Inulin biopolymer as a novel material for sustainable soil stabilization

The development of new urban areas necessitates building on increasingly scarce land, often overlaid on weak soil layers. Furthermore, climate change has exacerbated the extent of global arid lands, making it imperative to find sustainable soil stabilization and erosion mitigation methods. Thus, scientists have strived to find a plant-based biopolymer that favors several agricultural waste sources and provides high strength and durability for sustainable soil stabilization. This contribution is one of the first studies assessing the feasibility of using inulin to stabilize soil and mitigate erosion. Inulin has several agricultural waste sources, making it a sustainable alternative to traditional additives. Soil samples susceptible to wind erosion were collected from a dust-prone area in southwest Iran and treated with inulin at 0%, 0.5%, 1%, and 2% by weight. Their mechanical strength was evaluated using unconfined compressive strength tests and a penetrometer. In addition, wind tunnel tests (at 16 m/s) were performed to investigate inulin's wind erosion mitigation potential. The durability of treated samples was evaluated after ten wetting-drying cycles to assess the effect of environmental stressors. The results indicated a 40-fold increase in the unconfined compressive strength (up to 8 MPa) of the samples treated with 2% inulin and only 0.22% weight loss after ten wetting-drying cycles. SEM images revealed the formation of biopolymer-induced particle-to-particle bonds. Moreover, Raman spectroscopy indicated molecular (hydrogen) bonding of the biopolymer hydrogel-soil particles facilitated by the hydroxyl groups of inulin. The deterioration in stiffness and strength of treated samples was less noticeable after 3rd dry-wet cycle, indicating the durability of the samples. The durability of samples against wet-dry cycles was attributed to molecular bonding of soil-biopolymer hydrogel, as revealed by FTIR analysis.