The waste management that is preformed in an incineration plant is very clear. It is a controlled combustion process of the waste which is, in its majority, eliminated, and consequently the installation space is not depleted by accumulation of waste, as happens in landfills. In reference to municipal waste, in principle, the only fraction that should be treated is the non-recyclable, therefore, the amount of waste that should enter in these types of plants, in combination with controlled landfills, should be very small. To all this we must add the relatively small footprint these facilities occupy, in addition to the recovery of energy contained in waste. But unfortunately the level of recycling and recovery of waste is far from what would be necessary and a good part of municipal waste generated that reach the incinerators are recoverable.
During the combustion of waste a series of by-products are generated, some of which are pollutants and toxic. These by-products of combustion are ashes, slag (by-product left in the furnace once the waste is burned up, a small part of which may be recoverable, while the rest has to be taken to a landfill) and smoke (all combustion generates smoke and the emission of gases and particles into the atmosphere).
Figure 18. Municipal waste incineration plant of Tarragona
Photograph: O. Saladié
Dioxins are among the different chemicals released during combustion of waste. They are a group of organic-chlorine substances that have a high toxicity, are bio-accumulative and have a high persistence in the environment. For this reason they have been extensively studied over recent years and their carcinogenic effects have been widely debated. Thus, in some areas near incinerators studies have been and are being conducted to determine the incidence of these pollutants on the water, soils, natural vegetation, crops and especially on the population.
In the year 2009 Catalonia had four operational municipal waste incinerators: Girona, Mataro, Sant Adria de Besos and Tarragona. In these four plants more than 600 thousand tons of municipal waste were treated.
Even though there are advantages over controlled *waste disposal, waste incinerators also have environmental costs, to which we must add the economic costs of construction and operation, which is why this type of *waste treatment should not be the first priority.