Since most industrial processes consume electricity, it
is quite important to develop reliable inventory data for elec-tricity.
There is, however, a problem that only a few figures
concerning emissions related to electricity have been reported.
In this work, process models of power plants were developed
for the Japanese situation which simulate the mass flows and
estimate the missing figures of emissions dependent on techni-cal
parameters of the plants and fuels. In Japan, electricity is
supplied to the various regions by 10 electric companies. There-fore,
life cycle inventories for the electricity grid mixes of the
10 electric companies in 1997 were developed. The functional
unit is 1 kWh of electricity distributed to electricity users in
each region. The emission of CO 2 , SO 2 , NO x , CH 4 , CO, non-methane
volatile organic compound (NMVOC), dust (all par-ticulates)
and heavy metals (Ni, V, As, Cd, Cr, Hg, Pb, Zn)
from power stations as well as those from fuel production and
transport were investigated. Other pollutants into air, emis-sions
to water, solid wastes, radiation and radioactive emis-sions
from atomic power stations were not included due to a
limitation of the available data. Direct CO 2 emissions related
to 1 kWh of electricity distributed by companies ranged from
0.21 to 1.0 kg/kWh (average value: 0.38 kg/kWh). Direct emis-sions
of SO 2 and NO x from power stations related to 1 kWh of
electricity are 2.5*10 -4 and 2.2*10 -4 kg/kWh on the average,
respectively. SO 2 emissions calculated in this work were some-how
large compared with those reported by electric companies.
Detailed information concerning total sulfur content in oil con-sumed
in each oil-fired power station are required for an exact
calculation of SO 2 emissions from oil-fired power stations. In
addition, the ratio of sulfur that goes into slag in combustion
must be investigated further. The average amounts of CO, CH 4 ,
NMVOC and dust emissions were 5.0*10 -5 , 8.2*10 -6 , 1.8*10 -5
and 6.8*10 -6 kg/kWh, respectively. Heavy metal emissions from
power stations were on the order of 10 -9 to 10 -8 kg/kWh. De-tailed
information concerning heavy metal content in oil and
coals consumed in fossil fuel power stations are further required
for an improved assessment of heavy metal emissions. Contri-bution
of fuel production and transport to total CO 2 emission
was relatively small. On the other hand, contributions of fuel
production and transport to total SO 2 and NO x emissions were
relatively large. In the case of CO, NMVOC and dust, emis-sions
in fuel production and transport were predominant to to-tal
emissions. Heavy metal emissions into air during production
and transport of fuels were on the order of 10 -8 to 10 -9 kg/kWh.
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