Proceedings of the UNESCO - University of Tsukuba International Seminar on Traditional Technology for Environmental Conservation and Sustainable Development in the Asian-Pacific Region, held in Tsukuba Science City, Japan, 11-14 December, 1995.
Editors: Kozo Ishizuka, D. Sc. , Shigeru Hisajima, D. Sc. , Darryl R.J. Macer, Ph.D.
I have been to the TianJin city of China two weeks ago. In TianJin, I visited the municipal waste treatment plant, for a region with a million people, and the municipal waste mainly has been composted. This composting system is different from the Japan's in which the moisture of the waste composted was very low, around 30 to 400/0. The method was putting the waste at the height of 2 to 3 meters and maintaining it on aerobic fermentation about 2 weeks. After the fermentation process, the compost was separated to matured compost, heavy waste metals and plastics by separating machines, the matured compost were re-utilized as organic fertilizer by farmers.
In TianJin region, the amounts of rainfall per year were about 500 mm, so the recycle system mentioned above is possible and established. In south China, where the amount of discharged waste is on a large scale and the moisture is high, so that the land fill system will produce many kinds of acids and will melt the heavy metals in the waste, as a result, the ground water and lakes & rivers will be polluted. Furthermore, the T-N, T-P contents in the organic materials have to be treated for preventing the second pollution. So in practice, the percolating water treatment system has to be established.
For incinerating treatment, if the amounts of waste metals were much more, it will produce a large amount of the volatile hazard metal gas and other hazard gases when the waste are burnt out and this will cause air pollution. Dioxin comes from the buming of plastics. The dust produced by burning could collected by an electronic dust collector, but collecting the dioxin will not be cost effective with this present technology. So the biodegrabale plastics that will be degraded easily by composting should be used to accompany this. The social system must be changed to one where biodegradable plastics could be used commercially.