"Calcium carbonate is used in practically everything today, from plant-based milk to plastic windows. Our [planned] product is primarily intended for the manufacturing of construction materials," Alar Saluste, head of Ragn Sells' circular economy project OSA, told ERR's program "Osoon."

This study, conducted with Tallinn University of Technology researchers, extracts calcium from ash piles, binds it to the carbon dioxide in the air and produces a carbon-neutral product.

Ash hills vary in fineness and combustion because they are derived from different parts of oil shale. Current drilling work on the Ahtme ash hill tries to establish the precise composition of the ash pile.

"These [ashes] have similar elemental composition in that they all contain calcium, silicate, oxygen, iron and some aluminum. However, depending on the technology used to produce the ash, the mineralogical composition varies," Mai Uibu, senior researcher at the Tallinn University of Technology (TalTech) specialized in new uses for oil shale waste, explained.

The samples will now be taken to the University of Tartu for further analysis. Riho Mõtlep, a geologist from the University of Tartu, said that just by looking at the samples, they all contain common minerals like calcium carbonate, quartz and feldspar, as well as other substances that could be used in industrial processes. A good question is whether all this can be put to good use now.

Ragn Sells, a corporate group involved in waste management, plans to extract calcium carbonate from oil shale ash utilizing a chemical method that cleanses the calcium from the pulverized ash, transfers it to an aqueous solution and binds it with carbon dioxide derived from, for example, boiler dust, to produce calcium carbonate.

During the tests, the materials are crushed using AS Corestone's crushers next to the Ahtme ash hill that will reduce shale ash to particles as small as a few micrometers in diameter.

AS Corestone produces calcium carbonate as well, however their process is mechanical, not chemical, and so their product is somewhat different. It is primarily used as a raw material in the plastics industry. The company's CEO Keith-Neal Saluveer showed, as an example, 100 percent recycled pellets made from recycled plastic and quarry-sourced material.

Alar Saluste said that the Ragn Sells project aims to demonstrate that waste could be utilized to produce raw materials for everyday uses. Besides calcium carbonate, ash hills may yield other valuable raw material to be extracted in the future.

"We'll start with calcium carbonate because any useful material extracted from it will have to deal first with calcium. So it makes sense to begin with it and then move on to iron or magnesium, for example. Magnesium is in the top three of the EU's list of critical raw materials. We produce virtually no magnesium in the European Union today, but the Narva ash hills could meet the EU's magnesium needs for the next 30 years," Saluste said.

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