Environmental Engineering Reference
In-Depth Information
㻷㻶㻛㼗㼓
㻡㻜㻘㻜㻜㻜
㻠㻜㻘㻜㻜㻜
㻟㻜㻘㻜㻜㻜
㻞㻜㻘㻜㻜㻜
㻝㻜㻘㻜㻜㻜
㻜
Fig. 11.8
Upper heating values of selected fuels: Fossil fuels (
blue
), plastics (
green
), biomass
(
orange
)
are removed for the most part, leaving mainly carbon. Most biomass has a high
water content resulting in a low heating value. Water has two effects: it is not burn-
able and its vaporization consumes additional heat. The higher the water content
the lower the energy that can be recovered. The released heat of wet materials such
as kitchen waste is so low that fossil fuels have to be added in order to maintain
combustion.
Coal is commonly used as a reducing agent in blast furnaces (steel production)
and heating medium in power plants and cement kilns (cement production). The
partial replacement of coal by plastics causes a significant reduction in CO
2
. If coal
is completely replaced by waste plastics in cement kilns, a CO
2
reduction of 15 % is
achieved. In Japan the partial replacement of coal by waste plastics in power plants
and in the steel industry can reduce CO
2
emissions by 10 million t.
11.8
The Japanese Plastic Management System
In Japan, PET bottles and common packaging plastic waste are separately collected
from other waste fractions, allowing their utilization after use. Also plastic parts
from other waste streams such as cars and WEEE (waste electric and electronic
equipment) are separated and treated. Although waste plastics are considered a
