One issue for reusing construction/demolition waste (CDW) in cement clinker manufacture is establishing the supply chains and the associated transportation costs from urban areas to cement plants. Cement manufacturing plants are normally stationary for three major reasons: 1) they are built next to the quarry/source for the necessary raw ingredients; therefore, the life of the plant is usually attached to the life of the quarry; 2) they are usually very large, in order to exploit economies of scale, and therefore cannot be easily transported; and 3) to keep cement manufacturing, and associated pollution, away from residential areas. In this work, we will conceptualise and assess the feasibility of a mobile cement plant capable of travelling between urban centres for the manufacture of cement clinker from CDW on-demand. The radical idea of a mobile urban cement plant (MUCP) challenges the well-known concept of economies of scale; but, we aim to provide evidence that “economies of scale”, normally exploited in a linear economy, may not always be the best option in a green and circular economy.
It is envisaged that MUCPs will transform cement manufacturing from a linear economy (or open loop recycling) to a truly circular economy, mitigating the economic and environmental transportation costs of CDW and of the finished cement product, and diminish the severe environmental and economic costs of excavation while enhancing landfill diversion.
Cement manufacture is intensive in resources, carbon, and energy. CO2 emissions from the cement manufacturing process arise mainly from the calcination of limestone and the combustion of fuels for clinkering. MUCPs will enable near-complete decarbonisation of cement manufacturing by 1) reprocessing the already-decarbonised calcareous source (concrete fines) into cement, avoiding raw-material CO2 emissions; and 2) simplifying the electrification of compact cement plants powered by renewable energy; avoiding fuel-derived CO2 emissions. Combined electrification and closed looping of the CaO source in cement will allow near-complete decarbonisation of the industry that is responsible for 8% of global CO2 emissions.
The development of MUCPs will enable true implementation of the circular economy strategy by allowing the recycling of cement into cement. MUCPs will simplify the use of excavation waste (>50 Mt produced p.a. in the UK) and legacy waste in landfill sites; for example, the UK has 190 Mt of legacy iron/steel slags in sites across the country. These wastes can be combined with other raw materials to be converted into cement clinker. Furthermore, MUCPs will have huge applications for the rebuilding of regions/cities damaged by war or natural disasters.
Applications can be made using the information on this page https://www.sheffield.ac.uk/postgraduate/phd/apply/applying