Application of rice husk charcoal on remediation of acid soil

About 1 million tons of waste rice husk are generated in Taiwan each year. Rice husk has high concentrations of nutrients, such as silicon and potassium. However, it is not decomposed easily because it contains over 70% of cellulose and lignin and hence it is not suitable to be added into soil. In this study, a large quantity of rice husk is carbonized by vertical type continuous carbonization furnace without the presence of oxygen. After it is carbonized, it becomes rice husk charcoal (RHC) and vinegar (RHV). We have found that the addition of RHC carbonized at 600 and 700 degrees C to soil can increase the soil's concentrations of calcium, magnesium, potassium and silicon as well as its pH value (i.e., lowering its acidity level). Therefore, RHC is a great soil modifier because it can lower the soil's acidity and increase the soil's nutrients. According to our experiments, the pH values of the mixtures in different ratios exhibited an increasing and steady of final condition in the 80-day period. The reason was that the CEC (cation exchange capacity) of the mixtures were increased, the specific surface areas of the mixtures increased and the mixtures' acidity levels were lowered. Therefore, the incorporation of RHC in the soil would benefit the soil on a long-term basis.