Effect of Surfactant-Coated Charcoal Amendment on the Composting Process and Nutrient Retention

This research investigates the quality changes during composting of bagasse and pig manure amended with 30% of surfactant-coated charcoal (SC). Two treatments, 30% uncoated charcoal (UC) amendment and no charcoal (NC) amendment, were done as control. Charcoal was coated with 0.37 mM tetradecyltrimethylammonium bromide (TDMA), a cationic surfactant, at the dosage of 10 g/L. At the end of the composting period, the carbon to nitrogen (C/N) ratio of SC amendment was 9.7; whereas, the C/N ratios of UC and NC amendment were 12.6 and 21.4, respectively. Plant nutrients contents of the compost produced from SC amendment were 20.7 mg $NH_4{^+}-N/g$, 42.8 mg $NO_3{^-}-N/g$, and 41.7 mg P/g. High nitrate and phosphate concentrations in SC amendment were due to the adsorption of these anions on the positive charge of TDMA. Desorption of plant nutrients retained in the compost pellets was also investigated. It was predicted that nitrate was fully desorbed from a pellet at 23 days for SC amendment, which was later than UC (14 days) and NC (10 days) amendment. A slow release of nitrate from the compost pellet will reduce the nitrate leaching into the environment. Thus, the adding of SC in the compost pile is one of the alternative methods to improve the quality of compost and plant nutrient retention.