Effect of biochar on the mitigation of organic volatile fatty acid emission during aerobic biostabilization of biosolids and the underlying mechanism

Abstract

In order to declare the effect and the underlying mechanism of biochar amendment on volatile fatty acid (VFA) emission during aerobic biostabilization of biosolids, different types of biochar (i.e., wheat straw biochar [WHB], sawdust biochar [SDB], and food waste digestate biochar [FRB]; 5% in dry weight) on carbon transformation and VFA emissions during 45-day aerobic biostabilization of biosolids were investigated. The results showed that biochar amendment improved thermophilic phase evolution and product dephytotoxification. During the 45-day period, in comparison to control, biochar addition promoted CH4 reduction by 44.46%–76.90% and enhanced the content of total organic carbon reduction by 20.60%–56.80%. In addition, biochar addition lowered the emissions of acetic, propanoic, isobutyric, butyric, isovaleric, and valeric acids by respectively 23.43%–41.21%, 23.10%–43.92%, 42.62%–56.11%, 26.70%–58.20%, 10.56%–58.27%, and 33.74%–49.45% compared with control values. Moreover, biochar amendment facilitated organic matter humification during biosolid bioconversion as well. Among the applied types of biochar, SDB, with a higher surface area, was more efficient in organic matter degradation and VFA emission mitigation than WHB and FRB. In particular, biochar amendment increased the abundance and diversity of aerobic bacterial communities such as Acinetobacter, Desemzia, Georgenia, Nonomuraea, Psycharobacter, Planococcus, Paenisporosarcina, Physchrobacillus, Staphylococcus, Thermobifida, and Thermopolyspora, while inhibiting the reproduction of anaerobic bacteria including Bacillus, Bacteroides, Corynebacterium, Ruminofilibacter, and Terrisporobacter during biosolid stabilization, thus improving biosolid maturity and stabilization and reducing VFA emissions. These findings offer a novel method with appropriate recommendations for the use and the selection of biochar in increasing the efficiency of biosolid aerobic biostabilization.