The construction sector is experiencing sustained growth worldwide, leading to an increasing demand for building materials. In this context, integrating and valorizing solid waste in construction represents a promising strategy, offering notable benefits such as environmental protection, reduced energy consumption, and decreased use of non-renewable raw materials.

This study focuses on assessing the impact of incorporating compost, derived from recycled organic matter, into cement–sand composite materials intended for building applications. Compost was selected for its local availability, renewable nature, and potential to support more sustainable construction practices, in line with circular economy principles and the valorization of underused organic resources.

Standardized specimens were produced by incorporating varying proportions of compost into a reference cement–sand matrix. Mechanical tests, including flexural strength and compressive strength, were conducted in accordance with current standards to ensure the reliability and comparability of results.

The findings indicate that the addition of compost leads to a gradual reduction in mechanical performance, particularly at higher incorporation rates, due to increased porosity and less optimal bonding between the matrix and the reinforcement. Nevertheless, these negative effects can be offset by the environmental benefits associated with compost valorization in construction materials, making it a viable option for sustainable building strategies.