Rice straw addition and biological inoculation promote the maturation of aerobic compost of rice straw biogas residue

Rice straw biogas residue contains high lignin content, so the decomposition of this material by natural compost is slow. This study investigated the effect of the combination of rice straw addition and microbial inoculation (Aspergillus niger CICIMF0410andPhanerochaete chrysosporium AF96007) on the physiochemical properties of rice straw biogas residue in the composting process. Four composting treatment groups were designed: rice straw biogas residue (RR; T1), RR + rice straw (RS) (T2), RR + inoculants (T3), and RR + RS + inoculants (T4). The addition of rice straw significantly accelerated the initial temperature rise during composting, and microbial inoculation accelerated lignocellulose decomposition. After composting, the electrical conductivities of samples T1 to T4 were 1.22, 0.87, 0.99, and 0.82 DS ml(-1), respectively. Compared with other treatment samples, T4 showed noticeably increased degradation rates of HC, CL, and ADL after decomposition. The total humic acid levels of samples T1 to T4 were 9.5, 12.7, 10.5, and 18.6%, with humification index values of 1.45, 1.80, 1.69, and 2.46, respectively, after maturation. After 12 weeks of composting, T4 showed the highest increase in total nitrogen (37.6%), phosphorus (33.6%), and potassium (29.8%) levels. Furthermore, compared with other treatment samples, T4 showed the best maturity indices, such as morphology, color, and odor. Rice straw addition and biological inoculation for biogas residue composting not only significantly decreases the time required for decomposition but also eliminates the toxicity risk for crops and improves the stability of the biogas residue fertilizer.