Techno-economic optimisation of combined anaerobic digestion and gasification of food waste as part of an integrated waste management and energy system

Ireland produces 642,000 t of separated household organic waste or “food waste” annually. In 2016, only 420,000 t of biodegradable waste was permitted to landfill following the EU Directive 1999/31/EC. Growing population and restrictive directives are making landfills unfeasible. Anaerobic digestion (AD) offers an initial waste management measure of food waste (organic fraction of municipal solid waste). Gasification is an attractive process that can extract the remaining energy in the waste and reduce the final volume. This work explores the use of a food waste treatment network in Ireland in which AD and gasification are integrated with cogeneration of heat and electricity in a waste-to-energy national scheme. This work includes a parametric optimisation of AD and gasification of food waste based on experimental data and process modelling. A Geographic Information System algorithm locates and designs facilities for waste treatment, distribution and conversion to energy that minimise the energy involved in transporting food waste to treatment facilities. A techno-economic evaluation of the system is performed that minimises the levelised cost of power generation and maximises the energy output. This work presents the benefits of this waste-to-energy network and provides a sustainable alternative to current waste management practices in Ireland and other regions where landfills and other methods are environmentally harmful.