Background Agro-industries are major contributors to industrial pollution and Cyprus is no exception to the rule. These industries, which process agricultural raw materials such as milk, fruits, vegetables and meat, generate millions of tonnes of waste and unexploited by-products that end up harming the environment. The production of milk and dairy products in Cyprus and the rest of Europe has increased significantly during recent years and this has resulted in larger amounts of non-consumed, returned and expired products - and milk products in particular. Most of these end up in landfills contributing to hazardous leachate generation and uncontrolled gaseous emissions. Landfilling of these products does not comply with the EU Landfill directive (1999/31), which imposes strict limits for the disposal of biodegradable wastes. Thus, there is a clear need for the dairy industry to develop sustainable management and treatment strategies for the ever increasing quantities of expired products. Anaerobic digestion of milk products and simultaneous methane recovery as a clean renewable energy source can be a highly sustainable solution for expired milk products with environmental, financial and social benefits. Although this process is state-of-the-art in the treatment of sewage sludge and industrial wastewater, very few applications can be found for the treatment of expired products themselves. Objectives The DAIRIUS project’s overall objective is to demonstrate an environmentally and financially sustainable solution for the management and treatment of returned Expired Dairy Products (EDP). It aims to achieve this through the development and testing of a two-phase anaerobic co-digestion process of EDP with other substrates. The project will analyse the specific details of the EDP generation by the dairy industry in Cyprus. It will assess the optimal physical, chemical and biochemical conditions for the anaerobic co-digestion process to maximise biogas yields. This will include determining the ratios of potential substrates, such as manure, in the process through investigations at laboratory scale. A pilot anaerobic digestion plant will be designed and constructed; biogas from the process will be collected and used to generate energy. Running of the plant will permit further optimisations to the proposed process. The project will define the optimal plant operating conditions for EDP treatment to maximise biogas yields. It will also describe the best possible processes for aerobic composting or vermi-composting of the residual digested material. A cost-benefit analysis, environmental impact assessment, and lifecycle analysis will be performed and used to evaluate the exploitation and long-term commercialisation potential of the prototype pilot plant. The process is expected to be of wide interest in the dairy sector. Expected results: Clear demonstration of the wide-scale applicability and environmental benefits of anaerobic treatment of EDP; Successful generation, collection and use of biogas as a renewable energy product from EDP - as well as residual material for composting; and The definition of optimal conditions and technical specifications for the treatment process to maximise production of useful by-products.