Summary and conclusions, Miljøstyrelsen

Skal husholdningernes madaffald brændes eller genanvendes?

Summary and conclusions

The Danish Environmental Protection Agency has carried out a cost benefit analysis of the consequences of increasing recycling of organic household waste. In the cost benefit analysis both the economic consequences for the affected parties and the welfare-economic consequences for the society as a whole have been investigated. In the welfare-economic analysis the value of the environmental effects has been included

The analysis shows that it is more expensive for the society to recycle organic household waste by anaerobic digestion or central composting than by incineration. Incineration is the cheapest solution for the society, while central composting is the most expensive.

The total welfare-economic additional cost, compared to present treatment, of recycling about half of the organic household waste, equal to 300,000 tonnes, by anaerobic digestion is DKK 230 mill. per year . The additional cost of recycling 300,000 tons by central composting is DKK 270 mill. per year.

Anaerobic digestion of 100,000 tonnes will imply additional costs in the order of DKK 70 mill. per year, whereas central composting of 100,000 tonnes will lead to additional cost of close to DKK 80 mill. per year.

Furthermore, technical studies have shown that there are only small environmental benefits connected with anaerobic digestion of organic household waste compared with incineration of the waste.

Almost all of the environmental effects, that have been quantified, have also been valued and they have been included in the welfare-economic analysis. The analysis shows that the value of the environmental effects only accounts for 5 – 10 per cent of the net cost.

In addition, there are a number of positive environmental effects connected with recycling, but it has not been possible to include in the analysis, e.g. improved soil quality, less use of pesticides, and a better quality of the slag. It is assessed that the inclusion of these effects would not affect the results of the analysis.

The primary reason for recycling being more expensive than incineration is the necessary, but cost-intensive, dual collection of the household waste. Treatment itself is cheaper for recycling compared to incinerating.

In the analysis the extra cost of the dual collection is calculated on the basis of full-scale experiments/tests in several municipalities. The extra cost is about DKK 150 per household per year for single family houses and about DKK 110 per household per year for apartments. The extra cost must be below DKK 50 per household per year for single family houses and below DKK 20 per household per year for apartments in order to make anaerobic digestion more attractive than incineration. For central composting the corresponding costs should be below DKK 30 per household for single family houses and below DKK 10 per household for apartments.

The extra cost should therefore be reduced by 2/3 for single family houses and by 5/6 for apartments, under the assumptions in the analysis, in order to change the conclusions.

Sensitivity analyses show that the conclusions are not sensitive to changes in the assumptions of the analysis. This means that the ranking of the three alternatives – incineration, anaerobic digestion and composting – seems rather stable and not very sensitive to changes. Only a so-called optimistic recycling scenario, based on the most optimistic technical assumptions, is able to change the ranking of recycling and incineration, but this only applies for single family houses, and not for apartments.