Responses of microorganisms to different wavelengths of light radiation during green waste composting

Abstract

Light radiation can degrade recalcitrant materials like lignocelluloses in litter and serve as a physical condition to accelerate green waste (GW) decomposition, but few studies have considered the microbial effects of light wavelength on GW composting. This study innovatively investigated the effects of different wavelengths of light radiation, including full-spectrum, no blue light, no UV, no UV-A, no UV-B, and dark conditions, on accelerating the GW composting process. Especially, the study explored the dynamic changes in the degradation of lignocelluloses and evaluated the responses of microorganisms throughout the composting process under different light radiation wavelengths. No blue light (where radiation between 400 and 500 nm was blocked by the film) yielded the highest-quality compost within 40 days. In comparison to the dark (control), no blue light exhibited an elevated composting temperature (56.7 °C), an extended thermophilic phase (6 days), and increased degradation rates of lignin, cellulose, and hemicellulose by 13 %, 15 %, and 12 %, respectively. This study revealed that during the composting mesophilic phase, bacterial diversity performed best under no blue light, while fungal diversity excelled under full-spectrum. In the thermophilic phase, microbial diversity exhibited optimal performance under full-spectrum. During the cooling phase, bacterial diversity was highest under no blue light, and fungal diversity excelled under no UV-A. During the mesophilic and cooling phases, the bacterial ACE index for no blue light exceeded that of the other light radiation wavelengths, with values of 418 and 494, respectively. Under no blue light, the Shannon index of microorganisms remained within the range of 2.0-4.8, demonstrating superior performance. Meanwhile, the relative abundances of lignin-degrading microorganisms (Flavobacterium, Acaulium, and Acremoniu) under no blue light has increased, demonstrating improved microbial community structures. Therefore, no blue light radiation offered a novel approach to expedite GW composting.

Keywords: Composting; Green waste; Light radiation wavelength; Microbial community structure; Photodegradation.