Background Municipal solid waste can be treated through incineration, recycling, composting, or sent to landfill. Landfilling is considered the worst solution as it takes up valuable land space, and it also causes air, water and soil pollution. The share of landfilled waste has decreased to be replaced by incineration and the number of incineration plants around EU has increased. Though incineration is preferable to landfilling, it causes environmental problems namely the generation of flue gas waste (FGW) which contains chlorides and heavy metals. The FGW is classified as hazardous waste in the European Waste Catalogue. To remove the pollutant, the polluted gas stream is brought into contact with the scrubbing liquid in a wet scrubber. The contact with water over a large area removes the pollutants. However, in most cases in Denmark and Sweden, the FGW waste fails to meet the EU limit values for leaching (i.e. lead and chloride), and often the FGW from these two countries is sent to landfill. Approximately 200 000 tonnes of FGW is transported to landfill every year and, in some cases, alkaline treatments are needed to neutralise the acidic waste. Therefore, potential resources in the FGW are not utilised. A rough estimate, from previous small-scale tests, showed that about 465 tonnes of zinc and 4 000 tonnes of salt were wasted in an incineration plant, even by using the ‘state-of-the-art’ technology. Moreover, about 45 000 m3 of wastewater is generated from neutralising the scrubber liquid using precipitation chemicals. Objectives The main objective of the LIFE HALOSEP project is to demonstrate how two waste streams from incineration plants, fly ash and liquid, can be co-treated to reduce the amount of waste going to landfill. The innovative HALOSEP process converts the waste into a salt brine product and a zinc product and significantly reduces the amount of flue gas residues, which improves leaching properties so that the material meets safe limits for reuse. The new technology closes the material loops for chloride and zinc, and thereby contributes to the development of a circular economy. The main advantages are a shift from 100% disposal of FGW (flue gas waste) in dedicated landfills to material recycling with a reduction of disposed amounts by about 40-60%; 30-40% cost savings; and less material landfilled, with decreased need for transportation, less chemicals consumption, and increased material available for recycling. The project will demonstrate how the process can be integrated into existing incineration plants so that it can be replicated throughout the EU waste industry. The project will contribute to the implementation of the Waste Framework Directive and the Landfill of Waste Directive as it improves the recycling and reuse of metals (e.g. zinc) from fly ash and salt brine and reduces the amount deposited in landfills. The project also boosts the implementation of the Waste Incineration Directive aiming to prevent or limit the negative effects of emissions from the thermal treatment of waste; the ‘wet’ treatment technology proposed by the project leads to much lower emissions. Expected results: The LIFE HALOSEP project will play a significant role in helping the EU to minimise environmental problems arising from waste incineration. The project is expected to have the following results: Total costs for HALOSEP fly ash treatment (including scrubber liquid neutralisation) will be reduced by about 20%; Chemical consumption will be reduced by about 80%; Flue gas weight amount (dry matter) will be approx. 60-62% of the original fly ash input amount, representing a reduction of about 40%; HALOSEP product will be refined to obtain approx. 40% zinc content; The salt amount will be about 30% of the original fly ash input amount; The salt product to be recycled as a brine having approx. 10% salt content; Amount of wastewater from the incineration plant will decrease by 10-12 m3 per tonne of salt recycled; Up to 2 000 tonnes of salt may be recycled and used as road salt in the winter period; The amount of material to be returned to the incinerators ovens (oversizes) is less than 1%; and If implementation extends to the whole EU waste industry, the process could decrease the need for landfill sites, reduce the need for the transportation of fly ash, provide a feasible and environmentally-friendly method for neutralising fly ash, and represent a step towards a circular economy.