To combat climate change, it is imperative to reduce anthropogenic \({\text {CO}}_{2}\) emissions to net-zero by approximately 2055, especially in solid fuel combustion processes. In the present book, the focus is placed on the detailed investigation of the oxy-fuel process, where the combustion air is replaced with a mixture of oxygen, carbon dioxide, and water vapour, facilitating near carbon-neutral combustion. Research conducted within the presented research centre Oxyflame encompasses a diverse array of fuel types, spanning from pulverised fossil fuels such as bituminous coal and lignite to renewable biomass sources including walnut shells, beech wood or miscanthus. Substantial advancements in the experimental characterisation of reaction kinetics, particle dynamics, flame behaviour, and radiation effects in combustion environments of different scales are presented. The results yield into the development of robust models for combustion and transport phenomena as well as efficient simulation methodologies for designing combustion chambers, paving the way for efficient oxy-fuel systems capable of effectively reducing greenhouse gas emissions in alignment with global climate protection goals.