The use of solid-state fermentation to address the treatment of papermaking black liquor and improve the quality of fermented products

Abstract

Papermaking black liquor (BL) is rich in organic components such as lignin and hemicellulose, as well as nutrients such as nitrogen, phosphorus, and potassium. However, the difficulty of handling BL restricts its utilization. This study focused on the solid-state composting and fermentation treatment of BL. The results showed that after 30 d of composting treatment, the organic pollutants in the BL were significantly degraded, with a reductions of 82.25 % in acetic acid and 72.83 % in sulfides. The abundance of Bacillus and Glutamicibacter bacteria increased, the reaction temperature increased, the reaction time decreased, and 85 % of lignin decomposition and transformation was promoted. The obtained organic fertilizer had a humus content of 110.62 g/kg, HA content of 89.3 g/kg and HI index of 8.08. The application of BL fertilizer increased nitrogen by 22.55 %, phosphorus by 16.1 %, and potassium by 83.7 % in plants, indicating good application prospects. Moreover, the dynamic changes in temperature, pH, conductivity and microbial community structure during the composting process were analysed, and the impact mechanisms of each factor on the BL composting process and BL transformation were clarified. Compared with traditional processing methods, it improved processing efficiency, increased economic benefits, lowered investment and operating costs, and is more suitable for complex component processing. This study provides a new technological path and theoretical basis for the environmental protection, efficient treatment, and resource utilization of BL, which is expected to be promoted and applied in the papermaking industry and comprehensive treatment of agricultural waste.