［主題報告］

Sustainable Energy and Environmental Technologies
for Asian Developing Countries
Masayoshi SADAKATA〈University of Tokyo〉

1. Introduction
In this lecture, I propose the research for the solution of environmental and economical
problem in developing countries including China.
Environmental pollution of developing countries has become more serious problem
recently and it will lead to catastrophe of the global environment.
Causes of an environmental pollution and destruction of the developing countries are1) Poverty2) Rapid Increase of population
However, there is a close relationshipbetween poverty and population. According
to Asahi Newspaper, the pregnancy
frequency is anti proportional to annual
income per head at each country. (Fig. 1)
When annual income per head is lower than
1000 dollars/year, the pregnancy is sharply
increased by three times. Hence, only
economic growth seems to be the solution
for an environmental problem of thedeveloping countries. However, the historyof the developed countries teaches us that thegrowth of economy accompanies theincrease of energy consumption which leads
the increase of pollutant such as CO2 andSO2. Hence, the developing countries should
not follow the same path of an economic
growth as that of the developed country. The
developing countries like China and India
should follow “Tunnel Routes” which is thenew short path as is shown in Fig. 2. The
technologies required for the developing
countries are, generally,189

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1) Low input and low impact manufacturing technology
2) Environmental protection technology useful for an economic growth
The transfer of the environmental technology from the developed countries to thedeveloping countries is now urgently required. However, the transfer of technology
conventionally used in the developed country has been almost unsuccessful because of its
high cost, complicated operation, and significant energy consumption. Those contradict withan economic growth of developing country.
Requirement of an environmental technology which can be accepted by the developing
countries are1) Suitable for an economical, technological and social situation of the developing
country.
2) Useful for energy saving
3) Producing valuable byproduct4) Creating new employment
In this presentation, the energy and environmental technologies being selected as anexample, technologies and systems useful for developing countries from the sustainable
point of view are proposed.
2. Coal Utilization Technology for the Developing Countries
Coal is one of the main energy resources in China.
In order to solve an environmental problem caused by coal utilization and to improvethe efficiency of coal utilization furthermore, we need to develop the following technologies
suitable for developing country.
1) Coal combustion technology
For the reduction of an emission of SOx from a number of small and medium size
combustion furnaces which are one of the main sources of local air pollution in thedeveloping countries, it is preferable to improve the fuel rather than to put thedesulfurization process at each furnace. The high pressure briqueting combustion method is
one of the fuel improvement method. In this method, the raw coal is pulverized under 1 mmand mixed with limestone particles. The mixture of coal and limestone is fed to the highpressure briquetting machine, pressurized under 1 t/cm2 to 3 t/cm2 and changed to thebriquette. This method can realize SOx removal rate of 60–70% and improve a boiler
efficiency by 10–20%.
According to my calculation, both environmental improvement and energy savings canbe realized when the supply and combustion system of high pressure briquette is applied tothe medium and small size combustion facilities in Chongqing which is the most polluted
city in China.
2) Gasification of coalIn the developing countries, the coal combustion for the home cooking and heating is190

Sustainable Energy and Environmental Technologies for Asian Developing Countries

one of the main causes of local air pollution and indoor pollution as well as the coal
combustion of medium and small size factory. The clean city gas supply system is one of themethod to solve this problem. At present, the city gas is supplied to around 30 million homesof 146 big cities in China. However, as most of medium and small cities have no city gas
supply system, domestic heating sources are mainly depend on direct coal combustion. It isexpected to spread the city gas supply system for domestic use in order to improve local
atmospheric environment and energy usage efficiency of coal.
Prof. Horio and his group proposed to build a city gas manufacturing plant producing
fertilizer as a byproduct near the conventional local ammonia production factory existing at
each prefecture in China. This process can meet the condition appropriate for developing
country since it can make use of conventional ammonia plant and capable of producing
ammonia sulfate fertilizer which is useful for the improvement of agricultural productivity
in China.
3) Desulfurization process
Most of power stations in Asian developing countries are not facilitated adesulfurization process at present. Although some desulfurization processes are supplied
from developed countries such as Japan to the developing countries with the aid of ODA or
Yen loan, the supplied or transferred technologies are not spread yet in the developing
countries. This is because in addition to its high cost, the desulfurization process given by
developed country is not suitable for dirty flue gas from the boiler of the developing
countries as it is designed for relatively clean gas from the boiler of the developed countries.
Especially, the limestone-gypsum process which is popularized in our country will not beaccepted by the developing country because it requires a great amount of water and large
scale waste water treatment facility in addition to high cost.
The conditions of the process which can be accepted by developing country like China
are 1) Dry process 2) Low cost 3) Useful byproduct. The possible process which can meet
above conditions are as follows;(1) The process producing hydrogen sulfate as a byproduct.
(2) The process producing ammonium sulfate as a byproduct.
(3) Dry high efficient limestone-gypsum process.
In China, hydrogen sulfate and ammonium sulfate are very useful for agricultural
fertilizer or industrial raw material. Therefore, the process (1) or (2) will be broadly acceptedby developing countries if it can be commercialized. Although the conventional dry process
has demerits of low desulfurization rate and low value of the gypsum as the byproduct, thedry process (3) will be accepted if the new usage of gypsum is developed and thedesulfurization rate becomes high.
4) Coal fly ash usage technology
One of the important problem of coal combustion is the treatment of the residual ash
after combustion. In China, technologies for usage of coal ash has been developed so far
since 1950. In 1990, amount of ash used effectively is 1.8 million tons. Usage ratio is 26.5%
which is half of Japanese ratio. At present, coal ash is used as building material such as a191

環境分組 Environmental Session

brick, a block material and cement and a packing material for coal-mine, roadbed and soil
improvement material which has become very popular in China recently. In future, theproblem of coal fly ash treatment will become more serious with an increase of the coalconsumption usage in the developing country.
For the simultaneous solution of acid rain problem and desertation, we propose a newsystem that is a utilization of gypsum purged from desulfurization process for improvementof a sodium soil (Ref. 4). This system might be useful for the solution of food problem in
China as well.
3. Short Summary
The real causes of environmental problem in the developing country are rapid increaseof population and poverty. The coal utilization technology and environmental protection
technology of developed country tend to retard the economic growth and consequently makeworth the environment of developing country as the technology of developed country is highcost and needs high energy consumption. The acceptable technology for developing country
should be cheap, safe and increase a chance of employment of developing countries. Thesetechnologies cannot be developed on the extension of conventional technologies. We needto develop an innovate technology on the basis of new principle capable of meeting severe
requirements of developing countries.
4. How to Realize Ecotopia Society in Developing Countries
In 21st century, people hope to realize Ecotopia Society like Fig.3 where main energy
sources are natural energy like solar, wind and biomass, materials are completely recycledand people enjoy the life harmonized with natures.
However, at present, an environmental destruction is progressing rapidly especially indevelopment countries. For example, the increase rate of the desert is avaragely 2000km2/year in China. The tropical forest disappears significantly in Thailand. Another cause of theenviromentaly destruction in the developing countries is the destruction of symbiosis
relationship between Town-Village-Forest. As Fig. 3 shows, farmers leave village and move192

Sustainable Energy and Environmental Technologies for Asian Developing Countries

to the town when the agricultural land becomes poor and the productivity of crops goes
down. The propulation of the town is increased and consequently air and water is rapidly
polluted. The polluted air and water damages the agricultural land of village and forest
surrounding the town. Consequently, it lowers the productivity of the agriculture field
furthermore and accelerate the movement of village people to the town. On the other hand,once the agricultural land becomes poor, the farmers have to cut the trees of the forest aroundthe village to increase the agricultural land. The decrease of forest around the agriculturalland reduces the productivity of the land because the forest plays the important role ofsupplying natural fertilizer and protecting the water flood which removes the surface soilthat is very important for ground production. Therefore, it is urgently required to stop thedestruction of a symbiosis relationship and create the positive chain cycle leading to theeconomic growth and cleanliness of the environment.
The following are examples of technologies those can realize symbiosis relationshipbetween town, village and forest.
5. Improvement of Alkali Soil by Using Desulfurization Gypsum
Alkalization of soils has expanded rapidly in many irrigated areas of the world due tothe man misuse of the land. Alkalization of soils once formed change to much poorer soils
for vegetation than the case of salinization. Their adverse effects on plant growth can be
attribute to impaired aeration, restricted rooting depth, interference in nutrient uptake andplant metabolism, corrosion of root surface and sodium toxicity1.
The total area of the alkali soils in the arid and semi-arid regions of China reaches to
320,000km2. The most important fact has been revealed from the recent soil surveys carriedout by Japanese and Chinese soil scientists that more than 50,000km2 of Mollisol distributed
in semi-arid regions of China are suffered from alkalization.3 Therefore, it will contribute to
the better condition of self-sufficiency of food in China to rehabilitate these Mollisol
suffered from alkalinization, because normal Mollisol shows generally high productivity.
Alkalization of soils is characterized by the formation of soils with a high percentageof exchangeable sodium; often sodium carbonate and sodium bicarbonate are present too,increasing the pH beyond 8.5, often to 9 or 10. To reclaim alkali soils, a two-step process has
been done. The first step involved the replacement of exchangeable sodium with calcium;the second step is to leach the resulting sodium salt from the soil. Leaching, alone, of acalcareous soil on which a crop is growing can reclaim alkali soils but the process usually isslow. Of the amendments used to bring about exchangeable sodium replacement withcalcium, gypsum (hydrated calcium sulfate) is far and away the most-used material.4 It has
the advantage of being nontoxic to plants, easy to handle, and moderately soluble.
However, to use gypsum as an amendment material for alkali soils has badly been put
into practice in China. The main reason comes from the Chinese situation that gypsum ispressed for demands and its distribution as a soil amendment is not available. Hence, it canbe considered to use a gypsum from the desulfurization process in China as an improvement
reagent of sodic soil. The most spreaded desulfurization process in the developed countries
is the wet lime slurry method whose byproduct is mostly pure gypsum. In the developing
countries, on the other hand, a semi-dry process tends to be adopted owing to its low

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construction cost and running cost.
In order to examine whether the alkali soil can be improved by the gypsum at the actual
alkalic field, the field experiment was carried out at the alkali soil field of Kangping
Province located at 150km north from the center of Sheng Yang City (China) from May to
September in 1996. Considering that the corn is the staple crop around these area, the growthof the corn on the sodic soil was examined. The gypsum from the wet process or the semidry process was mixed with the different mixture ratio at each unit area with the chemical
analysis results of the each unit soil where unit 3 and 4 are the control area without gypsum.
The gypsum powder was scattered on the ground uniformly and mixed into the soil of 20cm
depth layer from the surface by the scoop.
The corn fruits were harvested 4 months after the seeding. There were no significant
difference between the unit area of the gypsum from wet process and that of the gypsum
from the semi dry process if the mixing ratio of gypsum is the same.
The following results were obtained;
1) 1% of the byproduct application to the alkali surface soil by weight gave thealmost same yield of wheat and corn in non-alkali soils, and the once application
effect continue for three years at least.
2) The pH and ESP of the alkali soil decrease to the normal level of non-alkali soils
within three months from the application time of the byproduct.
3) The addition effect on the pH of the alkali soils by the contamination of Ca OH 2,
CaCO3 and fly ash was not recognized.
6. Recovery of Forest and Reduction of CO2 by Using BiobrequettMore than 70% of total SO2 and CO2 from coal in China comes from the small andmedium size industrial boilers those are mainly storker type firnace. It is mostly impossible
to facilitate the De-SOx process after each furnace because the number of this type furnace
are more than 450–500 thousand in China. The most probable method for the control of SO2
from the industrial furnace is the brequett combustion method since the emission of SO2 canbe reduced by 60–70% by mixing calcium into the brequett and the boiler efficiency can beincresed from 50% to 60 or 70% by the improvement of combustion efficiency. However,there are some disadvantages in the brequett combustion. The cost of brequett coal is 1.5 to
2 times higher than that of the raw coal and black smoke is sometimes generated during
combustion.
Biobrequett is more advanced brequett which was invented by Dr. Maruyama of
Hokkaido Industrial Research Center more than 20 year ago. Biobrequett has some merits
as follows.
Biobriquett is the brequett in which 20–30% biomass like corn leaf or wheat straw ismixed in the brequett . The merits of biobrequett are1) The cost becomes lower because the agricultural byproduct is free.
2) The soot emission during the combustion is significantry reduced because ofeasy ignition.

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Sustainable Energy and Environmental Technologies for Asian Developing Countries3) The 20–30% CO2 emission can be reduced by mixing 20–30% biomass in thebrequett.
we introduced biobrequett machine made in Japan into Shengyang and produced biocoal with the help of Shengyang Environment Protection Agency. I hope to report theexperimental result of biobrequett combustion in near future.
7. Summary
In conclusion, the most important thing to solve the environmental problem ofdeveloping countries like China is to make them rich without environmental destructions.
For that purpose we should study how to develop agricultural area of developing countries
from the point of view of technology and policies.
References
1

Buringh, P., Introduction to the study of soils in tropical and subtropical regions, 29–44, Center for

Agricultural Publishing and Documentation, Wageningen (1970)
2

S. Matsumoto and M. Aoki, Journal of the Japan Institute of Energy, 74, 1023 (1995)

3

S. Matsumoto, Zhao, Q. G., J., Zhu, S., and Li, L., Soil Salinization and its Environmental Hazard on

Sustainable Agriculture in East Asia and Neighboring Regions, Global Environment, 1, 75–81 (1998)
4

F. Iino, N. Aoki, Y. Nitta, S. Matsumoto and M. Sadakata, Journal of the Japan Institute of Energy, 76,

119–124 (1997)

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