A bioprocess for rapid compost production from rice straw using C/N ratio improvers and indigenous microorganisms at the lab and pilot scales

Abstract

Abstract Management of agricultural waste like rice straw is essential in reducing environmental pollution and also creating added value. For this purpose, microorganisms with high hydrolytic activities were isolated from a simulated composting process. The effects of different materials, including rice straw, chicken manure, urea, olive pomace, and two groups of microbial boosters were assayed at lab-scale and pilot-scale for 60 days. The lab-scale results showed that two treatments containing chicken manure and microbial cocktails (E and F) improved the composting process significantly better than others. They had maximum temperature (59°C), C/N reduction rate (76.7%), and macro/microelements contents. Treatment E showed maximum wheat growth indexes, including dry (1.1 g) and wet (4.7 g) weight of aerial parts, plant height (47 cm), leaf area index (18.9 cm2), and leaf specific area index (45 cm2/g) compared to the control. The pilot-scale results showed that E treatment could reduce C/N (73.48%) better than F (58.32%) and control (13.03%) and it also caused most of the temperature changes up to 69°C. Finally, considering the highest germination index (96%) and lack of phytotoxicity, and also the greatest impact on wheat growth indexes, treatment E was selected for industrial production of compost.