Composting of rice straw-derived biochar with food waste and its application as soil improver for paddy growth

One of the most important agricultural residues produced is rice straw, which represented as one of the major by-products from rice production process. The huge excess of rice straw in paddy field was due to the increases in size of paddy areas and rice productivity. The farmers from all over the world usually used a method of on-farm burning to eliminate this straw after the harvesting season. Rice straw can be manage by composting process, but it required a longer time for the decomposition process to happen since the main fraction of rice straw is lignocellulose which was difficult to degrade. In order to solve this problem, rice straw will be burned before being used for composting process. The main objective of this study was to produce soil improver by composting of rice straw-derived biochar with food waste at two selected temperature of rice straw burning with three different initial C:N ratios and three different aeration rates. The final compost will be tested to soil paddy field as a soil improver before the cultivation process to recover the nutrient content loss during the removing process of rice straw from paddy field. Two selected temperatures (300°C and 400°C) of rice straw burning at 30 minutes was chosen to be composted with food waste, from the burning of rice straw at different temperature range from 100°C until 800°C. There are three different aeration rates (0.4Lmin-1.kg-1, 0.6Lmin-1.kg-1, 0.8Lmin-1.kg-1) and three different initial C:N ratios (20, 25, 30) was used during composting process for each selected temperature of rice straw burning making that the total of 19 treatments of rice straw derived-biochar compost including control (rice straw without burning) were done. Each treatment of rice straw derived-biochar compost was analysis for pH, temperature, moisture content, organic matter, carbon content, C:N ratio, NPK values and germination index. The composting process was conducted in a laboratory-scale bin composter reactor for 30 days and 60 days for control. The final product of compost produced was applied towards the paddy field soil before the next cultivation season. The suitability used of compost produced as a soil improver was analysed in term of paddy production and potential yield. The best treatment of compost for rice straw burning at 300°C, was the rice straw derived-biochar compost treatment of T2-300-CN-30-AR0.6 because it recorded the highest thermophilic phase with temperature exceeding 55°C for 6 days for pathogen destruction, has a maximum germination index of 97% compared to the others treatments at the same temperature of rice straw burning. Meanwhile, the best treatment of compost for rice straw burning at 400°C, was the rice straw derived-biochar compost treatment of T11-400-CN-30-AR0.6 because it also recorded the highest thermophilic phase with temperature exceeding 55°C for 5 days for pathogen destruction and has a maximum germination index of 91% compared to the others treatments at the same temperature of rice straw burning. These two treatments also shown a higher value of nitrogen, phosphorus and potassium content. The application of final compost for treatments G1 and G4 towards paddy field soil as a soil improver has recorded the highest total paddy production with 2021gm-2 and 1797gm-2, respectively. Beside, these two treatments of G1 and G4 also recorded the best values for each component of potential yield for paddy growth.