The subject of the research presented in the article is biochar and the possibility of using this additive in aluminate-calcium cement-based mortars. The influence of this additive in the amount of 1, 3 and 5% on compressive and flexural strength was tested. It is a material created as a result of thermal transformation of organic waste of plant origin. The possibility of using this additive in cement composites has not yet been described in detail in the literature, however well inscribe within frame of sustainable development and circular economy. The aim of the research presented in the article was to design and test a mortar showing increased resistance to a number of extreme physical operating factors, including frost-resistance and the impact of high temperature, while maintaining strength parameters. The selection of material components of mortars, including the choice of calcium-aluminate cement as a binder and biochar as a partial replacement for cement, was dictated by the desire to combine all the above-mentioned mortar features in one composite. The result of the research is the development of recommendations for optimizing the composition of the biochar mortar at the future stage of implementation. A variable effect of the addition of biochar was obtained. Depending on the content of this additive, both decreases and increases in strength were noted. The presented results constitute a stage of a broader research program.