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Hydrothermal liquefaction aqueous phase mycoremediation to increase inorganic nitrogen availability

Summary

When biomass is converted to biofuel through a heating process called hydrothermal liquefaction, it produces a waste liquid containing nutrients but also toxins. Scientists used a type of fungus called Trametes versicolor to clean up this waste and convert the nitrogen into forms that plants can use. After three days of treatment with the fungus, nitrogen levels that plants can use increased dramatically. Adding helpful bacteria further improved the results, making this waste potentially usable as a fertilizer for growing vegetables hydroponically.

Background

Hydrothermal liquefaction (HTL) of biomass produces biocrude oil as an alternative fuel, but generates hydrothermal liquefaction aqueous phase (HTL-AP) as a potentially toxic byproduct. HTL-AP contains nutrients and is pathogen-free due to high temperature and pressure conditions, making it potentially suitable for reuse in hydroponic systems after treatment to increase inorganic nitrogen availability.

Objective

To investigate whether the white-rot fungus Trametes versicolor can increase inorganic nitrogen concentrations (NH3/NH4+ and NO3−) in HTL-AP through mycoremediation, and to determine the optimal cultivation time for maximum treatment effectiveness. Additionally, the study evaluated whether combining fungal treatment with nitrifying bacteria would further enhance NO3− concentrations.

Results

After 3 days of fungal treatment, NO3−-N increased 17-fold (to 30.67 mg/L) and NH3/NH4+-N increased 8-fold (to 32.20 mg/L) compared to initial 5% HTL-AP. Laccase activity increased throughout cultivation, indicating fungal metabolic activity despite minimal biomass accumulation. When nitrifying bacteria were added after fungal treatment, NO3−-N concentration doubled compared to fungal treatment alone, reaching 34.8 mg/L. COD decreased 51.33% in the first 24 hours but subsequently increased, likely due to fungal byproduct release.

Conclusion

T. versicolor shows promise as a potential treatment for increasing inorganic nitrogen in HTL-AP, with 3 days identified as the optimal treatment duration. The addition of nitrifying bacteria further enhances NO3− production, making this combined approach suitable for preparing HTL-AP for use as fertilizer in hydroponic systems. However, future research must address HTL-AP toxicity, reduce NH3/NH4+-N levels preferentially, and evaluate actual crop production in hydroponic systems after treatment.
  • Published in:Heliyon,
  • Study Type:Experimental Study,
  • Source: PMID: 38882322, DOI: 10.1016/j.heliyon.2024.e31992
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