Abstract
A pot-based study examined the socio-economic advantages and appropriate technology for ameliorating cadmium contamination soil using broiler biochar derived from pelleted broiler litter (PBL) prepared (a) in a alab-scale pyrolysis rector (LPR) or (b) in a 200 litre oil-drum kiln (ODK), at a maximum temperature of 500 ºC. The biochar from PBLLPR and PBLODK was subsequently mixed with soil at four rates of 5, 10, 15 and 20 t ha-1. Each mixing rate was treated with 5 levels of Cd concentrations consisting of 0, 20, 40, 60 and 80 mg Cd kg-1 soil. Soybean plants (variety Chiang Mai 60) were grown on the Cd-contaminated soils and its effect evaluated for plant growth and production. The results indicated that PBLLPR and PBLODK were capable of reducing the Cd concentration in soil. Optimal results of residual Cd in biochar-mixed soil were obtained using PBLLPR and PBLODK at a mixing rate of 20.0 t ha-1. Although the Cd-treated soils contain Cd as high as 80 mg Cd kg-1 soil, the residual Cd after treatment with biochar was approximately 35.0 and 31.4 mg Cd kg-1 soil for PBLLPR and PBLODK, respectively. The residual Cd after treatment with biochar was below the maximum allowable Cd level of 37.0 mg Cd kg-1 soil for habitat and agriculture. Furthermore, PBLODK helped to reduce Cd in soybean seeds to 0.182 mg Cd kg-1 soybean seed at Cd-contamination levels of 20.0 mg Cd kg-1 soil, while PBLLPR reduced Cd in soybean seeds to 0.187 mg Cd kg-1 soybean seeds at Cd contamination levels of 60.0 mg Cd kg-1 soil. This suggests that PBLODK was more efficient than PBLLR in reducing Cd levels in the soybean seeds. This meets The Codex Committee on Food Additives and Contaminants (CCFAC) standard that permits Cd in soybean seeds at levels not exceeding 0.200 mg Cd kg-1 soybean seed.
