Influence of the structure and properties of lignocellulose on the physicochemical characteristics of lignocellulose-based residues used as an environmentally friendly substrate

Abstract

The extensive use of nonrenewable peat does not meet the strategic goals of sustainable development. This study explores the advantages and disadvantages of using lignocellulose-based agricultural and forestry wastes as peat substitute in substrates for soilless cultivation; further, it also investigates the key factors influencing the physical and chemical properties of the substrates. Accordingly, the physical and chemical properties of four gramineous crop straws and two woody forestry wastes were determined and compared with those of peat and coconut bran. In addition, cellulose, hemicellulose, and lignin were extracted from wheat straw and pine sawdust, and their basic characteristics and structures were compared and analyzed. The results showed that the influence of particle size on the physical properties of substrates was significantly higher (P < 0.01) than the influence of the substrate type, especially with respect to the water-holding and aeration porosities, which had effect sizes (Eta2) of 73.8% and 68.2%, respectively. The electrical conductivity values of the four straws (1.87–3.42 mS/cm) were higher than those of peat and coconut bran (0.50–0.96 mS/cm), which was mainly due to the high hemicellulose contents (28.52%–30.10%) and total nutrient contents (28.46–47.81 g/kg) of the straws. In contrast, the electrical conductivity values of the woody waste substrates were lower (0.28–0.33 mS/cm) than those of peat and coconut bran. Peat and coconut bran contained the lowest cellulose (17.84%–20.95%) and hemicellulose contents (5.14%–7.19%) of all substrates, resulting in a low degradability and good stability. The crystallinity of coconut bran (23.06%) was significantly lower than that of all other substrates (30.36%–43.03%), which mainly contributed to the superior compressibility of coconut bran. The best pretreatment method for biomass waste used as a substrate should be selected according to the target properties of the corresponding components.