The drive of the EU countries and most of the world towards a circular economy and togenerate zero waste raised a need to study more efficient and less costly treatment processes. The treatment of secondary and by-product fractions to convert them from what is considered waste to a resource will contribute to the movement towards zero waste and circular economy. The fines fraction of construction and demolition waste (CDW) contains high organic materials measured as total organic carbon TOC above the allowed landfilling levels that are allowed for landfilling in Sweden, yet lower organic matter than is required for energy recovery by incineration.

The need for new processes to reuse and recycle materials have emphasized the work of thisstudy, this thesis research aims to develop viable, simple treatment methods and pathways ofrecycling systems to convert by-products that are considered waste to reusable and treatable fractions by reducing the total organic carbon TOC. Which have been defined in the researchquestion of this study “How can functional recycling become more effective through the development of innovative treatment pathways for by-products of the recycling system”? and its sub-questions.

This study examined a fines fraction from the CDW sorting in Norway using mechanicalseparation methods including single and combined sequential processes of air classificationand float/sink density separation.

Using single process batch separation of float/sink had produced a 73.80% weight of the original fines fraction, with reduced TOC from originally 35.54% DM to 4.09% DM which can be considered to be landfilled as non-hazardous provided that it meets all other leachateanalysis criterion, on the other hand, the process produced concentrated the organic carbon inthe float fraction giving a TOC of 40.14% DM to consider treating it with energy recovery.

Using a single separation process of high air velocity with the zigzag air classification has lowered the TOC of 19.49% weight of the treated fraction to 1.8% DM from 35.54% DM of the original fines fraction, which can be considered to be landfilled as inert waste if it meetsall other leachate analysis criterion, or can be considered to be used in road base layers, and concentrated the organic carbon in the other fraction to TOC of 19.90% DM that which need further treatment. Using sequential air classification followed by float/sink sequentialseparation produced different low TOC fractions suitable for landfilling in the categoriesinert, non-hazardous, and hazardous waste in Sweden and concentrated the organic content toTOC levels of 20-48% DM TOC which can be considered for energy recovery recycling. The use of sequential density separation processes can lead to better results and can be controlled more to produced better fractions. The conclusion of this study, using float/sink and airclassification separation methods as single or combined sequential processes had successfully produced two fractions firstly the reduced the total organic carbon separated fraction to be suitable the landfilling requirements in Sweden at the same time concentrated the organicmaterial of the other fraction to be suitable for incineration.