Author(s)

S. Mishima & T. Inoue

Abstract

We evaluate nutrient use and cadmium (Cd) load on agricultural production and how these would change if chemical fertilizer, livestock waste and sewage sludge were used for agricultural production. The total input of nitrogen (N) and phosphate (P2O5) by chemical fertilizer and livestock waste, the disposal of livestock waste and the incidental Cd load would be reduced more than conventionally, if livestock waste were used to maintain soil fertility and substituted part of the chemical fertilizers. This indicates that active use of livestock waste would be beneficial in reducing the environmental impact. Sewage sludge could be used instead of chemical fertilizer. This would reduce the amount of material to dispose, however it would increase the Cd load. Therefore, we have to consider sewage sludge use on agricultural production. Keywords: livestock waste, sewage sludge, nutrient, cadmium. 1 Introduction In Japan, 94,300,000t of livestock waste and 85,500,000t of sewage sludge were discharged in 1997 [1]. They were about 40% of the total industrial waste [2]. Because livestock waste and sewage sludge contain fertilizer elements (nitrogen, N; phosphate, P2O5), their use for agricultural production would be beneficial in reducing the amount of material to dispose of, from the point of view of recycling and reduction of use of chemical nitrogen and phosphate fertilizer. However, these materials contain heavy metals such as cadmium (Cd). Therefore proceeding with recycling of these materials without any restriction would cause the contamination of food, feed and farmland soil by Cd. There are statistical data about the estimated amount of nutrient elements and Cd in each kind of waste, however there are few integrated reports about wastes.

Keywords

livestock waste, sewage sludge, nutrient, cadmium.