Environmental Engineering Reference
In-Depth Information
Fig. 3.7
Four phases of tech-
nology. (Nakanishi
1994
)
Additionally, Nakanishi carried out a cost comparison between these two cases
which indicated a cost of 9092 ¥ for recycle and 6373 ¥ for landfill. Landfill was
cheaper than recycle, but the cost difference vanishes if the cost of landfill increases
by at least 3 times relative to the cost at that time of 25,000 ¥/t. Based on this es-
timate, recycling of PET bottle was more expensive than landfill, but was consid-
erably more effective in protecting the environment. This is a typical example of
conflict between economy and environment.
Nakanishi (
1994
) developed this relationship between environment and econo-
my to a general guidance involving a simple graph describing four phases of tech-
nologies as shown in Fig.
3.7
which can be used to decide priorities in both devel-
oping and developed countries. This graph is composed of an economy axis and an
ecology axis dividing into four phases designated as I, II, III, and IV. Phase I is the
most desirable phase whose technologies are good for both ecology and economy.
Unfortunately however, most technologies still fail to meet this ideal criterion and
economies are faced with using technologies with various degrees of environmental
harm. Nakanishi suggests that developed countries should be expected to move to-
wards phase 1 faster than developing countries. Thus, developing countries are per-
mitted to use technology which is economically effective even if there is ecological
weakness (Phase II
1
); whereas developed countries should put a higher priority on
ecological factors and be limited to Phase IV
1
as well as Phase I. Phases other than
I, II
1
and IV
1
are not permitted at all, because those are bad for ecology and also lack
economy effectiveness.
While some leading technologies belong to Phase I such as low-energy, clean
production or in-process technologies, most technologies in use today were estab-
lished in the twentieth century and are thought to be located outside Phase I. For
example, subsidized recycling technologies and antipollution technologies (end-of-
pipe technologies) may belong to Phase IV
1
. To shift these technologies to Phase I
and also to create new technologies in Phase I is important to establish a sustainable
society.
