Harnessing fungicide potential of hydrothermal liquefaction water from livestock manure: A new vision of integrated crop-livestock system

Abstract

Hydrothermal liquefaction (HTL) can turn livestock manure into biocrude oil, but the aqueous phase (HTL-AP) attracts increasing concerns owing to its large amount and high toxicity. In this regard, a novel integrated crop-livestock system paradigm was proposed where HTL-AP from livestock manure was used as fungicide for phytopathogen control. To verify this strategy, Alternaria solani was employed as indicator phytopathogen, whereas cow manure (CM) and swine manure (SM) were used as the feedstock to obtain fungicide compounds via hydrothermal liquefaction (HTL). Results showed that the minimum inhibition concentration (MIC) of two HTL-APs was about 12%, where the main active compounds probably were phenols and nitrogenous compounds. The fungicide application would increase the manure carrying capacity by over 10%. Further observation revealed that HTL-AP exhibited inhibition through multiple pathways such as changing the mycelial morphology and cell membrane structure, resulting in metabolic disorders via impacting the generation of H2O2, ATP, reducing sugar and protein. The synergistic interaction among pathways was finally analyzed. Then, the effect of HTL-AP on seed-borne fungi control was evaluated via 36 groups of seed germination tests. For all that, this study provides new insights into the valorization of HTL-AP form livestock manure via unlocking its potential as sustainable fungicide constituents for phytopathogen control, further contributes to green development of current integrated crop-livestock system.