Application of two-step composting process to rice straw compost

Abstract

Abstract A two-step composting process was applied for converting rice straw into compost with a high cation exchange capacity and humic acid content. The 1st step of fermentation (hereafter refered to as istSF) involved lignin degradation using white-rot fungus Coriolus versicolor, and the 2nd step of fermentation (2ndSF) involved a general composting process. The amount of lignin decreased by 4.1 and 10.1% during the second and fourth weeks of the IstSF by C. versicolor, respectively. The cation exchange capacity of the compost from fermented rice straw which after 4 weeks was 28 meq/100 g at the initial stage of the 2ndSF increased to 74 meq/100 g after the 2ndSF for a period of 4 weeks using sewage sludge as seed source. On the other hand the cation exchange capacity increased from 25 meq/100 g at the initial stage of the 2ndSF to 60 meq/100 g when only 2ndSF was applied. Humic acid content after the 2ndSF for a period of 4 weeks was 7.3% in the compost from fermented rice straw and 6.0% in the unfermented one. These results indicate that the two-step composting process was effective in accelerating humification during rice straw composting.