都市鉱山はCO2削減にも効果があり、SDGsSDGs持続可能な開発目標(Sustainable Development
Goals)の略。2030年までに持続可能な社会を目指す17のゴールと169のターゲットが定められた国際目標。Sustainable Development Goals, an international goal
with 17 goals and 169 targets aiming to achieve a
sustainable society by 2030.
ゴール12『つくる責任
つかう責任』にも大きく関連しているのじゃ。
Urban mining is a key to resource problems. What is it like?
Minor metal and Major metal
Why do so many people crave
metal resourcesmetal resourcesA kind of mineral resource. It is further classified into
minor metals and major metals.
? That’s because it is indispensable for home appliances and
cutting-edge technology. In this chapter, we would like to talk about
those metal resources. We have used the word “metal resources" so
far, but actually it is largely separated into two kinds. They are
minor metalsminor metalsElements that satisfy the following conditions: 1.
relatively low abundance in the earth's crust, 2.
technically difficult to extract as a single element, and
3. unevenly distributed in resource-producing
countries.
and
major metalsmajor metalsA metal which is easily refined and exists a lot, such as
iron, copper, zinc, and aluminum. Also known as base
metal.
. Major metal is metal that is easy to refine and there exists a lot
in the earth, although some elements are classified as major metal in
spite of their rarity (six kinds such as gold, silver, etc).
Have you ever heard of minor metal? Minor metal is elements that meet
these standards:
relatively less in the earth’s crust than other elements
hard to take out from ore as simple substance
unevenly distributed in the world
Minor metal includes 47 elements such as lithium and chromium.(table
2.1)
table 2.1 Minor metal and rare earth in periodic table Data Source : より引用
Major metal is used for electric wire and cable and plating while
minor metal is used for high technology like smartphones,
superconducting material, shape memory alloys and metal hydride
alloys. Minor metal is essential to our lives and called “vitamins of industry."
We disassembled a feature phone and a smartphone. You can check the
experiment here.
table 2.2 How much minor metal is included in a smartphone, laptop
PC, desktop PC? (g)
* Metal resources are sometimes classified into three kinds, minor
metals, major metals, and
precious metalsprecious metalsGold (Au), silver (Ag), platinum (Pt), palladium (Pd),
rhodium (Rh), iridium (Ir), ruthenium (Ru), osmium (Os),
and rhenium (Re).
. In this case, nine elements including gold, silver, etc. are
classified as precious metals.
What is Urban Mining?
In 1988, Professor Michio Nanjo at the Research Institute of Mineral
Dressing and Metallurgy, Tohoku University, advocated the concept of
urban mining in order to solve resource problems and this is the theme
of this website. Urban mine is defined as follows in
Wikipedia: “An urban mine is the stockpile of
minor metalsminor metalsElements that satisfy the following conditions: 1.
relatively low abundance in the earth's crust, 2.
technically difficult to extract as a single element, and
3. unevenly distributed in resource-producing
countries.
in the discarded waste electrical and electronic equipment (WEEE) of
a society. Urban mining is the process of recovering these mi nor
met als through mechanical and chemical treatments.” Let’s learn
about urban mining together with some data.The graph below(Fig. 2.1) shows the amount of
primary resourcesprimary resourcesResources that have not yet been dug out of the
ground.
and
secondary resourcessecondary resourcesResources that have already been dug out of the
ground.
of some metals.
Fig. 2.1 Proportion of primary resources and secondary
resources Data Source : 日本金属学会より引用
As you can see in this graph,
half of each metal resource is secondary resources, in other words,
already mined and on the ground. Therefore, it is very important to recover them, which are included
in small home appliances like cellphones. Now, you will probably
feel that they are not garbage but
invaluable resources. The amount of
small home appliances that are going to be thrown away is 5.74 million
tons and it is estimated to continue to increase. (Fig. 2.2)
Fig. 2.2 Projected electronic waste generation worldwide from 2019
to 2030 Data Source : Statistaより引用
Urban mine means these beneficial metal resources!
Urban Mining in Japan
Chipangu is an Island towards the east in the high seas, 1500 miles
distant from the Continent; and a very great Island it is. … You
must know that he hath a great Palace which is entirely roofed with
fine gold, just as our churches are roofed with lead, insomuch that
it would scarcely be possible to estimate its value. Moreover, all
the pavement of the Palace, and the floors of its chambers, are
entirely of gold, in plates like slabs of stone, a good two fingers
thick; and the windows also are of gold, so that altogether the
richness of this Palace is past all bounds and all belief.
— Marco Polo
You cannot possibly believe this, but Japan used to be introduced like
this. Although It is not clear whether Japan was so full of gold,
Japan had enough gold, silver, copper and so on to export them.
Especially for copper, Japan produced it the most in the world from
the late 17th century to the early 18th century. Now, how about metal
resources in Japan? After the war, people began to trade more freely
and a lot of minerals got into the island. As a result, its
self-sufficiency rateself-sufficiency rateThe percentage of goods, such as materials, consumed in a
certain area, or goods used as materials for products that
are produced or supplied in that area, indicating how much
of the total demand for those goods is met.
has been getting lower and lower. (Fig. 2.3)
Fig. 2.3 Japan's self-sufficiency rate of metals Book 資源論より引用
And now, Hishikari MIne is the only major mine that is working.
However,
Japan is rich enough in resources to yield to the other
countries! It had developed rapidly by importing a lot of metal resources from
overseas, exporting half of the products made of the resources. And
the other half is left on the island.
These products make up most of the urban mines in Japan and they are
great metal resources of Japan. For example, as you can see in the
graph below, Japan has 10 percent of all the gold in the world. As for
silver, 23 percent of silver in the world is in Japan. A
surprising number is reported not only about major metal but also
about minor metal. Japan accounts for 22 percent of Antimony,
which is used for refrigerant material in refrigerators, air
conditioners and so on. Japan has world-class reserves of other
metals. In addition,
gaps between countries that come from resource distribution can be
closed
by using urban mines. Moreover about Japan, it can play an important role as
an insurance that says to the other countries Japan has enough
metal resources to support themselves without import. Considering these advantages,
Japan must make use of urban mines.
Fig. 2.4 Reserve in Japan / Reserve in the world created while referencing toより引用
イットリウム博士Dr.Y
Urban mining also has a good effect on carbon dioxide emissions
reduction and is related to
SDGsSDGs持続可能な開発目標(Sustainable Development
Goals)の略。2030年までに持続可能な社会を目指す17のゴールと169のターゲットが定められた国際目標。Sustainable Development Goals, an international goal
with 17 goals and 169 targets aiming to achieve a
sustainable society by 2030.
12th goals, “Responsible Consumption and
production”.
Illegal Urban Mining
People in developed countries
leave e-waste in garbage disposal plants in developing
countries
because recycling e-waste costs a lot following the idea of urban
mining. Of course, they cannot afford to recycle them, so they throw
away nearby rivers and sea garbage that do not turn into ash after
burning. This causes various issues.
First, sulfur oxide and hydrocarbons produced when burning wastes are
more likely to cause chronic disability of the respiratory system and
sometimes blindness. Also, e-waste thrown away in rivers and oceans
and harmful substances such as lead and mercury are washed away by
rain and as a result people who drink the polluted water begin to
suffer. For instance, children in Guiyu, Swatow, China, which has
garbage disposal plants, have higher blood concentration of lead.
Probably because of this, the local children tend to be stunted and
the pregnant mothers are six times as likely to have a miscarriage.
There are more problems affecting local people. E-waste includes a lot
of iron, copper and aluminum. These
major metalsmajor metalsA metal which is easily refined and exists a lot, such as
iron, copper, zinc, and aluminum. Also known as base
metal.
are not very valuable in developed countries, but they are more
valuable in developing countries. So, there are so many people looking
for e-waste to make a profit from them in disposal sites.However, this is very dangerous. When
they destroy e-waste, harmful substances are generated and they are
exposed to the hazardous gas and substances. Major metal taken out in
such a dangerous situation is paid for up to a few dollars per
day.Moreover, such miners are composed mostly of
people under 20 who should have a
bright future. Developing countries cannot advance in this situation.
Now, let us look back.The fundamental cause is that
developed countries including Japan have refused to manage their
waste and forced the work on developing countries! Our future will be brighter if you make better use of urban mines
although there are a lot of obstacles hard to get over.
Summary Chart
Can you make sure that urban mining is the key to many important
problems?
を参考に作成
