Approaches for a low-carbon production of building materials: a review

High levels of GHG emissions are the result of the activities of the construction industry; for example, cement and steel production alone are responsible for 10e12% of global Green House Gas (GHG) emissions. In order to control climate change, while complying with the levels set by the Paris agreement and the IPCC 2018 report (a maximum of þ1.5 C above pre-industrial levels), serious measures need to be adopted so that GHG emissions can be reduced. Indeed, it is only through the adoption of the Circular Economy (CE) principles that the construction sector will be able to play a strategic role in the achievement of such reductions. Despite the importance of the topic, there are few comprehensive reviews of possible strategies to produce low-carbon materials; this paper analyses literature reviews on low-carbon material, starting from international policies on GHG emission reduction and CE principles, providing a critical summary of current knowledge. On the basis of a thorough literature review whose references have been made in accordance with the relevance of the topic of study, the approaches adopted in order to produce low-carbon materials, the materials investigated and the related issues and challenges, the work identifies in an original way eight approaches (known as Low-carbon Emission Approaches - LEAs) related to the production process that could help reduce the GHG emissions of construction materials. Comparing the results of the literature review analysis with the material life cycle by means of a matrix that relates LCA and LEAs, the paper underlines LEA's capability to reduce GHG levels. In particular, focusing on the 8 LEAs identified, it emerges that, in order to create low-carbon products for construction, it is possible to use alternative materials (up to 40% of GHG emission) and natural materials (up to 90%), to introduce secondary raw materials (up to 40/50%), to implement CCS and CCU systems in the production process (up to 70%), to increase the use of energy from renewable sources (up to 60%), and to increase product performance. The work also highlights some limitations linked to several factors, such as: the costs for initial investments, some changes in the cultural paradigm, the impossibility for the market to receive innovative products, and the lack of skills of technicians and companies, and so on; these problems need to be solved in the shortest time possible in order to achieve the goal set by the Intergovernmental Panel on Climate Change.