Comparison between Cold Plasma, Ultrasonication, and Alkaline Hydrogen Peroxide Pretreatments of Garden Waste to Enhance Humification in Subsequent Composting with Kitchen Waste: Performance and Mechanisms

Abstract

This study investigated the performance and mechanisms of three physiochemical techniques, including cold plasma, ultrasonication, and alkali-assisted hydrogen peroxide, to pretreat garden waste for advanced humification in subsequent composting with kitchen waste. Results show that all pretreatment techniques accelerated organic transformation to enhance humification in composting. Ultrasonication and alkalization pretreatments decomposed lignocellulose and produced humus precursors in garden waste to initiate humus formation in composting. By contrast, garden waste pretreated by cold plasma contained less humus precursors, but exhibited the disrupted surface structure and reduced crystallinity of lignocellulosic materials to strengthen microbial accessibility and thus increase lignocellulosic biotransformation for humus synthesis in composting. Microbial analysis also showed that cold plasma pretreatment supported a more robust bacterial community with enriched bacteria (e.g., Clostridium, Tepidimicrobium, and Thermobifida) for aerobic chemoheterotrophy, xylanolysis, cellulolysis, and ligninolysis. Compared to ultrasonication and alkali-assisted hydrogen peroxide, cold plasma is also a much faster and simpler pretreatment technique.

Keywords: Kitchen waste composting, garden waste pretreatment, cold plasma, humification, bacterial community and functions