In the incinerator, cinders will be left over from municipal waste, and a parking lot will be built from it in Prague

According to statistics, an adult Prague citizen throws about 200 kilograms of mixed municipal waste into the black bin every year. It will produce light and heat for Prague households after processing and subsequent energy use at ZEVO Malešice.

There will be approximately four kilograms of ash, which currently has no use, and slag, or incinerator slag. This makes up about 40 to 50 kilograms of the weight of the original mass and still ends up at the landfill, where it is used to separate and strengthen the individual layers of the deposited waste.

Currently, the landfilling of untreated waste in the Czech Republic should end by 2030, slag will thus lose its only use so far. Therefore, in cooperation with the Czech Technical University and the Academy of Sciences of the Czech Republic, the Prague services are looking into the question of whether incinerator slag has a chance to be used in other sectors. “The results are more than surprising,” said Komarnický.

The foundation of the future that can replace crushed stone

Research has shown that slag from incinerated waste could be used in the construction of transport infrastructure. It has similar properties to the currently used crushed stone or crushed aggregate, which is added, for example, to the base layers during the construction of roads and highways. There are fewer options for stone mining in the Czech Republic.

Quarries that have been in operation for years are closing and new ones are practically not being created. Cinder could be an alternative solution and a possible way. The Prague Services are now testing its use in practice right on their premises.

“At ZEVO Malešice, we started the construction of a parking lot for cars. For the first time in the Czech Republic, incineration slag material, created by burning mixed municipal waste, is used for the road construction. For these purposes, we processed a total of 700 tons of slag with an advanced separation system,” said spokesman Komarnický.

In any case, the incinerator slag will not only be used as a substitute for crushed stone in the road construction of the parking lot, but at the same time the possibility of its use in a hydraulically cemented base layer will be verified.

Before slag was even used as a building material, it underwent thorough testing. This has proven to be environmentally sound and eliminates the risks associated with ecotoxicity, so it cannot in any way endanger the environment. At the same time, the material meets the legislative and decree standards.

“In this way, we want to verify the technical suitability of the material and set a certain precedent so that all slag generated in municipal waste incinerators in the Czech Republic can be used according to our proposed model. Tens of thousands of tons of material are involved annually. Our ambition is to talk about it, for example, with those who deal with the construction of transport infrastructure – with the Ministry of Transport, the Ministry of the Environment, the Directorate of Roads and Highways, road administrators or representatives of regions, cities and municipalities and save people a lot of money from public budgets,” he said. ZEVO Malešice ecologist Tomáš Baloch.

According to him, from the point of view of the Czech Republic, this is a groundbreaking matter. In Europe, slag from incinerators is already used as a base material in the construction of roads and highways, for example in Denmark, the Netherlands, Belgium and Finland.

Its advantages are availability and price compared to traditional granular materials, due to the fact that it is a processed waste. “With this project, on the one hand, we fulfill the principles of the circular economy, when we treat waste as a valuable resource, and in addition, we can at least partially replace the classic crushed stone, which is becoming a very expensive and scarce commodity,” added the company’s spokesperson.