Reduction of nitrogen Loss in aerobic composting process using phosphorus-bearing waste

This study was undertaken to investigate the effects of bone waste on the conservation of nitrogen in aerobic composting process by inducing the struvite crystallization, which was known as a powerful method for conservation of nitrogen in composting reaction. Bone waste was dried at oven and crushed to less than 3 mm prior to use. The dosage of bone waste and Mg salt in composting reaction was determined to react one mole of ammonia nitrogen. It was found phosphorus content in bone waste was about 20.9% of the fixed solids from the leaching experiments using sulfuric acid. Addition of seed compost affected the progress of composting reaction substantially. In case seed compost was not used, the duration of initial low pH was greater than seed compost was added. This prolonged acidic pH may have a beneficial effect on the leaching of P from the bone waste and struvite crystallization. The struvite crystallization and resulting conservation of nitrogen by addition of bone waste was confirmed by both reduction in ammonia loss and increased ammonia content in compost. The addition of Mg salt and bone waste reduced the ammonia loss and elevated the ammonia content in compost. Struvite crystallization reaction was clearly observed by the analysis of ammonia contents in dried compost sample. However the level of struvite crystallization observed with bone waste addition may be less than the cases water-soluble phosphate salts were used.