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Letters to the Editors |
Letter to the Editor of South China Morning Post - Response to reader's letter on disposal of food waste and thermal waste treatment technologies
Dear Sir/Madam,
We wish to respond to Mary Melville on the disposal of food waste (SCMP, October 12) and Frank Lee on thermal waste treatment technologies (SCMP, October 24).
We have already examined the use of food waste grinder. It merely transfers the food waste from the solid waste disposal system to the liquid waste disposal system without any enhanced treatment.
It would also increase both sewage pollution loads and the amount of sewage, with adverse impacts on the existing sewerage network and sewage treatment works. The higher solid contents will lead to the need for higher sewer maintenance frequency and costs, as well as higher risks of sewer blockage.
In addition, food waste grinder is not conducive to source separation of food waste. Its adoption on a large scale does not seem to be consistent with the philosophy of sustainable use of resource.
We will continue to reduce food waste and develop modern large-scale organic waste treatment facilities using anaerobic digestion as the core technology.
The modern thermal waste-to-energy plant to be built near Shek Kwu Chau to deal with municipal solid waste (MSW) will be designed to meet the European Union Directive on Incineration of Waste, which requires very high heat flue gas combustion.
Plasma gasification technology is mainly used for treating industrial or special wastes. Its commercial application for large scale treatment of mixed MSW is uncommon and still has a limited track record.
The plant in Switzerland Mr Lee refers to uses pre-sorted waste, such as tyre chips and plastics, as alternative fuel to partially replace coal and coal is co-incinerated with limestone and other raw materials for cement production. This is different from the Green Island Cement (GIC)’s proposal. All along, we have suggested to GIC they should conduct an environment impact assessment.
The "White Paper on Alternative Waste Conversion Technologies" published by the International Solid Waste Association in January 2013 and the International Conference on Solid Waste held in Hong Kong in May 2013, affirm that modern moving grate incineration remains the mainstream proven technology for large scale MSW treatment.
Elvis WK Au
Assistant Director of Environmental Protection