Use of Anaerobic Digestate Inoculated with Fungi as a Soil Amendment for Soil Remediation: A Systematic Review

TL;DR

This review explores using fungi-inoculated anaerobic digestates to improve soil quality and remove contaminants, with findings showing benefits for plant growth and contaminant reduction.

Contribution

The novelty lies in systematically reviewing the use of fungi-inoculated digestates for soil remediation, highlighting their effectiveness and optimal conditions.

Findings

Digestates inoculated with fungi improve soil stabilization and contaminant removal.

Cattle manure as a biomass source enhances fungal colonization and organic matter degradation.

Optimal temperatures and fungal strains increase remediation efficiency.

Abstract

This systematic review gathers important information regarding the use of anaerobic digestates inoculated with fungi, considering their use as a soil amendment to enhance contaminant removal, plant growth, and soil stabilization. Notably, the excessive accumulation of nutrients contained in digestates, such as phosphorous and nitrogen, could have negative impacts on ecosystems; furthermore, contaminants—such as those derived from mining or industrial activities—represent a latent risk for animals and humans if they enter the food chain. Both these problems could be addressed by inoculating the anaerobic digestates used for soil remediation with fungi. For this review, a systematic search was performed to retrieve relevant scientific studies published in the past ten years. The combined application of anaerobic digestates and fungi contributes to contaminant reduction while improving soil structure. Important findings include that the biomass source used for anaerobic digestion plays a crucial role, with the sole use of cattle manure achieving the best results in terms of fungal colonization and organic matter degradation. It has also been suggested that optimal temperatures result in higher remediation efficiencies. Further research should focus on determining the specific vegetation, existing contaminants, and fungal strains to be used.

This systematic review aims to describe the current state of research on soil remediation utilizing digestates inoculated with fungi, as a cost-effective alternative. This study was performed according to the PRISMA 2020 guidelines, and nine papers were finally selected for review. The application of digestates augments the soil microbial community in terms of bacterial strains, mycorrhizal colonization, and enzymes. Digestates inoculated with fungi have notable impacts on soil stabilization. Some authors reported an improvement of up to 100% in plant growth when using digestates. HM removal rates of 17% for Si, 40% for Cd, and up to 80% for Pb have been achieved. Antibiotics and PFCAs showed low or no accumulation. The biomass source used for anaerobic digestion has a very important impact on the resulting digestate’s quality and effect in soils: the use of cattle manure resulted in an increase in biomass yield from 9% up to 100% when compared to manure co-digested with organic wastes. The fungal strain, environmental conditions, and existing contaminants must be considered with respect to the specific practical application. These insights can contribute to the management of environmental risks and the prevention of negative impacts on human health, ecosystems, and the economy.

Figures