2.2.1. Cement/Concrete

The cement clinker production is responsible for the majority of GHG emissions related to concrete use with around 65% of the CO2 emissions stemming from the calcination process and 35% emanating from the fuels used in the cement ovens, the so-called kilns. The main current emission abatement options comprise of replacing fuels in the cement kilns with waste- or bio-based fuels, reducing the amount of cement clinker by using Supplementary Cementitious Material (SCMs or so-called alternative binders), and optimizing the concrete recipes to use less cement [27,29,96,97]. Sweden is a frontrunner when it comes to alternative fuels [51] but is behind the rest of Europe in using alternative binders with a clinker share of 86% [98] compared to the European average of 73% [29]. In addition, the average cement/binder content used in concrete is higher in Sweden than in other countries, with around 420 kg binder per m<sup>3</sup> concrete compared to an average 400 kg binder per m<sup>3</sup> concrete in Europe overall [7,99,100]. It is worth noting that high levels of SCMs require process adjustments due to additional hardening times prolonging project timelines, while optimized concrete recipes impact site practices as multiple specific concrete mixes require further logistics and on-site coordination.

Other prominent abatement options include design optimization to slim constructions, increased prefabrication to reduce waste and minimized construction process emissions, and material substitutions towards wood-based solutions [37]. For building construction, the development of engineered wood products has increased the opportunities for building multi-floor building with a structural core of timber.

Indeed, engineered wood products have recently experienced annual growth rates between 2.5% and 15% [101], with a range of studies showing that buildings with wooden structures have a lower carbon footprint than buildings with other types of structures (see reviews in, e.g., Reference [57,102–105]).

However, even if current abatement options are combined to its full potential, transformative technologies are still required to reach the goal of close to or net zero emissions in the cement industry by 2045 [54]. Carbon capture technologies (CCS) with or without electrification of the cement kilns are key deep decarbonization alternatives. The Swedish cement industry roadmap is targeting climate neutrality by 2030, with the main focus being on biofuels together with CCS [98]. However, Cementa is also pursuing electrification together with Vattenfall through its CemZero project, with a pre-feasibility study released in 2018 [106].
