A new product is created by combining two types of industrial waste
06.02.2012
Mixing slag generated at Rautaruukki’s steel mill in Raahe with ash from wood incineration results in soil improvement pellets, a new product for forest fertilisation. The Clean Technologies research group of the School of Chemical Technology is examining how solid residues flows and waste generated in the process industry could be used in novel ways.
“We are examining whether waste generated by an industry could be used as a raw material by another,” explains Professor Olli Dahl, head of the research group.
When the waste generated by an industry as by-products are in the right form they can be reused. The Clean Technologies research group has developed symbiotic products in which a workable end result has been created by combining several types of solid process industry residues
The soil improvement pellet is one of the products developed by the Clean Technologies research group and studies are already under way to determine whether the product could have commercial applications. Such products as concrete that is slightly less strong and durable that virgin concrete but that nevertheless suits most purposes are also under development. Studies have shown that these products are technically workable and, according to life-cycle assessments, they are also extremely environmentally friendly.
Increasing the amount of solid waste helps to mitigate climate change
According to Professor Dahl, increasing the amount of solid process industry waste also helps to mitigate climate change because more thorough cleaning means that fewer substances will end up in the air and waterways. As the substances do not disappear, they can be recovered as solid residue flows. Combining solid residues generated by the process industry can result in such products as an effective forest fertiliser.
Moreover, the carbon dioxide emissions of the soil improvement pellet developed by the Clean Technologies group are also much lower than those generated by primary roducts. “When a thousand kilos of soil improvement pellets, or limestone, are produced synthetically, the carbon dioxide emissions are 12.2 GWP (kg, CO2-Eqv). For pellets made from industrial residue flows, they are only 1.6 GWP (kg, CO2-Eqv)” explains Dahl, illustrating the difference.
Can a landfill be turned into a raw material source?
Unfortunately, not all industrial raw materials are used in end products. This means that the flows of industrial residues would be recycled and not dumped in landfills. However, Dahl emphasises that with future technologies, it may be possible to use landfills as raw material sources or mines supplying valuable substances such as nickel and copper.
“Previously, the problem with industrial landfills was that different types of waste were not separated. Nowadays, landfills have specific sections for different waste fractions. With future technologies, it will be easier to recycle such residues lows, too. ”
Dahl believes that in the future, there will be an enormous increase in the flows of solid industrial residues: “In the future, management of material flows will be extremely important as both the human population and living standards are increasing all the time. There are only a limited number of chemical elements on the earth and they won’t last forever. This means that we must make material flows and cycles of valuable materials more efficient.”
Comprehensive understanding of the environmental burden generated by industries
According to Dahl, it is particularly important to have comprehensive understanding of the environmental burden generated by production processes (wastewater, atmospheric emissions and solid waste) and the factors influencing it. For example, players in the forest industry are not aware of the activities of nearby metal and mining industry and vice versa. However, the aim of the Clean Technologies research group is to manage the broad field of different industries so that residue flows could be recycled and valuable natural resources could be saved. At the same time, the group is also engaged in traditional research on wastewater cleaning.
According to Dahl, wastewater can be made entirely drinkable and atmospheric emissions 100 per cent clean. However, the cleaning processes require large amounts of energy, which means that the environmental burden is simply shifted to the plant generating the electricity.
“In the future, engineers must make value decisions and decide what kind environmental burden the process is allowed to generate. Should the pollution be released into the air or waterways or dumped in landfills? The Clean Technologies research group will take a comprehensive look at the matters so that we can find the most environmentally friendly solutions,” Dahl concludes.
Further information:
Professor Olli Dahl
olli.dahl [at] aalto [dot] fi