'The Journal of Transdisciplinary Environmental Studies' (TES)
Volume 2, Number 2, Jan. 2003

ISSN 1602-2297

Cadmium Flows in Recycling Waste to
Agriculture in Thailand

Nanette Levanius Schouw and Jens Chr. Tjell
Environment & Resources DTU, Technical University of Denmark
Email: nsc@niras.dk and jct@er.dtu.dk

Abstract: The heavy metal, cadmium is a toxic compound for all living organisms, and requires, therefore, special attention in risk assessment studies. As cadmium is a rather mobile ionic species under acidic soil conditions, which are dominant in Thailand’s agricultural lowland, one could expect it to be present in agricultural crops. Consequently, it poses the potential risk of entering human food products. Research conducted over the last decades has found that rice, which is the main staple food item, is the main contributor to the human intake of cadmium in Asian countries. The objective of this study is to assess the change in risk when using treated biodegradable waste products as a substitute for chemical fertilisers in agriculture. Chemical analyses showed that the highest flow of cadmium in organic waste is in municipal wastewater sludge and biodegradable kitchen waste, whereas human excreta only carries small amounts of cadmium. Thailand does not presently have any regulation on this potential risk element, consequently international standards may be used for comparison. Recycling urban waste to agricultural land would, potentially, not exceed the American and European Union’s threshold limit for waste application to agricultural soils. However, a few European countries (e.g. Denmark) have stricter threshold limits, due to specifically vulnerable soil and groundwater conditions (alkaline clay soils with the ability to accumulate heavy metals), and these would potentially be exceeded if some of the urban Thai wastes were applied to the soils. It is concluded that the recycling of urban waste to Thai agriculture poses only a very small potential risk of cadmium contaminated food products.

Key Words: Recycling waste, cadmium, risk assessment, Thailand, Songkhla Lake Basin, mass flow

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