Nitric acid-alkali two-stage pulping of wheat straw, industrial hemp, and Miscanthus x giganteus

Abstract

Index levels of the process of pulping wheat straw (WS), industrial hemp stalks (HS), and Miscanthus × giganteus (MS) using the nitric acid-alkali (NA−A) method (HNO3/KOH and HNO3/NH4OH two-stage sequential delignification systems) were determined. The research showed, as a rule, a lower total yield of NA−A pulps than kraft pulps from WS, HS, and MS, and a lower level of the tensile index and tear resistance compared to the properties of soda-AQ and kraft pulps presented in other studies, as well as the author’s own studies. Additionally, the levels of nitrogen (in different forms) and potassium in the combined post-pulping filtrate were determined. Their levels were found to be higher than in the fertilizer solution used to fertilize tomato crops grown on soilless substrates in greenhouses. However, application of filtrates from pulping of nonwoody plant straw using NA-A method requires determining the effectiveness of this type of fertilizer solution, its impact on the horticulture and agriculture plants, and the properties of their output including grains, tubers, and fruits.