The food waste produce fly ash (e.g. in EU, about 70% of food products contain ingredients of chemical synthesis). 

Dear Mack Shui Sun,

There are some merits & demerits of incineration of solid waste/food waste.the management of solid combustion residues and especially of fly ash by-products remains a primary issue.Air pollution control (APC) residues as collected in the APC equipment (i.e. scrubbers,electrostatic precipitators, and baghouses) including fly ash, sorbents, condensates and reaction products. The term “fly ash” usually includes APC residues.Municipal solid waste incineration (MSWI) ash is used in part as raw materials for cement clinker production by taking advantage of the high contents of SiO2, Al2O3, and CaO. It is necessary for environmental reasons to establish a material utilization system for the incineration waste ash residue instead of disposing these ashes into landfill.

Solid waste arises from human activities—domestic, commercial, industrial, agricultural, waste water treatment, and so on. If the waste is not properly handled and treated, it will have a negative impact on the hygienic conditions in urban areas and pollute the air and surface and ground water, as well as the soil and crops. A hygienic and efficient system for collection and disposal of solid waste is therefore fundamental for any community. Generally, the demands on the solid waste management system increase with the size of the community and its per capita income. Residues from waste treatment processes are returned to the waste mainstream and end up in the landfill with untreated waste. Hence, the backbone of any waste management system is an efficient collection system and an environmentally sound sanitary landfill,

MSW incineration is found at the most advanced level of the waste disposal/treatment hierarchy: indiscriminate dumping, controlled dumping, landfilling, sanitary landfilling, and mechanical treatment (for example, composting and incineration). Additional environmental control is introduced at each level and the disposal costs increase substantially. Although waste incineration significantly minimizes the volume of waste for disposal, residues that have to be disposed of in landfills will remain. These residues consist of bottom ash (slag) from the burned waste and fly ash and other residues from flue gas cleaning. Depending on the environmental and geotechnical demands, the bottom ash can be recycled for construction purposes or disposed of with no special measures. In all circumstances, the plant must have access to a properly designed and operated landfill for ultimate residue disposal. At the same time, a significant part of the most harmful substances is also retained because dust particles (fly ash) and pollutants adsorbed on the surface of the particles can be removed in efficient dust removal equipment like electrostatic precipitators. Basic emission control is a minimum requirement.

Particulate pollutants: Fly ash, including the heavy metals of antimony (Sb), arsenic (As), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), lead (Pb), manganese (Mn), mercury (Hg), nickel (Ni), thallium (Tl), and vanadium (V). Some of the heavy metals evaporate in the combustion process, then condense to a varying degree on the surface of the fly ash particles in the incineration section.

Electrostatic precipitators (ESPs) are therefore the preferred fly ash collectors at waste incineration plants. They may be designed with one, two or three independently controlled electric fields, according to the actual emission standard.

The adoption of alternative cleaner methods for the disposal of municipal garbage is necessary. According to the United Nations Environment Programme (UNEP), incinerators are the leading source of dioxin into the global environment he EPA, in a recent study, identified dioxins as the cause of many cancers, the worst component being TCDD (also known as Agent Orange).

An integrated solid waste management (ISWM) is essential to establish a waste hierarchy to identify the key elements. The general hierarchy should be comprised of the following order:

1. Reduce

2. Reuse

3. Recycle

4. Waste minimization and recovery of energy from waste by composting, anaerobic digestion, incineration etc.

5. Landfilling

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Mack Shui Sun Mak

in general mixing of MSW for incineration not advisable because food waste produced less energy. but if food waste mixing the MSW increasing the  quantity of ash 

Dear Elena Danila, Prem Baboo and Tamru Tesseme: Thank you very much for your answer. In Macau, the fly ash is treated as hazardous waste and dumped hazardous waste area because some of incinerated waste is mixed with e-waste. I am studying the pyrolysis method to treat the sewage sludge and food waste in stead of direct incineration in order to reduce the total quantity of fly ash in Macau. 

Food waste contains mineral elements, so after combustion you can always obtain a bit of ash. Some part of it you can find as a fly ash. Its quantity depends on combustion conditions and construction of combustion unit.

Dear Grzegorz Wielgosinski:

Thank you very much for your advise. I will consider this matter in my study.

Mack Mak Shui Sun