Driving forces of the humification process in composting: from a microbial perspective

Area of Science:

• Environmental Science
• Microbiology
• Soil Science

Background:

• Humification is crucial for compost quality, involving the polymerization of small molecules into humic substances (HS).
• Microbial metabolism is the primary driver of composting and humification.
• The precise relationship between microbial metabolic processes and humification polymerization is not fully understood.

Purpose of the Study:

• To examine humification polymerization mechanisms.
• To elucidate the role of microbial extracellular and intracellular metabolism in driving humification.
• To provide a theoretical framework for microbial mechanisms in humification.

Main Methods:

• Review of literature on humification polymerization mechanisms.
• Analysis of precursor functional group reactions and radical oxidative coupling.
• Systematic elucidation of microbial extracellular and intracellular metabolic contributions.

Main Results:

• Humification polymerization occurs via functional group reactions and radical oxidative coupling of precursors.
• Extracellular microbial metabolism, through hydrolases and oxidoreductases, influences polymerization.
• Intracellular metabolism provides precursors and energy (catabolism) and synthesizes precursors (anabolism).

Conclusions:

• Microbial metabolism, encompassing both extracellular and intracellular processes, is central to humification.
• Understanding these microbial mechanisms is key to optimizing compost quality and effectiveness.
• This review offers a comprehensive framework for the microbial drivers of humification.