PROJECT DESCRIPTION
BACKGROUND
Over 90% of the power supply in Estonia comes from oil shale–fired thermal power plants. Every year some 11 million tonnes of oil shale are burned, producing more than six million tonnes of oil shale ash (OSA). Currently this is mostly disposed of by spreading on land, which causes pollution of millions of cubic metres of rainwater each year. However, OSA can be used as a raw material in the construction industry, and could become an interesting and cost-effective replacement for cement and other expensive additives. In Estonia, this could offset the need to import up to 500 million tonnes of natural aggregates from non-renewable sources, usually involving heavy long-distance transport across Europe.
OBJECTIVES
The objective of the OSAMAT project was to show that it is possible to convert oil shale ash (OSA) into a material that can be used in the construction sector. Specific objectives of the project included: 1) To demonstrate the technical, environmental and economic feasibility of producing aggregates and additives from OSA that have applications in the construction sector; 2) To disseminate the results of the project to target groups such as municipalities, road managers, contractors, politicians, legislative authorities, scientists and other professionals and specialists in Europe as well as in Estonia; 3) To demonstrate the environmental benefits of materials and applications based on OSA using life-cycle assessments; and 4) To demonstrate the economic benefits for European companies of using OSA as an additive in certain civil engineering applications.
RESULTS
The OSAMAT project demonstrated the technical, environmental and economic feasibility of producing aggregates and additives from three different oil shale ash (OSA) applications in the construction sector. OSA was tested during road construction at two pilot sites in Estonia, Narva-Mustajõe and Simuna-Vaiatu, for road base course layer stabilisation and mass stabilisation of peat, and also in structural road base aggregates made from OSA and shale mining waste. The technical monitoring results showed that all three types of OSA are suitable for use in the tested applications for road construction.
These OSA applications were tested by the Estonian Road Administration for use in the construction of the main road between Tallinn and Tartu. In 2017, tests started for the use of OSA in the mass-stabilisation of soils in Rail Baltic railway construction, and coordinating beneficiary Eesti Energia is considering the material for the mass-stabilisation of soil in the construction of Tootsi wind park. An international collaboration, including ECOBA, large cement producers and civil-engineering companies in Finland, Sweden and Lithuania, has also been started.
The utilisation of OSA brings environmental, economic and social benefits. The environmental benefits of OSA utilisation as a binder in road construction, instead of cement, are reduced amounts of OSA deposited in landfill, reduced depletion of natural resources (cement and mineral resources), and reduced greenhouse gas emissions (CO2) due to improved resource-use efficiency. In fact, for every tonne of OSA used in large applications as a substitute for cement reduces, GHG emissions are reduced by over 0.6 tonnes, along with other air pollutants.
The results of the environmental monitoring indicated fluctuations in concentrations of some metals and anions in samples of surface water and soils during several years of monitoring (at both pilot sites), but none of the concentrations exceeded the target values of the environmental legislation. There was no influence on the flora around the tested pilot site. Instead, there was a bloom of vegetation. In general, it can be concluded that there are no significant negative impacts to the environment coming from OSA use in road construction and it proves itself as an environmentally-safe aggregate. According to the project’s life cycle assessment (LCA) carried out at both pilot sites, the environmental load can be decreased by using OSA as a construction material for road construction. The life cycle cost (LCC) study compared the relevant investment costs of the alternatives and found OSA to be cost-effective; it showed that the discounted annual cost per kilometre of road was lower for structures with alternative construction materials to cement, like OSA. The crucial barrier to its use is the cost related to transportation of OSA over long distances. In this case, being more cost-effective for stabilisation projects closer to the Eesti Energia Narva Power Plant where the OSA is generated.
The increased use of OSA entails positive social impacts such as higher employment through the involvement of service providers (including SMEs) in such projects. The decreased landfilling of OSA improves the living environment of the people in North-East Estonia. Additionally, the decreased need for the extraction of primary raw materials for the production of cement has a positive effect on the people otherwise, impacted by such mining activities.
By demonstrating recycling of OSA in road construction, the project directly contributed to the implementation of the Waste Framework Directive and the Circular Economy Package.
Project results and dissemination actions helped to change perceptions of oil shale ash, with road construction companies, authorities and the general public now more likely to see it as a valuable construction material rather than just a waste material. An additional benefit arising from the project was that OSA was standardised as a product for using in cement, concrete and gas concrete production in Estonia.
The project’s methods are readily transferrable, including potentially in stabilisation for other civil engineering purposes.
Further information on the project can be found in the project's After-LIFE Communication Plan (see "Read more" section).
