The non-ferrous metals content usually varies between 2-4% of the BA input. The primary recovered metal is aluminium (aluminium alloys) followed by brass, copper, zinc, lead, silver and gold.
Scrap iron with a commercial value (usually > 3 mm) varies between 5-13% of the BA input.
Such as silver, gold, platinum and palladium can be found in BA. Precious metals are part of the non-ferrous metals fraction and are usually sold directly in the non-ferrous mix or as concentrated heavy non-ferrous product.
The silver content averages about 10 ppm while gold averages 0.4 ppm per ton of BA.
Stainless steel metal content vary depending on the size which could be recovered. Usually only particles > 40 mm are recovered by handpicking.
Meatballs (Cu-Fe engines, etc.)
Meatball content is about 0.1-0.2 % of the input. Meatballs make up a part of the scrap iron fraction and therefore must usually be manually removed in order to fulfil the requirements for scrap iron (the copper content should be under a certain level).
The organic content varies based on the input material in the incinerator and incineration conditions. The organic content is usually between 0.1-5 %.
These are major components of BA which contain stone, glass and ceramics and have similar engineering properties to primary building materials (gravel, sand). The recycling of BA is not regulated on the EU level and therefore the market for the stony fraction is determined by local legislation. Countries such as Belgium, the Netherlands, France, Germany and Denmark have developed and adjusted their civil and environmental regulations so as to allow the use of bottom ash residue in road construction. The alternative of land filling in Europe varies in cost between € 20-80 per ton of bottom ash. Recycling of the stony fraction is complicated due to the safety and quality of the residue. Many countries have very strict leaching limits and therefore the utilization of bottom ash is very limited. The largest fraction (aggregate) is usually used for a variety of building applications (foundations, road construction, concrete, bituminous concrete aggregates, asphalt, etc.). The fine fractions of BA are somewhat pozzolanic as a result of the incineration process. A new application related to this property is the use of finely crushed aggregate as a cement substitute.