# Challenges of Engineering Skillsets Essential for Driving Circularity of Smart Cities
## 1 Introduction  
'Smart cities' have a famously ambiguous definition. There is no right or wrong solution, and many different researchers have attempted to craft their own definitions for smart cities based on several socio-economic and technical factors. The essence of smart cities is that they employ digital technologies such as the 'Internet of Things', which allows data to be analyzed and optimized for the system to make better informed operational decisions moving forward, with the purpose of improving several aspects of the city, which relates to the goal of being more sustainable. For example, Barcelona is a smart city; it uses information and communication technologies and governance in the economy and environment for effective urban management and is now considered a European success story of urban development [1,2]. Other cities employ such technologies and practices with the aim of replicating the successes of Barcelona, which is ranked as one of the top four best cities in Europe to start new businesses. However, employing smart technologies alone does not guarantee sustainable results. For a smart city to operate in such a way that sustainability goals are met, a circular economy (initiatives, technologies, and practices) must be introduced. A circular economy (CE) is an economic system aimed at eliminating waste and pushing the regenerative use of resources [3,4]. The EU Circular Economy Action Plan is a manifesto promoted by the EU to prioritize circular processes and sustainable consumption to circulate resources, which reduces the demand for raw materials [5]. There are many different thought processes that support the implementation of a CE. Primarily, there is the idea that by increasing a product's lifespan, people will need to buy the item less often, or if the item is recycled, then it means that the commodities and natural resources will have to be imported and used less often. However, looking at the bigger picture, it has much more to offer, ranging from new job opportunities to the eventual reversal of biodiversity loss [6], leading to positive impacts on climate change. Extending a product's lifespan has endless benefits, such as better value for the customer (due to lower costs and because the customer will be pleased knowing that they are consciously aiming to reduce waste) as well as an unprecedented positive impact on the sustainability aims of smart cities. The issue, however, is that the current level of circularity in the EU is not sufficient to offer the profound, visible, and immediate benefits listed above, with the EU's circularity rate, i.e., the share of material resources coming from recycled waste materials, being 11.7% in 2021 [7]. Based on the critical literature review of 100+ relevant articles available on Scopus and Google Scholar databases [8], the knowledge gap analysis reveals that no articles in the literature focused on or discussed the implementation of CE within smart city settings, particularly regarding engineering skillsets and transferable capabilities or even the hard and soft skills needed to facilitate CE implementation. The keywords used for the literature review include (i) circular economy, (ii) skill, (iii) capability, (iv) smart city, and (v) Internet of Things. Boolean operators based on the words \"AND\" and \"OR\" were used in the literature search on Google Scholar (advanced search option) and Scopus. The search for the most relevant literature (overlapping with at least two keywords) resulted in over 100 articles. However, our critical review reveals the acute shortage of research on engineering skills and capability required to implement circular practices in smart cities. This has led to the following research question: what are the critical skills required to generate growth in the adoption of a circular economy for smart cities? Therefore, this study aims to investigate the fundamental skills and education needed by industry practitioners to enact circular and smart cities.