Evaluation of microbial inoculants pretreatment in straw and manure co-composting process enhancement

Commercial microbial inoculants (MI) are usually inoculated during the co-composting of straw and manure to improve the compost process. In the present study, MI was prior used to pretreat straw before co-composting (MI pretreated) and compared with a treatment with inoculated MI during the cocomposting (MI inoculated) as well as a treatment without MI utilization (CK). Compared with the CK, MI utilization (MI inoculated and MI pretreated) significantly improved the compost maturity index of C/N (Sig. values 0.016), Cwater-soluble (organic)/N-organic (Sig. values 0.000), EC (Sig. values 0.043), and GI (Sig. values 0.009), as well as increased the final products' total nutrient content by 4-13%. The MI pretreatment disrupted straw structure and enhanced lignocellulose degradation before co-composting as shown by a decreased straw cellulose content by 8-18% and hemicellulose content by 20-23%. However, no noticeable difference was found in the maturity index between MI pretreated and MI inoculated treatments, although the microbial community of compost differed between them during the thermophilic stage. In conclusion, MI utilization is proposed during the composting process for enhancing compost quality. However, straw pretreatment by MI before co-composting is not recommended, as this practice showed limited effects on compost quality improvement. (C) 2019 Elsevier Ltd. All rights reserved.