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General ash use

Ash use

"Ash is used as an environmentally friendly resource in a sustainable society!"

In any combustion of solid fuels solid residues, ie including ash slag and flue gas treatment residues are being formed. Approximately one million tonnes of 1.3 millionof non-coal ashes was formed used as resources 2006 in Sweden. But two thirds of the use is in landfills that are in the stage of final coverage, a market that will be significantly reduced in about 10 years.

It takes a long time to develop and gain acceptance of new uses. Hence the work to find good applications outside the landfill must have a high priority now. We need long-term follow-up, good practices and environmental studies. The latter involves application and interpretation of existing and emerging regulations on the use of ashes in eg geotechnical structures but also to provide a basis for future regulations.

The use of ashes is complicated because the ash production varies because combustion take place in many units of varying sizes, from moderately large to very small units. There are various boiler types, different fuels and hence the bottom and fly ash are also varying. The quality of the ashes are also varied not only due to variations in fuel but also on how the boilers are operated such as if they run on low or high load. This means that the applications chosen must be able to tolerate these variations.

Safe utilization or disposal, simplicity especially regarding administration and minimal risk of future costs are often the most important parameters when using the ashes from both small and large facilities.

Use of ash as fertilizers to forest land is of great interest in order to balance the set of nutrients and base cations in the forest. If not using ash (or other fertilizer) sufficiently, there is a risk that it will forbidden to take out the bio-fuels from the forest.

There is a conflict between using ashes for recycling to forest and as a resource to use in geotechnical applications. The latter is less costly but an LCA study -Värmeforsk Report 1068 2008 Olsson et al Forest fuel ash as a nutrient resource and structural materials Environmental effects of different management options-  shows that using the ash in the forest is an environmentally better alternative, even if a fly ash can replace four times its weight of natural geotechnical construction materials.

Under the following headings are shown how ash can be utilized in various fields

>> Ashes to Forest and Land

>> Geotechnical Usage

>> Landfills

>> Other uses

>> Volumes of ashes


CR 100922



Left top: Test area with the ash as fertilizer in the forest

Right top: Grate bottom and fly ash in a very successful road construction at Hudiksvall

Left bottom: the installation of the leachate collection lysimeter at the end of the landfill cover with ashes

Right bottom: leachate collection of test road made of MSWI bottom ash from Dåva Umeå.


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