03.08.2015   Recycling of Biomass Ashes

Utilisations

The large quantities of combustion residues may be swallowed only by a mass market, that of materials for civil works. The largest single use in 2006 was as a

Table 11.2 The uses of combustion residues in Sweden in 2006 (survey performed by Svenska Energiaskor)

Area of use

Quantities (tonnes DS per year)

Landfill construction and closure Civil works outside of landfills Backfilling cavities

650.000

200.0 50,000

(e. g. mines and quarries)

Spreading to forest soil and arable land

35,000

Other uses and unknown uses

175,000

Total quantity used

1,000,000

Total quantity produced

1,300,000

construction material in the closure of landfills (as well as for capping), with approximately 650,000 t; see Table 11.2. The financial incentive for this use is the possibility to waive the tax on waste sent to landfill: the materials are used and replace virgin materials. However, many currently active landfills will be closed within the next 10-15 years. It should be noted that backfilling cavities in Table 11.2 concerns mostly air pollution control (APC) residues from combustion of MSW.

Spreading to forest soils is a small area of use, with approximately 35,000 t/year, but is of vital importance for the sustainability of the production of solid biofuels from biomass harvested from forests. The relevant biomass fraction is the logging residues, and harvesting it on top of the extraction of timber and pulping wood in conventional forestry not only removes the mineral nutrients in the residues that if left in the forest would have been available to the next generation, but also exacerbates the natural acidification of forest soils by conventional forestry.