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Minimering av lukt från kompostering av matavfall genom processoptimering : Ett nordiskt samarbetsprojekt

Sundberg Cecilia, Romantschuk Martin, Smårs Sven, Jönsson Håkan


The aim of this project was to develop recommendations regarding how composting processes for the treatment of source-separated food waste in Nordic countries should be designed and implemented in order to: • Minimise the risk of odour problems with the process • Minimise the risk of odour problems with the finished product • Achieve an efficient and reliable process • Achieve a high and uniform product quality. The hypothesis for the project was that total odour emissions from the composting process, as well as the risk of odour from the finished compost product could be minimised if the process turnover rate and decomposition were to be maximised. In the project, incoming biowaste and composting processes were investigated at three full-scale composting plants (at NSR in Sweden, YTV in Finland and IVAR in Norway) and for an experimental reactor (at SLU in Sweden). The results showed a strong correlation between pH and odour in compost pore gas. At low pH values (below 6.0) the odour concentration was very high, from 70 000 to over 2 million ouE/m3, while at pH over 6.7 it was at most 44 000 ouE/m3. The biowaste collected was consistently acidic, with pH between 4.7 and 6.0. Tests confirmed previous results that the decomposition process proceeds much more slowly at low pH (<6) if the temperature is allowed to rise above 40°C. However, if the temperature is kept below 40°C, decomposition is intensive, which causes the pH to climb rapidly. When the pH has increased to over 6.5, but not before, the temperature should be allowed to increase to around 55°C, since this maximises the decomposition rate. The most important recommendation as regards decreasing odour problems in composting of food waste is to control the process so that the pH is increased rapidly. This can be achieved by intensive ventilation at the beginning of the process, which promotes cooling and increases the oxygen supply. The pH can also be increased through addition of pH-enhancing material such as compost or ash with a high pH. This minimises the amount of intensely malodorous acidic compost in the system. In addition, it maximises the decomposition from the very beginning of the process, which leads to maximisation of the proportion of total odour emitted in the contained part of the composting plant, where the odours can be treated before being released to the environment. The amount of readily available energy in food waste is very high, while in stable and well-matured compost it is low. Therefore, a large amount of energy must be released during composting. This energy is largely used for evaporating water from the compost. Since food waste is so energy-rich, the amount of water in the incoming waste is not sufficient to allow evaporation of the amount required for the compost get enough cooling to become stable. To achieve an optimally rapid process in the contained section of the composting plant, it should therefore be possible to add water. Otherwise the degradation process halts until a sufficient degree of cooling is achieved, e.g. through water in the form of rain or snow being added during post-process maturation


kompost; pH

Publicerad i

RVF rapport
2008, nummer: 2008:10
Utgivare: Avfall Sverige utveckling