Hemp raw materials: The effect of cultivar, growth conditions and pretreatment on the chemical composition of the fibres

Hemp raw materials were analyzed chemically to determine their content of cellulose, hemicellulose, lignin and ashes. Correction for ashes was only necessary in the first step of the chemical analysis: the Neutral Detergent Fibre step. The hemp fibers contained 73-77% w/w cellulose, 7-9% w/w hemicellulose
and 4-6% w/w lignin, while the hemp shives contained 48% w/w cellulose, 21-25% w/w hemicellulose and 17-19% w/w lignin. Among the four investigated cultivars, Felina contained least lignin, while Futura and Fasamo contained least cellulose. Hemp yarn had the same color as retted hemp fibers but was more cellulose rich. Steam explosion, wet oxidation and hydrothermal treatment were used for defibration of retted hemp fibers. These pretreatments removed lignin and hemicellulose resulting in loss of dry matter of 15-73% w/w and in loss of cellulose of 0-69% w/w. Steam explosion treatment generally gave the biggest
losses. Alkali gave greater losses due to the effect of alkali in opening the structure of the molecules making them more accessible for degradation.