In 2006, 1.3 million tonnes of combustion residues was produced (estimate for 2008: 1.5 million tonnes) and almost 80% was utilised. A summary of the quantities and types of combustion residues is provided in Table 11.1. The presentation is split into more categories than is usual in surveys, because mixtures of fuels, some of

them particular to a type of industry and to type of furnace, are important for the properties of the residues.

As one may see, the problem for a provider of materials is that the sources are numerous and small. For example, the 600,000 t/year of MSW incineration (MSWI) residues is produced by more than 25 plants. Many district heating plants produce less than 2,000 t of mostly wood-based ash per year. The smallest ones, as well as small sawmills, do not produce more than 1 t/year. The really small capacity furnaces are not included in these figures, e. g. pellet furnaces in individual homes, or farm units firing agricultural residues.

If one sums up all categories of solid biofuels and mixtures, the total quantity of ash from solid biofuels is of the order of 370,000 t/year.

All types of furnaces are used, grate furnaces, pulverised fuel (PF) furnaces and fluidised bed furnaces, the latter being perhaps more common in Sweden than in the rest of Europe. The capacities range from a few hundred kilowatts to a couple of hundred megawatts on a fuel basis. Small furnaces up to 10 MW fuel are usually grate furnaces, and fluidised bed furnaces are preferred from 20 MW fuel and upwards. PF furnaces are not so common in Sweden. All these types of furnaces have their particularities, which affect the properties of the residues; see Sect. 11.2.4.