The demand for biofuels has recently increased because of rising prices of fossil fuels and diversification of energy resources. As a result, the demand for sugarcane and corn has been increasing, not only for food production, but also as sources of energy. In this context, securing supplies of phosphorus, required as an essential nutrient in agricultural production, has considerable implications that extend beyond food and agricultural policy. It is therefore important to consider the quantity and availability of phosphorus resources that remain untapped, because the demand and supply of phosphate ore is currently becoming very tight, and Japan has no domestic phosphorus resources. To identify potential phosphorus resources, we have investigated the material flow of phosphorus within Japan, including that in the iron and steel industry, on the basis of statistical data for 2002. Our major finding is that the quantity of phosphorus in iron and steelmaking slag is almost equivalent to that in imported phosphate ore in terms of both the amount and concentration. We also found, by means of a waste input- output analysis and a total materials requirement study, that the phosphorus potentially recoverable from steelmaking slag by a new process that we have proposed has considerable environmental and economic benefits. Concerning the restricted supplies of phosphorus resource, it is important to consider the quantity and availability of phosphorus resources that currently remain untapped. From that viewpoint, steelmaking slag would be expected to be a great potential resource for phosphorus.
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