The urban development process faces challenges due to the lack of citizen participation for a more democratic development. This issue results in several challenges, necessitating more active involvement from citizens to incorporate their ideas and opinions into urban development. One of the primary challenges is creating opportunities for more citizens to engage in the urban development process. Much of the current visual material provided to citizens often lacks real-time attributes and shows a deficient understanding of the development area. To address these issues, Digital Twins, usually described as a live coupling of the state of a physical asset or process to a virtual representation with a functional output, have recently begun to be utilised in the urban development process to function in real-time by connecting the urban landscape, stakeholders, and citizens. Compared to commonly used 3D visualisation technology, digital twins offer a more transparent and rapid participation process. The concept behind such a support system is to provide citizens with greater opportunities to express themselves and comprehend the urban development process. The objective of this research is to explore the design of digital twins and expand the knowledge of how digital twins can be integrated into urban development by connecting stakeholders and citizens through these technologies. Accordingly, the following research question has been defined:

 RQ. How can digital twins support citizen participation in urban developments?

This thesis has evolved from broad to more specific aspects to deepen the understanding of digital twin implementations in urban development. The process of creating Urban Digital Twin Framework has revealed a lack of knowledge regarding how different digital twins are interconnected and what alternatives exist within urban digital twins. This framework was subsequently utilised to determine the visualisation accuracy required for digital twins across various urban development processes. It emphasised the significance of unique digital twins and their interaction with the development process. This thesis has also analysed and compared three different datasets: LiDAR, Photogrammetry, and Remote sensing based on visualisation attributes. This led to a new metric called Visualisation Accuracy, which describes the datasets' capability to render urban environments in ways that are visually realistic and experientially meaningful when deployed in visualisation platforms such as virtual or augmented reality. Employing diverse urban spaces and digital methodologies to enhance citizens' opportunities to participate in the architectural design process presents an innovative approach, ensuring that every citizen can be involved in the process.  

This work explores the production of biocarbon from forest biomass through pyrolysis in fluidized bed reactors, emphasizing the relationship between the operating conditions, ash behavior, and physicochemical properties of the resulting solid biocarbon. Fluidized-bed reactors offer distinct advantages for biocarbon production, including efficient thermal transfer, isothermal operation, and scalability. These characteristics make them particularly suitable for integration into existing energy infrastructure. A key strategy investigated in this work is the use of a weakly oxidizing atmosphere composed of recycled flue gases from combustion processes as the fluidization medium. This approach enables heat integration with fluidized bed boilers and reduces the need for external inert gases, thereby lowering the operational costs and improving the overall energy efficiency and circularity of the system. The impact of this atmosphere on biocarbon yield and composition was studied in detail, particularly in terms of its influence on ash-forming element behavior. Special attention is given to the transformation and retention of inorganic elements, such as potassium and phosphorus, which affect the suitability of biocarbon for industrial applications. The experimental and modeling results show that fluidized bed conditions favor the selective removal or redistribution of these elements. Analytical techniques including Inductively Coupled Plasma (ICP), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), and thermodynamic equilibrium calculations (TECs) were used to assess the mechanisms of ash transformation. In parallel, the evolution of particle properties such as size, density, porosity, and surface area was evaluated under different conversion regimes. Structural degradation owing to attrition and fragmentation was found to play a significant role in carbon retention and fine generation. The elutriated fines, enriched in inorganic content, were also characterized and presented opportunities for valorization in applications, such as soil amendment. Overall, these findings support the development of integrated and sustainable fluidized bed systems for biocarbon production, offering practical pathways to reduce fossil carbon use and improve the resource efficiency of biomass valorization processes.