Additionally, emissions from other components and concrete production are assumed for Europe as 17.5 kg CO 2 /m 3 of concrete . The overall emissions from the reference concrete are thus estimated as 208 kg . A similar level of positive CO 2 emissions applies to the concretes containing C-LWA. However, by capitalizing on the C-sink potential of the C-LWA, these high emissions can be compensated. In fact, the concretes with C-LWA produced in this study had net-zero emissions thanks to the incorporation of about 20 %-volume of C-LWA, see Table . If the concrete mixture in this study had contained composite cements, with a similar amount of C-LWA the overall emissions of the concrete would become substantially negative. The C-LWA, despite using a primary binder (Portland cement) still display a significant C-sink potential. Our estimate based on the nominal parameters yields 𝐸 1.05 𝑘𝑔 𝐶𝑂 /𝑘𝑔 of C-LWA pellets in their cured state (see Section 3.1). The overall sustainability of C-LWA could be further improved by using secondary, possibly waste-derived binders with lower emissions (e.g. natural or industrial-waste pozzolana). However, it should be stressed that the emission balance would not be necessarily improved even if low-emission binders were used for pelletizing the LWA. The main effect on the total (negative) emissions of the C-LWA is thanks to their high carbon content. By switching to a binder with lower emissions, but at the same time with likely lower mechanical properties (lower strength and stiffness), the mechanical properties of the pellets would most likely decrease. Hence, with a weaker skeleton of the pellets, less biochar could be integrated in the pellets in order to maintain their desired mechanical performance. This would likely result in overall lower C-sink potential. For example, by cutting the emissions of the binder by half, the C-sink would increase by about 6% only. In comparison, a similar effect would be obtained (or, conversely, lost) if the biochar content would be increased by only 12% (or, conversely, reduced by it).