The changes in macronutrients and microbial community structure during the co-composting of white wine distillers’ grains and potassium silicate

Abstract

Composting is a low-cost, efficient, and environmental-friendly treatment method for organic solid wastes. White wine distillers’ grains (WWDG) are the byproducts of alcohol production from grains. How to deal with distillers' grains is becoming an urgent problem for distillers in China. In this article, the composting process of WWDG with an addition of potassium silicate (PS) or not being studied. The results showed that with or without PS, WWGD can be used as the main raw material to produce compost. However, the addition of PS increased the potassium contents in the final compost and contributed to the composting process especially during the early stage of fermentation. The ratio of WWDG: PS = 10:2.5 (weight ratio) was close to optimum for the co-composting process. The addition of PS increased the total potassium (TK) and available potassium (AK) content in the final compost. The TK and AK contents in J1, J2, and J3 treatments were 18.87, 36.76, 42.36 g kg−1, and 6.55, 7.98, 8.46 g kg−1, respectively. Bacillus, Tepdimicrobium, Lactobacillus, and Petrimonas were the key bacterial genera while Monascus, Aspergillus, and Penicillium were the key fungal genera observed during the composting process. The results of the seed germination experiment showed that the final compost was mature and had no phytotoxicity. The results of field trials also showed that the compost produced by WWDG and PS increased the sweet potato yield and improved the soluble sugar contents in sweet potato tubers. This research provided a new direction for the resource utilization of distiller grains composting.