Improvement of Environmental and Energetic Performance of Waste Treatment Facilities

The objective of this thesis is to contribute to the existing literature on waste processing by examining innovative approaches that can be implemented in both small-scale facilities and larger waste-to-energy power plants. The enhancement of the environmental and energetic efficiency of treatment facilities is associated with two significant challenges in the field. These challenges include minimising the amount of non-recyclable materials that are sent to landfills at the end of their useful life, as well as implementing sustainable methods for treating the wastewaters and leachates generated during the waste treatment process. The economic viability of centralised waste treatment is frequently impeded by the substantial expenses linked to the transportation of waste to dedicated facilities, which can concurrently lead to the emission of extra pollutants. Consequently, there is an increasing interest on the notion of decentralised waste treatments. In addition, there is a considerable amount of residual municipal solid waste that is produced in mechanical and biological treatment plant that is sent to nearby landfills, generating different criticalities. First, both the landfill lifetime and the soil usage are negatively affected by the continuum waste disposal until there is no more space. Secondly, the unrecovered material mixture is not valorised for energy production, either electrical or thermal, representing a real energy loss. Similar considerations can be made regarding wastewater treatment plants, where liquid waste is channelled for the purpose of undergoing purification treatment before being ultimately released into the surrounding ecology. The implementation of bioremediation technologies offers a viable and promising sustainable alternative to wastewater treatment plants, as it has the potential to mitigate the effects of liquid waste. Consequently, the ideas put forward in this work are intended for implementation in the context of local waste treatment, and are the following ones: • The gasification of municipal solid wastes and its integration with various energy systems is being explored to optimise the utilisation of residual waste and reduce the reliance on landfills for waste disposal. Their gasification can be used to solve this issue. The amount of waste sent to landfill would be considered lower the energy recovered might be used directly to cover the consumption of the mechanical-biological treatment unit or sell to the grid and lastly, the thermal power could be distributed with a district heating network system. • The paradigms of a green circular economy foster the reutilization of the waste into new resources like biofuels. Biofuels can be obtained in other ways in the field of waste treatment. Biomass pyrolysis may increase the performance of the process especially if integrated to large scale thermal waste treatments. • Wastewaters represents another critical aspect to consider in the design of novel and sustainable treatment solutions. The application of microalgae in the bioremediation of wastewater and leachates produced in these facilities, with the subsequent utilisation of the biomass for the production biofuel production, is being investigated.