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Evaluation of the Suitability of Engineered Growth of Fungal-Mycelial Networks for Reinforcement of Sands
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: Soil Erosion Research Under a Changing Climate, January 8-13, 2023, Aguadilla, Puerto Rico, USA .(doi:10.13031/soil.23045)Authors: Emmanuel Salifu, Huda Clemens, Edward Kavazanjian, Jr.
Keywords: Erosion, Fungi, Mycelia, Rainfall simulator.
Abstract
Naturally occurring sandy soils are often susceptible to erosion by water and/or wind, thus requiring stabilization. Conventional approaches used as temporary remedial measures prior to the establishment of vegetation (and where suitable vegetation cannot be established) are often associated with high potable water use, application and installation/maintenance costs, significant energy inputs, and increased carbon emissions. This study presents findings from bench-scale rainfall erosion tests conducted to evaluate the suitability of a nature-based engineered living system consisting of fungal mycelium for erosion mitigation. The vegetative component of filamentous fungal species, known as mycelium (Figure 1), grows in soils through the formation of massive 3-dimensional networks of natural fibers at micron-scale. These networks are capable of modifying the hydraulic and mechanical behavior of soils. Mycelia secrete extracellular polysaccharides that bind soil particles together thus improving the formation of water stable aggregates and beneficially altering the surface wettability of the soil grains. Previous studies have shown that mycelium could induce water repellency in sands (Salifu & El Mountassir, 2020), delay infiltration, and reduce hydraulic conductivity (Salifu et al., 2021) thereby reducing the erodibility of sand. However, the influence of engineered mycelium growth on soil erodibility under simulated rainfall conditions is largely unexplored.
Ottawa 20/30 sand amended with lignocellulose fibers was treated with a fungal spores‘ suspension (FSS) of Pleurotus ostreatus fungus. The treated sand was compacted into a 30x15x5 cm test pan and incubated at 25°C for 7-, 10-, and 14-days prior to a rainfall simulation erosion test. Untreated control specimens were prepared using water instead of FSS. A rainstorm of intensity ~6.7 cm/min falling from a height 25cm was induced using a calibrated garden sprinkler (adapted from a Nasco Soil Erosion Simulator Laboratory kit). The specimens were inclined at a slope of 30°. During each rainfall simulation event, runoff and eroded soil were collected from the base of respective specimens 1-minute intervals up to 5 minutes, and then at 3 minutes intervals until sample collapsed.
Untreated soil slopes collapsed after <2 mins of rainstorm, while all treated soil slopes remained stable for at least 8 minutes duration with significantly less soil yield. The 10-day sample withstood up to 13 mins of simulated rainstorm, as shown in Figure 2. Mycelium regrowth was observed in the treated samples 48 hrs. after the end of the erosion tests, showing the potential for long-term low-cost treatment using mycelium. Replenishing moisture loss during growth period could sustain mycelium growth and further enhance soil resistance to erosion over time. These results demonstrate that the engineered growth of mycelium in soils is promising as a nature-based environmentally friendly alternative to the current engineering practices for erosion mitigation.
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