Basic study on local carbon circulation by unused bioresources - Case study of rice husk and willow as biochar in hydroponics -.

In order to establish the local sustainable hydroponics system by unused bioresources, the objective of this study was to evaluate 1) the feasibility of alternative hydroponics substrates that utilized rice husk and willow as biochar by 1-1) cultivation trial and 1-2) estimation of carbon sequestration and 2) the effectiveness of biochar substrates in low irrigation by the cultivation trial. Rice husk char (RHC) and willow char (WC) were tried as substrates in addition to rock wool (RW) as commercial products to grow cherry tomatoes under different water conditions (low irrigation and conventional irrigation). As a result, the water content of RHC and WC was higher than RW under both irrigations. Nevertheless, under both irrigations, RHC and WC showed similar results of RW in the fruit yield and quality (brix value, acidity, and lycopene). While low irrigation treatment decreased the commercial yield, the quality was improved except for lycopene. Besides, these substrates can contribute to carbon sequestration if they were used for soil amendment after using substrates in hydroponics. The refractory carbon contents of RHC and WC were calculated as 35.5, and 67.5 t CO₂eq ha, respectively, in this experiment system. Thus, the utilization of unused bioresources as biochar showed the possibility of providing alternative substrates to RW, and the potential of carbon sequestration locally. [ABSTRACT FROM AUTHOR]