production agriculture with the extraction of fibre. The study was aimed at developing protocols for processing ryegrass to determine fibre content and to generate visible and near infrared reflectance (Vis-NIR) calibrations for estimating fibre fineness with the aid of a new reference airflow method. The method for determining fineness of processed fibres has been adapted from flax fibre protocols. A Vis-NIR calibration using partial least squares (PLS) regression method was employed to generate models with a calibration set consisting of 85 samples obtained from fresh and ensiled grasses. The PLS model was successfully validated with 21 independent samples with a prediction error of 1.26 dtex. An optimised PLS model (r² = 0.86) consisting of 106 samples has been developed. The quality assurance protocols could be used for assessing fibre content and quality of silage, hay and fresh grass.