Minimisation of odour from composting of food waste through process optimisation

A Nordic collaboration project

image of Minimisation of odour from composting of food waste through process optimisation

Composting of food waste often causes problematic odour emissions. This project develops recommendations to minimise the risk of odour problems and to achieve an efficient process and a high and uniform product quality. Three full-scale plants and one experimental reactor were investigated. The results show a strong correlation between pH and odour emissions, temperature and decomposition rate are also important factors. The main recommendation to reduce odour problems is to control the process so that pH increased rapidly, without increase of temperature, either through ventilation or by addition of compost or wood ash with high pH. Water may contribute to control temperature. Food waste is high energetic and a large amount of energy is released during composting. If energy is used to evaporate water, the compost will be kept cool. The amount of water in food waste is usually not sufficient to allow adequate evaporation and cooling. It should therefore be possible to add water to the process to help control of temperature end pH. The original report, in Swedish, is published at http://www.avfallsverige.se/m4n?oid=2399&_locale=1




The project showed a strong correlation between pH value and odour (Figure 26). Pore odour is 10–1000 times stronger at pH values below 6.0 than above 6.6. This means that the pH value is an important indicator of the odour potential of the material. It can therefore be concluded that for minimisation of odour during composting of food waste, it is very important to minimise the time taken for the pH to exceed 6.5. When the incoming material has as low pH values as source-separated food waste in the Nordic countries, special measures are required to rapidly increase the pH value and thereby minimise the risk of bad odours.


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