Environmental Engineering Reference
In-Depth Information
method, although the amount of import of phosphorus ore is reduced by 6.4 %
(6.5 kt-P), the amount of money used in the production by the entire domes-
tic industry with the introduction of the scenario increases by 7575 million yen,
compared to a saving of 972 million yen from a reduction in the import of phos-
phorus ore.
4. Yellow phosphorus recovery from the incineration ash of sewage sludge
A scenario is presumed in which phosphorus is recovered in the form of high
purity yellow phosphorus for utilization in the chemical industry sector, by sub-
jecting the entire 18.5 kt of phosphorus in sewage sludge to the technique of
incineration ash melting. In reality, all phosphorus contained in sewage sludge is
not transferred to incineration ash, but here it is assumed that the entire 18.5 kt of
phosphorus contained is transferred into the incineration ash melting process. In
this case, it is possible to recover 12.6 kt of yellow phosphorus from incineration
ash of sewage sludge containing 18.5 kg of phosphorus, and 3400 million yen of
electric power and 435 million yen of fuel are required for the recovery. How-
ever, by inputting the recovered 12.6 kt of yellow phosphorus into the chemical
industry sector, the amount of input of other yellow phosphorus that is imported,
decreases by an amount corresponding to 12.6 kt of phosphorus.
In summary, by introducing scenarios of carbonization of poultry manure and of
treatment of wastewater by the HAP method, the amount of import of phosphorus
ore could be reduced by 6.3 % (6.4 t-P) and 4.3 % (4.3 t-P), respectively, when
phosphorus is recovered and reused as raw material for fertilizer. Under the sce-
nario of recovering yellow phosphorus by melting and reduction of incineration ash
from sewage sludge, the amount of import of yellow phosphorus could be reduced
by 40 % (12.6 kt-P), the direct and indirect cost of utilities such as electric power,
which accompany the recovery of yellow phosphorus is 3836 million yen, and the
amount used in production by the entire domestic industry is 5991 million yen. It
can thus be said that these could be very useful recovery technology and recycling
scenarios in view of the possibility of improvements in the recovery technology and
the rise in prices of phosphorus resources.
9.4
Discussion
9.4.1
Implication for Stakeholder Dialogue
The results of the analysis on the material flow of phosphorus reveal that about
14 % of available phosphorus is being injected to support the production of rice,
a principal agricultural product in Japan. It is clear that in order to support a rice
production of 1 million yen, there are direct and indirect demands for a quantity of
10 kg of phosphorus, which is approximately six times the amount contained in the
rice itself. The amount of phosphorus yield loss for producing 1 million yen of rice
is 8.2 kg and much of this accumulates in the soil. The excessive fertilization of soil
