The research published in the journal Results in Engineering by authors Binbin Yang and Mingming Hu addresses the critical problem of soil degradation in mining areas, specifically focusing on molybdenum tailings in China. These industrial waste sites often feature soil that is too alkaline, lacks organic life, and is highly prone to becoming compacted or cracking under harsh weather. When the ground cracks, it creates easy pathways for moisture to evaporate and for dangerous heavy metals to wash away into the surrounding environment. To fix this, the scientists tested a combination of fly ash, an industrial byproduct, and biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More made from plant waste. Their goal was to see how these two materials work together to keep the soil moist and prevent it from splitting open during repeated cycles of getting wet from rain and drying out in the sun.

The results of the study show that using both materials together is much more effective than using just one. The most successful mixture consisted of 10 percent fly ash and 4 percent biochar. This specific blend allowed the soil to hold onto more than twice the amount of water compared to untreated soil after the very first time it dried out. The researchers discovered that this combination creates a unique internal structure where the fine particles fill in tiny gaps in the soil. Simultaneously, the fly ash undergoes a chemical reaction when it touches water, creating a cement-like substance that physically glues the soil particles and biochar together. This reinforces the ground, making it much tougher and more resistant to the stress that usually causes it to pull apart and crack as it loses moisture.

One of the most impressive findings was how this treatment performed over time. Even after being put through five consecutive rounds of heavy wetting and intense drying, the soil with the 10 percent fly ash and 4 percent biochar mixture continued to show improvement. In fact, while untreated soil became increasingly cracked and disorganized with every cycle, the treated soil actually became more stable. By the end of the experiment, the complex network of cracks in the treated soil was reduced by nearly half compared to the control group. This long-term stability is vital for real-world mining sites where the ground is constantly exposed to the elements and needs to remain intact to support new plant growth and prevent erosion.

The way moisture moves through the soil was also significantly changed by the additives. Normally, water evaporates very quickly from the surface of tailings soil. However, the study found that the fly ash and biochar blend delayed this initial rapid loss of water by many hours. Because the mixture fills up the pores in the dirt and creates a tighter, more compact structure, it blocks the “highways” that water usually takes to escape into the air. This results in a much slower, more gradual drying process that keeps the deeper layers of the soil moist for a longer period. This extra moisture provides a much better environment for tiny microbes and plants to survive in areas that would otherwise be a barren wasteland.

Ultimately, this research provides a practical and efficient way to recycle industrial and agricultural waste to heal damaged land. By turning fly ash and biochar into a soil-healing mixture, mining companies can reduce the environmental risks of their operations while improving the stability of the ground. While more tests are needed to ensure these materials don’t release their own pollutants over many years, this study offers a clear blueprint for using 10 percent fly ash and 4 percent biochar as a powerful tool for environmental restoration in arid mining regions.

Source: Yang, B., & Hu, M. (2026). Synergistic mechanisms of biochar and fly ash on water retention and crack suppression in molybdenum tailings soil under wet-dry cycles. Results in Engineering, 29, 109934.